oar os byes

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FT A

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Dl Taul]is TTT] ATLA
Bd PRAIA AeA
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23 ol ee stireshthppe ree

Fiours 1. Mean plottings of data obtained in Washington, D.C. (preflight), and in Santiago (layover).

ure 5 followed each of the three flights but, again,
only the increment effected by the East-West flight
was found to be statistically significant.

B. Back Shift. Time of departure for the re-
turn flight to Washington, D.C., was 2130 hours
(EST), total time in transit was 14-4 hours, and
arrival time was 1200 hours. The first day of
postflight assessment followed the day of arrival
in Washington, D.C.

Figure 6 presents the obtained data, and, here,
the basis for determining the effects of the flight
consists of the values obtained during the last day
of assessment in Santiago (Day +12). In this
figure, there is no evidence of phase shifts of rectal
temperature and heart rate, which is consistent

with what was noted for the primary period of
transition. The greater contrast between the two
periods of transition is provided by the psycho-
logical functions). Day +1 in Washington, how-
ever, was the day following the day of arrival,
whereas Day +1 in Santiago was the day of ar-
rival, which may account for the fact that the in-
crement in fatigue on Day +1 in Santiago was
statistically significant, whereas the decrement
seen for Day +1 in Washington is not.

IV. Discussion.

Bidirectional differences in time lag of the phase
shifts shown by the physiological functions were
obtained, but these differences did not reflect the





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Ficure 8. Comparison of daily means of subjective
fatigue reported during preflight and primary periods
of transition.

tent; however, although both flights did produce a
statistically significant increment in subjective
fatigue, only the East-West flight produced a
significant psychological deficit. Since the West-
East flight was not followed by a similar short
period of psychological deficit, the respective ef-
fects of time displacement and prolonged transit
time may be questioned; more specifically, which
of these two factors was primarily responsible for
the deficit seen for the East-West flight?

To obtain relevant data it was necessary to con-
duct the flight being reported so that the single
effects of prolonged transit time could be compared
with the joint effects of transit time and time dis-
placement. As has been seen, the psychological
results of the North-South flight were similar to
those of the West-East flight. Subjective fatigue
was generated to a statistically significant extent
but not psychological impairment. Consequently,
the question still remains: Is the East-West deficit
in psychological performance primarily attribut-
able to time displacement and therefore a corre-
late of physiological phase shifts of circadian
periodicity or to a total transit time of greater
than 18 hours? Whatever the answer, one impli-
cation is apparent. Considering the extents of

parle N+) bAved BAVA ONTO OweB GATTI OATOIE

Ficure 4. Comparison of daily means of reaction time
measured during preflight and primary periods of tran-
sition.

time displacements and total times in transit and
the engendered increment: in subjective fatigue, the
degree and duration of psychological impairment
was found to be far less than expected. This is of
practical significance despite the claim that, since
the subjects were passengers on the flights, greater
impairment should not have been expected. Ac-
tually, the subjects were actively engaged with
temperature readings, log recordings, ete. Fur-
ther, the anecdotal reports that generally indicate
marked psychological impairment do not differen-
tiate between passengers and flight crews. Other
explanations could be attempted, particularly in
retrospect, but the data obtained from the three
flights provide a basis for the following conclu-
sion: Rapid translocation through many time
zones does effect impairment of “well-being,” but
this is not accompanied by a commensurate change
in the efficiency of basic psychological functions.

V. Summary and Conclusions.

At periodic intervals throughout the biological
day, biomedical assessments were made for a week
prior to jet flight to Santiago, for 12 days at San-
tiago, and for a week following return to Wash-
ington, D.C. From a comparison of these data



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Cowsy— L ITIAGO- 3

PREFLIGHT DAY +1 DAY +2 = DAY +3

DAY+4 = DAY +6 DAY+8 = DAY +10 DAY + 12.

Fiause 2, Comparison of rectal-temperature recordings obtained during preflight and primary periods of transition.

degree of consistency expected. For example,
while the shifting of the rectal-temperature and
heart-rate phases was closely associated during the
transition period in Manila, pronounced dissocia-
tion was evidenced during the primary period of
transition in Rome. This inconsistency may be
attributable to effects of bidirectional time dis-
placement, to individual differences, and/or to in-
herent variability of the physiological functions
themselves. Nonetheless, one implication is
readily apparent: A more critical evaluation re-
quires more data.

In contrast, little difference in lag time was re-
vealed by shifts of rectal-temperature periodicity,
which was observed to be more consistently stable.
For the East-West and West-East flights, lag time
did not appear to differ by more than 1 day, sug-
gesting that while bidirectional flights effect op-
posable phase displacements relative to local time,
the time required for completion of the shifts of
phase is approximately equal.

From this fact, impairment of psychological
function produced by the East-West and West-
East flights might be expected to be of equal ex-


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Ficure 6. Mean plottings of data obtained on last day overseas (preflight) and following return to Washington, DC.



AM 65-30

PHASE SHIFTS OF THE HUMAN CIRCADIAN SYSTEM
AND PERFORMANCE DEFICIT DURING
THE PERIOD OF TRANSITION:

III. North-South Flight

G. T. Hauty, Ph. D.

T. Adams, Ph. D.
Approved by Released by
°}
Beli Lite PU Skge€ mo
J. Roperr Diuiz, M.D. P. V. Srzent, M.D.
Cuter, Crvis AEROMEDICAL Feperau Arr SuRGEON

Institute

December 1965

FEDERAL AVIATION AGENCY

Office of Aviation Medicine





-

REFERENCES

Avams, T., Fonxwoussr, G. B., and Kenpatt, W. W.:
Measurements of Evaporative Water Loss by a ‘Thermal
Conductivity Cell. J. Appl. Physiol, 18: 1291, 1963.

Apvams, T., Funkuouser, G. H., and Kenpary, W. W.:
A Method for the Measurement of Physiological Evap-
orative Water Loss. ©.A.R.I. Report No. 63-25, Fed-
eral Aviation Agency, 1963.

Haury, G. T., and Apams, T.: Phase Shifting of the
Human Circadian System. In Circadian Clocks,
Aschoff, J., ed., North-Holland Publishing Co., Amster-
dam, 1965.

Havry, G, T., and Apams, T,: Phase Shifts of the

Pa

Human Circadian System and Performance Deficit Dur-
ing the Periods of Transition: I. East-West Flight.
Office of Aviation Medicine Report No. AM 65-28, Fed-
eral Aviation Agency, December, 1965.

Haury, G. T.. and Apams, T.: Phase Shifts of the
Human Circadian System and Performance Deficit
During the Periods of Transition : II, West-Hast Flight.
Office of Aviation Medicine Report AM 65-29, Federal
Aviation Agency, December 1965.

. PEARSON, R. G., and Byars, G. E.: The Development

and Validation of a Checklist for Measuring Subjec-
tive Fatigue. School of Aviation Medicine, USAF, Re-
port No, 56-115, 1956.

U.S. GOVERNMENT PRINTING OFFICE : 1968 O - 211-397



324

OKC Pin t Displacement —!0_ hrs.
Ly t Flight 23'2 hrs.
N
234 A nN t Arrival O730.
aad
(N24)
tus 32,
= OKC > ROME t Displacement —7_ hrs.
- t Flight 152 hrs.
J a t Arrival 1230_
z a - >
o a * . : —T
a HK.
O 144
uw (N=4)
a
324
WASH > SANTIAGO t Displacement —O_ hrs.
t Flight 18 hrs.
: a t Arrival 1300
23 vat
‘4 TM. Oe
A —~ LU
P71 ~~,
J
14: (N=4)
PREFLIGHT DAY+1 © DAY+2 © -DAY+4 © DAY+6 © -DAY+8 ~~ ~DAY#IO. DAY + 12

Fieure 5. Comparison of daily means of decision time measured during preflight and primary periods of transition.

with those obtained from the East-West and West-
East flights, the following conclusions were de-
rived:

(1) While the East-West and West-East flights
effected a primary shift of phase of circadian
periodicity manifested by the physiological func-
tions, the North-South flight did not.

(2) The North-South flight produced a signifi-
cant increment of subjective fatigue, as did the
other two flights.

(3) Significant impairment of psychological
performance produced by the East-West but not
the West-East flight was not shown by the North-
South flight.


three possible responses was the correct response to
be made.

7. Numerical Ability. This was measured by
a 90-item, 3-minute test requiring the addition of
one- and two-digit numbers in sets of three (RPM
Number Facility—NF—Alternate Forms, 1959
Edition published by the Hogg Foundation, Uni-
versity of Texas). The score represents a rela-
tively factor-pure measure in speed and accuracy
of simple addition.

8. Subjective Fatigue. The level of subjec-
tive fatigue was measured by checklists developed
by the scale discrimination method and that
were shown to reflect significantly the effects of
perceptual-motor work and pharmacological
treatment.®

9. Critical Flicker-Fusion. Thresholds were
determined by computing the mean of three as-
cending measurements alternating with three de-
scending measurements.

D. Subjects. Four healthy, adult, male volun-
teers were drawn from the professional and tech-
nical staffs of the Civil Aeromedical Research In-
stitute. Following orientation and practice runs
in Oklahoma City, they were transported to Wash-
ington, D.C., for a period of 9 days, the last 6 of
which were devoted to preflight assessment. Dur-
ing all periods of assessment, preflight, overseas,
and postreturn flight, the subjects were quartered
in wards permitting supervision of activity.
Finally, the subjects were instructed to maintain
their daily living habits for both geographical
locations in accordance with the local time.

III. Results.

A. Primary Shift. Figure 1 presents the re-
sults obtained during the preflight (Washington,
D.C.) and postflight (Santiago) days of assess-
ment. For each function, the plotted values are
the means of the four subjects for each hour for
rectal temperature; for each assessment period for
palmar evaporative water loss, blood pressure,
heart rate, and respiratory rate; and for each day
of assessment in the case of the psychological func-
tions. Preflight values represent the pooled
means of the four subjects for the last 2 days of
preflight assessment.

1. Physiological Funetions. Circadian peri-
odicity is seen most clearly for rectal temperature
and heart rate as has been reported earlier.

Equally clear is the observation that the phase of
the periods manifested by these functions does not
evidence any shift following arrival in Santiago.

2. Psychological Functions. In contrast,
considerable differences are revealed by the com-
parison of preflight and postflight curves of psy-
chological functions. Of these, fatigue increases
to the greatest extent but then returns close to the
preflight level on Day +2. Decision time appears
to increase (i.e, become slower) and to decline
following Day +1. Whereas there is no change
in reaction time on Day +1, reaction time is seen
to be above the preflight level (i.e., become slower)
on Day +2 and the remaining days in Santiago.
In the instance of numerical ability, the increase
noted during each day of assessment in Santiago
actually represents greater proficiency. While
critical flicker-fusion thresholds were determined,
these are not reported owing to calibration difficul-
ties experienced in Santiago. Of these differences
in psychological function precipitated by the flight
to Santiago, only the increment in fatigue was
revealed to be statistically significant (P=0.01)
by analyses of the variance attributable to repli-
cated days of assessment.

3. Comparison of Flights. Data summarized
in Figures 2 to 5 indicate the comparative effects
of the East-West, West-East, and North-South
flights upon primary phase shifts and perform-
ance deficit. Figure 2 reveals: (1) the extent to
which rectal-temperature curves are out of phase
initially with the local time of Manila and Rome,
(2) the shifting of this function into phase with
local time on successive days, (3) the number of
days required for the completion of the phase
shift, and (4) the lack of phase displacement of
internal body temperature in Santiago.

Figure 3 shows that all flights resulted in an in-
crease in the daily mean level of fatigue reported
by the subjects, with the greatest increment being
produced by the East-West flight and the smallest
increment by the North-South flight. For each
flight, the fatigue increment was found to be sta-
tistically significant.

Figure 4 indicates that the greatest increase in
daily mean reaction time was produced by the
East-West, flight, which, moreover, was the only
flight to have produced an increment in reaction
time approaching statistical significance. In-
crease in daily mean decision time shown in Fig-


PHASE SHIFTS OF THE HUMAN CIRCADIAN SYSTEM AND
PERFORMANCE DEFICIT DURING THE PERIODS OF TRANSITION:

II. North-South Flight

I. Introduction.

Intercontinental jet flights designed to reveal
the bidirectional effects of time displacement in-
dicated ** that for one physiological function,
internal temperature, lag time of the primary
phase shift appeared to be of the same extent.
For other physiological functions, lag time was
substantially different. Further, while signifi-
cant increase in fatigue was reported during the
periods of primary transition of both flights, per-
formance deficit was occasioned by one flight but
not the other.

In order to appraise the effects solely attributa-
ble to prolonged flight, a North-South flight was
undertaken.

II. Method.

A, Flight. Originating in Washington, D.C.,
destination of the flight was Santiago, Chile.
Time of departure was 1900 hours (EST), total
time in transit was 18 hours, arrival time was 1300
hours (EST), and time displacement was 0 hour.

B. Schedule of Assessment. Periodic biomedi-
cal assessments were made in Washington, D.C.,
on alternate days during a week immediately prior
to flight, during a 12-day period of layover in
Santiago, and during the week following return
to Washington, D.C. Throughout each assess-
ment day, assessments were repeated at 0700, 1100,
1500, 1900, and 2300 hours (local time). During
each of these five periods, different psychological
functions were sequentially assessed by standard-
ized procedures, and, simultaneously, physiologi-
cal functions were measured. The time required
for such a period was approximately 25 minutes.

C. Assessments. The following assessments
were made.

1. Rectal Lemperature. Internal body tem-
perature was measured by a portable, indicating
bridge circuit, calibrated to a thermistor rectal
probe that was inserted to a depth of 10 cm, worn
continuously throughout each assessment day, and
removed only for bathing or evacuation. During
the waking portion of the day, the subject read

and recorded his own temperature to the nearest
0.1°C at 1-hour intervals; for the remainder of
the day, a technician recorded the sleeping sub-
ject’s temperature at the same interval.

2. Evaporative Water Loss. The method for
quantitatively measuring skin-surface evaporative
water loss has been described earlier. * For each
assessment period, a small plastic capsule * was
sealed to the skin at the center of the left palm.
Measurements of evaporative water loss from this
area were made continuously throughout each
assessment, evaluating both steady-state “basal”
levels during rest before and after each assess-
ment period and increased evaporative rates dur-
ing identified assessment increments.

3. Heart Rate and Respiratory Rate. A light-
weight, plastic and elastic chest strap was impro-
vised to house three silver electrodes for heart-
rate measurement and a mercury-in-rubber strain
gage to monitor respiratory rate as a function of
changes in chest circumference.

4, Blood Pressure. Both systolic and dia-
stolic pressures were measured periodically
throughout each assessment period by standard
auscultatory techniques using an inflatable arm
cuff and indicating sphygmomanometer.

5. Reaction Time. The speed of manual re-
sponse to three successive presentations of a single
auditory stimulus, three successive presentations
of a single visual stimulus, six successive and ran-
domly determined presentations of one of three
possible visual stimuli, and one presentation of
the single auditory stimulus was measured at each
of the indicated times of assessment during each
assessment day, as were the following psychologi-
cal functions.

6. Decision Time. This was obtained for
each assessment period by subtracting the mean
time of responding to the three presentations of
the single visual stimulus from the mean time of
responding with the correct response to the six
presentations of one of the three different visual
stimuli. This value is taken to represent the
average time required to “decide” which of the



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