Various tests related to studies concerning the effects of decompression sicknesses at varying pressure levels and physical activity are described. The tests indicate that there are no guarantees of freedom from decompression sicknesses when man transitions from a normally oxygenated normobaric nitrogen-oxygen atmosphere into an environment having a 0.4 atm or lower pressure and he is performing physical work

Genin, A. M.

English

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tNASA TECHNICAL MEMORANDUM
	 NASA TM-76015
(NASA-TH-76015) HAZARDS C? HIGH ALTITUDE 	 N80- 21977
DECORPRESSION SICKNESS MING FALLS IN
BAROMETRIC PRESSURE FRO2 1 ATE! iG A FRACTION
THEREOF (National Aeronautics and Space	 Unclas
Adainistration) 10 p HC A02/CF A01 CSCL 06S 63/52 47661
HAZARDS OF HIGH ALTITUDE DECOMPRESSION SICINESS
DURING FALLS IN BAROMETRIC PRESSURE FROM 1 AT:i
TO A FRACTION THEREOF
A. M. Genin
Translation of "Opasnost Poyavleniya Vysotnykh Dekompressionnykh
Rasstroystv (VDR) pri Perepadakh Barometricheskogo Davleniya of 1 ATM
do yeye Doley," Institute of Medical and Biological Problems, Ministry
of Health USSR, Moscow (Paper delivered at the 10th Conference of Joint
Soviet-American Working Group on Space Biology and Medicine, . Houston,_ .:
Texas, October 1979), 1979, pp 1-12
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NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
WASHINGTON, D. C. 20546
	 January 1980 6XI;n^
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STANOARO TITLE PACE
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NASA TM-76015
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A. Title sed 64"do	 : S. Row D*t*
Hazards of High Altitude Decompression Sickness January, 180  _
during Falls in Barometric Pressure from 1 ATM
to a Fr
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nab aeronaut cs and Space Adaiaistratica
wasningtons D.C.	 20546 14. tt	 M M	 tCs^
1:. Sohlewsot" Nobs
Translation of "Opasnost Poyavleniya Vysotnykh Dekompressionngkh
Rasstroystv (VDR) Pri Perepadakh Barometricheskogo Davleniya'ot 1
ATM do yege.Aoley.,"
	 Institute of Medical and Biolggical Problems,
Ministry of Health-USSR, Moscow ,(Paper delivered at the 10th
Conference of Joint Soviet-American Working Grodp on Space Biology
and Medicine, Houston, Texas, October 1979), 1979, pp 1-12
The article describes various tests related to studies concerning the
effects of decompression sicknesses at varying pressure levels• and
physical activity.	 These tests indicate that.there is no guarantee
of freedom from decompression sicknesses wheniman transitions from a
normally oxygenated normobaric nitrogen-oxygen atmosphere into an
environment having a 0.4 atm or lower pressure and he is performing
physical work.
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The choice of an artificial cabin atmosphere for spate ships has boon	 L
widely diserssed by specialists from the USSR and USA during all stages of
the devo)ovAont of space exploration. In the USSR the choice fell upon a
normsbaric oxygen-nitrogen atmosphere with a ratio of gases approximating
that of air. Arguments in favor of this decision are:
--relative fire eafety,
--indisputable physiological adequacy,
--high volumetric specific heat of the gaseous miliou,
--the possibility of using a wider assortment of materials and assemblies
for on-board systemus.
A normobarie environment has obvious shortcomings ) the primary one being
the need for maintaining a relatively high pressure in space suits or allowing
for an extended nitrogen desaturization period. The increased duration of
space flights and the prospects for their broader expansion increase the
importance of the positive features of a normobaric atmosphere. This cireum-
stanco, however, necessitates even greater attention to its shortcomings,
since extra-vehicular operations and human work in open space may evolve from
rare occurrences inte,daily, widespread activities.
This requires using reliable measures to ensure a safe working environ-
ment for a man in ' s space suit while providing maximum comfort, including a
high degree of mobility for all of the suit.'s articulations. The lower the
	 L
excess pressure in the suit, the simpler it is to achieve the latter, although
low pressure, in turn, carries with it the hazard of decompression sickness.
Aviation-related incidents of decompression sickness during drops in
atmospheric pressure from 1 atm, to a fraction thereof have been studied by
many researchers and laboratories around the world. The notion that there
is a precise boundary marking a dangerous drop in pressure, before reaching
which freedom from decompression sickness may be ensured, has long predomin-
ated. The concept of such a borderline was formulated on the basis of the
* Numbers in margin indicate pagination in original foreign text
1
rides of D. Holden. ♦ pressure of 270 sum H6 (or a pressure altitude of
8000 m4 was the generally accepted limit used in aviation. Criss of deeomw
pressioa sickness at higher pressures (lower altitudes) arose periodically.
These were rare episodes, however, and, although quite serious incidents of
decompression sickness have been described in groat detail, virtually no atten-
tion has been directed to the possibility of high-altitude decompression
sickness (08) occurring at altltudos below 8000 n. These ideas were not
shaken by the classic research done by Harvey of al., which showed that
in principle there are no danger limits for pressure drops, and that the
likelihood of decompression sicknesses occurring was determined by a nuteber.ef
ancillary factors, such as, for example, physical stress, duration of
exposure, etc.
In this connection, there are essential differences between incidents:
of decompression sickness in aviation, where the physical activity of the
crew members is extremely limited and exposure time is small, and in space
travel, whore extra-vehicular activity requires the performance of intensive
physical work over a long period of time. These differences have made it 	 L
necessary to conduct special experimental studies in altitude chambers, with
the subjects "ascending" to various artificial altitudes and performing
physical work after decompression.
Numerous researchers in the Soviet Union have so far amassed a consider-
able amount of material, which could be divided roughly into two parts. The
first part consists of research done with the participation of volunteers
and specifically directed at discovering the effects of decompression sicknesses
at varying pressure levels and involving varying types of physical activity.
Pressure suits were not used in these experiments, as a rule.
The second part consists of observations made on persons testing pressure
suit systems under differing conditions. These subjects were not concerned
with detecting the symptoms of decompression sickness but were oriented
towards accomplishing a task. So the goal of the subjects in this group,
moreso than the first group, was approximately that of cosmonauts. This is
a rather important consideration, since the complaints of these subjects were
practically the only criteria for detecting decompression sickness.
2
done by dramonitsky, Katuntsev, and Poleshehuk according to the initial
protocols. Ibis research has been published in part (1 9 2, 3 9 4), lb*
experiments wero den* with the participation of clinically healthy young seen
aged 12 to 42 years, from various different professions: students, laboratory
assistants, technicians, eteg
After a medical examination, the subjects went over to an altitude chamber L
and donned oxygen masks. In all the experiments, the rate of ascent from
ground level to 3000 m. was 10 a/see, from 3000 n. to 5000 n. -- 15 m/soe,
and from 5000 m. on -- 25 a/s*c. Duration of the stay at altitude was to
total 4-6 hours. During their stays at decreased pressure, the subjects in
all the experimental variations performed a standardised amount of physical
work, which included the following: while seated, the subject stretched out
both arms and raised 4 kg dumbbells 20 times in one minute, then climbed a
30 cm step 20 times a minute for 3 minutes (60 times in all), and then once
again raised the dumbbells for 1 minute. In accordance with prior instructions,
the subjects periodically changed the "working leg" while climbing the step.
One cycle of physical activity lasted 5 minutes. The work cycle was repeated,
after 15 minute rest periods, over the entire course of -the stay at altitude.
Thus, throe cycles of physical activity took place in each hour. Energy
expenditure for the given amount of work totaled 174 + 8.6 kcal/hour. In
the period of work performance, the expenditure came to 5.6 + 0.3 kcal/min.
If RDB occurred, the subjects informed the experimenters. The decision
to continue or halt the experiment depended upon the nature and degree of
illness. Repeated "ascents" were conducted no sooner than a week after the
preceding one.
A table summarizing the results of the experiments is printed below.
Bpecial notice should be made of ifte unexpectedly high percentage of	 L
decompression sicknesses occurring at pressures of 0.4 (48%) and even 0.43 atme
and the low effectiveness of desaturization.
3
In addition, it should be pointed out that there was not a single case
of severe decompression sickness in any of the experimental series. The
predominant symptoms were pains in points (94%), most frequently localised
In the knees (609591), and rarely in the shoulders (12.8%) and ankles (9.6%).
The joint pains were frequently accompanied by dermal pruritic, and
substernal palm and coughing sometimes appeared. The symptoms of RDS, an
a rule, disappeared following descent to ground lovel, and in only three
cases did a small amount of odema and tenderness upon movement of the joint remain
over 2 or 3 days.
We should also note the tendency of the latent period of decompression
sickness manifestation to decrease when the exposure "altitude" was incroasod.
Decompression sickness became more serious when the final pressure was
decreased. Thus, at 0.35 atm.,,in 17.8% of the HDS cases the subjects could
continue to complete the program, while 41% of the cases required rapid
recompression. At the same time, when the final pressure was 0.4 atm., 29%
of the persons with HDS completed the research program, while in only 17% of
the cases was rapid recompression necessary.
Therefore, the data from this series of experiments has shown that pressure
changes from 1 atm. to 0.40 and even 0.43 atm, did not provide freedom from
decompression sicknesses where a human was performing physical work.
These data contradict the work of Vakar, Masyn, at al. We These authors
conducted 483 studies on 70 subjects. The ages and professions of the sub-
	 L
jocts wore analogous to those in the preceding series. The general plan of
the experiments was the same as in the studies by Gramenitsky et al., but
the physical stress was considerably higher: average hourly work expenditure
was 400--450 kcal; the subjects raised a 15 kg weight to 70 cn and climbed a
35 an step; 30 exercises per minute were done for 40 minutes, and they were
begun again attor 20 minutes of rest.
Despite the fact that the intensity of physical exercise was materially
greater in the experiments of Vakar at al. than in Gramenitsky's, there were
far fewer cases of decompression sickness.
4
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Thus, at a final pressure of 0.4 atm. only 2 cases of decompression sickness
were observed out of 434 experiments (0.46%), while with a final pressure of
0.33 atm. there were 8 caner out of 49 (16 . 3%). Both case & of HDS at 0.4 atm.
manifested themselves as slight joint pains, while the HDS symptoms &rising
at 0.33 atm. were considerably more acute. We should note, however, that
in the control series of studies, in which Vakar et &1. used the standard
physical stress, an applied by Gramenitaky, the results obtained were close
to those of the first series of studieng
The second part of this work, as we have already remarked, was conducted
during tests of pressure suits and systems at an abso .ute pressure of from
0.21 to 0 .41 atm. ( 160•-310 mm HR). These experimerts were carried out
using differing goals and methodologies. The nature and intensiveness of
the physical exercises differed considerably in the various tests. This
c:rctr= tarse obliged Barer, Golovkin, et al., in trying to generalize the 	 L
material crow the observations (6), to break t hem up i.-.tc gevaral series and
groups. The basic conditions of the experiments and their results are presented
in table 2. As can be seen from the table, cases of HDS were extremely rare.
Without prior desaturization, they are absent at pressures of 0.38- -0.41 atm.
True, we must make note of the comparatively short exposure to this pressure,
the small quantity of observations, and the comparatively light physical stress.
Symptoms of HDS were also not observed at pressures of 0.36- -0.38 atm.
after prior nitrogen denaturization. HDS of slight or medium severity was
observed in 6--12% of cases at pressures of 0.21--0.26 ato. after 1 hour's
nitrogen denaturization.
Under these conditions, as well as the previous ones, there were no
cases of serious decompression sickness requiring special treatment. In
all cases the HDS were over after a return to normal barometric pressure.
They consisted of muscle and joint pain accompanied in some cases by pruritus
of the skin, As in the previous series, the predominant pain was in the
knees ( 63% of cases). We should also note the large proportion of pains in
the joints of the hands. Apparently this was associated with the need to
overcome the resistance created by the pressure suit's gloves.
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The cited studies and observations are extremely contradictory. The
basic cause of the discrepancies in the results of the studies is, evidently,
the nature and intensiveness of the physical stress. No direct relationship
way be found between the number of cases of HDS and the peak and average
hourly energy expenditure.
We might suppose that the decisive factor is the nature of the work
performed, local stress on muscles and joints, and the duration of periods
	 12
of work and rest.
Individual peculiarities of the persons undergoing decompression and their
subjective attitudes towards HDS also play a signiffcanc role.
It is nevertheless obvious that, without prior desaturization or with
denaturization of limited duration (less than 1 hour), we cannot guarantee
freedom from decompression sicknesses when man transitions from a normally
oxygenated normobaric nitrogen-oxygen atmosphere into an environment having
a 0.4 atm. or lower pressure and he is performing intensive -h-meal ..urk.
we can speak only of a greater or lesser probability of occurrence and the
reliability of this or that treatment for HDS. Laboratory research experience
an,' actual usage of pressure suits in space Plights have attested to the fact
that stich probabilities are extremely small. However, when it is necessary
to carry out systematic and prolonged work outside a space ship, in open space,
even small probabilities may become fact. So it is appropriate to review those
measures materially decreasing the probability of HDS occurring. In addition
to increasing the pressure within the suit, the following measures may be cited:
--special selection of cosmonauts,
--increasing desaturization time,
--replacement of the artificial atmosphere's nitrogen with a weakly
soluble and poorly diffusing inert gas.
8


Hazards of high altitude decompression sickness during falls in barometric pressure from 1 atm to a fraction thereof

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