kod Percent Oxygen from Calculated:
Expiratory Dilution ‘Supply + r
_Mitrogea. Percent Supply. Aabieat Ambient 02 mtg.
Atttude Minute Minute Hinute Minute Hinute Hinote
(ft) Gondiztoa _2 3 py 3 BY 3 1 1 1 3
10,000 Rxerctes 48-52 GL SHB Pr, es, Se a a a
hading SLO 6S 6} HTS 1° 49 50 AHS
35,000 wserctee 51047 63 Pre ee Se eS Cd
: landing, 46066 8H SBR AZ 12 Se SHOT
30,000 txerctoe 430 45 SAT AG Por Oe | SS
fading 820 40053 SRA? 9 se 60808107
POSTFLICHT
Ground Resting «530 SHO? 3032
Exercise 63 6280 2022 iB
Bending 5600 SST 2 «3¢ SSS

TABLE 19. Percentage of Ambient
Ohio Chenical
of the End Expiratory
Zep-Aro Orifice (F 365-1080-2)

¢ Ate and Oxygen Content of Inspired Cae Using the
KeS Mack ae Derived From Estimates

Nitrogen. Subject
1) at Pressure of

t OZ.

f 70 pet

53

a a PO ae

oe



about 10 min of rest. Two 1-h evaluations using the same subject
are shown in Tables 20 and 21, The first was conducted at 25,000
ft at an oxygen supply pressure of 70 psi. For the second flight
the pressure was reduced to 60 psi-

An extended 1-h flight at 30,000 ft of subject JV (Tables
22-23) was aborted after 32 min because of the steady deteriora~
tion of the subject's blood oxygen saturation during light exer~
cise and, 38 a precautionary measure, because of the safety
observer's developing 4 light case of wends.

In the evaluation of oxygen mask effictency, one of the most
important factors 4s the partial pressure of gases in the inspired
air. A rebreathing mask defies direct measurement of these param
eters because of the rapidly varying nonhomogeneous gas mixtures
introduced from inscant to instant in the facepiece of the mask.

To estimate the composition of inspired gases, we pursued a
different indirect approach, This technique is based on the
assumption that the end expiratory gases from the lungs have mixed
and represent a homogeneous mixture.

As an inert gas, nitrogen does not participate in metabolic
exchange. If. the absorption of oxygen and the production of
cardvon dioxide were exactly the same, then the amount of nitrogen
inspired would equal the amount expired; 1.€+5 nitrogen molecules
inspired = nitrogen molecules expired. The respiratory metabolic
RQ would be equal; i.e., RQ2 1. The metabolic RQ (1.e., RQ *
C02 produced

“Oy consumed) 4s not normally exactly equal. Under these

conditions there may be a relative differeace in the percentage
of inert nitrogen inspired and expired. The metabolic RQ depends
on the predominance of carbohydrates (1.0), protein (0.82) or fat
(0.71) in the diet. The normal value of a thixed diet approximates
0.83. The respiratory RQ may vary temporarily from the metabolic
RQ because of unsteady states, such as hyperventilation. The
increased lung ventilation produces 3 blowoff of carbon dioxide
from the blood and an apparent put misleading increase in carbon
dioxide production with a xesultant RQ greater than 1.0, Con~
versely, hypeventilation and retention of carbon dioxide indicate
an apparent but misleading decrease in carbon dioxide production
that results in an RQ of less than 0.7.

One must keep in mind that the unequal exchange of oxygen
and carbon dioxide involves only that portion of the gases con=
sumed and produced. For example, if during the l-min period at
rest 0.3 L of oxygen was consumed and 0.25 L of carbon dioxide,
was produced (RQ = 0.83), the resultant difference of 0.05 L on
the 7 or 8 L passing through the lungs during the same period of
time is relatively small. This produces an error of only a few

20



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Scans of oxygen concentration were made at approximately 45°
above and below mask level but their values did not exceed those
at mask level, The design of the exhalation valve of the particu-
lar TSO-c64 Passenger mask used in this experiment tended to direct
the exhaled oxygen toward the sides of the mask and apparently
accounted for the higher values detected in this area about the
mask.

IV, Discusston.

The U.S, Air Force conducted a study to determine the increase
in oxygen concentration tn altitude chambers during routine physto-
logical training of flight crewmembers when the chamber was vented
and unvented qQ). Although it Net stated in the report, these
training chambers usually have a volume of approximately 1,000 co
1,500 ¢ and are occupied by lo students using demand regulators,
each of which would be expeeted to dump a miniman of VS to 20 L/min
of oxygen into the chamber (240 to 320 L/min total) when on 100
Percent oxygen. Even when the chamber w. Ss unvented at 25,000 ft,
the mean OX¥KEN percentage was only iner ed from 2) Percent
(content of oxygen in air) to 27.1 pereent for a difference of
6.1 percent, Various studies conducted by the National Aero-
Nautics and Space Administration (NASA) following the Apollo fire
have indteated that a concentration of Approximately 40 Percent
oxygen must be approached before there is a signifteant increase
in the flammability of materials, In addition, if 100 Percent
tirse aid oxygen is administered in flight to a Passenger aca
cabin altitude of, for example, 5,000 ft, tes partis pressure
{s reduced from 760 mmlly (14.7 I/in") ae sea level to 632 rami,
(12.2 lb/in") ae 5,000 ft with a tendency to reduce its potential
effect on flammability of materials,

Even if an t-te} tirse ata oxygen cylinder wore to be totally
dumped into a DC-9 with a volume of 5.840 ft) or a B-747 with a
volume ef 59,000 Ft3, the resultant inerease in oxygen concentra
tion would be infinitely small, Tw addition, the ventilation
capability and rate of air exchange of these g rerate wouid in all
Probability make these increases tn OX¥Een concentration
unmeasurable.

Considerable caution should be exereised in interpreting the
results of chis very brief and preliminary evaluation as many
factors, such as differences in mask design, quantity and direc
tion of a flow, diverting obstructions, ele. , would drastically
modify these results. °

113


effective time for this product is 15 min of oxygen flow at 4 L/aio
per canister, The canisters can be actuated sequentially for 45
min of continuous flow at 4 L/min or simultaneously for increased
flows of shorter duration. From a total of 30 canisters tested,

1 failed to actuate. This sample number 1a not sufficiently large
to give a good reliability index. All canisters tested maintained
oxygen generation for the full 15 min and with decreasing and
variable flows to 17 min, Mean oxygen flow rates exceeded the
advertised values and are presented in Tables 1 and 2,

TABLE 1. Average Flow (Liters/Minut., NIP) and Standard
Deviation Within Canister(s) Acroes Time (0-15 Min)

Single Canister Dual Canisters
Test No. X_+ S.p. Test No. X_+ s.p.
i 4,82 0.49 14 10,21 0.86
2 5.02 0.51 15 9.74 1.98
3 4.95 1.13 16 10.20 1.6)
4 4.93 0.63 7 9.13 1.58
5 5.36 0.94 18 10.02 1.04
6 4.87 0.76 19 10.14 1.70
7 5.30 0.73 20 9.45 1.15
8 4.87 0.90 21 9.99 1.32
9 5.37 0.71
10 5.30 0.66
i 5.26 0.71
12 5.15 0.69
13 5.64 0.62

TABLE 2. Average Flow (Liters/Minute, NTP) and Standard
Deviation Across Canister (s) by Minutes (0-15 Min)

Single Canister Dual Canisters.
ee L = By
Min. X_+ s.p, X_¢ s.p,
Z 4.00 0.77 7.92 1.39
2 5.44 0.80 10.70 1.20
3 6.05 0.71 11,82 0.58
4 5.51 0.56 10.93 0.78
5 5.30 0.68 20.00 1.37
6 5.76 0.38 10.99 0.56
7 5.52 0.74 10.71 0.67
8 4.63 0.50 9.35 0.62
9 4.86 0.43 9.48 2.49
10 4,73 0.49 8.57 0.77
u 4.84 0.36 9.06 0.79
12 5.06 0.45 9.59 0.93
B 4.99 0.19 9.85 0.67
14 5.06 0.56 9.22 1.10,
15 5.28 1.07 9.71 2.37
62



= aaat ,..,
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EB

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=

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2a aa . Ha
ALTITUDE THOUSAND FT.

FIGURE 2. Tracheal oxygen partial pressure following 3 min
of exercise at the indicated minimum oxygen flow
rates.

73



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10



References

Harwood, V. N.t Chemical Oxygen Generator for Business and
Utility Aircraft, Society of Automotive Engineers, New York,
N. ¥., March 1971.

McPadden, E. B.: Evluation of the Physiological Protective

Efficiency of a New Prototype Disposable Passenger Mask, FAA
Office of Aviation Medicine Report No. AM-66-7, 1966.

68



4

z

Unless carefully studied, interpretation of the nitralyzer :
recordings from a diluter-type mask can be misleading. One must +
keep in mind that these recordings represent changes in gas compo- Ff
sition and not necessarily volumes or respiratory excursions. A ,

line is drawn through the end expiratory points in Figures 4 and 5.
In Figure 4, taken after 1 min of exercise at 30,000 ft, there is
still a slight upward slope, indicating a slow increase in concen-
tration of nitrogen being introduced into the mask, In Figure 4,
after 5 min of exercise at 30,000 ft, the end expiratory nitrogen
appears to have stabilized,

The height and weight of subjects may have affected some of
the evaluations because oxygen consumption is directly related to
the body surface areas. Subject JV, at a weight of 197 1b, was
the largest subject evaluated, He experienced a low blood oxygen
saturation during the first phase of the evaluation at 30,000 ft.
During the extended flight at 30,000 ft, he again experienced a
low blood oxygen saturation at an oxygen supply pressure of 70
psi. When the pressure was cut to 60 psi, the saturation dropped
precipitously and a descent was initiated. Subject DD, a small
male subject weighing 135 1b, completed two 1-h flights at 25,000
ft, using oxygen supply pressures of 70 psi and 60 psi without a
significant reduction in blood oxygen saturation. In a third
evaluation, after 6 min of exercise at 30,000 ft, this subject's
saturation only dropped to 94 percent compared to 83 percent for
subject JV.

Control of respiration in individuals who are not acclima-
tized to altitudes, such as in the Andes Mountains, is primarily
regulated by a delicate balance of carbon dioxide partial pressure
in the lungs and its effect on the blood, Regulatory receptors in
the central nervous and circulatory systems are in turn affected
via the blood.

Oxygen lack does not play a part in increasing respiration
until an equivalent altitude of 10,000 to 12,000 ft is reached,
at which point hypoxic drive of respiration becomes a factor. If
a significant degree of hypoxia becomes established, a vicious
cycle caused by using a diluter-type mask may develop in that the
mask wearer may reflexly hyperventilate in response to hypoxia.
The increased ventilation during hyperventilation results in more
ambient air being drawn into the mask, diluting the oxygen and
resulting in decreased mask efficiency. The dilution of oxygen
in turn results in increased hypoxia, At an altitude of 25,000
ft the Cessna mask with the Zep-Aro orifice delivering 2.7 L/min
Produced an average blood oxygen saturation” equal to or in excess
of the ground-level controls. At 27,500 ft the blood oxygen
saturation of the one subject evaluated at this altitude was only
slightly lower than the ground-level control. At 30,000 ft several
of the subjects experienced saturations below 90 percent that during

27

298-212 O- 19-8



(£) Oxygen added to air by mask = 5.9 L/min = 39.3%
- YS L/min

In the case of the phase~dilution mask, it is assumed tliat
the respiratory rate increases from 10 to 12 in response to the
increase in minute volume. Tidal volume is then increased: i

Tidal Volume = 15 L/min * 1.25 L
12

The capacity of the reservoir bag under these conditions is
equal to:

Capacity of the reservoir bag + oxygen added during 1.5 8
inspiration = 1.10 L +15 L © 1.25 L

The reservoir bag, therefore, exhibits a capacity equal to
the tidal volume. If oxygen were being delivered at a rate of
15 L/min there would be no dilution. However» oxygen delivered to
the reservoir is only 5.9 L/min or 5.9 L/min = 0.49 L/min per
oo ymin P

breath and dilution according to equation (f) occurs.

The calculations and values presented in this discussion are
approximations and simplifications of more complex respiratory
equations and do not take into consideration leakage, physiological
1 dead space, and variations in individual diserete tidal volumes.

However, these calculations illustrate the superior efficiency and
performance of an oxygen-dispensing device for use with continuous-
flow oxygen that incorporates a means for the collection and storage
of oxygen prior to each individual inspiration.

97


NASAL PROBE

30 sec

FACEPIECE PROBE

Simultaneous measurement of nitrogen by probes
inserted in nostril and the Cessra masx facepiece.
A dashed line is drawn through the end exoiratory
points. Subject BH. Fifth minute of exercise at
30,000 feet. Recording must be read from right

to left.

34



TABLE 26. Blood Oxygen Saturation, and leart and Respiratory Rates of
Subject BH Wearing the Cessna Mesk During Cheaber Flights to
Staultaneously Measure Nitrogen in the Facepiece and Kares.

Zep-Aro Orifice (F 365~1080-2) at an Oxygen Supply Preasure of 70 pei

Altieude Oximeter Perceat Reart Rate Respiratory Rate
(fe) Condition Minute Minute Minute

Ground Level Preflight s Co 20
1 6 1 ry 1 &
14,000 Rest, Baseline 86 7 78 82 16 it
Exercise 18 nR 98 9 ” 7

MASK DONWED |

{

T z T a H 3 i

Resting 6 9 78 66 10 fT 1
T 6 7 $ i é
2,300 Rest ing 5) 78 % 76 TY 19
Exercise * ” 86 90 18 2

30,000 Resting 96° 7 % 72 ay 19 . A

Baercise 2 8 90 “ 23 22 :

TABLE 27. | Percentage of Ambient Air and Oxygen Content of Inspired Gas Using the
Cenona Mask at Chander Flight Altitudes of 27,500 and 30,000 {t. Values Derived
Prow Simitaneous Measurements of End Expiratory Mittogen in the Mask
Taceplece and the Mares. Subject BH. Zep-Aro Orifice (F 365-1080-2).

Onygen Supply Pressure - 70 pet ;
i
Aleteude End —————Petcent Onygen from ____ Calculated
(ft) Heasure- uptratory Dt lution Supply * Pe i
and went Mitrogen Percent Supply __Ambtent. Aabient, 02 i
Condition Location ~ Mimte Hinate Minute Minute Minute Hieute |
T Fa 1 z i zc T = 1 z fT z
00 met ST Sar ot 270 i28
Resting Mosk ca St © SP
sot ff PS as ae
2,800 Meester r 7 Te FS WSF se
Resting Hack ne ae ne, eS) ry 6 % te 457 AS7
27,500 Marsh = 404 Skat 9 60 128 18
Exercise Mask ba SO (OS SP
30,000 Masa = 2502332 ion 7 6 1s ase ae
Resting task ? e e 70072 6 6 % 8 1% 1h0
30,000 Kasst 330 gk gS ’ > 6) eo
Reading Mesk » - a bond bra - 9 ~ . %0 _- 1s +
30,000 Masa = 3307 ka aS 9 10 63 osteo
Exercise task eS a Ce ce? Ty 9 9 6F 6120 120
58



407 yas BREATHING BASELINES
VARIABLE DURATION - STABILIZATION

DON O2 MASK

ALTITUDE (THOUSANDS OF FT)

54 io,

O° Vd LI I TLITtirir i \ }
¥ T T T T T ul
fe) 10 20 30 40 50. 60

_— ELAPSED-TIME (MIN) mad

GROUNO LEVEL CoO REST GROUND LEVEL
BASELINES CO EXERCISE BASELINES (POSTFLIGHT)
(PREFLIGHT) COUREADING C02 DETERMINATIONS

FIGURE 1. Altitude chamber flight profile and subject activity
of 10 subjects wearing the Cessna mask.

30



completion of the test, gave a personal assessment of the mask for
fit, leakage, and comfort, The order of mask testing was randomized
for each subject to control the influence of the first mask encounter
on the evaluation procedures. Oxygen was precisely metered to each
mask, first at 3 and then at 4 L/min, or the reverse, depending on
the randomization process, while the subject exercised on a constant
work ergometer for 4 min each in a sequence of 0, 120, and 400
kilogram meters/min. Tracheal oxygen partial pressures were deter
mined continuously as in the second phase.

III. Results.

The Life Support generator systems (Fig. 1) measured
23 x 10 x 19 cm for a volume of 4,370 cu? and for a total weight
of 2.2 kg. This weight included three unexpended canisters, hose,
mask, and case. The canisters measured 116 x 56 m. in diameter

and weighed 380 g each. i

FIGURE 1. Life Support oxygen generator system.

Loading canisters into this unit simply requires insertion
of the canister and closing the cover. This unit contains three
actuator buttons of a recessed design, which reduces the potential
for inadvertent actuation. This unit was provided with a “hospital
type'' mask of open-port design and a rebreather bag with the oxygen
inlet betveen the mask cavity and the rebreather bag. (The advertised

61


References
sfietences

\

Webb, Paul (Ed.): Bioastronautics Data Book, NASA-SP-3006,
Scientific and Technical Division, Washington, D.C., 1964.

Giles, J. A. (Ed.): Textbook of Aviation Physiology, New

York, Pergamon Press, 1965.

98

ane mam ine a aR I


TABLE 3. Blood Oxygen Saturation, and Heart and Respiratory Rate Baselines
of Several Subjects at 14,000 ft Wearing the Cessna Oxygen Mask
and Breathing Oxygen With the Zep-Aro Orifice (F 365-1080-2)

Resting, Mask Donned Following Air Breathing at 14,000 ft

Was
Oximeter Percent Respiratory Rate
Minute Hint
Subject Sex 0.75 0 9 0.75
DR M 83.0 98.5 95 80 - _-
at Mu 91.0 97.0 78 70 15 16
Ja F 93.5 97.0 102 1s 19 18
Range 83.0-93.5 97.0-98.5 78-102 70-115 15-19 16-18
Mean 89.0 97.5 92 88 17 1?
Exercising, Mask Oa at 14,000 ft
w= 2
1 3 1 3 1 3
at M 98.0 97.5 70 75 19 2.
JH F 93.5 97.0 102 115 19 18
Range 93.5-98.0 97.0-97.5 70-102 75-115 19-19 18-21
Mean + 95.8 97.2 86 95 Wes 1
39

LETT UTES TESTE eet

SO IIL ROTI OS ERR 2 ETM IT


The quick initiation of the emergency descent, 6,000 ft/min,
by the pilot helped control the severity of the decompression in
the passenger cabin. The wultitude of auctions taken by the flight
engineer for damage control and to conserve pressure are not
available.

Two separate decompressions of the aircraft are identified,
a rapid and severe decompression in the lower compartments and a
slower and less severe loss of preasure in the passenger cabin.
Two separate decompressions of different profiles e iblish a
pressure differential between the upper and lower compartment
systems. The presence of such a pressure differential is confirmed
by the implosion of the upper deck door to the personnel lift and
the forced opening of the lower deck lift doors. Structural damage
to the upper portion of the lower deck personnel. lift door con~
firms a pressure differential from the lift shaft to the lower
galley.

The upper deck cart lft door is approximately one~half the
area of the personnel door and is the stronger of the two.
Because the lift shafts are connected, the pressure differential
across the smaller door was relieved by the failure of the larger
personnel door. At the time of decompression, the cart lift was
in position in the lower galley and the personnel lift was reported
to be in position in the upper deck. During decompression, the
personnel Lift was reported to have been forced to the down, or
-lower galley, position. The capacity of this lift is rated at
250 1b and, with a surface area of approximately 20 x 37 in or
740 in?, a pressure differential of only 1/3 psi would load the
lift to rated capacity. The forces required to override the drive
mechanism and magnetic brakes are not available at this time.
While investigators were on site, physical attempts to raise the
personnel lift were not successful, It is reported that once
electrical power was restored to the aircraft, the lift was

operable. No visible signs of failure in the drive mechanism
were detected.

If functioning properly, the lower galley drain plunger
located in the bottom of the lift shaft would have no effect on
the decompression or events related to the lift. The possibility .
of connecting openings between the belly compartment and the
mechanism housing located in the lower lift shaft was discounted
following examination of maintenance manuals, This should be
confirmed on the aircraft.

III. Oxygen Systems.

The crew oxygen system consisted of Sierra quick-donning
masks, Model No. 358 (Sferra Engineering Company, Sierra Madre,
California), with Robertshaw mask-mounted regulators (Robertshaw

81



for use above 25,000 ft. Evaluations were oriented toward
deternining compliance with Federal Aviation Regulations (FAR),
National Aerospace Standard (NAS) 1179, and Federal Aviation
Administration (FAA) Technical Standard Order (TS0) C64, The
MBU-8/P mask demonstrated adequate physiological adequacy for
Limited exposures at 40,000 ft.

If workloads and therefore respiratory activity are increased
above those used in this study, oxygen flow to the mask should be
increased to compensate for these increases in activity.

Human Factors Report of the Investigation of the In-Flight
Decompression, November 2, 1973, of National Airlines Flight 27
(N6OONA)? A DpC-10 En Route From Houston Internacional Airport
to San Francisco With 127 Persons Aboard; Memorandum Report
AAC-119=74-6(S) +

This study of an in-flight decompression was conducted in
response to 4 request from the National Transportation Safety
Board for assistance from this laboratory because of our back~
ground in high-altitude and rapid-decompression research, Parti-
eipation in investigation of selected accidents and incidents 1s
also beneficial to the researcher, as it provides him with an
insight into real-life aviation safety problems and areas to
which priority should be placed in the design of research tasks.
One passenger Was ejected from the aircraft and assumed to be
fatally injured. Analytical study of this accident indicated a
rapid decompression of the lower galley and a slower, less severe
decompression of the main passenger compartment. Following sub-
mission of this report, spectral analysis of the cockpit voice
recorder verified thia sequence of events.

Effectiveness of a Paper Cup as an Aid to Providing Oxygen to
Laryngectomee Passengers; Memorandum Report AAC-119-74-17,

This report was completed in response to a question of the
validity of an operational procedure and method of administering
oxygen to a@ laryngectomee passenger as recommended by a major
airline. The lack of a reservoir bag to store oxygen between
inhalations and the inefficient characteristics of the use of a
paper cup are described and compared to alternative procedures.

Physiological Considerations and Limitations in the High-Alcitude
Operation of Small-Volume Pressurized Aircraft; 47th Annual
Scientific Meeting of the Aerospace Medical Association, 1976.

This report examines the relationship of the small volume of
certain jet aircraft to the rate of decompression, the location

and area of possible pressurization defects, and the resultant
physiological and medical consequences. It also points out the

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Altitude (thousonds of ft)
CO)owrcent ambient aie
CZZpercent 02 derives trom segutoter

FIGURE 7. Luft's histograph showing dilution of inspired gas
with ambient air at different altitudes and rates of
flow during evaluation of the K-S mask in 1961.

100¢-
90h
sor
Toh
= x
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5 50 y
~ Flow Rote
© flow Rote
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Hyperventitetion,
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Following 3 min Cnercise
Hor & 2.7 Lsmin
Following 3 min Reading
[en ee Se 1

it
5 10 15 20 25 30 38 40
Altitude (thousands of 1) -

FIGURE 8. Concentration of inspired gas using the Cessna mask
superimposed over Luft's plot of the K-S mask in
1951. Oxygen flow controlled by a Zep-Aro orifice
F 365-1080-2 with a flow of 2.7 L/min at a pressure
of 70 psi. Curve represents inspired oxygen required
to theoretically maintain sea-level conditions.

36



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67



oe
iY

TV. Discussion,

The National Aerospace Standard 1179 and the FAA TSO-C64 |
Provide frecise guidelines for the physiological performance test- . |
ing of passenger oxygen masks to be used in afr ca rfc. varcraft, .
These performance specifications require that a mean tracieal
oxygen partial pressure of 83.8 mag or greater be mainiz.ned for
the maximum altitude for which approval is destred, These guide-
lines further require that a respiratory miaute volume of aroroxi=

altitude within 5,000 fe of the Gaximum for which approval is
desired. Induced hyperventilation may be used to achieve this
@inute volume. However, the use of bvperventilacion has a tendency
to overrete the phystolcgical efficiency of a mask due to the
decreased PCO, and resultant increased pO. that occur after the
first few breaths, For a nore detailed discussion of the effects
of hyferventilation, see Conroe (7). The us: of regulated :xer-
cise has a tendency to underestimate the phys ‘ological efficiency
of a mask due to the increased oxygen consumption, particularly
when compared with testing procedures that utilize sedated sub-
jects. dowever, the identification of the Proper workload to
maintain the desired Tespiratory minute voluze for an individual
ie difficult, especially when che degree of apprehension is often
unpredictable.

In this study a workload was established for each subject
that would produce a Tespiratory minute volune of approximately
30 L/min 8TPS, this deteraination being accomplished at 16,000 fr
where the- effects of apprehension were minimal, The flow of oxygen
to the cest mask vas Precisely regulated to 4.35 L/min NTPD, or
37 L/min BIPS, at the 40,000-ft level. If the effects of anxiety
ate added to the ventilation rate produced by work, a minute
volume of 37 L/min would be spproached or even exceeded. In
either case, if a vapid irregular respiration is encountered, the
Teservotr bag could be ecptied and ambient air would then be dram
through the dilurion valve. If the tidal volume vere sufficiently

oxygen saturation data for the 40,000-ft aletieude demonstrates
the zesules of having obtained a Tespiratory minute volume higher
than expected; f.e., in excess of 30 L/min BIPS. H

Testing vas terminated during the third minute of exposure to
40,009 f¢ for subject 7, due to the development of acute hypoxta.

The quantification of inpedance Pmeunograph data ig diff feule
and, at tines, highly questionable; hovever, ft can readily be
used as an indication of ventilation rate, A comparison of Impe-
dance Preumograph Tecordings obtained at 14,090 £¢ with a workload

76


rn | Ig as

UNCLASSIFIED

~
E

RECE,

&
>
2 S62
%, é

Technical


ccoenannne Sc et EEL

atea required to produce these decompressions is only about
one-fourth the area of the cabin window. Simple calculations
such as these can only be approximations because of variables of
orifice configuration and location, flow efficiency, thermodynamic
considerations, and compressor input rates as well as numerous
other factors. Because civilfan aircraft flight recorders do not
record cabin pressure, the correlation of decompression calcula-
tions with actual in-flight incidents is difficult, if not
impossible.

For example, reconstruction of the cabin a*titude profile
of the DC-10 decompression near Albuquerque, New Mexico (4),
required approximately 7 mo and relied extensively on analysis
of the cockpit voice-recorder tapes. By relating segments of
time from the initial sound of decompression and the automatic
initiation and cessation of pressure breathing as provided by
the flight deck crew mask-mounted regulators, reconstruction of
the cabin altitude profile was pocsible.

Aerodynamic Effects. Negative differentials following
decompression may occur and the cabin altitude may actually

exceed the flight altitude as a resuit of the aerodynamic (Venturi)
effect. Blockley and Hanifan (5) describe this phenomenon in
large (bomber) aircraft. The removal of doors and hatches at
12,192 m (40,000 ft) and Mach 0.87 produced an increase in cabin
altitude of 610 to 2,438 m (2,000 to 8,000 ft); i.e., 12,802 to
14,630 m (42,000 to 48,000 ft). This effect could be more pro~
nounced at 15,240 m (50,000 ft), because less differential is
required to produce an equivalent increase in altitude.

Physiological Considerations. Oxygen equipment should have
the capability of providing adequate protection for both crew and
passengers in the event of a decompression to the maximum certi-
fied altitude of the aircraft. Alveolar oxygen partial pressure
of flight deck crewmembers must be sufficient to prevent hypoxia-
induced performance cegradation and loss. of useful consciousness.

The total pressure within the lungs follows the cabin pres-
sure during a decompression (if it does not, an excess differen-
tial may be produced with possible lung damage), instantly

altering the partial pressures of oxygen, carbon dioxide, and
nitrogen.

The alveolar gas composition for selected altitudes while
breathing air is presented in Table 3. An mination of these
data shows that in rapid decompressions to altitudes higher than
10,058 m (33,000 ft) while brearhing air, the liberation of oxy~
gen from the blood into the lungs (i.e., reverse diffusion) begins.
This condition is demonstrated (Table 3) by the percentage of
oxygen increasing above that of air (20.9%). However, the partial

102

aoa een in EO


——____-—_- =
TR alt hn wah ethn vee SCE octane borers astset alata celatatth

|

i
ol
¥



TP pee er

TABLE

mr

ALVEOLAR GAS COMPOSITION 2-5 SECONDS FOLLOWING RAPID
DECOMPRESSIONS TO SELECTED ALTITUDES. WHILE BREATHING AIR
(COMPILED FROM CLAMANN, ET AL!)

ALTITUDE
10,058 m §2,192m 13,990m 15,240m
| ; 33,000 ft 40,000ft 45,900ft 50,000ft
Pressure, total mmHg 197 141 105 87
Portiol pressure, #,0 47 47 47 47
Pressure, dry gas | 150 94 58 40
ORY GAS COMPOSITION
Portial pressure, 02 ‘ “30 22 (4 uw
Percentage 19.8 23.4 24.7 27.0
Portiot pressure, C02 33 27 24 16
Percentage 22.0 29.t 416 40.3
Partial pressure, Np , 87 45 20 13
Percentoge 580 47.5 34.4 32.7

103


breathing air at ground level (Table 21). An extended-duration
chamber flight to 30,000 ft was conducted with subject JV, At
the end of 6 min of light exercise following 16 min dwell time at
30,000 ft, the subject's blood saturation had dropped to 83
percent. At the end of the 24th min at 30,000 ft during resting
the oxygen supply pressure was reduced from 70 psi to 60 psi.
Light exercise was initiated at the end of the 27th min and by
the 32nd min the blood oxygen saturation had dropped to 75 percent.
At this point the remainder of the flight was aborted as a
Precautionary measure, not only because of the subject's deteri-
orating condition, but also because of development of moderate
symptoms of bends by the safety observer, which could only be
aggravated by further dwell at this altitude. Table 23 reflects
the calculated inspired oxygen partial pressure.

In the third phase two exploratory flights were conducted
simultaneously to measure end expiratory nitrogen in the nostrils
and mask facepiece and, hopefully, to correlate these two sampling
locales and determine their relationship,

The first of these flights consisted of a 12-min dwell time
at 25,000 ft with the subject engaged in 6 min of resting and 6
min of exercising. The chamber then ascended to 30,000 ft, at
which time the rest-exercise cycle was repeated. As in the pre~
vious extended-duration flights, subject DD maintained good blood
oxygen saturation (Table 24). Review of the calculated inspired
oxygen concentrations indicates that readings from the. mask vary
by only 2 to 3 percent from those in the nostrils (Table 25).
Figure 4 is a reproduction of the nitralyzer record during exer-
cise at 30,000 ft.

The second of these two flight profiles was identical to the
first except ascent was to 27,500 and 30,000 ft instead of 25,000
and 30,000 ft. Blood saturations of subject,,BH resting at 27,500
ft were equal to or higher than the ground-level control, dropping
only slightly below the ground-level control during exercise.
However, at 30,000 ft with light exercise, saturation dropped to
89 percent.

The calculated inspired oxygen concentration as derived from
nitrogen recordings in the mask and nostrils indicates.a variation
of 2 to 4 percent at altitudes of 27,500 and 30,000 ft (Table 27).
Variation was es much as 5 percent at 14,000 ft. The mask, how-
ever, had been donned only shortly before these readings were
taken. The subject was previously breathing air at 14,000 ft and,
as a result, readings were more variable because a steady state
had not been attained,

25



B. Electrical system failure Prevented automatic presenta-
tion of all oxygen units to the passenger cabin, The No, 3 DC+bus,
which provides power to close the switches in the passenger oxygen
release system, was inoperative,

C. The backup system for mask Presentation was manually
deployed by the flight engineer. It is not known if this was due
to calls from the lead attendant or was a routine operational
Procedure, Those oxygen systems controlled by the No. 3 AC-bus
were not ptesented. It is reported that the No. 3 AC-bus was
Anoperative. A comparison of the seating chart to mask presenta~
tions indicates that approximately 24 passengers were initially
without supplemental oxygen. A number of these passengers even-
tually moved to other seats, In five cases, passengers, and in
one case, an attendant succeeded in forcing open the seat backs
to gain access to the units.

D.. The seat backs that contain oxygen systems are so designed
to prevent passengers from opening the systems manually, Lifevests
are located in seat back compartments adjacent to the oxygen units,
Theee seat backs are designed to be opened manually by passengers
in the event of a ditching. It is estimated that 25 percent of
the lifevest compartments had been opened and, in most cases, the
lifevests removed while Passengers were looking for oxygen masks,
This caused considerable confusion and delay on the Part of a
number of passengers in obtaining aupplemental oxygen. A number
of passengers were also confused as to where the oxygen masks
would be presented; f.e., overhead drop vs. seat back systens,

E. At eight locations, when the masks were removed from the
Yetaining brackets and Pulled to activate the canisters, the
activation lanyards entangled in the Yetaining brackets, making
the mask unusable.

F. At one location, the oxygen reservoir bag was separated
from the mask facepiece. This type of mask has a lanyard from
the facepiece that Passes through the reservoir bag to the oxygen
inlet tube that provides strength to the assembly. When this type
of mask is presented from overhead, a Person is instructed to grab
the mask and pull, the force being absorbed end transmitted by the
lanyard. When this type of mask is presented ina seat back, tc
is possible for the user to grab the mask and bag, or only the

bag, Yesulting in a separation of the reservoir bag from the
facepiece.

G. At several lccations, plastic mask-components came in

contact with the canisters, causing burns that left the mask
useless.

H. At three locations, canisters were removed from seat
backs and dropped into seats. The reasons for these actions are

83



References

National Aerospace Standard 1179, Revised. Aerospace
Industries Association of America, Washington, D.C,, March
1961.

Technical Standard Order C64, Federal Aviation Administration,
August 1961.

McFadden, E. B.: Evaluation of the Physiological Protective
Efficiency of a New Prototype Disposable Passenger Oxygen Mask,
FAA Office of Aviation Medicine Report No. AM-66-7, 1966.

Tuttle, A. D., J. L. Marbarger, and U, C, Luft: K-S Disposable
Mask, AEROSPACE MEDICINE, 22:265-277.

Luft, U. C.: Evaluation of the K-S Disposable Oxygen Mask,
Special Report, USAF School of Aerospace Medicine, December
1950.

McFadden, E, B., H. Harrison, and J, M, Simpson: Unpublished
Data, Department of Transportation, Federal Aviation Adminis-
tration, Civil Aeromedical Institute, Oklahoma City, Oklahoma,

Comroe, J. H.: Physiology of Respiration, Year book Medical
Publishers, Inc., Chicago, Illinois, 1965.

78



{

Measurement and establishment of minute and tidal volumes
were made while subjects were weariug the crew masks just prior
to donning the passenger masks and decompression. When a constant—
flow passenger mask is worn, current techniques and instrumentation
do not allow measurement of respiratory volumes without compro-
mising mask performance. The dynamics of rapid expansion of gases
in the lungs during decompression increases the difficulty of
accurately determining respiratory volumes.

In addition, any type of gas analysis equipment that requires
a relatively large sample flow or volume compromises mask perform~
ance. Respiratory nitrogen was monitored and recorded by using
two Custom Engineering Model 300AR nitralyzers. These instruments
have a rapid response time and required only 3 cc/min of sample
at the pressure setting used. Continuous samples were drawn from
the mask through a needle valve and microcatheter tubs; of
0,03-in inner diameter. This small, extremely lightweight micro-
catheter tubing did not add significant weight to the mask or
necessitate its modification (factors affecting the character-
istics and performance of the mask) as may be the case with other
types of gas analysis equipment. One of the nitralyzers was used
to record minimum and maximum nitrogen on a breath-by-breath
basis, whereas a small inline sample mixing and damping reservoir
was used to attempt to integrate and determine the average or
mean nitrogen concentration by the other nitralyzer (Table 1).
Nitralyzers were calibrated and matched before each experiment.

Tracheal oxygen partial pressures were estimated as
follows:

Pp, = 100-F. (8-47)
T,
05 Ny

where 100 = sum of nitrogen and oxygen in the inspired gas
yy = fraction of nitrogen in the inspired gas
B= barometric pressure at ambient altitude in mmHg

47 = vapor pressure of water in mmHg at body
temperature (37°C)

Pr = tracheal oxygen partial pressure
2


TABLE 12, Percentage of Nitrogen as Measured tn the Mask
Facepiece and reaching Bez at 37,000 fr

wer i
Exerciotag Reading -
First and Third Minutes at 30,000 ft Fourth and Sixth Miautes at 30,009 ¢¢
“Range Peak Meas Sarge Peat We,
“Winute Minute ‘Hinuce Winute Lrewrry
Subject Lecation 1 3 1 2 1 3 bs 4 6 ~
me eg 1O-2S 20-1623 29S dak 9 U

Mask 30-60 32-65 67 oT a? so 25-63 28-4259 6 » nx

sr oag S40 5-40 600 501010590598 4s ta -
Mask 16-46 22-62 504032753 22-52 5957S
mu hag I-53 S126 os 3 8 S10 S10 15 ae 8 ?
Mask 25-60 WOO 63 5545 6285S S55 8) S8 tk
ag elo 4 1 1 1 #6 Bh? 5 2 3 2 °
Mack 3261 37-63 66 6568504859 as? 62 oka
12 tag es we? 3 2 15025 2-10 27 a9 3 4
mark 1657 15-57 6570S SASS 1550 6S 588k
DH tag OO &2 oO 3 ° 1 OL @o 1 ° 0.5 0 ~~
“eek 1058 ASB 006974156 1-57 57a
crag SIS $10 15 23 7 6 S20 8 35 mw ?
Mak Qeel 2th 62° 5642” 38 ass e825? gS
BH ag 4-10 2-2 10 2 ? 2 F110 S10 193 3 s
360 25-60 66 63 4S 4S 82-61 90-50 6S? fon
wv 10 & 6 oO 6 6 3 S13 11S 30a?
O58 A238 600 GL 506850 52 kkk
vz x10 625 1333 eR cg Cot es SY i
Mak sg ler 6263 kas 3s oss le 42 ‘
48
t
‘
eo ef



Condition B: The effective opening of 1/8 in
Yestricted to one-half tie perimeter of the doors.

8° Coat eer) (7)

Ct, " approximately 18.5 s

Condition C: Condition B with a decompression to
30,000 fe equivalent.

Volume of lover galley 1,670 fe3
Area of orifice approximately 0.19 te2
Pa equivalent co 10,000 ft 225 malig
P. 15

1
to 1,670 fc3
E (as Tr?) G30 tee) (*: )

t, " Spproximately 11.1 5

The decoupression in the lower gatley was basically due to
the loss of pressure in the forward cargo compartment and, as such,
should be treated as a dependent function. The number of unknowns,
such as input flow to the lower galley from the sir cond ittoning
system, the lift compartment, and the Pressure relief valve and
additional Outflow chrough the galley exhaust jet Peap (as pre-
sented in the decompression scheratic) make a detailed mathemati-
cal analysis impractical. These estimates support the conclusion |
of a rapid decompression to an equivalent altitude of around

A signtficantly different decompression profile occurred .
ia the passenger cabin, In the Upper deck, two Penetrations of
' 160 tn? each occurred. One Penetration, directly in the passen-
ger cabin, was the loss of the window at seat 17H. The other

Penetrations are large, they are working against a large cabin
volume, 16,600 ft}, and a high input from the No. 1 and Ko. 2
compressors, 150 ib air/min each,

90

é RN EE een pee me

Volume of lower galley 1,670 fc3 5
Area of orifice 1/8 in x (4 x 220) in

x (so doors 28 in?
Atea of orifice approximately 0.19 fr2



\

PHYSIOLOGICAL EVALUATION OF THE PROTECTIVE CAPACITY OF THE
PROTECTIVE MBU~B/P MILITARY PASSENGER OXYGEN MASK

E. B. McFadden, D, deSteiguer, and J. M, Simpson
I. Introduction.

The civil air carrier fleet's use of flight altitudes to
41,000 ft has been the primary impetus for the development of
modern passenger oxygen systems, The systems are designed for
automatic mask presentation in the event of decompression. They
must provide an oxygen flow sufficient to maintain a mean tracheal
oxygen partial pressure of not less than 83,8 mmHg at a tidal
volume of 1,100 cc and a minute volume of 30 L/min BTPS up to and
including 40,000 ft, as specified in the Federal Aviation Regula-
tions, National Aerospace Standard (NAS) 1179, and FAA TSO-C64,

As a component of oxygen systems, U.S. air carriers use a
continuous-flow reservoir mask of the phase=dilution type, A mask
of this design meets the performance requirements for passenger
use; does not require excessive oxypen flow rates; may be used
with gaseous supplies or chemical generators; and is relatively
simple in design though not in principle, The continuous-flow

reservoir mask incorporates a flexible bag between the oxygen
delivery tube and the mask inhalatio:

m-valve, The continuous flow
of oxygen accumulates in the reservoir. bag during the exhalation
portion of the respiratory cycle, thereby providing a drawdown
capability during inhalation, During inspiration the mask wearer
receives 100 percent oxygen until completion of the inhalation
Process or collapse of the reservoir bag. Once the reservoir bag
has been emptied, a sensitive di

lution valve is activated to pro~

vide the necessary volume of ambient air for completion of the
inspiratory process. In this manner, 100 percent oxygen is pro~
vided at the most advantageous time (i.e,, the first part of the
inspiratory cycle) and oxygen diluted with ambience air is provided
during the latter portion of the inhalation, filling the upper
portion of the respiratory tract where gas exchange is nil.
Furthermore, the air-diluted oxygen is exhaled first and conse~
quently washed from the system prior to the next inhalation,

Performance is reduced by inboard mask leakage due to poor
facial fit, a respiratory minute volume that is considerably
greater than the flow of oxygen to the mask, and improperly
sequenced valving.

Reduced performance becomes critical as the
decompression approaches 40,000 fr,

However, at altitudes of less
than 40,000 ft, the dilution of supplied oxygen with ambient air
through the dilution valve is utilized as a means of conserving a
finite aircraft oxygen supply while simultaneously Providing the
necessary mean tracheal oxygen partial Pressure for the passengers.
With proper facial fit, modern masks of this type are capable of
providing the necessary protection in the event of decompression

69



ECG (For Heart Rate Only)

99.3% 99.4%
Oximeter

200-4
1504 Heart Rate

100 eng pew nem en atin te t0 OCLC IORI AANA COLCA

$0~-

30,000 ft

Respiration

20,000 ft 4 Altitude

14,000 ft =

1,250 ft ~] Ground Level

Time t min

ry
—
AUULAARABAALARIALALABAALELASDAEALIALIALIOARLILILEAILALL EDDIE SSRIRLLL

FIGURE 2. Blood oxygen saturation, heart rates, and resptration
of subject DM at 30,000 feet wearing the Cessna mask.
Second minute of exercise. Note the stabilization of

heart rate.

31

se Ln EN TNT ANOS



TABLE 6. Percentage of Nitrogen ae Mesoured in the Mask

Facepiece and Rebreathing ¢ 20,000 fe
we 10
Exercising Reading ‘
Firet_and Third Minutes at 20,000 ft Fourth and Sixth Minutes at 20,000 f¢
Peak ‘Mean Range Peak Mean
Winut Hinute Hinute Minute Ninute Minute
Subject Location 1 3 1 3 1 3 4 6 4 6 4

mR Bag 10-38 15-30 42 as v 23 8-20 5-17-20 20 ty ity

Mask = 43-65 45-68 67 70 34 57-37-59 38-5969 66 ar By : |
st Bag S57) «(7-35 60 bd w is 8-55 10-40 55 39 nv 23
Mask «= «35-55 34-3764 @L 4s 47-35-61 35-5261 ” a 43
au Bag 8-12 14-160 13 38 10 is 10-15) 5-5 28 as 1d $
Mask = 40-65 40-68 «68 10 3s 15-35-58 30-55 60 38 “a as _-

uz Bag 10-20 5-15 roy ua 10 3-100 4 B12 10 6 6
Mask = 30-58 38-5759 60 a? 47 40-55 40-5557 8 a7 ar

w Bag 7-18 12-26 42 0 10 us S-15 S13 25 32 7 8
Mask 30-59 35-65 68 68 45 32 20-55 25-5357 o8 38 %

et Bag 1-3 1-3 3 6 2 2 ke 4 ba 6 6 2 2
Mask «=—-:12-67 16-67 68 ZY 43 43 22-65 15-67 65 68 a “

cr Bag 20-30 15-23 42 40 2 17 10-15 1015-23 16 13 13
Mask 40-65 - 40-59» 67 2 33 50-43-96 45-3758 60 30 32

n

aH Bag 2-15 21S 26 w 10 6 10-20 5-10-40 Mu wz 8 \

Mask «=—-35-65 35-62 68 63 82 48 43-61 43-6165 70 32 32

wy Bag 15-28 25-38 = 30 40 uv 32 15-25 10-23. 37 26 18 as
Mack 42-63 48-64 «67 “ $2 3 42-53 35-58 Sa be] as av

oz Bag 5-20 10-2325 23 a v 13-23 13-2525 26 16 we
Mask 20-65 «(35-67 67 6s as 30 35-61 40-60 62 63 “a as

42



OXYGEN CONCENTRATLONS IN THE VICINITY
OF A PASSENGER RECEIVING FIRST ALD OXYGEN

E. B. McFadden and M.S. Pinski
I. Introduction,

To preclude providing an ignition sourees smoking aboard air
carrier atrerate is prohibited at arbitrary distances or at speci-
fied seat rows from passengers who are receiving first ald oxygen.
The basis for these separational distance requirements ant whether
they are adequate or unduly restrictive are not known,

During the administration of first aid oxygen less than LO
percent of the oxygen breathed ts normally adequate te meet me:
belie need: the remaining 90 percent is discharged inte the ambient
air. With increased oxygen flow, 96 te 98 percent of the oxygen
may be discharged inte the surrounding area, Knowledge ot che
extent to which the surrounding air is inereased in oxygen content
would allow a more realistic evaluation of che modifteation of che
flammability of materials in the fumediate vicinity of the oxygen
source,

Utilizing medern state-of-the
we conducted a brief preliminary study of the oxygen content of
the air surrounding a subject breathing 100 per en to chart,
localized oxygen coreentrat ions vs. distance from che subject.
This study does not concern che suctal acceptability or health
hazard potential of smoking.

art analytical dustrumentacion,

Il. Methods.

The subject w
some degree of air

seated in a room where there was probably
low, but at a Level undetectable by human
senses. He then donned a standard passenger oxygen mask, designed
to FAA TSO-C64 and NAS 1179, and an oxygen flow of 4 L/min was
initiated in accordance with that commonly provided by the regu=
lator of a first aid portable oxygen cylinder, The prebe of a
highly sensitive and accurate mass spectrometer capable of rapid
response was utilized to continuously scan oxvgen concentrations
at various angles and decreasing distances from the subject.

Ill. hesults.

At 6, 5, 4, 3, and 2 ft no increases fii oxygen concentration
were detected above that for air. As distances were decreased to
1 ft and Jess, the following increases in OXYReN concentration
above that of air were detected (Figure 1).

The oxygen flow was then increased to 30 Levtyy or 74 times the

normal tirst aid flow with the following results taken at the same
points (Figure 2).

ll


Feerograsss F

Fesecyrasss

sezasasses f

Reezeuwaez

TABLE 12, Percentage of Aabient A:

Using the Cessna Mask at 30,000 ft a Derived From

Estimates of End Expi

we=20

Fetory Nitrogen

Exercising, First and Third Minutes at 30,000 fe

Percent Oxygen from Calculated
‘Supply + *,

Bad
Exptratory Dilution

tr and Oxygen Content of Ineptred Gas

Su Ambient Aabient
Miaute Miouce Minute
Fy 1 3

a) eS ae nn TT

32 Al 689 7 9

7 83 SH 9

S20 Sha

3 M62 8 ?

23 oo ‘ 3

3 hb 56 ? 9

44425658 9 s

Soo ST esas

2 43 S53 Sg roo

320 352 40.5 44.3 59.5 55.7 Beg 9.3

i Reading, Fourth end Sixth Minutes at 30 000 fe

|

4 6 4 6 4 6 4 6 4 6 4 6
33 7 oh 5g 9 10 6S soto
rs a? a Y or oar? 9 9 65 65 tet
‘7 ary a? 43 33" s7 10 9 63 66 3 1B
br a, a rs rr? bo Shs 97108
Sc; OC) Os rT ee? 9 6 66 79 azz one
3 2% 7 tT 73 seg
Hs 4853 sk whe 6288 at ty
Sy so we os UD 100 Ss? 63 tors
BO Bar 52 53 wo 62 6y ata
3333 kgs s6 9 9 65 65 ate ate
We WE $6.0 43.8 54.0 S602 16 9-2 636 65.6 113.8 Aare

47



TABLE 7. Blood Oxygen Saturation, and Heart and Respiratory Rates of Subjects
at 25,000 ft Wearing Cessna Mask With the Zep-Aro Orifice (F 365-1080-2)
. ‘at an Oxygen Supply Pressure of 70 psi

we 10

Exercising, First aud Third Minutes at 25,000 fe

_Oximeter Percent ___Heart Rate __Respiratory Rate __
Minute Minut Minute
Subject Sex 1 1 3 . 1
DR " 99.0 97.5 85 105 cad _
Jt Mu 98.6 97.4 70 80 18 16
au vr 98.3 98.3 108 108 22 22
MZ ¥ 97.8 98.2 92 100 23 27
Be 4 Fr 97.8 97.3 118 118 23 26
DM F 98.0 98.4 105 us 27 29
cr " 99.4 99.4 98 98 25 22
Bu n 97.0 99.0 78 mm uv 7
wv " 95.8 95.2 100 100 22 21
pz " 96. 97.5 96 * 18 16
Range 95.8-99.4 95.2-99.4 70-118 Th-118 17-27 16-29
Hean 97.8 97.8 95 99.2 22 2
Reading, Fourth and Sixth Minutes at 25,000 ft
4 & 4 6 4 6
DR “ 97.5 99.0 105 95 12 12
st x 97.4 98.4 7s 18 2 15.5
a r 98.3 99.0 14 106 17 16
MZ r 97.8 98.0 8 by 12 12
iz F 98.0 98.2 98 103 16 vy
DM. Fr 98.9 98.8 96 ty 12 12
CF " 99.4 99.6 104 98 5s 13
BH " 99.3 99.4 86 88 uv s
wv n 97.0 97.1 4 95 wv wv
Dz 4 98.3 99.3 4 92 16 16
Range 97.0-99.4 97.1-99.6 75-116 78-106 12-21 12-17
Mean 98.2 98.7 95.8 94.3 15.5 14.2
43

WIE O- THT



- ~ \
|
gS 14a
SATURATION
ay i= jr]
a
a
EF
z
v
3 6a
z :
i og
ul
2 Nua
oO
FY .
oO bE row
wd
! 2.22
2a 3a Hoa
ALT i TUDE THOUSAND FT.
FIGURE 1. Blood oxygen saturation following 3 min of
exercise at the indicated minimum oxygen
flow rates. °
72
--



ne nent

Controls Company, Anaheim, California) coupled to a 885 supply,
The crew oxygen system appeared to function correctly, Poor
communication through the mask microphones was reported, This
may have been due to high background Noise, low amplifier adjuse~
ments, or system malfunction, As power was Not avatlable co the
aircrafe during our inspection, the reason Was not determined,

The cabin oxygen system consisted of Sierra continuous-flow,
Phase-dilution conical nasks (PN 289-601-5) coupled to Score

firing mechanisn, 8 SPring-activated striker pin, Upon activation,
the Primary chemical reaction in the Senerator core 1s the thernal

2 Fe + 9 + 2Feo + HEAT

Malfunctions that occurred in the cabin oxygen system
include the following:

two attendants, who were undergoing rapid and Severe decompression,
until afcer they had lost consciousness, .

82 ,



TABLE 1. Blood Oxygen 5S: turation, and Heart and Respiratory Rate
¢ Ground Level Breathing Air at Rest
Immediately Prior to Ascent to Altitude

N= 20
‘
Oximeter Heart Respiratory Age Height Weight H
Subject Sex (percent) Rate Rate Gyr) fin) (ib) :
De " 100.0 a8 - 34 ns 184 ‘
i “ 99.0 75 12 7 m1.0 155 :
3H F 98.4 100 v7 36 66.5 135
uz F 97.0 16 15 3 64.0 115
w F 95.6 200 n 15 62.0 110
DM F 97.0 90 23 33 64.0 15
oF " 95.0 96 22 3 68.5 130
BH M 96.8 78 16 30 71.0 168
wv M 95.6 78 16 rr) 68.0 197
bz M 96.0 82 9 3 68.0 180
Range 95-100 75-100 9-23
Mean 97.0 86 4s “

37



Noble et al. (8) report a case history of a pilot who, on
experiencing a decompression of a T-39 (Sabreliner) afreraft at
13,716 m (45,000 £t), lost consciousness within an estimated time
comparable to those above.

Breathing Oxygen Prior to Decompression. Luft (9) describes
experiments in which subjects wearing masks and breathing 100
percent oxygen at 10,058 m (33,000 ft) were vapidly decompressed
to altitudes of 15,850 to 16,154 m (52,000 to 53,000 ft). If the
total exposure to the latter altitudes exceeded 6 8, subjects lost
consciousness about 16 s from the beginning of decompression even
though they breathed 100 percent oxygen throughout the experiment.

Additional data detailing the limits of Protection afforded
by prebreathing oxygen have been Presented by Blockley and
Hanifan (5) (in a review of German. Air Force data) and Luft et
at. (10). These data show that even though 100 percent oxygen

Breathing Oxygen Under Pressure. Limited rellef to this
dilemma can be achieved through pressure breathing. Blockley
and Hanifan (5) state that wearing a mask Prior to raptd decom-
Pression to a maximum altitude of 15,240 m (50.
vent loss of consciousness provided
deliver at least 90 percent oxygen at no:

However, the regulator must instantly. pravide positive pressure
breathing with the mask tightly sealed against the face in order
to intercept and reverse the rapid decline in alveolar oxygen
Partial pressure. Rapid increase in the diffusion of venous
carbon dioxide into the lungs compounds this problem by jeopardiz-
ing the Tecovery of an adequate alveolar oxygen partial pressure,

For positive Pressure breathing to be. effective, the indi-
vidual must be tecently highly trained; otherwise, he may invol-
untarily hyperventilate to a point of hypocapnia-induced incapaci-
tation. Calculated alveolar oxygen histories at 15,240 m

(50,000 ft) for the three previously described situations are
shown in Figure 2.

For certain research operations by highly trained cTew-
members, marginal Protection may be Provided by a flight deck
procedure wherein the pilot and copilot alternate in wearing a
Pressure~demand mask connected to an appropriate pressure-
breathing regulator supplying no less than 90 percent oxygen.
Upon decompression, the regulator must automatically initiate
pressure breathing to a level consistent with altitude require-
ments. For this procedure to be fully effective, the crewmember
breaching oxygen should remain on oxygen until the relieving
crewmember accomplishes adequate nitrogen washout; otherwise, both
crewmembers would be vulnerable should decompression occur during
the exchange of this function.




TABLE I

AIRCRAFT TYPES, TYPICAL APPROXIMATE VOLUMES,
AND CABIN WINDOW AREAS

. Pressurized Volume Cabin Window Area
Aircraft Model m> tr5 em? int
LR-24, 25 7.5 265 2684 416 (a)
NA~265 12.2 430 839 130
NAR-1121 12.5 440 903 140
DH-125-400 16 565 652 tol
DH-125-600 17.8 630 652 101
L-329 35 1,250 1407 218
G-1159 52.4 1,850 2510 389
oc-9 165 5,840 884 137
B-737 227 8,010 903 140
B-727 256 9,045 903 140
0c-8-50 366 12,920 1768 274
8-707 4 14,495 903 140
oc-10 935 33,000 la19 158
L-lo0ll 991 35,000 774 120
8-747 1671 59,000 903 140

(o) Later mode! 24 and all 25 aircraft are 665 cm*® (103 in®)

100


This investigation covered;

A. A study of the Physical propercies of the generator
systems. This phase was conducted in an altitude chamber with a
Pressure equivalent of 8,009 ft, the normal cabin pressure of
inflight atr carrier aircraft, This altitude provided for the
maximum volume expansion of generated gases expected to be
encountered with the intended use of these systems. Flow rates

the mask ourlec. A randomized design was used to select the particu-

lar generator and canister for each test,

B. A study of the Physical Properties of the generator sys-
Physiological response from the use of these systens,
As in the firse phase, ignitor reliability, flow Yates, and total
oxygen generation tires were recorded, Testing was conducted in
an altitude chamber at a pressure equivalent of 8,000 ft and at
1,250 fe, or round level at Oklahoma City. The test Population
were healthy, 18- to 28-yr-old male and female subjects, with a .
Tatio of 4 males to 1 female, and within the male subjects, a ratio
of clean shaven to bearded of 4 to 1, Ivmediately before the test

until a ventilation rate of 15 L/min was established through
the approprtate test mask and began exercise at the Previously

Ths test continued until such time thet oxygen production by the
generator ceased. Two small microcatheter tubes for 846 sampling
were positioned through the facepiece sf the test mask in 4 manner
not to compromise the mask performance or significantly alter tts
weight or facial fit. The output from :hese sample tubes was deliv-
ered directly to 8aseous nitrogen analyzers for end expiratory
nitrogen determinations, From the ind expiratory nitrogen values,
tracheal oxygen Partial nre-, sres were calculated on a breath-by-
treath basis (2), adds. sed tg the equivatent of sea level or zero
elevation; the Meus, standard deviations, and other appropriate
tests were performed with computer techniques,

Cc. A study of the Physiological effictency of three tyzes of
oxygen masks in common use in the medical or avier' + professions,
The three types tested were: (1) an open-port formed mask with
4 rebreather bag of the type cormuly used in lospitals, (if) a
Phase~dilucion conical type v'in a ferther edge used 4n the avie
ation industry, and (iii) a Phase-dilution, modified conical type
with inner facial seal and stacked valves ueed in the aviation
industry, Each subject was tested with all three masks and, on

60° ’

ornare:



TABLE 10,

Subject Sex
DR 4
wT M
3H Pr
Mz r
4 r
DM Fe
cr M
BH 4
wv “
bz "

Range

Mean
DR "
JT M
Ju F
MZ F
wz F
2
cr n
aH 4
wv 4
Dz "

Range

Mean

Blood Oxygen Saturation,

at 30,000 ft Wearing Cessna Mask

at an Oxygen Sup;

and Heart and Respiratory Rates of Subjects

With the Zep-Aro Orifice (F 365-1080-2)

ply Pressure of 70 pst

Ne 10

Exercising, First and Third Minutes at 30,000 ft

Oximeter Percent Heart Rate Respiratory Rate
Minute Minute Minute
3 r 3 3
98.0 94.5 90 105 - -
98.4 97.6 70 82 18 19
98.5 98.6 108 112 21 21
95.8 92.0 103 122 15 20
97.0 96.8 112 115 27 26
98.5 97.3 105 MSs 26 27
99.4 99.3 100 100 23 2
94.5 89.0 90 88 16 20
87.0 89.0 104 104 19 22
97.4 93.6 % 6 vv 19
87.0-99.4 89.0-99.3 70~112 82-122 15-27 19-27
96.4 94.7 98 104 25 22
Reading, Fourth am! Sixth Minutes at 30,000 fe

4 6 4 & 4 6
96.5 98.0 105 90 13 1s
97.5 98.6 82 75 18 19
98.3 99.0 116 108 16 21
91.0 95.0 112 118 20 16
97.0 97.46 106 100 W 3
98.0 97.2 200 100 18 18
99.0 99.4 100 98 i 12
92.0 99.0 90 90 Vv v7
93.0 95.0 87 86 1 17
97.8 98.6 96 96 20 49
91.0-99.0 95.0-99.4 82-116 75-118 11-20 22-22
96.0 97.7 99.2 96.2 16 7

46



s
FAR 25.1443 (there may be ‘a means to reduce flow to 2 L/min), then i
the maximum oxygen available by the paper cup technique may be
estimated. |
An 8-oz cup is considered to be a nondistensible container

with a total maximum volume of 0.24 L. At the instant inspiration

fg initiated, assume the cup contains 0.24 L of 100 percent oxygen

and during the 1.5 8 of inspiration an additional 0.099 L of oxygen

fs introduced into the cup (at a flow rate of 4 L/min = 9,066 L/s,

0.066 L/s x 1.5 s * 0.099 L). The cup will not contain 100 percent
oxygen because it contains large quantities of air and some carbon
dioxide from the previous exhalation.

(a) The maximum oxygen available during a 1.5-s inspiration

is:
Volume of 8-oz cup 0.240 L
Volume of oxygen added during inspiration 0,099 L
0.339 L
or 0.34 L

(b) The theoretical percentage of oxygen that could be added
to airs fate 492.

This calculation assumes no leakage of air around the periph-
ery of the cup or leakage through the opening In the cup through
which the hose is inserted. However, in practice, extensive leak-
age is required because the cup, being noncompliant, must instantly
on initiation of inspiration allow ambient air to be drawn into the
system to replace oxygen removed from the cup in order to satisfy
the remainder of the 0.7-L tidal volume requirement.

The calculation above also theorizes that during exhalation
the cup is refilled by a continuous flow of oxygen. Even though
oxygen is flowing into the cup during exhalation, the act of
exhalation continuously washes out the small amount of oxygen
(0.3 L) introduced during the 4.5 s prior to the next inspiration
and leaves the cup with a high concentration of carbon dioxide and
air exhaled from the previous inspiration. This residual consti-
tutes the initial gas inhaled. on the next inspiration rather than
the theoretical 100 percent oxygen referred to above. Therefore,
the calculation is not representative of the true situation.

If one considers the paper cup to be rigid extension of the
oxygen hose supplying oxygen at a continuous flow rate of 4 L/min,
and during each inspiratory event air is being inspired at a rate
of 25 L/min, then during inspiration oxygen is mixed and added to
air according to the following percentage.

(c) Oxygen flow = 4 L/min = 16%
Peak inspiratory flow = 25 L/min ’

95


Percentage points, well within the accuracy of determinations of
end expiratory nitrogen, \

All nitrogen diluting ‘the inspired gas originates from ambient
air with the exception of n:

trogen derived from the tissues, which
to 8 min under a stead.

Y-state condition has been shown to
constitute less than 1 Percent of the lung volume (2),

Using calculationa

Suggested by Luft (3) in 1951, one can
determine the admixture of air; t.e,;

Admixture of air =
oeekture of air

Inspired nitrogen fraction
100

Nitrogen fraction of air

By substituting end expiratory nitrogen for inspired nitrogen:

Admixture of air « End expiratory nitrogen

Nitrogen fraction of air

Using these formulas one may derive the Percentage of dilu-
tion, supply oxygen, oxygen from the ambient air, and total
oxygen according to the following calculations:

! End Expired Ny x 100
Percent Dilution = Np of Air (79.03)

Oxygen from Supply = 100 - Percent Dilution

Oxygen from Ambient = Percent Dilution x Ambient

Oxygen (20,94)
Total Oxygen =

Oxygen from Supply + Oxygen from Ambient

Calculated inspired oxygen partial Pressure =
(3 ~ 47) x Percent Total Oxygen
Where: Pg = Total Pressure in mmHg at ambient altitude

47 = Pressure in

of saturated water vapor at
body temperature

21



PUYSIOLOGICAL EVALUATION OF A CESSNA CONTINUOUS-FLOW
OXYGEN MASK FOR UNFRESSURIZED GENERAL AVIATION AIRCRAFT

BE. B. McFadden, H. F. Harrison, and J. M. Simpson
I. Introduction.

This report describes altitude chamber exper{menta conducted
with human subjects using a Cessna-designed disposable oxygen mask,
Basically, the mask is almost identical in design to the disposable
K-S wask developed by Koze and Stockam {n 195) (under the guidance
of Dr, A. 0. Tuttle of United Air Lines) for passenger supplemen-
tary and first aid oxygen (1). Using new types of material, che
designers have attempted to produce a mssk that will provide a
better seal to the face and increase comfort, durability, effi-
efency, and wearer acceptance for relatively long durations at
altitude in unpresaurized airerafe.

The mask is of the rebreather-dilucer type with a regulated
constant flow of oxygen provided to the rebreather portion of the
mask. The mask consists of two flexible plastic film compartments.
The smaller or facepiece compartment ia sealed within the larger
ov rebreather bag. Two holea connect the facepiece to the
rebreather bag to allow gaseous exchange with the oxygen supply
and rebreather bag. Two additional dilution ports are provided
in the facepiece to allow access co ambient air... The mask. is...»
retained to the face by means of an elastic band, The soft metal
wire encased fn pliable plastic, which forms the periphery of the
mask facepiece, {9 formed to the contours of the face for a prover
fit. Prototype masks were fabricated in three basic sizes: small,
medium, and large.

Determination of efficiency of an oxygen system must be based
on the system's capability to produce an adequate duspired oxygen.
partial pressure resulting in a sufficient alveolar oxygen partial
Pressure in the lungs to insure a blood oxygen saturation of an
acceptable level,

Physiological responses to minor changes in oxygen partial
pressure vary widely depending on factors such as age,.general .
Physical condition, and/or the presence or absence of cardtac,
circulatory, or respiratory pathology.

One basic disadvantage of all continuous-flow oxygen systems
is an inability to adjust automatically to the respiratory changes
associated with changes in emotional and physical activity of the
wearer. A healthy young male breathing air at rest normally exhib-
ite an approximate tidal volume (volume/breath) of 550 mL and a
minute volume (volume/min) of 7,700 ml or 7,7 L. Emotional and/or
physical activity may cause values to fucrease many fpld,

7



PHYSTOLOG ICAL CONSIDERATIONS AND LIMITATIONS IN THE HIGH-
ALTITUDE OPERATION oF SMALL-VOLUME PRESSURIZED AIRCRAFT

E. Be McFadden and D. deSteiguer

I. Introduction.

Several small-volume, pressurized, general aviation jet air-
eraft are currently certified to operate at a maximum altitude of
13,716 m (45,000 fe), and flight to 15,240 m (50,000 ft) is under
consideration. While these aircraft may be qualified, from an
engineering analysis, for operation at these altitudes, & question
remains as to the physiological consequences tO the crew and
passengers of an aircraft in the event of a decompression of the
pressurized cabin. A review of aircraft operat tonal history
demonstrates that such decompressions do occur in poth air carrie?
and pressurized general aviation aircraft designed with the best
of modern technology (1,2). This paper reviews the capabilities
and Limitations of oxygen equipment and the operational procedures
for preventing hypoxia and thus {ts incapacitating, effects in the
event of decompression tO altitudes within the operational regime
of these aircraft. The various othet physiological and psychologi~
cal effects of rapid decompression, which may contribute to and/or
produce incapacitat ion with or without the existence of hypoxia,
are not discussed in this paper even though they may compound the
difficulty of survival.

11. Discussion.

Aircraft Decompression Factors. The rate and severity of
aircraft decompress ions have been aet ined and discussed by Fritz
Waber and Hans Clamann (3) of the USAF Schvol of Aviation
Medicine.* These authors define two tactors in a decompression,
a time constant (t,) and a nonlinear function of pressure ys
with the time of decompression (Ty) being the product of these
factors (Ty * t.P)- The time constant is defined as the volume
of the cabin divided by the product of the area of the Leak
orifice and the speed Of sound in air. The pressure factor is
a nonlinear function of the difference between cabin and ambient
air pressures divided by the cabin pressure. For a cabin equiva-
Jent altitude of 2,438 (8,000 ft) and a flight altitude of
15,240 m (50,000 ft), this factor has 4 value of about 3.3.

Typical aircraft volumes and ivdividual window areas are
presented in Table 1. From these data, and with a knowledge of
cabin and flight altitudes, one may estimate the size of the leak
orifice or defect area for a given cabin volume to decompress to
an altitude of 15,240 m (50,000 ft) in a given time interval.
Data on 10-5 decompressions from 2,438 to 15,240 m (8,000 to
50,000 ft) for cabin volumes of 7.5 m2 and 17.8 m? (265 fe? and
630 £t7) are presented in Table 2. It will be noted that the

kNow the USAF, School of Aerospace Medicine.

99



. . ceetiaaieiaa

References

Tuttle, A. D,, J. P, Marbarger, and U, C, Luft: K-S Disposable
Oxygen Mask, J, AVIATION MEDICINE, 22:265-277, 1951,

Balke, B.: Continuous Determination of Nitrogen Concentrations
During the Respiratory Cycle. Project Number 21-1201-0014,
Report No. 5, USAF School of Aviation Medicine, 1954,

Luft, U. C.: Evaluation of the K-S Disposable Oxygen Mask,
Special Project, USAF School of Aviation Medicine, 1951,

Boothly, W. M. (Ed,): Handbook of Respiratory Physiology,
USAF School of Aviation Medicine, 1954, Ps 164,

National Aeronautics and Space Administration: Bloastronautics
Data Book, Scientific and Technical Information Division, 1964,

Odland, L. T.: Fatal Decompression Iliness at an Altitude of
22,000 Feet, AEROSPACE MEDICINE, 302840-846, 1959,

Toone ae



B. Even if masks are worn and 100 percent oxygen ts pre-
breathed, loss of consciousness will still occur in approximately
20 8.

Cc. If pressure breathing is used and at least 90 percent
oxygen {8 not prebreathed, residual nitrogen in the alveoli may
Negate the advantages of pressure breathing.

B. If pressure breathing is used and 90 to 100 percent
oxygen is prebreathed, a highly trained, physically fit indi-
vidual may tolerate the pressures required to maintain useful
conscfousness. Using a counterpressure garment and pressure
breathing combined with prebreathing 90 to 100 percent oxygen
is a safer alternative.

E. In decompressions of the severity under consideration,
it may be assumed that passengers will lese consciousness. The
ultimate phystological consequences and recovery will be depend-
ent not only on the decompression but also on other factors, such
as duration of exposure, age, weight, and past medteal history.
If suffictent protection is to be provided the passenger, he or
she must be able to tolerate pressure breathing, be highly
trained, and be wearing ‘pressure-breathing oxygen equipment
prior to decompresston.

FP. The marginal safety of rapid decompresstons to 13,716 m
(45,000 ft) ts rapidly degraded with further inerease in altitude
and at 15,240 m (50,000 ft), even the breathing of 100 percent
oxygen betore and after decompression will fail co prevent loss
of consciousness, The extended exposure time at critical alti-
tudes as a resule of increased descent time, the possibility of
the Venturt effect, and addittonal physiological insults of
decompression to 15,240 m (50,000 ft) compound the hazard.

108


‘TABLE 17,

Percentage of
Zep-Aro Constant-Fi,

Exptratory Mitrogen. Subjec

at Pressure of 70 pet

Altitude
f€t) Condition
Ground Preflight

14,000 Resting

Exercise
DON MASK

Exercise
Reading

Exercise
Reading

Exercise
Reading

POSTFLIGHT
Reat ing

Exercise
Reading

Wearing Ohio Chemica

From Eatinates of the End
Zep-Aro Orifice {F 365-1030-2)
|
End
Exptratory Dilution
Mitrogen Teent
Altteude Minuet: Mini
Aft) Condition 1 1
20,000 Exercise 42 a7 33 6
Reading 45 40 0 Sh
25,000 Exercise 42 43 33 “M
Reading 49 a st 52
0,000 Exercise 64 48 56 61
Reading 46 43 38 56
POSTFLIcHY
Ground Resting $3 so o 63
Exercise $5 3S 70 70
Reading $4 bo) 68 6s
im
TABLE 18. Blood Oxygen Sat

‘uration, and Heare and

33

yw 3 yy
3 as ts
zw 2 we on OR

37

so
46

aes ask With the Zep-aro Orifice if 365~1080-2)
st an Oxygen Supply Pressure of 70 pat
i eee
' Oximeter Percent Heart Rate Respiratory Rate
Minute Minute Minute
n 3 3 1 3
” 82 8
93.0 92.5 92 92 10. 3
87.0 86.0 0 110 2 20
98.0 98.0 102 6 18 15
99.3 99.5 92 6 1“ uv
91.0 92.0 108 102 as iu
99.4 99.3 96 3% 7 18
90.0 86.8 “106 Ls 16 19
97.6 98.0 100 98 19 18
98.7 99.0 78 82 az 10
98.8 98.0 88 90 10 v
99.0 99.3 82 e2 b u

Mablent Atv and Oxygen Content of Inspired Cae Ustog the
ov Mask (Cesena t No,

Respiratory Rates of Subject pz

52



'
i
|

80

@ AT 388m (273 11) PRIOR TO

704 DECOMPRESSION.

60+

NITROGEN — PERCENT

204

107

FIGURE 1.

i
50+

it
404!

304

© OURING 41-508 DECOMPRESSION
FROM 2,436-12,192 m (8,000 —

\ 40,000 1) FOLLOWING 2 min

\ BREATHING AIR. MASK DONNING

1 AT 8,839—9,449 m (29,000 —
31,000 tt).

it FROM 1,029~12,497 m (6,000 ~
Hy 41,000 tt) NO PREVIOUS

AT 7,620-9,449 m (25,000 —
34,000 ft).

a
i:

T T T T T T v
15 30 45 60 75 90 105 120
TIme- SECONDS

Nitrogen washout prior to and during decompression.
Quick-donning crew oxygen mask and panel-mounted

pressure demand regulator.

106

& OURING 41-508 DECOMPRESSION

iN DENITROGENATION. MASK DONNING



to 40,000 ft. A more detailed discussion of this and other types
of passenger oxygen masks is presented by McFadden (3).

With the concurrent increase in flight altitudes and the
rapid expansion of air transportation following World War I1, con-
siderable attention was directed to the development of safety
standards for passengers and crew in the event of a failure of
cabin pressurization, The development of the K~-S disposable mask
by United Air Lines personnel and the subsequent physiological
testing by the University of Illinois and the USAF School of
Aerospace Medicine are reported by Tuttle et al, (4), Luft (5S),
and also by McFadden et al. (6) of the FAA,

Tuttle et al. (4) describe the mask as the rebreather dilu-
tion type with constant flow of oxygen and consisting of a double
bag of light, transparent plastic material. The inner bag fits
well over the oronasal region and communicates through two holes
with the outer rebreather bag into which oxygen is supplied. Two
smaller holes in the inner bag give direct access to ambient air.
An adjustable elastic strap secures the mask around the head and
a soft metal strap inserted into the upper rim of the facepiece
can be molded readily to the nose and cheeks of the individual,

Physiological testing with the K-S mask demonstrated that
satisfactory arterial oxygen saturation could be established and
maintained following decomressions from 6,000 to 25,000 ft when
an oxygen flow of 3 L/min STPD was provided to the mask. The use
of this mask was not recommended for decompressions above 25,000
ft. Shortly thereafter the K-S mask was adopted by the military
for use in flights carrying troups and dependents. In the ensuing
years jet transport aircraft that utilized flight profiles to
41,000 ft were introduced. These flight altitudes far exceeded
the performance capacity of this mask to provide protection in the
event of a serious decompression. Consequently, the procurement
of a replacement mask that would provide protective capabilities
to 40,000 fe was initiated. This is a report of the physiological
testing for the military of the prototype MBU-8/P mask to FAA and

National Aerospace Standards applicable to civil air carrier jet
transport aircraft.

Il. Method.

Ten (five civilian and five Air Force personnel, all having
been chamber qualified to 40,000 ft), yvoung-to-middle-aged, healthy,
male subjects were used during the physfological performance por-
tion of the mask evaluation. Ten experienced chamber safety
observers were provided from Air Force and FAA pérsonnel,

Five prototype Air Force MBU-8/P continuous-flow reservoir-
type passenger oxygen masks (Sierra Engineering Co., Sierra Madre,
Calif.) were used during the testing sequence,

70



Pain md

nem RN RM RENE PEN KER NESE SBN RM

Although the saturation of subject JH dropped to 89 percent, the 4
tracheal partial pressure was calculated at 120 mm.

In Table 12 one may note a further reduction of nitrogen in ‘
the rebreather bag.

After descent to ground level, the mask wae left on six of
the subjects and determinations were made of the carbon dioxide
in the mask facepiece and rebrenther bag, The recording of blood
oxygen saturation, heart rates, and respiration were continued
and are show in Table 13,

The 3-min periods of reading at each altitude were recorded
on an Ampex recorder and later evaluated in terms of volume and
clarity (Table 15), During reading the subjects' speech intelli-
gibility was generally quite good, That few of the subjects did
not talk directly into the microphone resulted in some compromise
of clarity and the mask appeared to produce a slight muffled
effect in some instances,

Measurements of carbon dioxide content of the mask facepiece
and rebreather bag are shown in Table 14, With the exception of
subject DR, maximums of 3 and 5 percent carbon dioxide were
detected in the rebreathing bag and mask facepiece respectively.
The S-percent maximum value, approximating an end expiratory
sample, ie equal to 34 mm of partial pressure, somewhat less than
that of the normal 40 mm partial pressure of end expiratory gas
composition. Subject DR, a SCUBA diver, exhibited a tendency to
skip breathe, a technique habitually used by some divers to con-
serve air. This subject's respiration during the carbon dioxide
determination was so shallow and irregular that a meaningful
impedance pneumograph recording was unobtainable, This subject
showed a maximum carbon dioxide level of 8,9 percent in the
rebreather bag. However, it is felt that the carbon dioxide
measurements at ground level do not indicate a problem at altitude
with the increased flow and ventilation due to gaseous expansion
of the supply oxygen at altitude.

For example, at 20,000 ft, the 2.7-L/min flow STPD ground
level would equal approximately 7,5 BTPS. In addition, a concen-
tration of approximately 14 percent carbon dioxide would be
required to produce an inspired partial pressure of 40 mmlig at
20,000 ft (4,5). At ground level 5.8 percent carbon dioxide pro-
duces an inspired 40 malig partial pressure. In evaluating carbon
dioxide concentration one is again faced with a nonhomogeneous
mixture of gases in the mask and rebreather bag, The end expira-
tory carbon dioxide concentration appears to be the more reliable
measure because it reflects conditions in the lungs,

Review of Table 14 indicates the average carbon dioxide
maximum values to be lower than expected, approaching in some

23.



Their equation for defining a rapid decompression is:

‘2 (e-)(")
Where: ce = Cotal time of decompression tn seconds
Ve = volume of the compartment in cubic feet
A © area of leak orifice in square feet
S = speed of sound fn feet per second
P| * nonlinear function of Pe-Pa

1 Pe
Pow compartment presaure

Pa = absolute pressure

The atrerafe decompression Fesulted from four basic penetra-
tions in the fuselage: (1) the tose of one cabin windows (11)
Penetrations into the center accessory compartment; and (1{1) two
Penetrations into the forward cargo and belly compartments.

Openings into the forward cargo and belly compartments con-
sisted of « forward Penetration with an area of 230 in? and an
aft penetration with an area of 140 tn?. The forward penetration
was clean, Passing through the fuselage and inner liner, The afte
Penctration was complete through the fuselage; however, the inner
liner was in Place, though ruptured. This would indicate that

Two possible decompressions of the forward cargo and belly
compartments are Presented:

Condition A:

Volume forvard cargo compartment 1,375 f¢3
Volume belly compartment 690 fe3
Total volume 2,065 fe3
Area forward Penetration 230 tn?
Area aft penetration x y 70 tn?
Total area 300 in?
Total area approximately Zeer
Pe 590 matig
Pa 148 mmig .
Py) 2.5

88



physiological limitations of current oxygen equipment; requirements
for pressure breathing and crew recognition and reaction time;
and other factors in relation to the final pressure, the rapidity
of decompression, and time~altitude profile.

Oxygen Concentrations in the Vicinity of a Passenger Receiving
First Aid Oxygen; Memorandum Report AAC=119=77~4(S).

To preclude providing an ignition source, smoking aboard
air carrier aircraft is prohibited at arbitrary distances or at
specified seat rows from passengers who are receiving first aid
oxygen. The basis for these separational distance requirements
and whether they are adequate or unduly restrictive sre not
known. Applying modern state-of-the-art analytical instrumen-
tation, a brief preliminary study of the oxygen content of air
surrounding a subject breathing 100 percent oxygen at a standard
and very high flow rate was conducted to chart localized oxygen
concentrations vs, distance from the subject. This study does
Mot concern the social acceptability or health hazard potential
of smoking.



Two small microcatheter tubes (PE 60) for gas sampling were
positioned through the facepiece of the mask in a manner that would
not compromise the mask performance OT alter its weight or facial
fit to any significant degree. The output from one sample tube
was delivered directly to a gaseous nitrogen analyzer (Custom
Engineering and Development Co., Model 300 AR Nitralyzer) for end
expiratory nitrogen determinations. The output from the second
sample tube was passed through a small reservolr-integrator to a
second nitrogen analyzer for the determination of mean mask nitro~
gen. A sample rate of 3.ce per minute for each was established

by maintaining an absolute pressure of 0.6 mmlg at the analyzer
detectors.

A constant-torque bicycle ergometer was positioned in the
altitude chamber for operation from an auxiliary chair. Regulated
exercise was used to establish the desired respiratory minute
volume in preference to the practice of hyperventilation.

The flow of oxygen to the mask was regulated by an altitude-
sensitive regulator of the type used in the passenger oxygen sys-
tems of jet transport aircraft. The output from this regulator
was routed outside the chamber, passed through the output orifice,
then through a flowmeter and needle-valve arrangement to obtain
precise measurement and-control, and was then passed back into the
chamber to the test mask. Oxygen flow was Limited to the minimum
rate as provided by the outlet assembly (P/N 110112-02) used in
the C-141 aircraft (Figs. 1 and 2).

Immediately before ascent the test subject was Anstrumented
for EKG monitoring with three-position chest esectrodes and for
blood oxygen saturation with a Waters Model 350 Oximeter attached
to the pinna of the right ear.

Visual recording of the subjects during the flight profile
was accomplished with cinematographic techniques. Cameras were
positione| .or observation of the subject's face and of the reser-
voir ber ve the test wask.

Following a test of the subject's ability to equalize ear
pressures, the chamber was decompreseed to 14,000 ft. The subject
rested quietly until blood oxygen saturation stabilized and base-
lines were recorded. A prief period of controlled exercise on the
ticycle ergometer followed to verify the measured response of
blood oxygen saturation to hypoxia. The subject then donned 4
crew-t,pe demand oxygen mask that provided 100 percent oxygen and
returned co exercising on the bicycle ergometer. The exercise
level was slowly adjusted until a respiratory minute volume of
25 to 30 L/min was achieved. After establishing the desired
minute volume, exercise was discontinued and the subject changed
from the crew mask to the MBU-8/P passenger mask. The test

71



regulated to give a minute volume of 25 to 30 L/min BIPS to the
corresponding recordings from 40,000 ft indicates that the ventila-
tion rate of subject 7 could have exceeded the 30 L/min desired

by almost 50 percent while at the higher altitude. That the reser-
voir bag was being emptied during inspiration, with the resultant
activation of the dilution valve, is confirmed through close
examination of the motion picture film of this test.

To a lesser degree, the same problem was encountered in con-
trolling the respiratory rates of subjects 4 and 6. These sub-
jects did not exceed the minute volume to the extent that subject
7 did; however, analyses of the data and motion picture film
indicated that activation of the dilution valve did occur. With
the exception of subject 7 (with a PTo9 of 83 mg), all subjects
had a PTO. greater than 83,8 while restirg at 40,000 ft.

Vv. Conclusions.

A. ‘The prototype MBU-8/P passenger mask demonstrated an
adequate capability to maintain human subjects in an acceptable

physiological condition for limited exposures to 40,000-£t
altitudes.

B. ‘The use of controlled exercise to achieve a specified
respiratory minute volume is the method of choice as opposed to
hyperventilation. However, allowances should be made for the
effects of apprehension if excessive respiratory tates are to be
avoided, The effects of apprehension are ‘most pronounced from
30,000 to 40,000 ft, the most crucial portion of a mask evaluation.

C. Analyses of physiological data and motion picture film
indicate that the desired respiratory minute volume was exceeded
by 3 of the 10 subjects while exercising at the 40,000-ft level.
As this portion of the test was beyond the requirements of
NAS-1179 and FAA TSO-C64, the test was not repeated.

D. If workloads and respiratory minute volumes in excess of
those obtained in this study are anticipated, oxygen flow to the
mask should be increased to compensate for increases in activity.

77 ’



eee ee re ene Renta NRA ARNG CGR ORR
meena prea HIRD Hasan ee em ‘
coer emer in penny

List of Abbreviations

BIPS - body temperature, pressure saturated

CO, - carbon dioxide

c/s ~ cycles per second

Fe - iron

FeO ~ iron oxide

mmHg - millimeters of mercury
Ny - nitrogen

NaCl - sodium chloride
Naclo, - sedium chlorate

04 - oxygen

Pax - passenger

PR - barometric pressure « 4
pO, ~ oxygen partial pressure t

i Pry ~ tracheal oxygen partial pressure
j 2

psi - pounds per’ square ‘inch

RQ - respiratory quotient

STPD - standard temperature, pressure dry



~wy

TABLE IZ
ALVEOLAR GAS COMPOSITION 2-5 SECONDS FOLLOWING RAPID
DECOMPRESSIONS TO SELECTED ALTITUDES WHILE BREATHING OXYGEN

(COMPILED FROM CLAMANN ET AL!)
ALTITUDE

10,028 m 12,009m 13,503m  15,240m
32,900ft 39,400ft 44,3008 50,000 ft

Pressure, toto! mmHg 198 145 tS 87

Partiot pressure, H,0 47 47 47 47

Pressure, dry gas 151 98 68 40

ORY GAS COMPOSITION

Partial pressure, 02 107 : W 45 . 20
Percentage 70.6 72.0 66.4 50.6

Portiat pressure, CO2 35 23 '9 18
Percentage 23.4 23.6 28.0 94.2

Partiol pressure, N, 9 4 4 2
Percentage 6.0 44 4.6 5.2

Ail decompreasions from 1,006 m (3,300 ft).

105 ,


Pn eRe mT 5 tee mre ne tne

BS 162
3a #140
ul
uJ E
EF c
r as “\2g
=
a 3a
un Cc
lu LJ
© 2a liaa
2a 32 4a
ALT I TUDE THOUSAND FT.

FICURE 3. Heart and respiration rates following 3 min of
standardized exercise at the indicated altitudes
with the minimum oxygen flow provided as in
Figures 1 and 2.

75



TABLE IL

ESTIMATED 10-SECOND DECOMPRESSIONS

TO 15,240m (50,000 ft) FOR TW

0 CABIN VOLUMES

AIRCRAFT A

AIRCRAFT 8

Cabin Volume
Cabin Altitude
Flight Altitude
Time of Decompression
Approximate Area

of Orifice
Approximate Diameter

of Orifice

7.5m? (265 f°)

‘| 2,438 m (8,000 ft)

10s
69.7 cm? (10.8 in?)

9.4 cm (3.7 in)

17.8 m® (630 ft)

2,438 m (8,000 ft)

15,240m (50,0001) 15,240 m (50,000 ft)

10s
167 cm? (25.9 in’)

14.5 om (5.7 in)

101


a“ ‘
\
\
i
‘
f
3
be,
roHes arom com rade | [ree ggggsenr
pa ig ———_ ¢ —___.
i
HT i ——
{ UTILITY, TUNNELS. UTILITY TUNNELS
| H | $< fee 4 CTR, accessory
| CTR.CARGO|lart canco| {arr BELLY come. vr je ie eaey
! \ | comp. 4 {| comp. , |! comp. 1g
ie. ar
! LITII=== MII IIIc rr- se ‘LOWER GALLEY
Watt e m me ae
1
{ ~ Fwo.carco | | ewo. seuy
ee a ea a ee a come, comp. |

¥ io
AT OURECT PENETRATION & ~ ComPaRTMENT DooRS
o- ¢ : F ~ PRESSURE CONTROL VaivE~
ce . NORMAL OPERATION
o- * . G~ CUSP NOLES. |
OP ~ PRESSURE AELIEF VALVES:

Ye — JET pump
X= Exnausr

“7 LIFT HOUSING @ sNarr
“KRY Exnausr —

REVERSED Flow

FIGURE 1, Simplified schematic a

ind projected airflow
diagram based on decom;

Pression events,

86



Altitude
ee
Ground

44,000
Dow

25,000

Ground

14,000

Dow MAS!

TABLE 20. Blood Onygen Saturation, and Heart and Reapiratory Rates of Subject DD

During Two i-Hour Extended Chamber Flights at 25,000 fc.
Cessna Mask With Zep-Aro Orifice (F 365-1080-2).
Alternate Periods of Exerciva and Reet at 25,000 ft

Sendicion

Peet lighe

Renting

Exercise
wasK

Exercise

Resting
Uxercive
Resting
Exercise
Resting
Exercine
Rest ing
Exercise

Prettight

Resting

Exercise
K

Exercise

Resting
Exercise
Resting
Exercise
Renting
Exercise
Resting
Exerctee

Subject

Oxygen Supply Pressure ~ 70 pat

oD

68 fo
135 1b
35 yr

Subject Wearing

Quieter Percent Heart Rate Respiratory Rate
Minace Minute Minute
95.3 az
T i 6f 3 D 3
Lx 0 Tze TT 6
pr OY 3 8 &
O7.0 65.4 85.0 = 138 136 ww
I 3 fT i] T 3
68 5 | (NT Tie Ww iy
99.4 99.6 © 102 102 vy As
99.8 98.5 116 122 as 0
99.0 9 102 100 rt 12
99.0 16 n
98.0 - 8 13
98.8 % a7
98.0 Az ‘33
99.0 15 4
9.5, 90 uv
1 a 3 T 3
ws 350 = 100 “Tos oF
I z 6 6 3 é i g
rr) > rae 57} 7
T 3 I 3 i 3
rr a | ee Te Te

99.0 300 102 8
9.32 8 12
9.3 92 100 1s
97.6 8 120 13

6 2 hig 10

ns ne “ 07

2 108 98 wz 9

99.0 110 110 1s “
54

-9
1-16
12-25
26-31
32-4
42-67
48-57
58-59

1-9
10-16
1-29 ~
26-31
32-41
42-47
48-57
58-59

seta



RR SE SRSEgsz le

TABLE 14. Summary of Neasuresents of the Carbon Dioxide Content of the

Mebreathing Bag and Mask Faceptece ae Determined at
Ground Level Immediately Postflight

errus
358's

88

8 38

0.39 3.20 0,50 8.90 3.20 8.90 3.00 ee
nee 20 0.75 3.00 1.00 0.50 0.50 0.50
0.50 2.00 0.70 301,00 3.00 1.00 3.00 0.50 2.00
0.50 4.00 0,50 80 0.70 4.80 0,70 4.30 0.70 6.30
0-50 4.00 1,00 4,30 0.60 4.40 0.40.00 0:40 4.20
0-30 4.00 0.30 4.80 0.30 5.00 0.60 4.70 0.50 4.30
0:50 3.80 0.30 4.80 0.40 5.00 0.30 4.50 0.10 4.40
1.00 3.50 1.00 4.00 1.00 4.00 1.30 1.00 0.50 1.00
0:20 6.00 0.20 6.00 0.50 6.30 1.50 6.09 1.00 6.00
0-50 5.00 0.30 5.50 0.30 6.00 0.30 6.00 0.50 5.30
1,00 2.00 0.70 2.00 1.00 1.00 1.00 3.00 1150 2:80

41 = Cooena Mask

2 = Zep-Aro Ma

(Cesena Part No. C 16009-0401)

3+ Ohio Chemical K-S Kak

owercemer

TABLE 15. Summary of Subjective Evaluations of 5;

en
ie
x

FETE nasa |

While Reading at Various Altitudes

BEesb%

re peeece

gs

re
8s

peech Intelligibility

CESSKA MASK
Woice transmitted through the mask)
Ground
20,000 ft 25,000 fe 30,000 fe Postflight
Volume = Clarity Volume ~ Clarity Volase = Clarity “Volume ~ Clarity

Sox 4 Sx G 5S oe 4

ax 4 Sx 5 Sx 4 5S x 5
Sa 5 Sx 5 Sx 5s

3S x 5 Sx 5 Sx 4

Sx 6 4x 3 Sx 3

5 x 5 S xs Sx 5

Sixes 5S x 5 Sx 4

Sx 5 Sox 4 sx 3

Sx 5 Sx 5 Sx 5

Sx 5 Sx 5 Sx 5

ORTO CHEMICAL K-S Mask
Wotce tranemitted through the mask}

5S x 5 Sx 5 Sx 5 Sx 5
ZEP-ARO MASK (CESSNA PART NO. ¢ 66009-0401)
Wotce transmitted through mask-mounted a@icrophone)

Sx 5 Soe 5 Sx 5 Sx 5

50

§
3:



ef he

0 2 4 6 8 100 120 40 60 180
SECONDS

FIGURE 1. Comparison of electroencephalographic slow waves
to loss of useful consciousness following rapid
decompression from 12,000 to 40,000 ft. Passenger
oxygen mask flow 30 liters per minute. Light
exercise on bicycle ergometer,

Loss of useful consciousness 6-7 cycle slow waves
(inability to maintain
sequential counting)

| Emergency descent oO 3-4 cycle slow waves

IV. Discussion.

To conserve the oxygen supply and extend its duration,
passenger oxygen systems and masks used on transport category
aircraft are designed to provide reduced oxygen flows and allow
specific quantities of ambient air to enter the mask through the

, dilution valve at lower altitudes to meet human. breathing
(ventilation) requirements. Nowever, the minimum oxygen partial
Pressures as specified in the FARs must be maintained, As the
altitude is increased, oxygen flow must be increased and dilution
decreased or eliminated as the maximum cabin altitude is approached.
Uncontrolled dilution by inward leakage of nitrogen-rich ambient
air reduces the efficiency of the mask and may jeopardize its
Protective capability. This factor is variable, depending on”
the design and fit of the mask and the facial configuration and
Structure of the wearer.

In the absence of leakage assoctated with fit, the perforn-
ance of a phase-dilution mask’ is largely dependent on oxygen flow,
inhalation and dilution valve sequencing, reservoir bag volume,
and respiratory activity of the wearer. By literally flooding. the
mask with oxygen, inward leakage may be minimized or even converted
to outward leakage; however, to flood the mask could require an

: ’

13



e
A

Fesesangsss

Mean

Is

zzzzaanazz [f

Rezuxvssazz

of Ambient Air and Oxygen Content of Inspired Gas
Using the Ceasna Mask at 20,000 ft as Derived From
Ketimates of End Expicatory Nitrogen

we 10

Exercising, First and Third Minutes at 20,000 ft

Eod Percent Oxygen from Calculated
Expiratory Dilution Supply + Py
Nitrogen Percent Suppl Ambient Ambient 0;
Minuti Minuti Hinute Wifouti Minut Winute
1 3 1 3 1 a 1 3 1 3 1

37 bed 12 67 28 33 ss we a3 ar 130 142
4a) 40 Sa a a6 49 u i 7 60 piri 181
45 48 37 61 43 39 1z 13 3s 52 16600 «1ST
sz 50 66 6) uM ” ua 3 48 30 M5 1s.
“5 az 3s? 53 43 ay Az n 35 38 166 us
ar 42 60 33 40 ar a3 yy 33 38 16000 LTS
40 46 31 38 ag 42 mM 12 60 34 i163
43 a7 “ 60 46 40 aL ay 37 33 172 160
46 52 58 66 42 uu iv] “ 34 48 163 145
ww 48 60 52 40 10 v 62 33 187 160
45.6 46.7 57.7 59.2) $2.3 40.8 «12.1 12.5 54.4 53.3 164.2 160.9

i Reading, Fourth and Sixth Minutes at 20,000 ft
4 6 ay 6 4 6 4 6 4 6 4 6

46 “7 61 60 9 tO 13 32 33 137160
5. rn i |) SY a Cs ( OS |) 1)
az, a 33 36 a? oy au 12 3B 56 5 169
47 47 60 60 253 3 HD
33,0 3642 6H 9 10 67 68 202 193
4750 42 60 S30 55a
as 4s 36 by “a 43 12 12 36 3s 169 166
4% 46 58 8B 22k SSH 163183
45 47 57 60 3 40a 5S 53 166

46 ay ol 60 3 40 “43 13 52 33 137 160
43.90 43.6 55.7 58.7 47.9 46.3 17 11.9 S602 56.2 169.3 169.6

4.



TABLE 9. Percentage of Nitrogen as Measured in the Mask {
Fecepiece and Rebreathing Beg at 25,000 fe 1
n= 10 : .
Exercising Reading
First_aod Third Minutes ac 25,000 fe Fourth and Sixth Minutes at 25,000 ft
Range Peak Hea Range Peak Heao
Minute Mioute Minute Minute Minute Minute
Sebject Locatton 2 3 1 3 2 3 4 6 ‘4 6 4 $
DR Beg = 12-20 15-28 423816 SS 20160 8 10
Mack = «35-62 40-63 67) 68 49 SL BSS 35-55 67 6S 7
ST ag 5-40 6-40 50 66016 1h KO 230 60 3B
Mack = 26-55 25-60 6362 hh 3S OSS 33-57 59 TG
JH Rag %10 1010 25 = 10 S$ 10 $10 S10 20 «17 ry 8
Mosk = 25-64 35-66 650 6B AS S53 35S 35-53 S70 6S?
wz ohag 2-6 22 9 2 3 2 310 3:3 10 s s 3
Mack = 25-55 25-55 57° S93 423555 26-53 5659 4S .
12 Beg 2-8 216 10 17 3 3 S45 $10 23007 6 6
Mack = -23-59 28-62 66 = 6562 4522-50 25-50 6355 kB
mH ag O1 oOo 2 ° 02 G6 O2 3 6 3 2 2
Mask = «14-57 17-62 60 7h 38 SBS? 17-62 59 GR
cr hag Tote 16-300 3872223 27 1B Ta a
Mask = 30-59 38-63 64065 45 4735-55 35-55 57h OSS
mm oBag 2-3 +3 8 3 3 30 5-13 2-6 16 8 10 4
Mask = 31-61 25-60 6765 68 38-62 38-60 6566 SO
woes S10 S15 23032 S$ 10 20-23 5-15 25 3 15a
Mask = 40-65 45-65 6767) Sh Sh 3854 35-55 5757S
DZ ag 7-15 B19 223A. 9. 1B H16 29S ak . ;
Mask 20-66 25-65 67 6846 AS 35-56 35-60 5961S :
45 ,
of



sequence consisted of (1) the adjustment of the chamber pressure
to the desired altitude, (if) a brief rest period for the subject
while instruments and flow rates were adjusted and stabilized, and
(141) 3 min of exercise by the subject. The test sequence was
repeated at 14,000, 21,500, 29,000, 35,000, and 40,000 ft.

III. Results.

National Aerospace Standards recognize respiratory gas analyses
and blood oxygen saturation determinations as the two methods to
be used in altitude chamber tests of passenger oxygen masks, Both
these methods were used simultaneously for monitoring the physio
logical performance of the MBU-8/P mask.

Blood oxygen saturation was measured directly with a Waters
350 ear oximeter. Blood oxygen saturation with corresponding
oxygen flow rates following 3 min of exercise is presented in
Figure 1, The determination of biood oxygen saturation with ear
oximetry cechniques provides a quick, real-cime essment of the
degree of hypoxia an individual might be experiencing; however,
there 1s frequently considerable variation in the results obtained
and the technique is perhaps best used as a quick monitor or safety
device. Alternately, more accurate analyses can be obtained from
gaseous techniques; however, these data require considerable
processing and are more difficult to utilize for quick physio- :
logical assessments.

Tracheal oxygen partial pressure is calculated from the end
expiratory nitrogen as follows:

Pry 7 (B47) O-Fyy,)
Where: Pty = tracheal oxygen partial pressure

2

B = ambient barometric pressure i

47 = vapor pressure of water at body temperature i
and at 100 percent saturation

Le unity

Fin = fraction end expiratory nitrogen
2

These data, derived from the third minute at each specified
altitude, with the corresponding oxygen flow rates, are presented
in Figure 2. Correlation of these data is in close agreement with
comparahle values presented fn the literature. Values for heart
and respiration after 3 min of exercise are presented in Figure 3,

74 ,

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000‘°T OE- 9S 7B OE s¢ $9 €% fh Buzspozaxg
So aL ts 49 zz oy TT LT Buz Asay ”
002‘ 6¢- ss 88 97 9S 89 «6T) ty Bupspoqexg
TOT 98 ST Te 49. 2T 9% j2urasey
8I- $9 8 8 oF $9 9 Te :Buyasoy €
002‘T ce ws 88 (Of es 89 8t OSY Buyzspo1exg
Lz- 9s TZ € 2g ss 8T OF 2uyasey
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OOT‘T ze- zs 98 ST as 49 tT SY Bupsyoqexg
So BL ns rr <4 oy IT et Buyasey T
@9) Eres? ava (Byam) eo. [4OR “UTK Ueey XEN UTH UeeH uoFifpuoy 3dafqns
voyssazduozeg yum g°¢g 1g ead eed
@1039q (Sala) #0 eansseig [eyIzeg % uUTU/T OF 32 Zo uUya/T OF Iz
PENTOA TEPTL 1g Zo peeyoeay asexesy Juedseg ty auaciag

eansseig TezIIeg weSXxQ Teeyoeal peae[NoTeD pue uozIeIqssU0D was0IIT_

ASeY Isal reBuesseg ay Buzavay
3224 000‘07 93 000'ZT wozz pesseaduodag At pzdey sr0efqng jo

°T algvi



! coal

\
\
|

TABLE 13. Blood Oxygen Saturation, and Heart and Respiratory Rates of Subjects
Resting at Ground Level, Poatflight, Wearing Cesena Mask With Zep-Aro Orifice
(F 365-1080-2) at an Oxygen Supply Pressure of 70 psi

N*6
Oximeter Percent Heart Rate Respiratory Rate
Minute Minate Minute
Subject Sex 1 3 1 3 in 3
DR 4 99.5 99.5 %6 2 ~ ~
aT " 99.5 99.6 60 62 ~_ ~
a F 100.5 100.5 | 81 a1 18 16
BR “ 97.7 97.7 60 66 16 re]
wv uM) 98.7 98.6 16 rR mb
bz u | 988 98.8 ¢ 2 2 12 9
Range | 97.7-200.5 97.7-100.5 60-81 62-81 12-20 9-17
Mean |. 99.0 99.1 n n 16 rat)

NOTE: The oxiweter saturations indicated in excess of 100 percent breathing oxygen
at ground level appear to be due to a shift in baseline due to an increase
of temperature of the pinna of the ear vesulting in vasodilatation and
increased perfusion. Earpiece had been worn approximately 1 hour.

49

ete oo ten hl TM


Technical Keport Documentation Poge i
We

To Weempent's Cat

| T Government Acconwan No.

a

| |eanean-79-13
Cras aa sire

3. Woport Date

1
“OKYGEN EQUIPMENT AND RAPID DECOMPRESSION STUDIES eS | [Br Wetierime Orponsenen Code =
as | Cee cee vente yh —_—-
- Le Porto. tenon Report Ne.
7 raat A
Compile: E. B. /MeFadden
9. Pertorming Name ond Address VO. Wark Unit No. (TRAIS)
FAA Civil Aer medical Institute “2
P.O, Box 25082 -_ * Grant Ne.
Otlahoma City, Oklahoma 73125
U3, Type of Report and Period Covered
12. Sponsoring Agency Neme end Address Joo
Office of Aviation Medicine foo an
Federal Aviation Administration
800 Independence Avenue, S.W, Ta Sponsoring Agency Code
Washington, D.C. 20591 :
TS. Supplementory Notes >
Work was performed under Task AM-B-77-PRS-13 and preceding tasks. v :

Te, Abstract

This is a collection of reports of evaluations of the protective capability of

various oxygen systems at high altitude and during rapid decompression, Results

of these studies were presented at scientific meetings and/or published in

preprints or proceedings with limited distribution,

K

V7, Key Words
Life support Document is available to the U.S, public
High altitude through the National Technical Information
Decompression Service, Springficld, Virginia 22161.
Oxygen equipment

18, Diswibotion Statement

19. Security Closwt, (of this report)

Unclassified

20, Security Clowssl, (ol this page? FI Ne, ot Pages | 22, Price

Unclassified 114

Form DOT F 1700.7 (8-72)

Reproduction of completed

POL
Dh a i



In both units the temperature of the oxygen produced during
generation equiiibrated with the environmental temperature well in
advance to mask delivery, Tactile examination of the generator
surfaces during operation did not identify any areas of excess
temperatures which might produce’ contact burns, Precautions should
be exercised when handling spent canisters until sufficient cooling
has occurred.

Of the three types of masks tested in the third phase, the
subjects identified the hospital-type mask as the mask most com-
fortable to wear; however, they indicated they felt the modified
conical with inner face seal to be the best mask. Tracheal po.
values were higher with the modified conical mask for the flow rates
tested. These data are presented in Table 7.

IV. Summary.

Two commercially available oxygen generators designed for the
medical profession were tested for applicability to first aid use
aboard pressurized aircraft, Except for brief deviations, both
units produced oxygen above the advertised rate and beyond the
advertised time. For medical uses, these deviations below the
specified flow would appear to be inconsequential,

A comparison of the flow rates and tracheal pO, values main-
tained by the two generator units demonstrates the better effi-
ciency obtained by using an aviation-type conical mask as compared
to the open-port hospital-type mask, especially when low variable
flows are involved. The Scott generator unit maintained a higher
tracheal pO, with a lower oxygen flow rate than that maintained by
the Life Support generator unit, This advantage is derived pri-
marily from the reservoir bag and valves of the aviation=-type mask
Provided with the Scott generator unit,

Three commercially available oxygen masks, an open-port
hospital type, a Phase-dilution conical aviation type, and a
Phase-dilution modified conical aviation type were compared at
Precisely controlled flows of 3 and 4 L of oxygen per minute,
A higher tracheal PO was maintained at these flow rates by the
modified conical aviation mask when the subjects were resting
quietly. As the exercise level of the subjects was increased,
the performance of all the masks tended to converge and very
little difference was detected.

At these very low “low rates, the.valves of the conical
aviation mask had a tendency to sequence in reverse order. This

was not a significant problem with the modified conical aviation
mask. 4

66



IIL, Resulta.

The ground-level blood oxygen saturation, heart, and respira-
tory rates of the 10 subjects in Table 1 appear normal with the
exception of some elevation of heart and respiratory rates of
several subjects. This response appeared to be a result of some
degree of apprehension. There was considerable variation in blood
oxygen saturation baselines breathing air at 14,000 ft. The low-
est average value of 86.6 percent was obtained in the sixth minute
at 14,000 ft following 3 min of light exercise. The lowest single
individual saturation was that of subject BH, who exhibited a
78-percent saturation after 3 min of exercise and a total dwell
time of 6 min at 14,000 ft (Table 2), Table 3 shows the rapid
resaturation of several subjects resting at 14,000 ft following
mask donning and subsequent maintenance of saturation during
exercise, The average blood oxygen saturations at 20,000 ft
reading and exercising were slightly higher than the ground-level
baseline controls (Table 4). In Table 5 the average calculated
tracheal partial pressures of approximately 160-169 mmig were also
higher than the 140-mm breathing air at ground level (Oklahoma
City), In Table 6 nitrogen values measured simultaneously in the
bag and mask facepiece emphasize the very large fluctuation of gas
composition occurring in a diluter rebreathing mask with each
breath. This table also provides an estimation of the existence
and extent of expired gas entering the rebreathing bag.

Examining Table 7 one may note that the average blood oxygen
saturations at 25,000 ft were slightly in excess of the average
ground-level control, :

The calculated inspired oxygen partial pressures at 25,000
ft (Table 8) ranging from 139.6 to 145.5 mmlg are equivalent to
slightly in excess of the ground air breathing oxygen partial
Pressure of 140 mmHg. In Table 9 one may note that the concentra-
tion of nitrogen measured in the rebreather bag at 25,000 ft is
reduced when compared to 20,000 ft.

The average blood oxygen satufation at 30,000 ft (Table 10)
indicates only a slight reduction. However, several individual
subjects indicated a significant reduction to 87-89 percent
saturation, Heart rates and respiration were also elevated
slightly above corresponding measurements at 25,000 and 20,000 ft.
Calculated average inspired tracheal oxygen partial pressures
ranging from 114 to 122 are consistent with the average blood
oxygen saturation readings (Table 11). .

Subject JV, who exhibited a low blood oxygen saturation
{87-89%) (Table 10), also exhibited a low inspired” oxygen partial
Pressure (100 mum - 98 mm). One female subject's saturation
dropped to approximately 91 percent with a corresponding drop of
the inspired tracheal oxygen partial pressure to 102-97 mm,

22

ete ae eer



ae cee rene

Loading this generator requires removing protective caps from
the canister, inserting the canister, arming and locking the actu-
ator assembly, and then screwing the actuator assembly set into
position. This unit contains two acttator assemblies with locks
that function as a deterrent to inadvertent activation, This unit
was provided with an “aviation type” conical, feather edge, phase-
dilution mask that incorporated a reservoir bag to which the oxygen
flow is directed.

The advertised effective time is 25-30 min of oxygen flow at
3 L/min per canister. The canisters may be activated sequentially
for 50-60 min of continuous flow at 3 L/min or simultaneously for
increased flows of shorter duration. From a total of 31 canisters
tested, 1 failed to activate. All canisters tested maintained
oxygen generation for 27 min with decreasing and variable flows
to 32 min. With two exceptions, oxygen flow rates exceeded the
advertised values and are presented in Tables 4 and 5.

All flows are corrected to NIP. The small and variable
amounts of moisture were disregarded, The values presented are
for the first 27 min, with all data points included,

One canister was below the 3 L/min flow for several minutes
and dropped as low as 1.48 L/min. One other caniszer dropped
below the 3 L/min flow for about 2 min, with a low of 2.23 L/min.

TABLE 4, Average Flow (Liters/Minute, NTP) and Standard
Deviation Within Canister(s) Across Time (0-27 Min)

Single Canister Dual Canisters
Test No. X_+ S.D. Test No, X_+ S.p.
1 3.66 0.44 is 7.23 0.62
2 3.85 0.72 16 6.78 0.70
3 3.46 0.46 Vv 6.24 0.62
4 3.52 0.37 18 6.77 0.68
5 3.51 0,36 19 6.99 0.55
6 3.34 0.40 20 5.99 0.75
7 3.24 0.47 21 6.22 0.68
8 3.12 0.56 22 6.39 0.56
9 3.60 0.63
10 3.66 0.44
u 3.68 0.52
12 3.60 0.50
13 3.63 0.40
14 3.56 0.39 . i
64 |
4
|
weet a |


TABLE 24. Blood Oxygen Saturation, and Heart snd Respiratory nates of

Subject 9D Wearing the Cesena ‘Mask During Chamber Flights to
‘Simultaneously Measure Nicroges io the Facepiece and Keres.
Zep-Aro Orifice a 365-1080-2) at an Oxygen Supply Pressure of 70 pat

Altteode Outnerer Percent Heart Rate Respiratory Rate
Condition Minute Minute Minute
Ground Level Preflight 6 82 we
iy 6 6 i 6
14,000 Rest, Baseline = 98 78 86 $2 9 9
tuercise 80 1% 12 108 8 1
MASK DONMED
T Z a 3 1 3
Resting es 33 86 76 10 6
T @ T 6 L €
25,000 Resting 9s oS 30 co iz 8
Exercise 9S 95 98 102 9
30,000 Resting 9% % 82 86 7 10
Exercise 9s % 402 106 a3 13
TABLE 25. Percentage of Asbieat AF and Oxygen Content of Inspired Cas Ustog the
aaaeca Mask at Chander Fight Alcicudes ores 900 and 30,000 ft. Values Derived
vos Simitanecus Neasurenente of Fad expiratory Kitrogen in the Hask
Facepiece and the Mares. Subject DD- Zep-Aco Orifice (F 365-1080-2).
Oxygen Supply Pressure ~ 70 pet
Altieude End Percent Cxygen from Calculated
(it) Neasure=. Expiratory Dilution Sapply* Py,
aod ment mit: Percent Supply pobtent. Ambient, ‘02 wats
Condition Location ~ Minute Minute Mioute Minute Minute Ries
7? T z 7 z 7 z i z 1 z
14,000 Masel 40 —s a nS Cer!
fasting Mask rs er nr co ad 1 62 GO 248 240
my 3 T @ T - a c T a a
25,00 wat i i MO rs) 1 + Ty SR)
Resting Mask pT ac a: Sn > hed 7 70 72 7S 89
wooo Masel | 3337 AAT OS} 9 10 67 63138148
taercise Mask 3 OCs HD 9 10 6S 63153 168
30,000 asad = 20 2 23ST 5 5 eo 82 143 167
Reeting Mask 20 23 2 7 7 3 3 808 A3 14D.
30000 Mast «25 3S AA oe 6 7 9-75 «6S BM 116
Exercise Mask 2% 33 HTH ¢ 9 76 «65136 126.

s7



oxygen partial pressures of Table 1 and yalues may be estimated
for alveolar oxygen partial pressures as follows:

Pp, oP, -?P or, in simple form, LN = Py - 40
Mo, To, Seog 0p 0p

where Pr, = tracheal oxygen partial pressure

. Poo. = alveolar carbon dioxide partial pressure
2 .

P

“oy

The average alveolar oxygen partial pressure of the resting
subjects following decompression to 40,000 ft caleslated by the
above method was approximately 30 mmbg. It is generally accepted
that alveolar oxygen partial pressures an the range of 20 mmHg to
35 mmHg (zone of performance degradation) may be expected to prom

« alveolar oxygen partial pressure

of unconsciousness), pressures in this range will produce imminent
Joss of consciousness. The alveolar oxygen partial pressure of
the subjects while exercising averaged 15 mmlg. The reactions of
the subjects, including useful consciousness determinations and
electroencephalographic findings as shown in Tables 2 and 3 and
Figure 1, support the alveolar oxygen partial pressures calculated
above,

Previous ground-level ev2lyations of the proposed passenger
mask (2) indicated that it did not provide the minimum tracheal:
oxygen partial pressures required by Part 25 of the FARs when
evaluation was extended to the maximum altitude for which approval
was sought. Decompression of subjects to the maximum altitude
produced even lower tracheal oxygen partial pressures, resultant
hypoxia, and loss of useful consciousness (as determined by the
subjects' inability to maintain sequential counting) in several
subjects while resting and in all the subjects while engaged in
light exercise. The passenger oxygen mask evaluated in this study
did not provide the minimum tracheal oxygen partial. pressures
required by Part 25.1443 of the FARs and should not be approved
for use on transport category aircraft.

15

duce mild to severe performance degradation. Below 20 mmHg (zone -



ECG (For Heart Rate Only)

99.0 % 99.3%
Oximeter

200 Heart Rate

too

50—

Respiration
30,000 tt + - .
20,000 tt 4 Altitude > :
14,000 tt + >

1,250 t! + Grouna Leval

lime 1 min

0 TTEETT TEETER TET

TTT

FIGURE 3. Blood oxygen saturation, heart fate, and respiration

: of subject DM at 30,000 feet wear ing the Cessna mask.
Second minute of Teading. Note the vapid inspiratory
excursions of the chest characteristic of Speech.

32



TABLE 16.

Blood Oxygen Saturation, and Heart and Respiratory Rates of Subject BH

Wearing « Zep-Aro Constant-Flow Mask (Cessna Part No. C 166009-0401) With the
Zep-Aro Orifice (F 365-1080-2) at an Oxygen Supply Pressure of 70 pei.

Mask Equipped With a Microphone

Oximeter Percent Reart Rate Respiratory Rate

Altitude Minute Minute Minute

(ft) Condition 1 3

Ground Preflight ” 68 nt

14,000 Resting 86.0 86.5 7% 1% 10 10
Exercise 85.0 88.5 % 94 18 1s
DON MASK

20,000 Exercise 97.4 97.8 72 %6 12 12
Reading 97.4 98.8 a7) 78 16 4

25,000 Exercise 98.0 97.0 57) 76 5%] 16
Reading 96.2 98.3 82 84 16 16

30,000 Exercise 91.5 86.0 -- - 12 12
Reading 84.0 88.0 - - ty 15
POSTFLIGHT °

Ground —- Resting 99.2 99.3 58 60" 12 Ty
Exercise 99.2 99.0 10 1% 13 TY
Reading 99.2 99.3 68 68 12 8

BTA Oo 19-8

51



Il. Methods.

The study was divided into three phases. The first phase was
conducted with 10 volunteer subjects, 6 males and 4 females, rang-
ing from 15 to 44 yr of age. Two of the male subjects and all the
female subjects were considered naive subjects us they had no prior
experience in altitude chamber flight. The remaining four males
had previously been exposed to one or two chamber flights but would
not be considered to have had extensive experience.

The altitude chamber flight profile for each of the 10 sub-
jects is shown in Figure 1. Electrodes were affixed to the sub-
ject to obtain ECG, heart rate (cardiotachometer), and respiration
(impedance pneumograph). An oximeter earpiece was affixed to the
pina of the ear of the subject to obtain a measure of blood oxygen
saturation. The information was fed to appropriate amplifiers and
signal conditioners, monitored and recorded continuously on a physio-
graph recorder (Figures ‘2 and 3) throughout the altitude chamber
flight.

The operators of this equipment could observe the subject at
all cimes by use of closed-circuit television. In addition, a
safety observer accompanied each subject in the chamber.

Two Custom Engineering and Development Company nitralyters,
Model 300 AR, were used to continuously measure the mask nitrogen.
These instruments exhibit an initial response of 0.024 second, a
90-percent response being obtained in 0.044 second. At the pres-
sure setting used (0.6 mmilg), the sampling rate was 3 cm°/min.

Continuous samples were drawn through needle valves and
wicvocatheter tubing (PF 60) of 0,030-in internal diameter con-
nected into the facepiece and rebreathing compartments of the
mask. The small, extremely lightweighe microcatheter tubing
connected to the mask did not require addition of significant
weight or modification of the mask, factors that might compromise
the fit and operational characteristics of the mask.

After instrumentation, subjects were seated in the chamber
and ground-level baselines recorded (Table 1). An ascent was
made to 19,000 ft and a descent was made to 5,000 ft to determine
the subject's ability to clear ear pressure before ascending to
higher altitudes. The chamber ascended to 14,000 ft and air-
breathing baselines were recorded during 3 min of resting and
3 min of light exercise (Table 2). The mask, equipped with a
Zep-Aro orifice (F 365-1080-2) operating at a supply pressure of
70 psi and providing 2.7 L/min STPV, was donned. This pressure
and flow were maintained throughout the first phase of the evalu-
ation. Observations of blood oxygen resaturation’ were made on

18



unknown. This caused a fire in one seat, location 7D, that was
extinguished with canned soft drink. The canister was transferred
to the galley sink by an attendant. In the other two locations
seats and seatbelts were scorched. The attendants were not aware
that heat was involved in the proper operation of oxygen generators.

I. In preparation for the emergency landing, the passengers
were instructed to assume a position with head down and arms
extended over the head and with hands to the seat back in front
of them, The presence of the hot canisters in. the seat backs
caused considerabJe confusion.

J. Oxygen installations in the attendant seater are located
in a compartment that is slightly ratsed above the floor. There
is a large circular opening in the bottom of this container that
allows considerable quantities of dirt and trash to collect in
and around the mask and canister.

K. Portable oxygen units were covered with plastic bags.
K-S disposable face masks were sealed in plastic bags and stered
with or near the portable unit. The mask was not connected cto
the gas supply. In the lower galley, one portable unit had a
smoke mask attached but was covered with a heavy plastic bag.
One attendant managed to tear the bag partly open before losing
conscfousness. The K-S dispusable mask is not sufficient for
altitudes above 25,000 feet (4,5).

L. The presence of smoke and fumes in the passenger cabin
‘is ‘believed to have been due to the presence of Skydrol-500-B
vapors from the hydraulic system.

IV. Evacuation.

Military firefighting units wore alerted and in position
along the runway before the aircraft landed. A normal landing
was accomplished on runway 26. Foam was dispensed by the fire-

fighting units to control possible fires associated with leaking
fuel around the No. 3 powerplant.

Final atrcraft position was 210° and a 17-knot wind st 270°
was in effect during the evacuation. All exits were manned by
attendants except the overwing exits 31. and 3R, which were manned
by one attendant because of ‘the general incapacitation of one
attendant from the lower galley. All exits were opened for evacu-
ation. The slide at 1L did not deploy automatically and the
attendant attempted manual deployment. The slide did not inflate...
and this exit was not used for the evacuation, The slide at 1R
did not deploy automatically and was deployed manually. All other
slides deployed automatically; however, the wind blew the lower
portion of 3R back upon the wing. The passengere attempting to
evacuate at 3R were directed to 3L.

84

Seeeeeeenaa et oad



TABLE 2,

of Subjects Breathing Air at 14,000 ft, Resting and Exercising.

|

Blood Oxygen Saturation, and Heart and Respiratory Rate Baselines

Inepired Tracheal Oxygen Partial Preseure 83.8 anlig

Resting, First end Third Minutes at 14,000 ft

N= 98
—Oximeter Percent ___—iWeart Rate ___-Respiratory Rate
Minute Minute Minute
Subject Sex 3 1 3 1
DR M —_ — _ cond _— ~—
ST x“ 96.0 91.0 80 78 _ —
JH F 93.0 93.5 108 102 19 19
4 F 93.6 95.3 78 80 12 4
LZ F 91S 92.8 96 90 15 20
DM Fe 96.0 92.5 90 93 18 17
GF M 90.4 92.0 100 100 7 19
BH M 79.0 78.0 14 84 12 13
Ww M 89.5 90.2 86 85 16 —
vz M 92.0 93.0 88 88 i 10
Range 79.0-96.0 78.0-95.3 74-108 80-102 11-19 10-20
Mean 92.0 91.0 89 89 15 16
Exercising, Fourth and Sixth Minutes at 14,000 ft
4 6 4 6 4 6
DR M 92.0 83.0 108 123 - _
Jt M ~~“ — - - - —
Ja F _ _— ad Cd -- _
MZ F 94.0 86.0 80 102 19 29
1Z F 88.0 90.0 132 142 24 30
m ¥ 92.0 93.0 116 120 26 28
GF M 90.2 91.0 100 105 24 26
BH M 76.0 72.0 92 94 20 v7
Ww M 86.0 86.0 105 108 19 18
DZ M 90.0 92.0 100 100 22 22
Range 76.0-94.0 72.0-93.0 80-132 94-142 19-26 17-30
Mean 88.5 86.6 104 112 22 24
‘Number of subjects for whom data were obtained.
{
38
nnn

perms ata tan)

rar

Daren Tye



HUMAN FACTORS REPORT OF THE INVESTIGATION OF THE
IN-FLIGHT DECOMPRESSION, NOVEMBER 3, 1973,
OF NATIONAL AIRLINES FLIGHT 27 (N60NA):

A DC-10 EN ROUTE FROM HOUSTON INTERNATIONAL AIRPORT
TO SAN FRANCISCO WITH 127 PERSONS ABOARD

D. deStetguer

I. Introduction.
mae reduction.

James M. Simpson and Don deSteiguer, FAA Civil Aeromedical
Institute, were directed on November 5, 1973, to proceed to
Albuquerque, New Mexico. They arrived on the afternoon of
November 5, reported to the FAA Coordinator, and were assigned
to the Human Factors Group by che National Transportation Safety
Board Tnvestigator-In-Ciarge, On November 5, 6, and 7, they
Participated in examination of the aircraft interior, decompres-
sion events, and equipment function and use, From November 8
through November 27
the decompression and other events that occurred. DC=10 main-

er were examined in
ility, Tulsa, Okls-
vailable to these

II, Decompression,
e were:

The major Penetrations into the aircraft fusela
@) a cabin window at seat location 17H, area 160 in*s (41) into

the center accessory compartment, area 160 in?; and (1414) two
into the forward cargo and

tration, area 230 in’
There were numerous small penetrations.

A rapid and severe decompression Occurred in the forward
cargo compartment, This decoupresaion w,

as caused by large pene-
trations directly into a compartment: having a small volume,

galley. Ther, { penetrations into thia compartment,
The major sow ‘as through the perimeters of
the two careo

(144) the flow

drop of the Personnel lift; and (Vv) the loss of consciousness by
the two attendants,

79



TABLE 22. Blood Oxygen Saturation, and Heart and Respiratory Rates
of Subject JV During l-Hour Extended Chaaber Viight at 30,000 fe.
Subject Wearing Cesena Mask With Zep-Aro Orifice (F 365-1080-2).
Alternate Periods of Exercise and Rest at 30,000 ft

Oxygen Supply Pressure - 70 pet

oe ener

Altitude :
(ft) Condition
Ground Preflight
14,000 Resting 63.0 62.5 88 Cy a rt)
Exercise 16.0 11.0 108 ana 22 22
DON MASK
“TT Minute T Niaute. i Winute
Resting 98.0 80 vy
30,000 Rest ing 94.0 96.0 8h 82 16 as 9
Exercise 90.0 83.0 102 108 2 25 10-16
Resting 95.0 96.0 86 82 18 rT) 17-26
Oxygen Supply Pressure Reduced From 70 to 60 pal
Resting 95.2 9.7 86 a1 18 18 25-27
Exercise 80.0 15.0 106 us 2 26 28-32
Remainder of Chamber Flight Aborted - Descent
TABLE 23. Percentage of Ambient Air and Oxygen Content of Insptred Gas Using
the Cessna Mask During I-lour Extended Chamber Flight at 30,000 ft.
Subject JV. Zep-Aro Orifice (F 36$-1080-2). Data Derived
From Estimate uf the End Expiratory Nitrogen,
Alternate Periods of Exercise and Rest at 30,000 fe
Oxygen Supply Pressure - 70 pat
Condit ton
and Time
at End Percent Oxygen frva Calculated
Altitude Altitude Exptratory Dilution Supply + Pp
3 Qinuce) _ Nitrogen Percent Supply Aabtent Ambient O? mats
14,000 Resting 48 or v 13 sz _ 208
0,000 Neattng 3 20 6 2 9% 15 0.8 5 97 60) 87h
Exercise 38 40 so 51 3249 10011 62 1 7
Toke 60 10:
esting 3219 40 60 76 Cy 63 8 4
Hy 5 haa
Supply Pressure Reduced to 60 pet
Resting 28 28 33s 65 6S U
esti ? 72007200 29a
Exercise 47 68 60 6L 40 39 pop 33 52 3 93
28-32 ,
56



- i

A slower and less severe decompression occurred in the
Passenger cabin and flight compartment, The loss of the cabin
window at seat 17H was directly resyonsible for the Passenger in
that seat being ejected from the aircraft. The area of Penetra-
tion associated with the cabin vindow was temporarily and partly
blocked with the body of the ejected Passenger. This passenger-~
amale, 5 ft 11 in, 160. 1b~« had his seatbelt fastened loosely,
The window was slightly to the rear of the Passenger, and the wind
blast exerted a force that caused the body to straighten and slip
under the belt (as opposed to a forward force that would have
doubled the body over the seatbelt), The actions of another male
Passenger in attempting to hold the ejected passenger by the legs

Because of the large areas of connecting ports, the Penetra~
tion into the center accessory compartment should be considered
as a direct penetration into the Passenger cabin.

Warning lights and signs that are coupled to a 10,000-fr
pressure switch were on, A cabin altztude rate indicator reading
of 5,000 ft/min was reported by the flight engineer; however,
maximum cabin altitude was not determined, Oxygen masks in the
Passenger cabin were not automatically deployed, This indicates
that either the Passenger cabin did not, reach the 14,000-fr
equivalent altitude or the controlling electrical system, the
No. 3 DC-bus, was nonfunctional, Preliminary information indicates
the No, 3 DC-bus was inoperative. The cabin altitude warning horn
did not sound. This device is also Powered by the No, 3 DC-bus,

Statements by the flight attendants and pilot are in accord~
ance with a mild decompression in the passenger cabin, One
female Passenger is reported to have lost consciousness in a
forward lavatory, As this ts the only reported case of loss of
consciousness in the Passenger cabin, one must consider the
Possibility of a lower Pressure in the lavatory, related to the
lavatory ventilation end exhaust System, as compared to the main
cabin pressure, A second Possibility is individual varfation in
Susceptibility co hypoxda. A third Possibility is Physiological
Problems completely unrelated to the decoupresston or additive
to the effects of the decompression, ‘The exact cause of this
Passenger's loss of consctfousness cannot be established from
available tnformation, The lack of loss of consciousness (in
consideration of the number of persons involved), even when
Several people performed considerable physical activity without
supplemental oxygen, support a mild decompression,

80

Peeetemen siceoat corer tind



TV. Discussion,

In the selection of an oxygen system, one must consider a
number of factors: environment and altitude, aircraft character-
istics, flight mission, and the wearer's knowledge and training
relative to oxygen requirements and equipment. .For example, a
diluter type of mask that may be satisfactory in providing protec-
tion under steady-state conditions at a given altitude may not
Provide adequate protection following rapid decompression to the
same altitude. All evaluations conducted in this study were based
on the assumption of mask utilization in unpressurized aircraft.

wit

Several comments should be made relative to the physiological
variability of the subjects and the limitations of the measurements.

It was noted that when subjects were at 14,000 ft, breathing
air and resting, the oximeter would vary considerably in response
to changes in respiration. This fluctuation or hunting at times
would amount to 4~ to S-percent saturation in response to a par-
ticularly deep respiration following a relatively long period of
shallow and irregular breathing. After the mask wae donned and
Tesaturation established, this fluctuation during reading reduced
considerably and the subject exhibited maximal stability during
exercise. Evaluation during reading was carried out because of
the possible effect on dilution of high inspiratory flows
characteristic of speech. In addition it is not uncommon for the
pilot and passengers of unpressurized light private aircraft to
engage in conversation. A third reason for the reading was to
evaluate speech intelligibility and the possible effect of the
mask on aircraft-to-traffic-control communication. The differ-

ences between respiration during exercise and reading are shown
in Figures 2 and 3.

Short periods of voluntary hyperventilation have been used
in the past to evaluate the effect on mask efficiency of changes
in respiration induced by emotional factors, However, it is
Practically impossible for a sedentary subject to maintain
voluntary hyperventilation for more than 2 to 3 min without
experiencing severe symptoms of hypocapnia (dizziness, pares-
thesia, muscle cramps, etc.). Drastic changes in blood chemistry

and cerebral blood flow also detract from the use of voluntary
hyperventilation in mask evaluation.

In lieu of voluntary hyperventilation a light exercise was
used to stimulate vespiration and concurrently simulate light
Physical activity as compared to complete sedentary resting
conditions. It is admitted that exercise will produce an increase
in oxygen consumption, but at the level utilized in this study ~

this would approximate only 0.3 to 0.4 L/min above the resting
level,

26


\

electroencephalography and tnabiiicy to maintain sequential
counting as indicators of loss of useful consciousness end points.
The proposed mask was unable to maintain subjects in a consciour
state following rapid decompression to 40,000 ft, failed to pro-
vide the required inspired oxygen partial pressures, and was not
approved until extensive redesign, modification, and reevaluation
were completed.

Physiological Evaluation of a Cessna Continuous-Flow Oxygen Mask
for Unpressurized General Aviation Aircraft; Memorandum Report
AAC-119-77-8(S).

This study was conducted in 1966 to evaluate the physio-
logical adequacy and protective capability of a Cessna Aircraft
Company-designed modification of the disposable K-S mask devel=
oped by Koze and Stockam in 1951 for airline passenger supple-
mertal and first aid oxygen. | The proposed modification of the
K-S mask was to be used on unpressurized aircraft for relatively
long durations with a specific oxygen flow and oxygen line
supply pressures and was to be utilized for the flight crew as
well as passengers. Results of this study indicated that flows
to the mask should be increased for altitudes above 25,000 fr;
above 28,000 ft to 30,000 ft, a much safer alternative is the use
of a nondiluting mask supplied with an adequate flow to insure
100 percent oxygen. — fan .

Performance Characteristics of Portable First Aid Chemical
Oxygen Generators; Proceedings, Eleventh Annual Symposium ‘of the
Survival and Flight Equipment Association, 1973.

This study was initiated to determine the feasibility of
utilizing readily available, off-the-shelf, portable first aid
chemical oxygen generators marketed to the medical profession
for first aid application aboard aircraft. This investigation
was limited to an evaluation of initiation reliability, oxygen
Production, physiological adequacy, and effictency of the oxygen-
dispensing device (mask) furnished with the unit.

Physiological Evaluation of the Protective Capacity of the
Prototype MBU-8/P Military Passenger Oxygen Mask; Proceedings,
Eleventh Annual Symposium of the Survival and Flight Equipment
Association, 1973,

The rapid development of the civil aie carrier jet and its
operation at flight altitudes of up to 41,000 ft have been the
primary impetus for the devetopment of modern passenger oxygen
systems in the event of decompression.’ This report describes a
study conducted at the request of the U.S. Air Force of a Proto~
type phase-dilucion passenger mask developed by the Air Force to
replace the K-S open-port passenger mask, which is not recommended

2



TABLE 4.

. Exercising, First and Third Minutes at 20,000 ft

i
1
Blood Oxygen Saturation, and Heart and Respiratory Rates of Subjects {
st 20,000 ft Wearing Cesena Mask With the Zep-Aro Orifice (F 365-1080-2) :
at an Oxygen Supply Pressure of 70 psi i

N10

Oxiweter Percent Hearc Rate Resptratory Rate
Minute Minute Minute
Subject Sex 1 3 1 3 L 2
DR “ 97.5 97.5 80 100 - -- '
aT * 97.6 97.6 70 80 21 19
Jn F 97.6 97.6 108 1S 2 2
¥z F 97.0 98.3 99 98 2 19
iz F 96.7 97.4 2 12 24 25
OM F 99.4 99.4 105 108 25 26
GF x 98.6 98.0 98 96 24 23 '
BH M 98.4 98.7 74 14 18 7
wv x 96.7 96.3 98 100 19 20 \
bz M 96.6 96.5 96 38 19 16
Range 96.6-99.4 96.3-99.4 70-112 74-115, 18-25 16-26
Mean 97.6 97.7 4 97 2 a
Reading, Fourth and Sixth Minutes at 20,000 ft
4 6 4 6 4 6
DR M 97.5 100.0 100 90 12 10
aT 4 98.0 98.6 75 70 16 7
au F 97.5 98.0 105 110 16 is
Hz Fr 98.3 98.3 87 84 rt) 10
uz F 97.8 98.0 98 98 vv 3
Du F 99.8 99.4 100 100 13 ul
GF 4 98.2 99.2 100 100 20 16
8H M 99.0 99.8 86 82 17 14
wv M 97.3 97.8 88 87 1s 4
Dz 4 97.9 98.8 96 9% 4 3
Range 97.3-99.4 97,8-103.0 75-105 70-110 12-20 10-17
Mean 98.1 98.8 % 92 15 13

40



OXYGEN EQUIPMENT AND RAPID DECOMPRESSION STUDIES

INTRODUCTION

This 1s a collection of reports of various studies and
evaluations of the protective capability of oxygen systems and
equipment used or proposed, including developmental and proto-
type designs for use at high altitude and/or following rapid
decompression. These studies were generally designed and ori~
ented toward (1) obtaining answers to particular questions or
problems posed by Governmental approval authorities or the aviaq-
tion industry with respect to the life-support capability of a
given device or procedure and/or (11) advancing the state-of-
the-art in high-altitude life support and aviation safety.
Certain of these reports were presented at scientific meetings
and/or published in preprints or proceedings with limited
distribution,

Reliable physiological evaluation of an oxygen system
requires continuous determination of inspired and lung-oxygen
tensions on a breath-by-breath basis. At the time these studies
were conducted, analytical equipment with sufficiently rapid
response to accurately measure oxygen on a breath-by-breath
basis was not available; thus, development of an indirect method
employing analysis of other respiratory gases and computing
oxygen tensions by difference was required. The recent develop-
ment of practical respiratory mass spectrometry has allowed
simultaneous breath-by~breath analysis of all gases invelved in
respiration and has revolutionized this area of respiratory
physiology and equiprent evaluation. Because some of these
studies were preliminary in nature and were conducted over a
period of 15 yr, employing available and experimental techniques
and instrumentation, information contained in these reports is
subject to additional evaluation or change on review of the data,
conduct of add‘tional testing, or receipt of additional facts,

SYNOPSES OF REPORTS

Continusis Functional Testing of Passenger Oxygen Masks at
Ground Level and During Rapid Decompression; Memorandum Report
AAC-119-77-9(S).

This study was conducted in 1964 to improve the previously
developed techniques and instrumentation for the evaluation of
oxygen equipment and explore the development of methods for evalu-
ating oxygen at ground level. The study employed a relatively
large number of untrained subjects as opposed to a few selected
trained subjects at altitude. A secondary, but integral, phase
of the study was to evaluate a proposed passenger oxygen mask
design and concurrently evaluate and compare the use of .

L



100 %
§ 90%
B so%t
S 70%
5 60% : I
s N kK iN
E 50%} x NN N N
S NN N N
2 4o%7 N N N \ \ \ N N
Ss N N N N NN N A
=~ 30% \ N A N \ N N
3 2o%tNN NNNNNNA
ont NNNNNNNNNNNN
§ !oxt NN N N N NN NNN
o) NN NNN NN NN NN
Time-Minutes / 3/3 6/7 333 64/ 313 6
Activity Exercising | Reading | Exercising | Reading | Exercising) Reading
Altitude 20,000 25,000 30,000

IS % 02 Derived from Supply % Ambient Air

FIGURE 6. Histograph showing dilution of inspired gas with
ambient air as calculated from the end expiratory
nitrogen concentration. Subjects exercising and
reading at 20,000, 25,000, and 30,000 feet while
wearing the Cessna mask.

35

291-212 O- 19-8


Reference

1. Stork, R. L., and T. R. Morgan: Oxygen Accumulation in

Hypobaric Chambers, USAF School of Aerospace Medicine Repott
SAM-TR-76-14, Brooks Air Force Base, Texas, April 1976

114



eightfold or greater increase in the number of oxygen cylinders I
installed on the aircraft, imposing severe and unacceptable space :
and weight penalties. i

Use of the minimum or maximum concentration of nitrogen for
the calculation of tracheal oxygen partial pressures is not jus- !
tified because: (i) the minimum concentration of nitrogen may be
attained as a result of a constant flow of oxygen washing out the
mask dead space; or (ii) the maximum concentration of nitrogen
during peak dilution in the mask occurs through the introduction
of ambient air by the dilution valve, The mean nitrogen concen-
tration appears to provide a more realistic value and was utilized
in this study for computation of the tracheal oxygen partial pres-
sure. A more precise and accurate determination of the tracheal
oxygen partial pressure while wearing a mask should be based on
breath-by-breath analysis of all end expiratory gases as a basis
for determination of the partial pressures of these gases in the
air sacs (alveoli) of the lungs, New developments in instrumen-
tation with improved sensitivity and response, including the use
of polarographic gas analysis and mass spectrometry, may allow
direct determinations of all alveolar gases practical on a routine
basis.

It is not surprising that the tracheal oxygen partial pres-
sures were considerably lower following rapid decompression than
those predicted in previous testing (2) at ground level. During
the dynamics of decompression, a number of effects prevail that
are absent under steady-state ground-level conditions. These
include rapid expansion of gases in the lungs and accelerated
diffusion of carbon dioxide into the alveoli of the
lungs as a result of reduced pressure. The accelerated diffusion
of carbon dioxide into the alveoli displaces oxygen, thereby
increasing the level of hypoxia. Once initiated, hypoxia-induced
hyperventilation tends to increase, the dilution of oxygen delivered
by the mask thus establishing a vicious cycle which is directed
toward further increasing the level of hypoxia,

As alveolar oxygen partial pressure is in near equilibrium
with the blood, determination of the partial pressures of alveolar
gases provides a more precise indication of the physiological
condition of the mask wearer. However, a mask (as an item of. -
equipment) is, in itself, only capable of delivering a breathing
mixture with an increased oxygen partial pre:sure. This philosophy
is reflected in the passenger oxygen requirements of the FARs.

Carbon dioxide in the blood exerts a significant effect on
the control of respiration and, in conjunction with other con~
trolling mechanisms, normally regulates and maintains a carbon
dioxide partial pressure of 40 mmHg in the alveoli of the lung.
By applying a derivation of the alveolar equation, the partial
Pressure of carbon dioxide may be subtracted from the’ tracheal

14



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TABLE OF CONTENTS
METRIC CONVERSION FACTORS

LIST OF ABBREVIATIONS

INTRODUCTION
SYNOPSES OF REPORTS

CONTINUOUS FUNCTIONAL TESTING OF PASSENGER OXYGEN MASKS
AT GROUND LEVEL AND DURING RAPID DECOMPRESSION by E. B.
McFadden, P. C. Tang, and J. W. Young

PHYSIOLOGICAL EVALUATION OF A CESSNA CONTINUOUS-FLOW
OXYGEN MASK FOR UNPRESSURIZED GENERAL AVIATION AIRCRAFT
by E. B. McFadden, H. Harrison, and J. M. Simpson

PERFORMANCE CHARACTERISTICS OF PORTABLE FIRST AID
CHEMICAL OXYGEN GENERATORS by D. deSteiguer, E. B.
McFadden, and J. M.. Simpson

PHYSIOLOGICAL EVALUATION OF THE PROTECTIVE CAPACITY OF
THE PROTOTYPE MBU-8/P MILITARY PASSENGER OXYGEN MASK
by E. B, McFadden, D. deSteiguer, and J. M. Simpson

HUMAN FACTORS REPORT OF THE INVESTIGATION OF THE IN-
FLICHT DECOMPRESSION, NOVEMBER 2, 1973, OF NATIONAL
AIRLINES FLIGHT 27 (N60NA): A DC-10 EN ROUTE FROM
HOUSTON INTERNATIONAL AIRPORT TO SAN FRANCISCO WITH
127 PERSONS ABOARD by D, deSteiguer

EFFECTIVENESS OF A PAPER CUP AS AN AID TO PROVIDING

“OXYGEN TO LARYNGECTOMEE PASSENGERS by E. B, McFadden

PHYSIOLOGICAL CONSIDERATIONS AND LIMITATIONS IN THE
HIGH-ALTITUDE OPERATION OF SMALL~VOLUME PRESSURIZED
AIRCRAFT by E. B. McFadden and D. deSteiguer

OXYGEN CONCENTRATIONS IN THE VICINITY OF A PASSENGER

Pinski

7

59

69

79

94

99



pressure of oxygen is simultaneously reduced in response to a
reduction in total ambient pressure and to the increased diffu-
sion of carbon dioxide into the alveoli from the venous blood.
Loss of consciousness generally follows when the alveolar Poe
drops below 20 mig, while a decrease in performance generally
occurs at alveolar p02 values below 35 mmiig.

The alvolar gas composition for selected altitudes while
breathing oxygen is presented in Table 4. An examination of
these data demonstrates the dangerous alveolar po. level follow-
ing rapid decomressions to 15,240 m (50,000 ft} eVen though
oxygen was prebreathed.

Breathing Air Prior to Decompression. Crew and passengers
breathing air at a cabin altitude of 2,438 m (8,000 ft) prior to
rapid decompression to 15,240 4 (50,000 ft) would lose useful
consciousness even though they had donned oxygen masks at the
beginning of decompression. In addition to washout of nitrogen
from the respiratory system, the air in the mask and the regulator
hose must also be replaced with oxygen. Mask-mounted regulators
and equipment modifications tend to alleviate the problem of
equipment dead space, but little can be done to modify the human
lung nitrogen washout short of wearing a wask and breathing
oxygen prior to the decompression. Data obtained in this labora-
tory on quick-donning crew oxygen masks during decompressions,
simulating a B-707 decompression, illustrated the delay imposed
by nitrogen washout (6) (Figure 1). Hyperventilation may accel-
erate nitrogen washout to some degree but is in itself a danger-
ous expedient.

An analysis by Blockley and Hanifan (5) indicates that
following a 1.5-s decompression from 2,438 to 15,240 m (8,000 to
50,000 ft) (for subjects breathing air prior to the decompression),
the alveolar pO, is predicted to drop below 20 mmiig and produce
loss of consciousness with no possibility of recovery at this
cabin altitude, even though 100 percent oxygen is breathed 3 5
after the start of decompression.

Rapid decompression experiments conducted by Baron (7) in
which two subjects breathing air were decompressed in 5 s--one
from 2,438 to 13,661 m (8,000 to 44,820 ft) and one from 2,438
to 13,714 m (8,000 to 44,995 ft)--confirm there predictions.
Even though both subjects donned or attempted to don their
masks 12 s from the start of decompression and the dwell time
at maximum altitude was limited to 5 to 6 8, both subjects lost
useful consciousness 14 to 16 s after the start of decompression.
Other subjects in this series were unable to complete a simple
performance test even though they had donned their masks in 8,
5, or even 3 s after the start of decompression.

104



All flows are corrected to NTP, The small and variable amounts
of moisture were disregarded. {The values presented are for the first
15 min, the advertised time, with all data points included.

Tracheal oxygen partial pressure varied greatly between sub-
jects and appeared to be highly influenced by respiratory rate and
tidal volume as limited by a 15-L minute volume. These data are
briefly generalized in Table 3.

TABLE 3. Tracheal Oxygen Partial Pressures Maintained
in Human Subjects by S.0,S. Generator Units

Mode of Operation

Single Canister Dual Canister

Low Subject 180-190 mmp0z 250-300 mmp0
High Subject 350-400 mmp02 400-430 mmp02

Note: All values are calculated from end expiratory
nitrogen and are corrected to NIPD.

The generator system of the Scott Med-Ox unit (Fig. 2) meas~
ured 37 x 12 x 23 cm for a volume of 10,212 cm? and for a total
weight of 3.4 kg. This weight included two unexpended canisters,
hose, mask, and case. The canisters measured 248 x 64 mm in
diameter and weighed 720 g each. *

FIGURE 2. Scott oxygen generator system.

63



several subjects within L min after they donned the mask at

14,000 fe and subsequently after 1 and 3 min of exercise (Table 3).
Determination of mask nitrogen was naturally not available until
after mask donning was accomplished.

Following mask donning an ascent was made to 20,000, 25,000,
and 30,000 ft with a dwell time of 6 min at each altitude. During
the first 3 min at each altitude the subject engaged in light
exercise, using a bicycle ergometer at a speed of 40 r/min and
load of 50 w (approximately equivalent to walking at 3,0-3.46 mi/h)
(Tables 4-12), During the last 3 min the subject. read articles
from aviation or similar magazines through the mask into a recorder
microphone.

Postflight ground-level determinations of resting blood
saturation, heart, and Tespiratory rates were recorded on six
subjects (Table 13) in conjunction with carbon dioxide measure-
ments at ground level while wearing the mask (Table 14), An LB-L
infrared gas analyzer was utilized to determine the carbon dioxide
in the mask facepiece and rebreather bag. The relatively high
flow requirements (500 mL/min) of this analyzer dictated that the
sample be circulated through the analyzer and returned to the mask
compartment from which it was removed. This process appeared to

represent the worst Probable condition for carbon dioxide
accumulation,

Tape recordings of the subjects reading at altitude were
subjectively evaluated for intelligibility in terms of volume
and clarity by a former radioman (now.a sound technt¢ian) who
was unfamiliar with the content of the recordings (Table 15).

Two of the ten subjects included in the first phase of the
evaluation, duplicated the firse flight profile wearing a differ-
ent type mask. The first subject (BH) wore the Zep-Aro constant-
flow mask (Cessna Part No. C 166009-0401) (Tables 16-17), The
other subject (DZ) wore the Ohic Chemical Company K-S mask"~"”
(Tables 18-19). The same orifices and oxygen supply pressure
were maintained as in the Previous 10 subject flights.

In view of the Probable use of the mask at altitude for
relatively long Periods of time, it becomes apparent that addi~
tional evaluations should be conducted for extended duration to
Produce a more reliable Steady-state condition of the unacclima-
tized subject. In this second phase of the evaluations the sub-
ject remained at altitude for 1h with alternate periods of

19

Id O- Tee



CONTINUOUS FUNCTIONAL TESTING OF PASSENGER OXYGEN MASKS
AT GROUND LEVEL AND DURING RAPID DECOMPRESSICGN

E. B. McFadden, P, C, Tang, and J, W. Young
I. Introduction.

The development of the turbine-powered aircraft with its
capability to efficiently operate at high altitudes around or
above adverse weather and maintain more regular schedules has
Provided the principal impetus for the Phenomenal growth of air
transportation. However, the Potential of this mode of transpor—
tation could not be fully realized until development of the
Pressurized cabin and its associated enviroumental and life-.
support systems, Because cabin pressurization faflure imposes
an inmediate threat to life at the altitudes at which these air-
craft operate, Passenger and crew oxygen systems are provided as
an emergency life-support backup,

i

The capability of a Passenger oxygen system to provide the
required level of protection at altitude is highly cependent on
the performance of the mask and its capability to interface with
and satisfy human breathing and oxygen requirements. Passenger
oxygen masks used aboard transport category aircraft are of the

Phase-dilution type designed to the NAS-1179 and FAA TSO-C64 of
which it is a pare,

The primary purposes of this study were tot (4) extend the
use of passenger mask testing techniques Previously developed (1)
and used at ground level (2) to the testing of a limited number
of subjects exposed to a rapid decompression to the maximum
certified altitude of the aircraft; (11) evaluate the use of an
electroencephalogram (EEG) to indicate impending loss of con-
sciousness; and (iit) compare the performance of a Proposed
Passenger mask design Previously evaluated under ‘Steady-state

It, Method,

Because the percentage composition of nitrogen tn the
ambient air at ground level and altitude (up to 80.000 ft) is
quite stable (79.03%), a reliable standard reference or tracer
gas in high concentration exists in the surrounding environment
of the subject. When the subject is breathing 100 Percent oxygen
or oxygen diiuted by a known amount of air, any additional
nitrogen-containing air introduced by. inward mask leakage may
be continuously monitored and measured by nitrogen analysis on
4 breath-by-breath basis. More importantly, the oxygen partial
pressure of the inhaled gas may be calculated by difference and

5



i

instances that expected for mixed expired Base Therefore, it is
doubtful that measurements of carbon dioxide in the mask facen
piece provided consistently the degree of accuracy required for
precise determinat ions of the end expiratory carbon dioxide+

Rebreathing of excessive carbon dioxide concentrations
should have produced a significant change in respiration and
heart rates+ Examination of Table 13 indicates "0 such effects.

Inspired concentrations of carbon dioxide of up to 2 percent
have been shown to have jittle or no physiological effect (5)-

‘Two additional chamber flights were made with two current
types of rebreathing masks using subjects BH and DZ, who also
participated as subjects in the first series.

In Table 16 the results are shown for subject BH wearing

the Zep-Aro (Cessna part No. © 66009-0401) mask equipped with a
mask-mounted microphone. At 30,000 ft, saturation during exercise
dropped lower than the 14,000-£t paseline and the equivalent pre-
vious test wearing the Cessna mask, Resaturation was not subse-
quently accomplished during reading 88 in the previous evaluation.
Calculated inspired oxygen partial pressures ranged from 93 mmig
to 102 mmig (Table 17)+

Results of subject DZ wearing the “K-S mask are shown in
JTable 18. Saturation dropped to Qi percent at 25,000 ft during
exercise but, was reestablished during subsequent reading. At
30,000 fr, saturation dropped during exercise to 84.8 percent,
lower than the 14,000-£¢ baseline, but was again reestablished
during reading. During the previous test the saturation of
subject pz wearing the Cessna mask showed no indication of
reduction at 25,000 ft during exercise. At 30,000 ft, there was
some reduction in saturation with the Cessna mask during exercise
put not of the magnitude experienced with the K-S mask. Calcum
lated inspired tracheal oxygen partial pressures of 98-102 mmlg,
(Table 19) are consistent with the plood oxygen saturations

i»-. obtained.

In Phase 2 the Cessna mask was evaluated during extended-
duration chamber flights. at altitudes of 25,000 and 30,000 ft.
Longer periods of exercise and rest were utilized, and the resting
condition was substituted for reading. Table 20 presents the
plood oxygen eaturation, heart. rate, and respiration of subject
DD during two 1-h flights at 25,000 ft. The second flight varied
from the first only in that the oxygen supply pressure was reduced
to 60 psi. H

Blood oxygen saturation remained above the air-breathing

ground-level control at all times during the flights’ Inspired
tracheal oxygen partial pressures: were generally above that for

24



\

VI. Summary.

1. Lower deck galleys should be prohibited in future produc- '
tion aircraft. :

2. All oxygen systems intended for use in lower galleys should i
have a dual Presentation system, one slaved to the upper deck aneroid
switch and one coupled to an aneroid switch in the lower galley,
This oxygen unit should also be manually accessible,

3. A close examination should be made of the electrical sys-
tems and operational Procedures to ineure that electrical Power for
mask presentation is maintained,

4. The seat back oxygen system should be vTeengineered to:
(1) make removal of the canisters by passengers improbable;
(414) improve the thermal isolation of che canister; (111) change
the mask bracket to preclude lanyard entanglement; and (iv) modify
the mask to Prevent separation of the reservoir bag from the

6. Design the oxygen containers in the attendant seat instal-
lations to Preclude entry of dirt and trash into the interior of
the unit,

7. Attendant Portable oxygen units should be accessible and
immediately usable. The use of Plastic bags around these units
should be discontinued.

8. The K-s disposable face mask does not provide sufficient
Protection in the event of severe decompresstons, These masks
should be immediately removed from all air Carrier aircraft and
replaced with masks apptoved to FAA TSO~C64.

9. Examine the effect on Potential injuries of deployed seat
back oxygen Systems during emergency landings where impact would
be encountered. a

10. Conduct a detailed Study of the pressure differentials
that develop in and through the lift shaft as a result of rapid
decompressions in the lower galley,

11. Examine the Pressure differentials that develop through
and across compartments as a result of rapid decompression,

12. Include cabin pressure a8 a component of the flight
recorder. ’

92

Sort eenenameena emma


One invalid male was evacuated through 3L. The efforts of
one attendant and one able-bodied man were required.

The attendants estimated the evacuation time to be 30 s, while
the firefighters estimated closer to 60 8.

No serious injuries were reported. Ten persons complained of
and were treated for ear pains. Ten other persons complained of
amuke or fume inhalation. One person sustained a burned finger
from a canister, one sustained an abrasion from a slide, and one
reported a back sprain from the evacuation.

Vv. Discursion.

The decompression schematic (Figure 1) outlines the major
airflows assoctated with the loss of pressure that occurred
following fuselage penetratfon by No. 3 powerplant components,

The schematic does not present any input from the No. 1 or No. 2
compressors, nor does it present the magnitude of flow in any direc-
tion, The lack of available data necessary for precise computations
limits this analysis co rough estimates at best. However, these
estimates should be useful in explaining the sequence of events

that occurred, particularly in the lower galley.

Statements Crom the two Chight attendants atationed in the
lower galley indicate a rapid decompression by: (1) a rapid
reduction in air temperature; (11) the vpening of doors from
modular components; (110) flow of paper articles in the afte
direction; (iv) the drop of the personnel Tift; and (v) the loss
of conscfousness by the two attendants. Direct penetritions into
the galley were not detected.

The time of consciousness during a rapid decompression while
breathing air can be estimated. Ina decompression from 10,000
to 30,000 ft, a consciousness time of 40-60 s can: be predicted
(Figure 2) (6).

The decompression proftle may be roughly estimated for the
various aircraft compartments {f certain ugsumptions are acceptable
in lieu of precise data. These assumptions include: (1) zera
inflow of air into the compartsent during the decompression;

(iL) disregarding airflow acroes the Penetration area; (iff) zero
impediment to airflow within the compartment; (iv) no correct fons
for the multitude of time changes tn gas temperatures, ete.3

(v) no corrections for che pattern of airflow through the pene-
tration; and (vi) maintenance of critical flew.

The equation for rapid decompression as presented by ©
ant Clamann (7) is suffictent in view of the assumptions.

85



related to human oxygen requirements regardless of the altitude
and the source of the diluting gases. This indirect approach is
required since instrumentation with sufficiently rapid response
to measure oxygen directly on 4 breath-by-breath bas‘s is not
currently available.

The development and evaluation of the nitrogen analysis
technique for evalucting the performance of oxygen masks is
described in references 1 and 2.

Five subjects who had previously received high altitude
chamber training were instrumented and rapidly decompressed from
12,000 ft ro 40,000 ft in 36 to 76 8. Decompression profiles
were based on the predicted decompression time of four-engine
turbine-powered transport aircraft after failure of a main cabin
window. At least one decompression was conducted with the sub-
ject in the resting condition, The same decompression profile
was repeated with the subject in the exercising condition to
stimulate breathing to the levels specified in FAR Part 25.
Subjects exercised on a bicycle ergometer in lieu of the tread-
mill used in the former study (2), Substitution of the bicycle
ergoneter was required because the altitude chamber ceiling he-ght
was inadequate to accommodate the treadmill, Howover, the bicycle
ergometer was adjuste+ to duplicate the exercise levels employed
in the previous study (2) but at an altitude of 12,000 ft just
prior to decompression, Exercise was continued ari oxygen fle
maintained at 30 L/min BTPS during and following the rapid de. s.-
pression. in addition to the determination of nitresen, subjects
were instrumented for electroeacephalographic and electvo-
cardiographic changes. Crew-type oxygen masks and demand regu~-
lators were set to the 100-percent-oxygen position before
decompression for pulmonary nitrogen washout, This process was
monitored and continued until the washout curve was asymptotic
ané the remaining nitrogen was negligible. Just prior to dece
pression the subjects held their breath, removed the crew mast
and donned the passenger masks with oxygen flowing at a rate
equivalent to 30 L/min BIPS at 40,000 ft. The type of mask +.
was the same proposed passenger oxygen wask evaluated at grou.d
level in the previous study (2). A subject's inability to main-
tain sequential counting and/or initiation of convulsive moye-
vents was established as the end point for loss of useful
consciousness. Electroencephalographic charges were monitored
and recorded for comparison of their onset, duration, and fre-
quency as related to the development of hypoxia and loss of use-
ful consciousness. Depending on the onset and severity of loss
of useful consciousness, descent was initiated, and either the
passenger mask was removed by the safety observer ana replaced
with a crew mask delivering oxygen under pressure o: the passen-
ger mask was flooded with oxygen. Those subjects who did not
exhibic obvious symptoms of inipending loss of consciousness were
maintained at altitude for at least 5 min before descent was
initiated.

a



CENTER CABIN MAIN DISTRIBUTION
AFT CABIN DROPPER DUCT

STORAGE OIFFUSER
COMPARTMENT

LOSz

4

es
—"

0M 000 00 M00 0000

UTILITY TUNNEL

FIGURE 3, Cabin air circulation and exhaust diagram.

The high background noise described by the pilot might be asso~
ciated with the rapid movement of air through openings in the deck
of the flight compartment to the forward accessory compartment,
hence to the utility tunnels and out the penetration in the center
accessory compartment. This background noise could also be asso-
ciated with the rapid expansion of input air from the inlet ports,
the result of an increased pressure differential. A rate change in
altitude of 5,000 ft/min was observed on the cabin altitude rate
indicator; however, maximum cabin altitude was not determined.

The "No Smoking” passenger warning signs and cabin overhead
lights were observed to be on, indicating the passenger cabin had
passed through the 10,000-ft equivalent altitude.

Statements by the flight attendants describe a mild to moderate
decompression in the passenger cabin. The absence of fainting by
passengers and attendants who, in some cases, performed considerable
activity without supplemental oxygen, indicates the maximum equiva-
lent altitude reached in the passenger cabin to be less than 18,000-
20,000 ft. .

In effect, two different decompressions are identified: a
rapid and severe decompression in the lower compartments, and a
slower and less severe decompression in the upper compartments.
\
91



. It would appear that standard phase-dfilution passenger misks
qualifying to FAA TSO-C64 and National Aerospace Standard 1179
would be a better alcernative. These masks in the form of a cylin
der or modified cone conform to various contours with the mask
facepiece terminating in a circular opening (24-34 in) approximating '
that of the paper cup (3 in). The phase-dilution mask incorporates
a 1,10-L reservoir bag that stores 100 percent oxygen during
exhalation and allows the wearer co breath 100 percent oxygen at
the beginning and throughout inspiration ff the reservoir bay is
full and the tidal volume does not exceed 1.10 L including the
flow added during inspiration,

The phase-dilution mask provides a Large quantity of 100
percent oxygen at the initiation of tnspiration, which ts delivered
to the physfologically active areas of the lungs. If the tidal
volume exceeds 1.10 L (plus the quantity ef oxygen added by con-
tinuous flow during inspiration), a check valve opens to admit
ambient air. Ambient air may only penetrate inte the trache.
bronchi, and bronchials, which are nonphysiologically activ as
of the resptratory system. Under these conditions the ambient air
introduced doves not dilute che high concentration of oxygen in the
alveoli of the lungs yet is used to fulffll a portion of the
respiratory demand. On exhalation the ambtent air {s swept from
the mask and replaced by alveolar gas high in oxygen concentration,
which constitutes the initial Portion of the subsequent duhalation,
If one applies the criteria of (¢) and assumes no Teakage or tidal
volumes in excess of the volume of the reservotr bag, then the
calculation in (c) for a phase-dilution mask is as follows:

(4) Oxyxen flow = 4 L/min = 57%
Minute volume 7 L/min

FAR Part 25.1443 specifies 4 L/min STPD. At a cabin altitude
of 5,000 ft, 4 L/min SITD is increased to 5.9 L/min BIPS*, inereas-
ing all of the above pereentages.

However, the assumption of a 7 L/min minute volume is con-
servative. The data of Ernsting (2) indicates that seated, inactive
flight crewmembers exhibit a minute volume of 10-15 L/min BIPs,
nearly twice the above value. Applying the more realistic value
of Ernsting (2) (a minute volutte of 15 L/min, peak iusptratory
flow of 55 L/min and at a cabin altitude of 5.000 ft), estimation
vf oxygen added to the inspired air by the paper cup and by the
mask may be calculated as follows:

(e) Oxygen added to inspired air by paper cup = 5.9 L/min = 10.7%
. 55 L/min

*Body temperature 98.6°F, pressure 632 mmlly, saturated with water
vapor.

96



FIGURE 1,

Thereas,
Of air ar

flow oXysen ata ¢

4 L/mi
i

eS in oxygen concent vation aboy
whe:

© that
en breathing co
C4. ny

atinuous.

Oxygen
K lever
SBen at g flow

Soneent ration
when breath in
of 4 L/min,

above char
RS cont Anuous-



PERFORMANCE CHARACTERISTICS OF PORTABLE
FIRST AID CHEMICAL OXYGEN GENERATORS

D. deSteiguer, E. B. McFadden, and J. M. Simpson
I. Introduction.

Portable equipment for administration of first aid oxygen to
airline passengers has been carried aboard air carrier aircraft
for many years. Although these systems use high pressure gaseous
oxygen, the past history of their deployment and use has be:-: rela-
tively free of accidents or serious incidents. Howe+-, several
recent accidents involving these units stimulet-. interest in the
airline industry in replacing them with ch «:cal oxygen generators
on a fleet-wide basis. In addition to safety considerations,
reduced weight, ease of operation, taintenance simplicity, and
cost factors make replacement witi. a chemical system attractive.

Essentially, chemical oxygen generators consist of a quantity
of an alkali-metal chlorate enriched with a solid fuel such as tron
to produce sufficient heat for decomposition of the chlorate and
liberation of oxygen. Additional chemicals and filters are added
or superimposed downstream in the generator to insure oxygen
purity (1).

This investigation was limited to a study of tae applicability
in aviation of using readily available, off-th shelf, portable
first aid chemical oxygen generators warke*.d to the medical profes-
sion. Chemical oxygen generators for «..ergency passenger use in
th event of decompression have bee-. developed and qualified for
aviation and are being used aboa~a the CSA, DC-10, and L-1011 air-
craft. Chemical first aid oy en systems evaluated in this study
in no way replace emergency systems; they are meant to be used for
first aid therapy only under normal conditions. Airlines report
the use of first aid oxygen to be relatively Frequent compared to
the use of passenger emergency oxygen. To facilitate administra~
tion of first aid oxygen by the cabin crew, a first aid portable
unit should be lightweight, reliable, and simple to operate,
should produce therapeutic oxygen flows, and should not create a
hazard in itself.

HI. Method.

Two commercially available chemical oxygen generators designed
for medical applications were evaluated for reliability, oxygen
production, and physiological efficiency (ability to maintain an
increased tracheal oxygen partial pressure in human subjects). The
units tested were the Scott Med-Ox (Scott Aviation, Lancaster, New
York) and the Life Support $.0.S. (Life Support, Melbourne, Florida)
generator systems with respective canisters and masks.

59



TABLE 5. Average Flow (Liters/Minute, NTP) and Standard
Deviation Across Canister(s) by Minutes (0-27 Min)

briefly generalized in Table 6.

Mode of Operation

nitrogen and are corrected to NTPD,

65

Single Canister. Dual Canisters
@W= 14) @ = 8)

Min. X_+ $.D. X_+ S.D.
T 3.90 0.74 7.37 0.46
2 3.84 0.51 7,25 0.54
3 3.71 0.50 6.38 0.75
4 3.95 0.68 6.37 0.79
5 3.60 0.90 6.59 0.79
6 3.62 0.80 6,83 0.97
7 3.77 0.91 6.67 1.146
8 3.70 0.51 6.95 0,92
9 3.89 0.42 7.02 1,12
10 3.75 0.53 6.50 1.22
pe 3.70 0.53 6.63 1.29
12 3.37 0.48 6.61 0.63
13 3.20 0.67 6.30 0.63
14 3.39 0.29 6.25 0.61
is 3.29 0.34 5.97 0.70
16 3.33 0.22 6.03 0.51
17 3.29 0.22 6.28 0.47
18 3.36 0.27 6.43 0.26
1g 3.28 0.23 6.37 0.36
20 3.24 0,27 6.39 0.40
21 3.32 0.28 6.51 0.35
22 3.42 0.19 6.40 0.17
23 3.41 0.16 6.37 0.42
24 3.46 0.23 6.84 0.40
25 3.54 0.16 6.66 0.52
26 - 3.51 0.26 6.85 0.48
27 3.59 0.45 6.80 1.02

TABLE 6. Tracheal Oxygen Partial Pressures Maintained
in Human Subjects by Scott Med-Ox Generator Units

Single Canister Dual Canister
Low Subject 200-250 mmp0 300-350 mmp0z

High Subject 300-350 mmp02 450-520 tampO>

Note: All values are calculated from end expiratory

Tracheal oxygen partial pressure varied greatly between sub-
jects and appeared to be highly influenced by respiratory rate and
tidal volume as limited by a 15-L minute volume, These date are



Subjects wearing the mask were exposed to a rapid decom
pression in the altitude chamber to support this conclusion.
During light exercise following decompression from 12,000 to
40,000 ft, the subjects wearing this mask maintained useful
consciousness for periods of only 36 to 98 s (Table 2). The one
subject: (a high-altitude researcher) who was capable of maintain-
ing useful consciousness for a period of 98 8 has, by the process
of acclimatization and hyperventilation, previously demonstrated
an ability to maintain consciousness without oxygen for record
periods of 30 min at 30,000 ft. He was observed hyperventilating,
possibly from habit, with a tidal volume in excess of 2,500 cc
during the resting decompression. Hyperventilation and large
tidal volumes tended to increase both leakage and oxygen dilution
when this subject wore a phase-dilution passenger mask, thus
accelerating the onset of hypoxia with the result that he was
forced to descend before the 5-min dwell at altitude was completed.
In his succeeding decompression while exercising he appeared to
be overcompensating by breathing slowly and shallowly, thereby
maintaining useful consciousness for a period of 98 6, consider-
ably longer than any of the other subjects during exercise. This
subject's data should not be considered representative, These
data point out, however, both the deleterious and advantageous
effects one may exert on the performance of this type of oxygen
mask by the introduction of voluntary hyperventilation and
hypoventilation. . '

Mean heart rates increased considerably during decompression
and dwell at altitude, returning to the preflight level on descent
to ground level (Table 3). This increase indicates that a certain
amount of apprehension and stress was associated with the decom-
pression which, in turn, would produce increases in minute and
tidal volumes over the levels established just prior to decom-
pression. Direct measurement of minute and tidal volumes was not
possible, however, when the passenger masks were worn during
decompression.

Increases in minute and tidal volumes as a result of appre-
hension and stress, when superimposed on those levels established
during exercise prior to decompression, could well have increased
ventilation above experimental design levels. Increased ventila-
tion and the resultant leakage could account in part for the
tracheal oxygen partial pressures being considerably lower than
predicted from the previous study at ground level (2). Of prime
interest, however, is that in only one instance, even when the
subject was quietly resting, did the tracheal pO. following
decompression to 40,000 ft meet the minimum requirement of
Part 25.1443 of the FARs (Table 1). The approximate point at
which exercising subjects lost useful consciousness, as deter-
mined by their inability to continue sequential counting, is
compared to the onset, frequency, and duration of electro-
encephalographic slow waves as shown in Table 2 and Figure 1.

ll

39107 O- 1-3 ,



References

Reteren*

Harwood, V. Nt Chemical Oxygen Generators for Business and
Utility Aircraft. SAE Report No. 710390, 1971.

Douglas Service Supplement, DC-10 Oxygen, Revision 1, 1973.

Douglas Aircraft Company Specification Control Drawing No.
88277, Generator, Oxygen, Chemical. August 19, 1969.

Luft, U. C.: Evaluation of the K+S Disposable Oxygen Mask.
USAF School of Aviation Medicine, Special Project, December
1950.

McFadden, E. B., We Narrison, and J. M, Simpson: DOT/FAA
Civil Aeromedical Institute, unpublished data.

NASA Life Sciences Data Book, 1.D.-l, Decompression Events
and Unconsclousness, June 1962.

Haber, F., and HW. G. Clamann: USAT School of Aviation Medi-
cine Project 21-1201-0008, Report No. a, 1953.

93

seeerengrennen nearer ee one


References.

Bendix Corporation, Pioneer-Central Division: Final Report
on the Investigation of Mask Leakage in Passenger Oxygen
Masks, FAA Contract Number PA-885, 1962.

McFadden, E. B., J. W. Raeke, and J, W. Young: An Improved
Method for Determining the Efficiency of Crew and Passenger
Oxygen Masks, FAA CARI Report No. 62-21, 1962.

Federal Aviation Regulations Part 25,1443, Department of
Transportation, Federal Aviation Administration.

16

anes patina pe se NS tren De

}
{



of Ambient Air aod Oxygen Content of Inspired Cas
Cesena Mask at 25,000 ft as Derived Froe
Estimates of End Expiratory Nitrogen

welo

Exercising, First and Third Minutes at 25,000 ft

End Percent Oxygen from Calculated
Exptratory Dilution Supply + Pr
Nitrogen cent Supply Ambient Ambient 2 emt
Minut Miout

Subject Sex N 2
oR " ah 4756 4e 40 5H 5a
aT " 35 3682 9 10 65 62 183146
au r 38 408. S20 49) 10h ZG
we r 38 40 52 49 1062 GC
w r 33500 S683 9 10 65 «63853148
on F % 2833 6768 7 7 Te Th 189
cr « 45 4357 43 66 PSS STH
Bit “ 40203351 o 38 on 9 60 6F Ah 158
w m aS 4257 4300 4000 12358553,
Dz " 3s 38h BSH 82 9 10 65 62 153 146
Mesa 38.1 39.1 68.2 49.6 $1.8 50.6 10.2 10.5 61.9 60.9 145.5 163.3
Reading, Fourth and Sixth Minutes at 25,000 ft
i

4 | 6 4 & 4 6 4 & ih C3 4 6
pR " 38 400 BSR 52 aa 2k
a " 400 430 SLO th gw 6057
Ju r 4 45527 aw 22 39 58138129
1 F 42 62 5353 lL 58 SB 136136,
ey F 7 35 47 bh SH 9 63 6348153
oat r 1 r,t 7 es) 7 1000 730 63s
cr n peas nS a) © © S| OS YS
oH " 430 8h Sa S246 Bak 5759 ae a
wv " sz 600 53 SR aga 58 60 aa F
Dz " pare Su > OO SOY ES oP
Mean 39-3 40.6 49.7 51.6 50,3 68.6 10.4 10.8 60.7 59.4 142-7 13906

4a



|
tee 2,065 fe} ) (? )
(2.7 fe?) 0,130 te7s) 1

t " approximately 2.2 5
Condition B:

Total volume 2,065 fe?

Area forward penetration 230 in?

(aft penetration not included)
Total area apprexinately 1.60 ft2

- 3
8” (rey Comes teas) ("1)

te = approximately 2.8 5

Walle these decompression times are only est inmates, they do
reflect the Severity of the decom

pression in the forvard cargo
and belly compartments, the result of a large penetration area
working against a small volume,

| The forward cargo Compartment ts se;
galley by ewo cargo doors. These doors,
constitute a Pressure-tight bulkhead.
mounted around the perine

Parated from the lower
though closed, do not
There {8 a rubber seal
ter of each door on the forward face.

to these doors indicates a Tapid decom-

€Y, contro!ling the Pressure differential
ts.

Pression in the lower gall.
between the two compar trent

Using the equation of Haber and Clamann (7), a decompression .
for the Salley compartment could be estimated as follows:

Condition Az

Volume of lower galley 1,670 fr3
Area of orifice 1/8 tn x 220 in
x two doors 55 in?

Area of orifice (approximately) 0.38 fe2

©” sree tHe) (1)

te ". approximately 9,7 6

89



one extended-duration flight dropped to 83 percent at 70 psi and
75 percent when the supply pressure was reduced to 60 psi.

It must be realized that these tests were carried out under
laboratory conditions with masks of the proper size and correctly
donned. Under actual conditions of use, care and caution may not
be as ideal.

The data indicate that flows to the mask should be increased
for altitudes above 25,000 ft. Above 28,000 to 30,000 ft a much
safer alternative is to use a nondiluting mask supplied with an
adequate flow to insure 100 percent oxygen.

Probably the largest amount of experience relative to the
occurrence of hypoxia at altitudes of 25,000 to 30,000 ft was
gained by the Army Air Corps in World War II in B-24 and B-17
aircraft. Hypoxic incidents were four times more frequent in
the B-17s operating at an average altitude of 25,000 ft than in
the B-24s operating at an average altitude of 22,000 ft, The
average highest altitude for the B-24 was 25,000 ft; for the B-17,
30,000 ft.

The Army Air Corpse reported 10,700 cases of hypoxia resulting
in unconsciousness and 110 deaths during World War II operations.

In addition to hypoxia at flight altitudes of 25,000 to
30,000 ft, in unpressurized aircraft there is the problem of
dysbarism or effect of reduced pressures on the body exclusive
of hypoxia, The literature is so extensive in this area that it
will not be referenced in this report. However, the altitude
range of 25,000 to 30,000 ft is considered a critical area in
which bends are likely to develop in as little as 15 to 30 min.
Obesity is a predisposing factor and deaths have been reported
as low av 22,000 ft (6).

28

saat en



‘

cent nig pec SOT

BET 09 86 0-04 ts 06 is Buys zozaxq
OL 6s Ose ole 7S 99 9S BuzI89q S
s? 9S 9f Orly 99 . 96 09 Bupsporaxg |
9e9 74 _ 0°99 18 92T a Bupasey 9
69 ss Ww 0°99 09 92T BL Buyspo1axg
987 Tot _ O°9e 69 £6 ze , SuzIsay
76 $9 “9 Orly 09 62T 09 Buyasey £
09 zs 1s O°6€ 99 TT tL Butsyo1exy
61zZ 9s €8T Ooty 98 80T ZIT ,2uTisey
ete 98 ied 0°9L 09 ze (a4 ‘Buyasey z
6 zs 69 ol” gL . dtr (za Buysyo10xg -
977 BL _ S"0v as 18 09 aupasey T
(opnataqe 38 6) (Byam 28 UF eT) ~ (8) IBTJIseg Woysseaduoseq Bystizeaa UOFIFpuoD oafqns
Pe zepszuy Zo. qBnod Teyauanbas autlL saley veg
qua2saq dy upequpey o2 uoyzssaidmosag
AdTTIQeuy

SBA JuUeDsep pus £1032e;sTIes SEA UOTIFPUOD TedTZoToTS{ud $,20ef
*23 000'SE 02 Q00'ZT wory passerduooap sea ‘pazou UoFIFpuoy Buz

“Sup? pezeotpuy ayy Je porezazuy
Qns ay IeyI sajestpuy auTT peyseaz

asay ‘¢ ‘oy Joafqns

, (33 000'0% 03 000‘zT

2@TP Jorg votssezdmosaq)

ASP AsV] szasuasseg ay Suyzeoy
s299fqns 30 sewpy aansodxg pue ‘saqey 2039 ‘saT}302q Uotssaidzozag = -¢ gZTEVL

cee

12



Altitude
(fey

14,000
25,000

14,000
25,000

TABLE 21. Percentage of Ambient Air and Oxygen Content of Inspired con Vatng

the Censns Mask During l-Hour Extended Chamber Flight at 25,000 fc.

Subject DD.

Alternate Pert:

rived

Zep-Aro Orifice (F 365-1080-2). Date

Prow Estimate of the Rad Expiretory Nitregen.

of Exercise and Rest at 25,000 f¢

‘Oxygen Supply Preseure ~ 70 pet

Condition End ————Tefeent Onygen from Calculated
and Tise Expiratory Dilution Supply + ro,
at Nitrogen Percent ‘Supp ty Ambient Ambient 2
Altitude Minute Minute Minute Minute Minute Minute
Minute) 3 1 3 aL 3 LL 2
Raerclee 50 S263 657i gs 200192
Resting 2000 2200 25 kr 03, 3 6 8 79 188 186
tasretee 3 0 6 os 56 9 12 63 6 asa ka
necting 3 20 ow) 8 n 9 6 67 77) Ase ash
tasrciee % 4s so to 12 6h Saag
Nesting S| a, ac, ne TY p) 6 6 i568 a
tasrelee. 3 4 ogg 33 9 10 676358 tas
nestine %® 22 to 6 6 78 15k age
taerclee oo” 40 47 6053 S10 6d
38-59 .
' Oxygen Supply Pressure - 60 pet
i Ye 188196
3332s gt ? 7 2 1s 69 aa
Az hg a ab 655853 ae
4h teks 9 3-65) 8753209
oF sw oo gg 60 kak
3 35 2) 6s on 1? 6 2 7 eso
3945 sgh 9 100 hk ask aay
a 8 ’ 7 63 93. 53. are
a a a) 9 M65 60 ayaa

55



Using a partial
ure sufe) in
and pressure

pressure vest Ga pr re jerkin or part
combinat fon with prebreathing 100 percent oxy;
breathing is a safer alternative.

N
°

8

Boyle's Low Cotculation

© Lutt Experimental Votus

oa
°

INITIAL INMAL ATION

Oz AT 3OmmMg POSITIVE PRESSURE

2
°°

wo
iy

y
°o

ALVEOLAR OXYGEN PARTIAL PRESSURE (mmHg)
3

yy
Po, at 4,
LAM MLE —

19 = 130,000 ¢
an aoe on ee 3]

o t 23 4 5 6 7 6 9 10 " 2
TIME FROM START OF DECOMPRESSION (s)

FIGURE 2.0 Caleulated alveolar oxygen histertes «

15,240 m (50,000 tt) (Atcer BlookLe

LIL. Summary.

In the event of raptd decompression to flight alttendes of
15,240 m (50,000 ft), the following consideragtons are paramount :

A. 1f-masks are not in use and afr is be

fug .breathed, loss
of conse fousne:

s will occur In approxtmatety lo sor less. The
use of quick-don masks will be ineffective in preventing toss of
conse tousness. :

Los.



10.

lhe

References

Mohler, S$. R., J. A. Sirkis, and R. J. Barowski: Civil
Executive Jet and Air Transport Decompression Experience,
Presented at the Annual Scientific Meeting of the Aerospace
Medical Association, Washington, D.C., April 10-13, 1967.

McFarland, R. AJ: ltuman Factors fn Relation to the Development
of Pressurized Cabins, AEROSPACE MEDICINE, 12:1303-1318, 1971.

Naber, F., and H, G. Clamann: Phystes and Engineering of
Rapid Decompression, Report No. 3, Project No, 21+1201-0008,°
USAF School of Aviation Medicine, Randolph Field, Te:
August 1953.

Nattonal Transportation Safety Beard: Aircraft Acctdent Report
DC-10-10, N6ONA, Report No. NTSB-AAR-15-2, January 1975.

Blockley, W. V., and D. T. Hanifan: An Analysis of the Oxygen
Protection Problem at Flight Altitudes Between 40,000 and
50,000 Feet, Final Report, Contract FA-955, February 1961.

McFadden, E. Be, and M. T. Lategola: Evaluation of the
Sierra MHanging, Quick-Don, Crew, Pressure-Breathing Oxy;
Mask, FAA Office of Aviation Medicine Repert No. AN-66:
1966.

Barron, C. Let Research Studies on Investigation of the
Effects of Slow and Rapid Decompression Upon Humans at
45,000 ft, Final Repert, Contract FA~3082, May 1963,

Noble, L. E., J. C. Davis, I. Margolis, and K. D. Kable:

Hyperbaric Oxygen Therapy in a Case of Prolonged Hypoxia

Following Rapid Decompression, Published in the Preprints
of the Annual Scientific Meeting of the Aerospace Medical
Association, Bal Harbour, Florida, May 6-9, 1968.

Luft, U. C.: Physiological Aspects of Pressure Cabins and
Rapid Decompression, Chapter 8, pp. 129-142, In W. M.
Boothby (Ed.): Handbook of Respiratory Phystology, USAF
School of Aviation Medicine, Randolph Field, Texas, 1954,

Luft, U. C., BR. W. Bancroft, ‘and E. Carter: Rapid Decom-
pression With Pressure-Demand Oxygen Equipment, Report No. 2,
Project No. 21+1201-0008, USAF School of Aviation Medicine,
Randolph Field, Texas, 1953.

Clamann, H. G., U. C. Luft, and 8, F. Adter: Alveolar Gases
in Rapid Decompression to High Altttudes, Report Ne. 1,
Project No, 21-02-046, USAF. School of Aviation Medicine,
Randolph Field, Texas, 1948.

110


METRIC CONVERSION FACTORS

1 RAN AnAnAN u An nl

; j F Po it
Hil nh oi fad
i bess Wis of. | a td

nnn
a

i 885 Banks of. FEE

. ;
Poa bas

i weve wks ae 22 sink

;
é .
=| 3 J 2
Ssacs Befose Ho§.. Fs.se . Ss} 2
g] 33 F al eae Bl sts 2
3 : Fi
. §# :
ES

Ann |

be
rnp

q

nn

oe sheanen tae Me ba Te
erty

Ta, were cmb

stat bia cmniee Vo ear tonne
Seva 0 Race eat aoe



BAROMECTRIC PRESSURE —mm Ho

aes pee ane OE A ANE REMERON RRS SS PK I,

40
60 | . -] 60,000
80 -— e
; + 50,000 w
too L- Rapid decompression starting at 40,000 feet ___ | w
Breathing 100% O, throughout | 45,000 1
120
000 8
140 40, S
160 ad
rad
eo =| 35,000 J
&
200 z
w
220 J 30,000 3
240 >
3
260 w
260 x1 28,000
300
° 20 40 60 80 100 120 140
TIME OF CONSCIOUSNESS — SECONDS
FIGURE 2. ‘Two decompression conditions and the time of

consctousness for each type as a function of
barometric pressure at the end of decompression
and for comparison of a third curve showing the

effect of removing the oxygen ma:

at altitudes

from 30,000 to’ 43,000 ft. ‘ihe rapid decompres-
sions shown for air breathing throughout start
at 10,000 fc. (Adapted from Af Manual 160-5,
1954; and Blockley and Hanifan, final report

on contract FA-955, FAA, 1961.)

87



\
80.0- NASAL PROBE -

30 sec

80.04 |. FACEPIECE PROBE _—

59.0

FIGURE 4. Simultaneous measurement of nitrogen by probes inserted
in nostril and the Cessna mask fatepicce. A dashed
line is drawn through the end expiratory points.
Sudject DD, First minute of exercise at 30,000 feet.
The slope indicates the increase in end expiratory
nitrogen during transition from resting to exercise.
Recording must be read from right to left.



EFFECTIVENESS OF A PAPER CUP AS AN AID
TO PROVIDING OXYGEN TO LARYNGECTOMEE PASSENGERS

BE. B. McFadden

Several air carriers have incorporated instructions in their
training manuals describing the disconnection of the standard
phase-dilution passenger oxygen mask and insertion of the oxygen
hose through a hole punched in the bottom of a paper cup for
administering first aid oxygen to laryngectomee passengers. The
use of a paper cup attached to a hose delivering a continuous
flow of oxygen to a tracheostomy breather, or even to an oral
breather, {s a most inefficient and ineffective approach to admin-
istering first aid or emergency oxygen.

The characteristics of human respiration as related to the
administration of oxygen by continuous flow are not generally
well understood. The inadequacy of the paper cup technique may
be illustrated by considering the following characteristics and
approximate values of respiration for an individual at rest: (1,2)

Minute Volume ~ 7 L/min (total volume of air breathed over
a span of 1 minute in liters per minute)

Tidal Volume =~ 0.7 L (volume of air breathed each breath
in liters)

Respiration Rate - 10 (number of respiratory excursions over
a span of 1 minute)

Where: Respiratory Rate = Minute Volume = 7 L/min = 10

Tidal Volume 0.7L
and
Tidal Volume = Minute Volume = 7 L/min = 0.7 L
Respiratory Rate 10
or
Minute Volume = Respiratory Rate x Tidal Volume =

10 x 0.7 L* 7.0 L/min

The peak inspiratory flow is the rate at which air is inspiréd
during the 1.0 to 1.5 seconds of each tidal volume (at a rate of
three to four times the minute volume) (1,2), which would in this
‘case approximate 25 to 30 L/min. Moderate exercise or activity
may increase the peak inspiratory flow to 60-65 L/min.

If one considers that the maximum oxygen flow required from
a first aid portable oxygen cylinder is 4 L/min STPD* per

*STPD - Standard temperature O°C, pressure 760 mmiig, dry.

94



100 % :
§ 90%) '
3 80%}
ec
& 70%
a 60%; |
E 50%] 3 NY N
Fg VIN \\ N
a 40% N N N N N N
. VVNVNN NNN
5 30% N N N N N
= S
3 2o%t | VV NNN NN N \
E io%t NN N N \ N N N \
3 NNN NNN NNN
Time-Minutes |_/ 3] 3 6]/ 3]3 6[/ 3|[3 6
Activity Exercising | Reading | Exercising | Reading |Exercising) Reading
Altitude 20,000 25,000 30,000
I$ % 02 Derived from Supply % Ambient Air
FIGURE 6. Histograph showing dilution of inspired gas with

201-212 O-19-8

ambient air as calculated from the end expiratory

nitrogen concentration.

Subjects exercising and

reading at 20,000, 25,000, and 30,000 feet while

wearing the Cessna mask.

35