TABLE I

Acquisition and Donning Times of
the Prototype Life Preserver

Subject Age Acquisition Donning Total
Number (yr) Time (s) Time (s) Time (s)
006 22 6.8 12.8 19.6
008 56 4.7 18.9 23.6
010 27 5.3 13.6 18.9
019 34 7.6 23.1 30.7
022 34 4.8 16.4 21.2
024 31 7.5 14.8 22.3
031 29 * 30.9 *
048 22 5.0 20.3 25.3
051 33 * 13.8 *
052 46 * 12.3 *
063 47 5.7 24.9 30.6
069 59 * 12.6 *
081 60 * 28.4 *
084 45 * 12.5 *
087 66 15.4 21.6 37.0
090 43 * 18.0 *
092 21 * 11.1 *
098 59 9.3 12.0 21.3
100 35 4.7 11.2 15.9
104 42 * 13.0 *
112 55 5.3 16.0 21.3
116 61 11.2 13.6 24.8
119 63 9.7 25.9 35.6
122 56 22.5 24.6 47.1
126 47 * 16.4 *
130 61 * 17.5 *
Mean 44.4 8.4 17.5 26.3

*Could not determine beginning of acquisition time because subject's
body position blocked the view from preset camera angle.

14


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Figure 3.

Standard Personal Flotation Device

(Back View).

A. High inflatable collar for
support of head and neck

B. Waist strap


TABLE V

Estimated Times to Reach Two Predicted Lethal Rectal Temperatures

Time (h) to 34.4 °C Time (h) to 30.0 °C

Subject Vest 1 Vest 2 Vest 1 Vest 2
JA 14.7 19.0 34.5 43.4
PP 12.0 6.6 25.4 14.3
MS 3.7 3.9 8.7 8.6
KB 3.2 4.1 7.3 9.4
OB 1.8 6.4 4.4 15.3
BP 2.3 2.6 4.7 5.4
MJ 1.7 2.7 3.7 5.9
AR 2.1 3.4 4.1 7.5
kT 1.2 1.8 2.7 3.9
GR 1.0 1.5 2.2 3.3
Mean 4.4 6.5 9.8 11.7

Standard

Deviation 4.9 6.9 11.0 11.8

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TABLE VII

Urine Volumes (in Cubic Centimeters)
for Subjects During Cold Water Immersion Tests

Wearing Wearing

Subject Vest 1 Vest 2
JA 510 540
PP 720 730
MS 830 330
KB 400 670
OB 230 260
BP 300 485
MJ 200 535
AR 170 500
KT 230 200
GR 375 540
Mean 397 479

Standard

Deviation 226 169

54


13.

14,

GPO 920-074

Hayward JS, Eckerson JD. Physiological responses and
survival time predictions for humans in ice-water.
Aviat. Space Environ. Med. 1984; 55(3):206-11.

Bynum GD, Goldman RF, Stewart J. Whole body cooling
with protective clothing during cold water immersion.
U.S. Army Research Institute of Environmental Medicine
Technical Report T 1/80, 1980.

/296802!
bee

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46


Not only is there a failure of the vasomotor tone, but
death due to cardiac arrest may also occur. Golden (4)
stated, "In humans, death due to cardiac arrest appears
to occur between 24 °C and 26 °C, but there have been
cases of accidental hypothermia surviving core
temperatures of 18 °C."

Metabolic Heat Production

Under basal conditions when no work is being done,
all the metabolic energy appears as heat. During
physical exertion, more than 75 percent of the increased
metabolism appears as heat within the body, while the
remainder of energy is converted to work (12).

If an unclothed man is exposed to an environmental
temperature below 28 °C, a rise in heat production
occurs. This rise in metabolic rate occurs primarily in
the skeletal muscles, even before shivering is initiated
(12). During cold water immersion when shivering
reaches its maximum at a core temperature of 35 °C (4),
the overall heat production may be as much as 4.5 times
the resting rate (10). Although shivering increases
heat production, it also presents problems in conserving
heat. Boutelier (1) explains this phenomenon as;

This production of heat by shivering is not entirely

beneficial. Indeed, rapid muscular shaking has the

effect of disturbing the boundary layer of still
water in the vicinity of the skin and, consequently,
leads to an increase in the coefficient of heat
exchange in water. In addition, shivering helps to
maintain a higher temperature difference between the
skin and the water than in the case of passive
cooling and increases the losses by convection.

Finally, the increased oxygen consumption leads to

an increase in ventilation and in the heat losses

through the respiratory tract.
When core temperature is between 27 °C and 30 °C, the
metabolic rate returns to a resting level (4).

Cooling Rate

If protection is not provided in water temperatures
below 25 °C, heat loss overcomes heat production and
core cooling results (10). The cooling rate of humans
immersed in cold water is largely dependent on
individual variation. The major factors that influence
cooling rate are human differences (body size, body
build, subcutaneous fatness, and shivering response) and
behavioral effects (activity and posture). The
following outline describes these factors (10):

Individual Differences

Body Size: Small body size has a greater
surface area relative to volume. The greater

18


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LIST OF FIGURES

Figure
1. Standard Personal Flotation Device (Front View). -
2. Standard Personal Flotation Device (Side View) . .«
3. Standard Personal Flotation Device (Back View) . .
4. Prototype Life Preserver (Front View). . + + ++ +
5. Prototype Life Preserver (Side View)». + + +++
6. Prototype Life Preserver (Back View) »- - + + e+ ¢
7. Package Comparison . + + + + s+ e+ ee se ee ees
8. Subject Instrumented With Adhesive Chest

Electrodes . . ee ee ee te te et ee ee et
9. Subject Demonstrating a Face-Up Flotation Position
While Wearing the Prototype Life Preserver .- + + +
10. Subject Demonstrating a Face-Up Flotation Position
While Wearing the Standard Life Preserver. - + + +

11. Change from Initial Rectal Temperature (°C) Over
Time During Immersion - Subject JA... + + ee es

12. Change from Initial Rectal Temperature (°C) Over
Time During Immersion - Subject PP.» + + + s+ 6 +

13. Change from Initial Rectal Temperature (°C) Over
Time During Immersion - Subject MS . . + + + + + +

14. Change from Initial Rectal Temperature (°C) Over
Time During Immersion ~ Subject KB. + + + + +e s

15. Change from Initial Rectal Temperature (°C) Over
Time During Immersion - Subject OB . . + + + se +

16. Change from Initial Rectal Temperature (°C) Over
Time During Immersion - Subject BP . . + + + se +

17. Change from Initial Rectal Temperature (°C) Over
Time During Immersion - Subject MJ. . + + + ss +

18. Change from Initial Rectal Temperature (°C) Over

Time During Immersion - Subject AR. «+ + + e+ es +

10
11
15

23

25

26

29

30

31

32

33

34

35

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A. Prototype life preserver
B. Standard personal flotation device

15



Each subject gave his informed consent to participate
after being familiarized with all the procedures and purposes
of the experiment. The safety criteria required that no
subject be using any medication. In addition, subjects were
required to pass a medical examination. This examination
required a medical history, a physical examination given by
an FAA physician, and the donation of blood and urine for
analysis.

After acceptance by the physician, the subject proceeded
to the survival tank to participate in a trial test. The
subject placed a flexible rectal thermistor probe approxi-
mately 10 cm (4") beyond the anal sphincter for the
measurement of internal body temperature. The subject was
also instrumented with adhesive chest electrodes (Figure 8)
to which wires were connected for the recording of heart rate
and electrocardiogram (EKG). After instrumentation was
completed, the subject donned the standard PFD or the
prototype life preserver and entered the water for a 15-min
period. This trial test gave the subjects an opportunity to
become familiar with test procedures and to determine whether
or not they were willing to participate in the study. If the
subject passed the medical examination and was willing to
participate, the tests were then scheduled.

Experiment Design

Table III outlines the experiment design for this study.
Iwo subjects were tested at one time. Two positions in the
pool were selected to ensure that both subjects were equal
distances from the water current generated by the inlet
ports. The prototype life preserver was assigned to position
1 and the standard PFD was assigned to position 2. Each
subject wore the prototype in one experiment and the standard
PFD in the other experiment. At least 48 hours separated the
two experimental tests. The prototype life preserver and the
standard PFD were tested on the same day. All subjects wore
standard cotton shorts and athletic supporters during the
tests.

Instrumentation

The subjects were fitted with three adhesive chest
electrodes (Beckman well electrodes, Ag/AgCl, Beckman
Instruments, Inc., Fullerton, CA 77036) to which wires were
connected for the recording of heart rate and EKG. The CM5
single lead was used to monitor EKG function. The EKG cable
was connected to remote monitoring and recording equipment.
The EKG was monitored on an electrocardiograph (Burdick EK-
5A, The Burdick Corp., Milton, WI) and simultaneously was
continuously recorded on a polygraph (Grass Instrument Co.,
Quincy, MA). The heart rate was also monitored on a heart
rate meter that continuously averaged the preceding four
beats (Burdick CSS-61, The Burdick Corp., Milton, WI).

21



states the effectiveness of counter~current heat

exchange as:
This veritable thermal "shunt" is a particularly
effective mechanism; on the one hand, the arterial
blood reaches the extremities at a low temperature,
so that the heat loss in the extremities is limited
by the fact that the temperature difference between
the environment is reduced and, on the other hand,
the gradual rewarming of the venous blood from the
periphery reduces the cooling of the central parts
of the organism.

Most of the heat loss from the body in moderately cold

water therefore takes place from the trunk and not the

limbs (11).

In very cold water (less than 10 °C), cold-induced
vasoconstriction may be replaced by cold-induced
vasodilation due to the cold paralysis of the vascular
smooth muscle (10). This reaction is generally confined
to the extremities and involves sudden bursts of
vasodilation, which brings a flow of warm blood to the
extremities (1). However, this condition may be
insignificant to increases in core cooling rate.
Hayward (10) explains the possible effects of cold-
induced vasodilation as:

This condition is very obvious from the reddening of

the skin of subjects during prolonged immersion in

cold water. However, this author has not observed
sudden increases in core cooling rate commensurate
with skin vasodilation. It is probable that
constriction of deeper vessels in warmer tissues is
being maintained such that skin blood flow is
negligible despite skin dilation.

This rewarming of the skin appears to be considered a

protective mechanism in the prevention of cold injuries

to the skin.

In regard to other cardiovascular responses to cold
water immersion, the heart rate, blood pressure, and
cardiac output are also affected. In the initial
stimulatory phase, the heart rate increases
dramatically and there is an increase in arterial
pressure and cardiac output, accompanied by intense
peripheral vasoconstriction (1). As hypothermia becomes
established, the heart rate and the cardiac output
decrease simultaneously with the drop in body
temperature (1). This cardiac response appears to have
no consistent relationship to peripheral vasoconstric-—
tion. Boutelier (1) stated:

Peripheral resistance shows an opposite change from

that of the cardiac output, increasing as the body

gets colder. However, if the rectal temperature
falls below 25 °C it decreases, showing that there
has been failure of vasomotor tone.

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30


for small females is attained when the vest is inflated.
Another guideline for sizing was the waist measurement..
Thirty-eight inches was selected. This is 14.6 inches larger
than the 5th percentile adult female waist and 1.6 inches
smaller than the 95th percentile male waist. The large waist
measurement was chosen primarily to enhance the ease of
donning for the large individuals. When inflated, the proto-
type life preserver contracted approximately 3 inches in the
waist. To provide a better fit and to restrict water entry
for smaller adults, a belt that could be cinched was attached
to the lower part of the prototype. The belt is also needed
to maintain the bladder tightly against the body during
immersion. The closed-cell neoprene in the back provided
ample stretch for the larger individuals.

So that it would self-right the wearer in 5 s, the vest
was designed to place the majority of the buoyancy in the
upper chest portion of the prototype life preserver.

Early in the development, a waterproof zipper (open at
both ends) was considered. However, this design concept was
deleted because the zipper was difficult to close and was
expensive. Unlike conventional zippers, the waterproof
zipper had to be turned to the inside before it could be
fastened at the bottom.

Another discarded design concept was the use of goose
down feathers placed inside the air bladder. The feathers
were considered due to their high insulating value and
compressibility. However, from a manufacturing standpoint,
it was impractical because of the difficulty in keeping the
feathers inside the bladder during the production process.
They also increased the cost significantly.

One other design feature tried, but discarded, was the
placement of closed-cell neoprene around the armholes and
at the waist to increase sealing and prevent movement of
water inside the vest. It was found, however, that this
design feature slowed donning efficiency.

Achievement of Goals Other Than Thermal Protection

Goal 2: Provide at least 35 pounds buoyancy

The final prototype life preserver was tested for
buoyancy using an Instron Universal Testing Instrument
(Model 1123). The initial buoyancy was measured at 38
pounds. Buoyancy was measured at three consecutive 30-
min periods following the initial measurement and was
unchanged.

12


In order to further evaluate the practical significance
of increased thermal protection, the cooling rate data of the
Present study were used to predict time to reach two rectal
temperatures (34.4 and 30.0 °C) in 12.8 °C water. Hayward
and Eckerson's formula (13) was used with the cooling rate
data to estimate predicted survival time. For both rectal
temperatures, the mean estimated predicted survival time was
greater for subjects wearing the prototype life preserver
than when the same subjects wore the standard PFD.

Each subject's heart rate for each vest was recorded
continuously on an EKG polygraph. Recorded heart rates were
counted at 5, 10, 20, 30, and 40 min of immersion and again
during the last 4 min of each subject's immersion test when
the rectal temperature was expected to be at its lowest. A
paired t-test was used to determine significant differences
between heart rate with the two vests.

At 5 and 10 min of immersion, the type of design worn
did not significantly affect heart rate. However, beginning
at 20 min of immersion, the mean heart rate for subjects
wearing the prototype life preserver was significantly lower
than for subjects wearing the standard PFD. The significance
became greater with time of immersion.

CONCLUSIONS

The following general conclusions were drawn from the
study:

1) Under the conditions of the test, the prototype life
preserver provided additional thermal protection for 8 of 10
subjects.

2) The prototype life preserver provided greater than
35 pounds of buoyancy.

3) The prototype life preserver was able to self-right
the wearer in 5 seconds.

4) The prototype life preserver provided a satisfactory
‘fit for a wide range of adult sizes.

5) The prototype life preserver provided an average
donning time of 17.5 seconds, with 60 percent of the subjects
able to accomplish donning in 15 seconds or less.

6) The prototype life preserver weighed no more and
required no more storage space than currently used personal
flotation devices.

Based on these findings, the prototype life preserver
has features that indicate an improvement in protection for
aircraft passengers in the event of accidental submersion in
cold water compared to currently used designs.

56


project was accepted by a graduate student, Ms. Karla
Knoepfli, under the supervision of her Major Professor,
Dr. Donna Branson.

Ms. Knoepfli's work and the initial work of the Survival
Research Unit were reported in a Protection and Survival
Laboratory Memorandum in October 1983 (6). In the early stages
of life preserver development, it was advantageous to develop as
many prototypes as possible. As the work progressed, it was
clear that some ideas should be discarded while others should
be pursued further. Among those discarded were the use of a
closed-cell flotation foam, hoods, slipover styles, D-rings
with snaps, buckles, and crotch straps. Some ideas retained
for further investigation included the use of Gore-Tex
covered Thinsulate as insulation, zippered fronts, high
collars, pull-type cinching straps, and expansion panels.

Ms. Knoepfli's subsequent work dealt primarily with
universal sizing techniques.

In December of 1983, the senior author accepted further
work on life preserver development with renewed emphasis on
thermal protection. The senior author accepted the project
as an OSU graduate student and subsequently as a member of
the Survival Research Unit, CAMI. Three prototypes were
developed; however, this report gives results of the
evaluation of the final prototype, which most closely met the
original goals.

DESIGN DEVELOPMENT

In the development of the design for the prototype life
preserver, consideration was given to all the goals stated
above, although the primary goal was to provide increased
thermal protection.

To be able to keep the weight and storage size at or
below those of currently used PFD's, any consideration of a
full protection suit was eliminated. To allow for ease and
speed of donning and yet provide thermal protection,
attention was focused on a life preserver that covered the
upper torso. Because of the limited weight, consideration
was given to lightweight materials and closure devices which
had the ability to be folded compactly, yet provide thermal
protection. Polyurethane-coated nylon was used for the air
bladder portion of the prototype life preserver. Heat
sealing equipment was used to bond the polyurethane film
together for an airtight bladder. A light weight conven-
tional zipper was used for closure and one-eighth inch closed
cell neoprene was used in the lower back region. A jacket~
style air bladder was designed so that the major heat loss
areas of the upper torso were protected. Studies using
infrared pictures (7) have indicated that the upper chest and
back, sides of the chest, and groin area are the major heat
loss areas during immersion. Protection for the groin area


collected and measured. During the rewarming phase, subjects
were provided Gatorade* to drink for rehydration. When
internal body temperature reached 36.5 °C, subjects were
allowed to take a warm shower, then dress.

Test Conditions

During the period of the study, the water temperature
was maintained at 12.8 °C (55.0 °F) +- 0.5 °C and the air
temperature was 21.1 °C (70.0 °F) +- 1.7 °C, Water
temperature was measured at various locations around the
tank, on all four sides and at varying depths. It was
measured with a rectal thermistor probe (Yellow Springs
Instrument 701). The range of water temperature measured
varied only 0.75 °F.

Data A sis

The subject's rectal temperature, while wearing each
vest, was graphed over time. Rectal temperature was measured
and recorded every 2 min. Least squares regression was used
to fit the data to a straight line for determining the slope
from which a cooling rate was established. A paired t-test
was used to determine significant differences between cooling
rates for subjects wearing the two vests. Differences were
accepted as significant at the 0.05 level of confidence.

To determine the rate of cooling, a "linear model" was
adopted for this study, which involves two parameters: the
time (t) that internal body cooling was established at a
fairly uniform rate for all subjects (20 min) and the rate of
cooling (r) following this time. The rate of cooling was the
slope of the regression line, which was determined from the
datum point obtained at t to the last datum point recorded.

Hayward and Eckerson's formula (13) was used with the
cooling rate data to estimate predicted survival time (pst).
It must be noted that the pst estimates are based on the
assumption that the linear cooling rates established during
the experimental tests would continue until a lethal level is
reached. In this study, estimates of pst for two rectal
temperatures (Tr) were determined: 34.4 °C, which is the
critical temperature as defined by Beckman et al. (5), and
30.0 °C, the critical temperature as defined by Hayward and
Eckerson (13). The same formula was used for both
determinations:

pst = (Tr at 20 min - lethal Tr)/cooling rate + 20 min

Each subject's heart rate was recorded continuously.
Recorded heart rates were counted from the EKG polygraph at

*Registered Trademark

27



A BIO-TEK analyser (BIO-TEK Instruments Inc.,
Burlington, VI) was used to check the equipment to ensure
that the hazard of electrical shock to the subject was within
acceptable limits.

Each rectal thermistor probe was calibrated with its
designated recorder via a constant temperature water bath
(Haake, Polyscience Corp., Evanston, IL) and a National
Bureau of Standards thermometer. Correction factors ranged
from -0.13 to +0.05 °F,

Experiment Protocol

Subjects were instructed to refrain from eating between
midnight of the preceding day to the end of the test period.
Subjects reported for their test session at 8:15 a.m. The
tests began at approximately 9:00 a.m. Performing the tests
at the same time each day minimized the differential etfects
on body temperature caused by diurnal variation.

When the subjects reported, they were examined briefly
by a physician to ensure that their physical condition had
not changed. Blood pressure, pulse, and oral temperature
were taken. If no changes were detected, they then proceeded
to the survival tank where they were instrumented as during
the trial test. Prior to instrumentation subjects emptied
their bladders as completely as they could.

After instrumentation was complete, the subjects entered
the water. Each test exposure lasted for 2 h or until any of
the following conditions occurred: (i) internal body
temperature reached 35 °C (95 °F); (ii) an
electrocardiographic abnormality was detected; (iii) the
subject requested termination of the test; (iv) the attending
physician requested termination; or (v) physiological
monitoring was lost. The physical activity during exposure
was kept to a minimum. The subjects adopted a face-up
flotation position (Figures 9 and 10).

While in the pool, the subjects were tethered and each
had his own individual observer. A physician, a lifeguard
and a video technician were always in attendance during the
tests. A team of support personnel was also in attendance to
monitor and record heart rate, EKG, and rectal temperature.
When the tests were complete, the subjects were brought out
of the water on a stretcher. The vests were quickly removed
and then the subjects were taken to an adjacent room where
assistance was provided to remove the wet shorts and to put
on a sweat suit. During the changing of the garments, the
rectal thermistor probe remained inserted and EKG electrodes
remained attached to allow postexposure monitoring of the
subjects. When the changes were completed, the subjects were
taken to a warm room where they remained until their internal
body temperature reached 36.5 °C, At this time, urine was

24


DEVELOPMENT AND EVALUATION OF A PROTOTYPE LIFE PRESERVER

INTRODUCTION

The Federal Aviation Administration (FAA) requires that
all commercial extended over water flights must carry life
preservers and other safety flotation devices for civilian
passengers and crews. However, no provisions are made to
protect immersed victims from cold water. Boutelier (1)
states that 47 percent of the ocean waters have a temperature
of less than 20 °C. The ocean waters off the coasts of the
northern United States and Canada range from 0 °C to 15 °C
during the winter. In the United States, 215 airports have
large bodies of water near the airport departure and approach
areas. A representative of the Air Line Pilots Association
reports that 78 percent of airliner accidents occur during
takeoff, climb, approach, and landing (2).

The problem of providing thermal protection for
individuals accidentally submerged in cold water is
acknowledged by the military, offshore oil industries, and
fishing fleets. However, with an increase in overwater air
traffic, the safety of civilian passengers who are being
exposed to the potential of accidental immersion in cold
water also becomes a concern. If this type accident occurs
in water below 18 °C, special protection is needed if victims
are to survive until rescue efforts are successful (1).
Currently, a personal flotation device (PFD) is provided for
civilian passengers; however, this device is designed only to
prevent drowning. Three commonly criticized design features
of the currently used PFD's are: (i) they encompass only
the neck area and no thermal protection is provided to the
rest of the body; (ii) the mean donning time ranges from
28.0 to 37.6 s (3); and (iii) when inflated, the cells form a
"vy" which channels the water directly to the face, increasing
the possibility of drowning.

If a life preserver provides a measure of thermal
protection, not only are the chances of death caused by
hypothermia decreased, but also the chances of death caused
by drowning decrease. For example, Golden (4) reported the
problem of drowning in cold water as:

Normally if you keep your back to the wave, the wave
goes over the head, but when you stop making that
physical effort to keep your back to the waves your

legs act as a sea anchor, the top of the body is
buoyant, the next wave that comes pushes the top of the
body around and you are facing the oncoming wave; you
quickly drown in that situation when you lose control of
respiration. It depends very much on the frequency of
the waves and how much you are able to control your
respiration and judge when the next wave is coming. The

1



Immersion —

Immersion —-

Immersion -

Immersion -

Immersion -

Immersion -

Immersion -

Immersion -

Immersion -

Figure
19. Change from Initial Rectal Temperature (°C) Over
Time During Immersion - Subject KT
20. Change from Initial Rectal Temperature (°C) Over
Time During Immersion - Subject GR
21. Rectal Temperature vs. Time During
Subject JA. 1... 2... ee eee
22. Rectal Temperature vs. Time During
Subject PP... . 2... ee eee
23. Rectal Temperature vs. Time During
Subject MS... 2... ee eae
24, Rectal Temperature vs. Time During
Subject KB... 1... wee eee
25. Rectal Temperature vs. Time During
Subject OB... . 2... eee
26. Rectal Temperature vs. Time During
Subject BP... ee ee
27. Rectal Temperature vs. Time During
Subject MJ... 1... we ee ee
28. Rectal Temperature vs. Time During
Subject AR. . 2... ee we eee
29. Rectal Temperature vs. Time During
Subject KT... 6... wee ee
30. Rectal Temperature vs. Time During

Subject GR... 1... eee eee

vi

Immersion -

Page

37

38

39

40

41

42

43

44

45

46

47

48


Goal 3: Be capable of being donned by an adult in 15 s.

Donning tests were conducted for the prototype life
preserver, and the results are presented in Table I.
The mean donning time was found to be 17.5 s, and 12 of
26 naive subjects were able to don the life preserver in
15 s or less. Acquisition time is also shown in the
table. Acquisition time is the interval from the time
both hands are on the unopened package until the time
the life preserver is clear of the storage package.
Donning time is the interval from the time the life
preserver is clear of the storage package until donning
is complete.

Goal 4: Weigh no more and require no more storage space
than currently used personal flotation devices.

One of the currently used personal flotation devices
weighs approximately 1 pound 8 ounces. Typical airline
storage space for one life preserver is approximately
5.5 inches wide, 7 inches high, and 3.25 inches deep.
The prototype life preserver weighs 1 pound 7 ounces and
can be packaged to fit in the required space. Figure 7
illustrates the comparison in packaging for the
prototype life preserver and the standard PFD.

Goal 5: Fit individuals from the 5th percentile of
adult females to the 95th percentile of adult males in
the United States population.

Not enough data were collected to ensure compliance with
this goal. However, during the donning test, the
prototype vest was donned properly by all 26 naive
subjects, and a good fit was achieved by the smallest
female (5'1/4" tall and 90.25 1b, clothed), the

largest female (5'4" tall and 254 1b, clothed), and

the largest male (5'8 1/2" tall and 235 1b, clothed).
Subjective observations indicated that it would fit an
even wider range of sizes.

Goal 6: Self-right the wearer in 5 s.

Self-righting tests were conducted with FAA personnel in
the CAMI survival tank and with OSU students at the OSU
indoor pool. Each of 12 subjects donned and inflated
the prototype life preserver, assumed a facedown
position in the water, and simulated unconsciousness.
All were righted to the face-up position in 5 6 or less.
The smallest individual was a female who was 4'10" tall
and weighed 90 1b. The largest individual was a male
who was 6'1" tall and weighed 215 1b.

13



Washington, D.C., B-737, January 1982, Unanticipated
aircraft crash into the Potomac River

1) O£ 79 aboard, 73 died of impact injuries, 1
drowned, and 5 were rescued.

2) A Park Police helicopter arrived at the site 21 min
after impact.

3) The one drowning probably did involve the effects of
immersion hypothermia. The water temperature of
near 0 °C (32 °F) was a factor.

The time it took for an effective rescue operation and
the cold water temperatures in the above accidents indicate a
need for a thermal protective life preserver.

In July 1981, as part of an FAA Water Survival Program,
the Director, Office of Airworthiness, requested that the
Office of Aviation Medicine (OAM) conduct research in the
area of survivability in unplanned crash landings in water
for transport and commuter aircraft. The Federal Air
Surgeon (OAM), requested that the Civil Aeromedical Institute
(CAMI) develop the content and resource requirements for a
Water Survival Research Program. The protocol for the
program was prepared by the Protection and Survival
Laboratory. The protocol was approved, and funding for the
program was received in April 1982.

The approved protocol divided the Program into eight
work areas. One of these eight areas dealt with concepts for
improved types of life preservers. In response to this work
area of the approved protocol, the development of prototype
life preservers was initiated.

In June 1982, the Supervisor, Survival Research Unit,
conferred with the Chairperson, Department of Clothing,
Textiles and Merchandising of the Oklahoma State University
(oSU) concerning the possibility of cooperative work on
pattern development using universal sizing techniques for a
vest-style life preserver which also provides thermal
protection. Goals for the prototype were to:

1) Provide increased thermal protection in the event of
accidental submersion in cold waters.

2) Provide at least 35 pounds buoyancy.

3) Be capable of being donned by an adult in 15 8.

4) Weigh no more and require no more storage space
than currently used personal flotation devices.

5) Fit individuals from the 5th percentile of adult
females to the 95th percentile of adult males in the
United States population.

6) Self-right the wearer in 5 5s.

In September 1982, another conference was held with
faculty members and graduate students. In December, the

3



relative surface area has an increased effect on
core cooling rate. Thus, children tend to cool
much faster than adults.

Body Build: For any one body weight and
fatness, ectomorphs have a greater surface area
relative to volume and, thus, cool faster than
mesomorphs.

Subcutaneous Fatness: Extra amounts of subcu-
taneous fatness decrease core cooling rate.
Shivering Response: There are considerable
differences (intensity and ability of main-
taining a high metabolic level) among
individuals in their shivering response to

cold water. Good shiverers tend to cool more

slowly.
Behavioral Effects
Activity: During physical activity, blood cir-

culation is increased to the arms, legs, and
skin. This causes core cooling to be 35 percent
faster than when the individual is holding
still.

Posture: In a curled-up position (arms against
the chest and the thighs against the chest), the
core cooling rate can be reduced by a signifi-
cant amount. —

Objectives

The objectives of this study were to (i) test and
evaluate the thermal response characteristics of human
subjects wearing the prototype life preserver and a
currently used standard PFD, and (ii) estimate a predicted
survival time for these subjects wearing the prototype life
preserver and the standard PFD.

Selection of the Sample

Because of the nature of the exposures during these
tests, no attempt was made to obtain a cross-sectional sample
of subjects. The sample consisted of 10 paid volunteer male
subjects, aged 18 to 35 years, in good health. Subjects were
selected who would be at minimal risk when exposed to cold
water. Table II describes subjects' characteristics.

Because the experiment design required subjects to be tested
on two occasions, the selection of subjects was focused on
individuals who would have a personal interest in the study.
Three subjects were solicited from the Oklahoma City Fire
Department Water Rescue Team, four subjects from the Oklahoma
tate University Scuba Club, and three from the general
public, including one pilot and one individual with prior
scuba diving experience. All subjects were acquired through
a CAMI subject contractor.

19



Technical Report Documentation Page

1. Report No, 2. Government Accession No. 3. Recipient's Catalog No.

DOT/FAA-~AM-85-11

4, Title and Subtitle 5. Report Date
DEVELOPMENT AND EVALUATION OF A PROTOTYPE LIFE September 1985
PRESERVER 6. Performing Organization Code

&. Performing Organization Report No.

7. Author's)B, J, Rueschhoff, E. A. Higgins, M. J. Burr,
and D. M. Branson

9. Performing Organization Name and Address
FAA Civil Aeromedical Institute
P.O. Box 25082 Ti. Contract or Grant No.
Oklahoma City, Oklahoma 73125

0. Work Unit No. (TRAIS)

13. Type of Report and Period Covered

12. Sponsoring Agency Name and Address
Office of Aviation Medicine

Federal Aviation Administration
800 Independence Avenue, SW. 14, Sponsoring Agency Code
Washington, D.C. 20591

15. Supplementary Notes
Research leading to preparation of this report was performed under tasks

AM-B-84-PRS-66 and AM-B-85~PRS-66.

16. Abstract

The purpose of this study was to develop a prototype life preserver that included
provisions for: (1) increased thermal protection in the event of accidental immersion
in cold water, (2) 35 pounds of buoyancy, (3) a donning time of 15 s for an adult,

(4) not weighing more nor requiring more storage space than currently used life
preservers, (5) fitting individuals from the 5th percentile of adult females to the
95th percentile of adult males in the U.S. adult population, and (6) self-righting the
wearer in 5 s. Evaluations were made to ensure that the prototype life preserver met
goals of items (2) through (6). However, the focus of the study was the assessment of
thermal response characteristics. To assess the thermal response of subjects wearing
the prototype life preserver and a currently used standard personal flotation device,
a laboratory study with 10 subjects was conducted. ‘Two subjects, one wearing the
prototype and the other a standard vest, were immersed during each experiment in 12.8
©¢ (55 OF) water in the Civil Aeromedical Institute survival tank for 2 hours. Rectal]
temperature, heart rate, and EKG were measured continuously. Eight of tensubjects,
while wearing the prototype life preserver, showed a decrease in the rate of cooling
when compared to the cooling rate when wearing the standard vest. The mean cooling
rate with the prototype life preserver was 1.15 °¢/h and 1.72 °C/h with the standard
device. Differences were statistically significant at the 0.05 level. Differences
in heart rate were also shown to be statistically significant. After 20 min of
immersion, subjects wearing the prototype life preserver experienced lower heart
rates than when they wore the standard personal flotation device.

17. Key Words 18. Distribution Statement
Water Survival Program, Life Preservers, Document is available to the public
Thermal Protection. through the National Technical
Z - Information Service, Springfield,
(feo preservers Virginia 22161,
Suavt (Ahk any ay shop th tes
T9. Security Classif. (dV this report) 20, Security Classif. (of this page) Ti. No. of Pages | 22. Price
Unclassified Unclassified 64

Form DOT F 1700.7 (8-72) Reproduction of completed page authorized



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42


Figure 1.

Standard Personal Flotation Device
(Front View).

A.
B.
c.
De.

Dual-chamber air bladder
16-g C02 cylinders
Adjustable waist strap
Oral inflation tubes


was not considered due to the additional weight and
storage space and the extra time that would be required
to don a life preserver that covered the groin area. The
air within the bladder appeared to be a practical way of
providing insulation without adding additional weight or
storage space.

The currently used PFD's are dual-chamber air bladders
that are U-shaped and encompass only the neck area.
Complicated retention harnesses are used to secure the life
preserver to the body (Figures 1 through 3). The current
PFD's do not provide thermal protection or allow for ease or
speed of donning. The study by Rasmussen and Steen (3) found
that the mean donning time for the currently used PFD's
ranged from 28.0 to 37.8 s. The same study found that the
mean donning time of experimental models (sleeveless jacket-
style boating vests) ranged from 15.8 to 16.8 s. Therefore,
to take advantage of this rapid donning characteristic, an
air bladder was designed as a jacket-style (Figures 4 through
6) with a conventional wide-toothed zipper positioned down
the center front for closure. This jacket-style design
provides for simplicity and familiarity so that passengers
could readily understand how to don the life preserver.

Universal sizing was achieved by the currently used
PFD's. However, to enhance thermal protection and retain fit
for a majority of the wearers, additional considerations had
to be made. Studies by Reins and Shampine (8) found that
thermal protection was significantly increased when a suit
provided a close fit to the wearer's body. To assist in
providing universal sizing, while retaining closeness of fit,
one-eighth inch closed cell neoprene was attached to the air
bladder in the lower back region (Figure 6). The neoprene
allows for 300 percent stretch. It also provides 60
pounds/square inch tensile strength which, reduces the
possibility of tearing when stretched.

Another technique for providing closeness of fit
involves the proper location of the heat-sealed areas of the
bladder (Figures 4 and 6). By heat-sealing the polyurethane-
coated nylon in the proper locations, the inflation assists
in holding the vest close to the body where desired. Exten-
sive design modifications were made to configure the air
bladder so that the life preserver would remain close to the
body in the areas of the neck and armholes, thereby
restricting water entry and water movement between the
preserver and the subject.

Guidelines for determining fit were obtained from
anthropometric data (9) for males and females at certain
critical measurements. The chest measurement for the
prototype vest (uninflated) was the 95th percentile male
chest measurement. Although it is 10.8 inches greater than
the 5th percentile chest measurement for females, a good fit

5



SUMMARY

A review of literature focused on physiological
responses to cold water immersion and various design concepts
previously developed and evaluated for protection against
hypothermia. The review of literature was a source of design
ideas for the development of the prototype thermal protective
life preserver.

In the development of the prototype life preserver,
goals established by the Survival Research Unit, CAMI, were
used as guidelines. The requirements for selt-righting,
donning time, universal sizing and weight, and storage space
limited the amount of thermal protection that could be
provided. In order to meet the donning time and weight and
storage goals, a single-chamber air bladder that covers the
major heat loss areas of the upper torso was designed. To
allow for ease of donning, the air bladder was developed into
a jacket-style with a front zipper closure. In comparison,
the current standard PFD is a dual-chamber air bladder that
is U-shaped, encompasses only the neck area, and has
complicated retention harnesses that prolong donning time.

Since thermal protection is significantly increased when
a suit provides a close fit, means of accommodating the need
for universal sizing and a close fit were sought.

Anthropometric data for male and female chest and waist
sizes were used to determine key measurements. A material
search resulted in the use of one-eighth inch closed-cell
neoprene in the lower back region of the prototype. The 300
percent stretch provided universal sizing and allowed for a
close fit for a wide range of subject sizes.

To test and evaluate the thermal response character
istics of the prototype life preserver and a currently used
standard PFD, a laboratory experiment with 10 subjects
immersed in 12.8 °C water was conducted. Each subject's
rectal temperature was measured and recorded every 2 min. A
cooling rate for each subject in each design was determined
by least squares regression. A paired t-test was used to
determine significant differences between cooling rates for
the two vests.

The mean cooling rate estimate of subjects wearing the
prototype life preserver (1.15 °C/h) was lower than when the
same subjects wore the standard PFD (1.72 °C/h). Differences
in cooling rate were statistically significant at the 0.05
level. Regression analysis showed that there was a high
degree of linear correlation between the immersion time and
the change in rectal temperature. Eight of ten subjects
while wearing the prototype life preserver showed a decrease
in cooling rate over the same subjects when wearing the
standard PFD.

55



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Figure 10. Subject demonstrating a face-up flotation position while
wearing the standard personal flotation device.

26


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Figure 9. Subject demonstrating a face-up flotation position while
wearing the prototype life preserver.

25



small scurring wave going across the big wave is
difficult to judge. The minute you inhale a bit of
water you start a cough reflex and you have lost all
control of respiration at that stage and you very
quickly drown. It may well be that the fifty percent
survival time figure that we have looked at in the
graphs is related to that; it is the time when
consciousness is impaired to a degree when drowning
occurs and that just occurs when you lose about 2 or 3
degrees in body temperature.

Thus, when determining the degree of thermal protection
required, the deep body temperature before the time when
consciousness is impaired should be considered. According to
Beckman, Reeves, and Goldman (5) conscious muscular activity
is lost at 34.4 °C core temperature.

The following accidents demonstrate the necessity of a
thermal protective life preserver (6):

SS Lakonia, December 1963, Ship fire with evacuation:

1) Two hundred passengers and crew, all wearing life
preservers, were immersed.

2) The rescue operation was effected in approximately
3h.

3) All passengers and crew survived.

4) The water temperature was 18 °C (64 °F) and was a
potential problem.

SS Prinsendam, October 1980, Ship fire with evacuation:

1) Five hundred and nineteen passengers and crew
entered life boats,

2) Though less than 100 miles from land, the rescue
operation, using ships and helicopters, required
12 he

3) All passengers and crew survived.

4) The water temperature of 14 °C (57 °F) was a
potential problem.

Shetland Islands, HS-748, July 1981, Unsuccessful
aircraft takeoff with water impact 50 meters from land:

1) Most passengers were not able to obtain life
preservers from under the seats.

2) Airport ground rescue equipment was near the site in
2 min but was not effective.

3) Two helicopters were over the site within 4 min but
were not effective due to the weather conditions.

4) Of 47 aboard, 17 drowned, 10 outside the aircraft.

5) The water temperature of 11 °C (52 °F) was a
problem.


Physiology of Immersion Hypothermia

The human body loses heat much more rapidly in water
than in air. The thermal conductivity of water is approxi-
mately 26 times greater than that of air. Thus, during
immersion heat is conducted away from the body to the
surrounding water at 26 times the rate it is in air (4). An
unclothed man immersed in cold water becomes largely
dependent on internal mechanisms to limit this loss of body
heat. The following section reviews the internal mechanisms
and other physiological responses of humans in the defensive
phase during cold water immersion.

Respiratory Responses

The initial shock of cold water immersion will
produce hyperventilation with respiratory rates
increasing to approximately five times the level of pre-
immersion rest (10). The hyperventilation response is
greatest during the first couple of minutes, and by 5
min the respiratory rate is reduced to a level more
dependent on metabolic rate (10). This response starts
from the cold receptors in the skin, which act directly
on the respiratory control center.

The consequences of hyperventilation can be serious.
The inital gasping response facilitates the breathing of
water and, thus, the possibility of drowning.
Hyperventilation also reduces the carbon dioxide of
arterial blood, which can lead to reduced cerebral blood
flow resulting in clouding of consciousness and reduced
swimming ability (10).

Cardiovascular Responses

The primary physiological defense during exposure of
the body to cold is peripheral vasoconstriction. This
causes a reduction in the circulation of blood in the
skin and, as a result, heat loss to the environment is
reduced. Boutelier (1) reports that peripheral
vasoconstriction is proportional to the intensity of
cooling and

«affects one, two, or all three arteriolar plexi;

if cooling is more intense, even some of the

muscular blood vessels are involved, particularly in
such extremities as the hands, forearms, feet and

legs (p. 34).

The effectiveness of peripheral vasoconstriction in
reducing heat loss is further increased by counter-
current exchange of heat between the arteries and veins
that run side by side in the limbs. Boutelier (1)

16


This conservation of metabolic energy appears to be a
possible explanation as to why subject PP did not show a
lower cooling rate when wearing the prototype life preserver
than while wearing the standard PFD. From visual observa-
tion, subject PP appeared to have significantly more total
body fat than any of the other subjects. It is, therefore,
hypothesized that this subject's own tissue insulation plus
the insulation provided by the prototype life preserver may
have decreased stimulation of deep thermoreceptors. This may
have reduced the intensity of the response to a change in
external temperature. As indicated in Figure 12, the
subject's rectal temperature appeared to level off at
approximately 60 min when wearing the standard PFD and at
approximately 100 min when wearing the prototype life
preserver. Thus, a longer exposure time may have resulted in
a lower rate of cooling when the subject was wearing the
prototype life preserver than when wearing the standard PFD.
More work would have to be done to verify this.

Another subject (MS) also did not show a lower rate of
cooling when wearing the prototype life preserver than when
wearing the standard PFD. A possible explanation relates to
the amount of urine produced during the tests. When subject
MS was wearing the standard PFD he had a urine volume of 830
cc. When he was wearing the prototype life preserver he had
a urine volume of 330 cc. As can be seen in Table VII, no
other subject produced as large a volume of urine, nor
demonstrated as great a difference between the two tests.
The subject reported that, while wearing the standard PFD, he
had a strong urge to urinate. Each time he tried to relax,
the urge to urinate would return which would cause him to
"tighten up and shiver." However, when the subject was
wearing the prototype life preserver, he reported that he
could relax and abstain from shivering for short periods of
time. Thus, it is hypothesized that if the subject had
shivered equally during each experiment, he may have shown a
small decrease in the rate of cooling when wearing the
prototype life preserver over the standard PFD. Again, more
work would have to be done to verify this. Subject MS was
also one of the heavier subjects with a greater body mass.

Based on weight and height alone, it also appears that
the heavier subjects (JA, PP, MS, and KB) would need a longer
exposure time for significant differences in cooling rate to
occur. As can be calculated from Table IV, the mean cooling
rate for these four subjects was 0.63 °C/h for vest 1 while
the remaining subjects had a mean cooling rate of 2.44 °C/h.
For vest 2, these four subjects had a mean cooling rate of
0.63 °C/h and the remaining subjects had a mean cooling rate
of 2.26 °C/h.

53



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TABLE IV

Results of Cold Water Immersion Experiments

Regression Percentage of
Subject Core Cooling Rates Correlation Improvement
(°C/h) Coefficient of Vest 2
over Vest 1
Vest 1 Vest 2 Vest 1 Vest 2
JA 0.22 0.18 0.97 -0.98 18
PP 0.33 0.57 -0.79 0.98 42
MS 0.89 0.93 -0.95 -0.96 -4
KB 1.08 0.83 -0.99 -0.98 23
OB 1.68 0.50 -1.00 -1.00 70
BP 1.86 1.55 -1.00 -0.99 17
MI 2.13 1.35 -0.99 -0.98 37
AR 2.18 1.06 -1.00 -1.00 51
kT 3.06 2.13 -1.00 ~-1.00 30
GR 3.74 2.43 -1.00 -1.00 35
Mean 1.72 1.15
Standard
Deviation 1.13 0.72
Level of
Significance 0.012

49



TABLE III

Experiment Design

Tank Tank
Experiment Position Position
Number i 2
1 $-2/V-2 S-1/V-1
2 S-l/Vv-2 $-2/V-1
3 8-4/V-2 8-3/V-1
4 8~3/V-2 $-4/V-1
5 S-6/V-2 $~-5/V-1
6 S-5/V-2 S$-6/V-1
7 S-8/V-2 8-7/V-1
8 S-7/V-2 S-8/V-1
9 S-10/V-2 $-9/V-1
10 8-9/V-2 8-10/V-1

Legend: S-l represents subject 1, S-2
represents subject 2, etc.;
V-1 represents the standard
personal flotation device, V-2
represents the prototype life
preserver.

22


TABLE VI

Heart Rates

Subject Heart Rate (bpm) Given at Five Timed Intervals (min) and at Exit

Exit
5 10 20 30 40 Water
vVl_V2 Vl V2 Vil v2 Vl v2 vV1l_v2 Vil v2
JA 91 79 84 84 85 85 85 82 88 78 94 87
PP 82 89 78 84 71 «(79 72 «79 79 86 100 62
MS 62 67 70 #77 77 70 88 77 84 82 102 90
KB 90 82 88 76 80 67 86 71 87 74 103 86
OB 78 93 82 86 82 79 79 78 76 79 83 OL
BP 83 78 81 70 76 70 81 73 80 75 88 81
MJ 107 106 104 92 104 93 120 92 122 94 120) 111
AR 103. 94 102 96 107 94 107 97 107 96 102 86
kT 106 108 110 105 107 99 107 101 105 102 106 103
GR 65 74 68 74 77 72 84 74 89 74 89 70
Mean 87 87 87 84 87 81 91 82 92 84 99 87
sD 16 14 14 11 14 11 15 11 15 10 11 14
Level of
Signifi- -917 +378 +019 -017 -038 +012
cance

Legend: Vl represents the standard personal flotation device; V2 represents
the prototype life preserver.

52


II.

Til.

Iv.

v.

VI.

VII.

LIST OF TABLES

Acquisition and Donning Times of the Prototype
Life Preserver ». . 1. 6 ewe wwe eee eae

Subject Characteristics. ........ eee
Experiment Design. . 2... 1. se we eee eee
Results of Cold Water Immersion Experiments. .
Predicted Survival Time Estimates. ......

Heart Rates. 2. 6 6 6 ee ew ee we eee ee

Urine Volumes (in Cubic Centimeters) for Subjects

During Cold Water Immersion Tests .......

iv

22
49
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52

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Figure 4.

Prototype Life Preserver
(Front View).

A.
Be
Cc.
De
E.
F.

Single-chamber air bladder
One 28-g COy cylinder

Oral inflation tube

Front zipper

Heat-sealed areas

Belt



The means and standard deviations for the two rectal
temperatures are given for each type of design in Table V.
For a lethal rectal temperature of 34.4 °C, the mean
estimated pst was 6.5 h for subjects wearing the prototype
life preserver and 4.4 h if the same subjects wore the
standard PFD. For a lethal rectal temperature of 30.0 °C,
the mean estimated pst was 11.7 h for subjects wearing the
prototype life preserver and 9.8 h if the same subjects wore
the standard PFD. For both rectal temperatures, the mean
estimated pst was greater for subjects wearing the prototpye
life preserver than if the same subjects wore the standard
PFD.

Heart rate data are given in Table VI for selected times
after immersion. On entry into the cold water, all the
subjects had an initial large increase in heart rate. Within
the first minute of immersion the subjects' heart rates were
35 percent and 33 percent above preimmersion levels while
wearing vest 1 and vest 2 respectively. By 5 min, heart
rates fell to levels slightly less than preimmersion levels.
Thereafter, heart rates increased gradually in either test
condition.

At 5 and 10 min of immersion, the type of design worn
did not significantly affect heart rates. However, beginning
at 20 min of immersion, the mean heart rate for subjects
wearing the prototype was 81 bpm and was 87 bpm in those
wearing the standard PFD. At 30 min, the mean heart rate for
subjects wearing the prototype life preserver was 82 bpm and
was 91 bpm when the subjects were wearing the standard PFD.
At 40 min, the mean heart rate for subjects wearing the
prototype life preserver was 84 bpm and 92 bpm when wearing
the standard PFD. During the last 4 min of immersion, the
mean heart rate for subjects wearing the prototype life
preserver was 87 bpm and 99 bpm when wearing the standard
PFD. These differences in heart rate were statistically
significant for 20, 30, and 40 min of immersion and during
the last 4 min of immersion. These differences suggest that
the prototype life preserver may have aided in conserving
energy, since heart rate is directly affected by both level
of physical activity and metabolic rate.

In a study by Bynum, Goldman, and Stewart (14), it was
found that the mean increase in metabolic heat production for
subjects wearing neoprene-insulated suits (15 W/m2) was lower
than when the same subjects were nude (130 W/m2). This
suggests that an important effect of additional insulation is
to conserve metabolic energy which is associated with
maintaining a given level of rectal temperature (14). This
study was conducted in 20 °C water over a 60-min period.

51



10.

11.

12.

REFERENCES

Boutelier C. Survival and protection of aircrew in the
event of accidental immersion in cold water. North
Atlantic Treaty Organization Advisory Group for
Aerospace Research and Development AGARD-ograph No. 211.

1979.

Brooks R. Water contact accidents. Second Annual
International Aircraft Cabin Safety Symposium. 1985.

Rasmussen PG, Steen J. Retrieval and donning of
inflatable life preservers. Unpublished CAMI Protection
and Survival Laboratory Memorandum AAC-119-83-5, 1983.

Golden C. Immersion hypothermia. North Atlantic
Treaty Organization Advisory Group for Aerospace
Research and Development, AGARD Report No. 620, 1973.

Beckman EL, Reeves E, Goldman RF. Current concepts
and practices applicable to the control of body heat
loss in aircrew subjected to water immersion. Aerosp.
Med. 1966; 37:348-57.

Higgins EA, Funkhouser GE, Saldivar JT. Progress on
the water survival program. Unpublished CAMI Protection
and Survival Laboratory Memorandum AAC-119-83-6, 1983.

Hayward JS, Collis M, Eckerson JD. Thermographic
evaluation of relative heat loss areas of man during
cold water immersion. Aerosp. Med. 1973; 44(7):
708-11.

Reins DA, Shampine JC. Evaluation of heat loss from
Navy divers' wet suit. Naval Air Development Center
Technical Report 102, 1972.

Churchill E, Laubach LL, McConville JT, Tebbetts I, eds.
Anthropometric source book Volume I: Anthropometry for
designers. NASA Reference Publication 1024, Webb
Associates, Yellow Springs, OH, 1978.

Hayward JS. The physiology of immersion hypothermia.
In: Pozos RS, Wittmers E, eds. The nature and treat—
ment of hypothermia. Minneapolis: University of
Minnesota Press, 1983.

Keatinge WR. Survival in cold water. Oxford, Great
Britain: Blackwell Scientific Publications, 1969.

Best CH. Physiological basis of medical practice. In:

Brobeck JR, ed. Neural control systems. Baltimore, MD:
The Williams and Wilkins Co., 1979.

57



Figure 6.

Prototype Life Preserver

(Back View).

A. High inflatable collar for
support of head and neck

B.. Closed-cell neoprene

11



TABLE OF CONTENTS

Abstract . 6 6 6 6 ee ee ee ee we ww eee ee i
‘Acknowledgment . 6 6 1 ee ee ee ee ee we ee ee ee Gk
Table of Contents. . 2. 6 ee ee ee ee ee ee ee ew GGG
List of Tables 2. 6 6 eee ee ee ee ee ee ee ee iv
List of Figures. 2. 6 2 6 6 6 8 ee ee ee ew ee ee v
INTRODUCTION . «© 2 6 ee ee we ee ee we ee ee ee 1
DESIGN DEVELOPMENT . . ~~ - + © © @ © @ wee ee es 4
Achievement of Goals Other Than Thermal Protection . 12
EVALUATION OF THERMAL PROTECTIVE CHARACTERISTICS . ... 16
Physiology of Immersion Hypothermia. . - + + + + + « 16
Objectives . 1 6 ee ee ee ee ee ee ee es 19
Selection of the Sample... + e+ + ee eee ee ee 19
Experiment Design. «© ss 6 se © ee ee ee ee ee 21
Instrumentation. . 6. ee ee ee ee ee ee eee 2D
Experiment Protocol. «. . - + + e+ + + es + ee eee 1 24
Test Conditions. . . se ee ee ee ee ee ee ee 2
Data Analysis. © 6 ee ee eee ee ee ee ee ee 27
Results. 2. 6 eee ee ee ee eee ee ee ee we 28
SUMMARY. 2.06 0 ee ee ee ee ee ew ee ee ee ewe SS
CONCLUSIONS. . 6 2 6 © 8 ee ee ee ee ee ee ee 56

REFERENCES . 2 ee ee ee ee ee ee ee ee ee ee 8T

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TABLE IT

Subject Characteristics

Subject Age (yr) Weight (kg) Height (cm)
JA 31 97.7 180.3
PP 18 90.0 180.3
MS 30 87.7 177.8
KB 25 93.6 180.3
OB 26 75.0 167.6
BP 24 74.5 177.8
MI 22 74.1 188.0
AR 23 63.2 175.3
KT 23 65.9 167.6
GR 33 72.7 182.9

20


ACKNOWLEDGMENT

The authors wish to acknowledge the excellent support given
by several individuals:

Mr. Gordon Funkhouser for significant contributions
throughout the study, especially for design, setup, and
conduct of the donning study, and for design, setup, and
maintenance of equipment for the conduct of the cold-water
study, as well as work with human subjects during sizing and
self-righting tests.

Mr. J. T. Saldivar for data reduction and plotting of
graphs and to Mr. Saldivar, Ms. Peggy Lyne, and Ms. Wilma
Fairman for assistance during the data collection phase of
the cold-water tests.

Jerry R. Hordinsky, M.D., for assistance in protocol
development and assurance of subject safety; and Clifton R.
Brooks, M.D., Dr. Hordinsky, Gary D. Sharp, P.A., and the
staff of the Aeromedical Clinical Branch for physical
examinations of subjects and medical monitoring during tests.

Mr. Fenton F. Winters, Mr. Lee Forrest, and Mr. David
Dyer for photographic support throughout the studies.

Ms. Jo Ellen Holt, Ms. Dene Lacy, and Ms. Linda
Alexander for consistent, patient help in obtaining needed
supplies, equipment, and contractual services for the studies
and Ms. Alexander for efficient handling of requests,
forms, and reports.

Mr. Joseph Young for providing information and
consultation concerning populations and requirements for
universal sizing techniques.

Dr. Earl Folk and staff of the Biostatistical Section
for support with statistical analysis.

Mr. Richard F. Chandler, Supervisor, Protection and
Survival Laboratory, for his constructive suggestions,
encouragement, and facilitation of the work.

Other members of the Protection and Survival Laboratory,
who provided assistance when needed.

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5, 10, 20, 30, and 40 min after immersion began. The rates
were also counted during the last 4 min of each subject's
immersion test when the rectal temperature was expected to be
at its lowest. A paired t-test was used to determine
significant differences between subjects' heart rates while
wearing the two vests. Differences were accepted as
significant at the 0.05 level of confidence.

Results

The complete rectal temperature/immersion time profiles
are shown graphically for each subject in Figures 11 through
20. These graphs illustrate the changes in rectal tempera-
ture as a function of elapsed immersion time. Figures 21
through 30 present the absolute rectal temperatures over
time. Each graph includes the two experimental tests
completed by each subject. The standard PFD is labeled as
vest 1 and the prototype life preserver as vest 2. Of the 20
immersion tests, five were terminated early due to cramps,
gastrointestinal discomfort, or the subject's request. One
had to be terminated early due to loss of EKG signal.

The results of the cold water immersion tests are
summarized, in terms of cooling rate per hour, in Table IV.
The means and standard deviations are shown for each design.
Regression correlation coefficients are presented for each
subject's cooling rate by vest design. Percentage of
improvement in reduction of cooling rate of the prototype
life preserver over the standard PFD is presented. for each
subject. As data show, the mean cooling rate for subjects
wearing the prototype life preserver (1.15 °C/h) was less
than when the same subjects wore the standard PFD (1.72
°C/h). Differences in cooling rate were statistically
significant. The regression analysis shows that there is a
high degree of correlation between the immersion time and the
change in rectal temperature. This indicates that the
assumption of a linear decline used to predict survival times
was, probably a valid assumption. While wearing the prototype
life preserver, 8 of 10 subjects showed a decrease in the
rate of cooling over the rate while wearing the standard PFD.

In order to further evaluate the practical significance
of increased thermal protection, the cooling rate data of the
present study were used to estimate durations to "lethal"
levels of hypothermia if immersed in water near 12.8 °C.

What constitutes a "lethal" level of hypothermia has been a
matter of controversy among researchers. Hayward and
Eckerson (13) used a rectal temperature of 30.0 °C as a
definition of "incipient death." According to Beckman et al.
(5), a rectal temperature of 34.4 °C is the time when
conscious muscular activity is lost, which can result in
death by drowning. Thus, for this study, the two rectal
temperatures (34.4 and 30.0 °C) were used to estimate
survival times. These are summarized in Table V.

28


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Figure 8.

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Figure 2.

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10