This dissertation has been microfilmed exactly as received 66-10,003
BOWERS, Richard William, 1938- DETERMINATION OF THE EFFECTS OF VARIOUS HE LIUM—OXYGEN AND AIR ENVIRONMENTS UPON METABOLIC AND THERMAL RESPONSES IN MAN.
The Ohio State University, Ph.D., 1966 P h ysiology
University Microfilms, Inc., Ann Arbor, Michigan DETERMINATION OF THE EFFECTS OF VARIOUS HELIUM-OXYGEN
AND AIR ENVIRONMENTS UPON METABOLIC AND
THERMAL RESPONSES IN MAN
DISSERTATION Presented In Partial Fulfillment of the Requirements- for the Degree Doctor of Philosophy in the Graduate School of The Ohio State University
By
Richard William Bowers, B.Sc. in Ed., M.A.
#**###
i -
The Ohio State University 1966
Approved by
Adviser Department of Physiology To my wife
Carolyn
-
.11 ACKNOWLEDGMENTS
To Professors Donald K. Mathews and Edwin P. Hiatt
I express sincere appreciation for their guidance and in spiration in my academic pursuits and in the realization of this study.
For his most generous technical assistance I am grateful to my colleague and friend, Dr. Edward L. Fox.
For their continuing help and criticism during the writing of this dissertation, I thank Professors Charles W.
Smith, Joseph Lipsky, and Harold S. Weiss.
I wish to thank the subjects, Walter Ersing, Guntis Kalnins, Robert Bartels, William Bock, and Donald
Harper for their cooperation and perserverance.
I wish also to thank The Mershon Foundation for support which it provided.
iii VITA
June 23, 1938 Born - Centerburg, Ohio
1960 B.Sc. in Ed., The Ohio State University, Columbus, Ohio
1961 M.A., The Ohio State University, Columbus Ohio
1960-1962 . . Graduate Assistant, The Ohio State Uni versity, Columbus, Ohio
1962-1964 Fellow, Central Ohio Heart Association, College of Medicine, Department of Physi ology, The Ohio State University, Columbus Ohio 1964-1966 • • Instructor, The Ohio State University, Columbus, Ohio
PUBLICATIONS Pox, Edward L., Bartels, Robert L., and Bowers, Richard W . , "Comparison of Speed and Energy Expenditure for Two Swimming Turns," Research Quarterly, 34 (3); 322, 1963.
Mathews, Donald K., Bowers, Richard, Pox, Edward, and Wilgus, William, "Aerobic and Anaerobic Work Efficiency Research Quarterly, 34 (3): 356, 1963. Bowers, Richard W., "Maximal Pace Running: A Challenge," Ohio High School Athlete, XXIV, No. 4 (February, 1965)
FIELDS OF STUDY Major Field: Physiology
Environmental Physiology. Professor Edwin P. Hiatt
Exercise Physiology. Professor Donald K. Mathews Minor Field: Physical Education
Physical Education. Professor Donald K. ..Mathews
v CONTENTS
Page
ACKNOWLEDGMENTS ...... Ill VITA ...... lv
TABLES ...... vil
j FIGURES ...... viii Chapter
I. INTRODUCTION ...... 1 Related Literature Statement of the Problem
II. METHODS AND PROCEDURES ...... 7 Methods Procedures
III. R E S U L T S ...... 18
IV. DISCUSSION ...... 29
V. SUMMARY AND CONCLUSIONS...... 37 Summary Conclusions
APPENDIX ...... 39
REFERENCES...... 51
vi TABLES
Table Page
1. Mean and S.E. (N=10) of Initial and Final Heart Rates for Each Condition • ••••••• 28
2. Summary of the Analysis of Variance of Oxygen Consumption • • ...... 40
3. Oxygen Consumption (Ml./MIn./M2) for All Experiments . • ...... 41 4. Summary of the Analysis of Variance of Mean Skin Temperature ...... 42
5. Summary of t-Test Between Air and He-02 Surrounding Environment ...... 43
6. Summary of Analysis of Variance of Rectal Temperature ...... 44
7. Summary of the Analysis of Variance for Mean Body Temperature...... 45
8. Respiratory Exchange Ratios (R) for All Experiments ••••.•• ...... 46
9. Expired Gas Volumes Expressed in Liters/Min. (STPD) ...... 47
vli FIGURES Figure Page 1. Isolator and Spirometry System ...... 8
2. Arrangement of Subject, Fan, Heater, Radiators, and Entry Port ...... 1.1
3* Illustration of Sic in Temperature Recording System ...... • • • 13 4. Means and S.E. (N=10) of Oxygen Consumption Expressed in Ml. Oxygen Per Minute for All Experiments ...... 19
5. Comparison of the Means and S.E. (N=20) of Oxygen Consumption for Environments In dependent of Breathing Gases and Breathing Gases Independent of Environment, O2 Con sumption Expressed as Ml. Per Minute ...... 21
6. Mean Skin Temperature (°F.) and,S.E. (N=10) for All Experiments ...... 22
7* Means and S.E. (N=10) of MST for All Air Environments (I and II) Compared with All He-02 Environments (III and IV) Expressed in °F...... 23 8. Means and S.E. (N=10) for Rectal Temperature Expressed in °F. for All Experiments...... 26 9. Means and S.E. (N=10 for Mean Body Temper ature In °F. for All Experiments...... 27
10. Theoretical Heat Loss (Cal./Hr.) by Con- duction-Convectlon In a Helium-Oxygen Environment Utilizing Data of DuBois (29). . . 32 11. Means and S.E. (N=10) for Heart Rate in Beats Per Minute for All Experiments...... 48
viii Figure ^ Page 12. Means and S.E. (N=10) for Isolator Temperature in °F. for All Experiments .... 49 13* Means and S.E. (N=10) for Isolator Relative Humidity Expressed in Per Cent •••••••• 50
ix CHAPTER I
INTRODUCTION
With the advent of space travel and the necessity of astronauts to be provided with an environment which will allow them to survive in space, the investigation of arti ficial environments becomes essential. Because of the tendency for man to develop bends while decompressing in an atmosphere containing nitrogen, this gas is not considered to be the most ideal in artificial environments (2, 8). An environment of pure oxygen also has certain disadvantages including the possibility of pulmonary atelectasis, fire hazard within the space capsule, and damage to the central nervous system which can be serious and permanent (2).
According to Bond (2), among the inert gases, helium and neon appear to be the most favorable as a substitute for nitrogen. It is known that man and lower animals can exist in a helium-oxygen environment, but the physiological mani festations on living organisms following the removal of nitrogen and its replacement by helium have not been ex tensively studied. Experiments on mammals have indicated that metabolism is increased. It has been suggested that this observation is the result of a prominent cellular effect 1 of helium acting as a catalyst in intermediary metabolism
(4, 5» 6, 7» 25, 30)* A second explanation is based upon the assumption that the presence of helium in the environment causes a greater heat loss from the surface of the skin due to the higher thermal conductivity coefficient of helium in relation to nitrogen (8, 10, 20, 22, 28); the effect is to cause a compensatory increase in oxygen consumption. One might also propose that the increase in oxygen consumption is the result of a combination of both mechanisms.
Related literature
The majority of studies involving the effects of a helium-oxygen environment on metabolism have been in vitro and in vivo experiments on small insects, poikilo■thermic vertebrates, and mammals. Cook (4) has reported increases in oxygen consumption for larvae (16*7 per cent), pupae
(18.5 per cent), and adult stages (5*3 per cent) o f Tenebrio molitor. Mice were also studied and found to have an ac celerated carbon dioxide production. Frankel (12) attempt ing to duplicate Cook‘s experiments found no acceleration in metabolism among the insects. Cook, South, a n d Young (7) reported a 40 per cent increase in oxygen consumption and a 27 per cent increase in carbon dioxide production when mice were exposed to a helium-oxygen environment for six . * hours. The authors felt that the increases were definitely related to cellular effects of helium since they found sig nificant elevations in oxygen consumption of diaphragm (22.4 per cent), liver (13.1 per cent), and ventricle slices
(10.4 per cent). Young and Cook (30) reported that body size in mice affected the extent of increased oxygen consumption wlien the animals were exposed to 80 per cent helium-20 per c e n t oxygen. The larger animals showed greater changes in oxygen consumption than the smaller animals when exposed to th.e artificial environment. South and Cook (25) found an increase in oxygen consumption and carbon dioxide production to the same extent in mouse liver slices in a helium-oxygen atmosphere. Cook and South (6), following up their previous work:, chose to investigate the effects of a helium-oxygen atmosphere on oxygen uptake of mouse tissue slices and on sarcoma A274 slices. The results showed an 8.5 per cent in crease for brain slices and a 28.1 per cent increase for sarcoma. In a 60 per cent helium-40 per cent oxygen environ m e n t at 0.5 atmospheres pressure Cook and Leon (5) found ah increase of 8 per cent in oxygen consumption of white rats o v e r a seventy-two hour period.
In recent years, emphasis has changed from investi gation of the cellular effects of helium to investigation of tlie possibility that the difference in thermal conductivity between helium and nitrogen was responsible for accelerated metabolism. Using laboratory white mice, Leon and Cook (20) measured oxygen consumption during exposure to three differ ent environmental temperatures (19.5° C., 25.0° C. and 29.7°
C.)« At a chamber temperature of 19*5° C. oxygen consumption of the experimental group was 46.4 per cent higher than con trols, whereas a chamber temperature of 29*7° C. resulted in a 4.6 per cent difference. The greater oxygen consumption in helium-oxygen was attributed to greater heat loss as the temperature gradient increased. Weiss et al. (28) have shown that chicks hatched and raised in an 80 per cent helium-20 per cent oxygen environment consumed 16 per cent more feed while their weight gains were the same as controls, indi cating greater metabolic activity. The greater metabolic activity and the observation that the chicks tended to hud dle more in helium-oxygen were theorized to be the result of
•j Increased heat loss by the chicks in helium.
Boriskin et al. (3), experimenting with chick and frog embryos, found no differences in development of these organ isms. They also found no differences in the growth of chicks, white mice, and dogs. However, animals in helium-oxygen environments required an environmental temperature approxi mately 10° C. higher than that required by control animals to maintain "normal activity." The skin and muscle temper ature of a dog in helium-oxygen at an ambient temperature of
23 to 26° C. was 0.7 to 0.9° C. lower than normal, energy ex penditure was elevated, and heart rate was ten beats higher than normal. When the temperature in the chamber was raised to 28° C., body temperature and activity became equivalent to that of a dog In air at an ambient temperature of 19*5 to 22.5° C. 5 Dianov (8) reported the effects of prolonged exposure to a helium-oxygen environment. Two subjects were studied for ten and twenty-five days, respectively, during which time they displayed gradual increases in resting ventilation and heart rate, as well as gradual increases of ventilation during mild exercise.1 However, it was emphasized that the changes were not associated with the presence of helium, but were due to the prolonged state of hypodynamia and the re lated isolation. All Increases were reversed and returned to normal upon termination of the experiment.
In an experiment in which human subjects were placed in an altitude chamber at one atmosphere pressure and ex posed to 79 per cent helium-21 per cent oxygen, Raeke (22) found a 7*9 per cent Increase in oxygen consumption over a six hour period.2 He also found evidence of greater meta bolic heat loss as reflected in decreasing mean skin temper atures. Fox (10) found that the skin temperature of human subjects who were exercising in an environmental temperature of 71° F. was lower in helium-oxygen than in air during rest, exercise, and recovery periods. When the ambient temperature was elevated to 95° F. there was no difference
1 Values were not presented in the translation. ^Raeke did not statistically analyze these data. Application of the t-test showed no significance. In skin temperature ‘between helium-oxygen and air experiments.
Pox (10, 11) theorized that the helium-oxygen became more effective in promoting metabolic heat loss as the temperature gradient between skin and air increased. He based his con clusion on the fact that the coefficient of thermal con ductivity of helium is about six times greater than that of nitrogen (14, 19).
Statement of the problem
Whether there is a catalytic effect of helium due to its presence at the cellular level, a physical effect due to the presence of helium in the environment, or a combination of these physical and catalytic influences remains equivocal.
The purpose of this study, therefore, is to determine the individual and combined effects of these factors on resting oxygen consumption and skin temperature in man during a two hour period. Previous Investigators made no effort to separate the physical and cellular aspects of this question. In addition, the subjects In these earlier studies (8, 22) had been clothed thereby tending to minimize heat loss ef fects upon the body. The length of exposure and the. clothing of the subjects have been chosen with a view to maximal practical metabolic and environmental effects. CHAPTER II
METHODS AND PROCEDURES
In studying the effects of various combinations of gaseous environments on resting oxygen consumption in man, a subject was placed in a polyvinyl isolator. The breathing gas reservoir consisted of three spirometers outside the isolator. This design allowed independent control of en vironmental and breathing gases (Figure 1)*
The physical factors controlled were: isolator temperature, relative humidity, environmental gases, and breathing gases. The physiological variables measured in cluded: oxygen consumption, carbon dioxide elimination, skin temperature, rectal temperature, and heart rate.
Methods
Five healthy males were selected as subjects. They varied in age from 20 to 35 years, in height from 67 to 76 inches, and in weight from 138 to 238 pounds. All experi ments were conducted in the early morning hours with the subjects post-absorptive and having had six to seven hours of sleep. In order to determine interaction and establish reliability of the experimental procedure, each subject was tested twice. FIGURE 1
ISOLATOR AND SPIROMETRY SYSTEM 9 Conditions. The conditions of this study included a controlled environmental temperature of 85° F. and a relative humidity of 35 per cent. The following gaseous environments were included:
1. Condition I (air:air)1 : Subject surrounded by and breathing air. 2. Condition II (He-Og:air): Subject breathing 79 per cent helium-21 per cent oxygen, Burrounded by air.
3« Condition III (air:He-Og): Subject breathing air, surrounded by 79 per cent helium-21 per cent oxygen.
4. Condition IV (He-C^sHe-Og): Subject surrounded by and breathing 79 per cent helium-21 per cent oxygen.
Subjects were exposed for two hours to each condition.
When a subject breathes helium-oxygen, the body will have a helium saturation of more than 85 per cent within two hours
(1). To eliminate the possible effects of relative humidity on heat loss, a relative humidity of approximately 35 per cent was chosen. Within a range of 20 to 80 per cent rela tive humidity, there is no alteration in heat loss due to the humidity (29). The isolator. The isolator, similar to that de scribed by Trexler (27) and modified by Pox (10), was con structed of polyvinyl and measured four by six by seven feet.
Entrance was through a 30 inch port in the floor of the isolator.
1 Hereafter, the first gas referred to is the breath ing gas while the second gas is the environmental gas. The environmental gas is defined as that gas which is in contact with the surface of the body. 10 Isolator temperature control. Two gas thermistors were suspended ten Inches from the celling of the Isolator. One thermistor used for recording Isolator temperature was attached to a switch box. The switch box also had a tele thermometer attached to It for the purpose of Indicating
Isolator temperature. The second thermistor, used as an environmental temperature sensor, was attached to a tempera ture controller* The temperature controller was connected with both heating, and cooling sources.
A portable heater-fan provided heat while cool air was provided via two twelve Inch by twelve inch by two Inch radiators connected in parallel. Ice water waB pumped through the radiators by means of a small self-priming pump from an Ice bath located outside the isolator. Uniform circulation throughout the isolator was pro vided by a portable fan located in front of the heater and radiators. Isolator temperature was maintained at 84.8 +
0.5° P. Figure 2 illustrates the arrangement of fan, heater, ice bath, radiators, and subject.
Relative humidity. A portable de-humidifier running at maximum output maintained relative humidity at 33 to 38 per cent as measured by a hair hygrometer.
Gaseous environment. For the helium-oxygen experi ments, commercially prepared 80 per cent helium-20 per cent oxygen was fed into the isolator after pump evacuation of room aii». Helium concentration was continuously maintained 11 above 70 per cent as shown by a helium analyzer (based on the thermal conductivity of He). For those experiments in which air surrounded the subject, room air was pumped into the isolator.
FIGURE 2 ARRANGEMENT OF SUBJECT, FAN, HEATER, RADIATORS, AND ENTRY FORT
ICE BATH ENTRY SUBJECT AND PORT PUMP ’AN
HEATER RADIATORS
Breathing mixtures. Three spirometers, located out side the isolator, connectedin series and having a total capacity of 1070 liters, provided a reservoir of gaB for inspiration. For the helium-oxygen breathing experiments, cylinder gas was used to adequately flush and fill the spiro meters so that the reservoir contained a helium concentration of 76-79 per cent. For air breathing experiments, room air was pumped into the spirometers.
Oxygen consumption. Oxygen consumption was measured by open circuit spirometry and was calculated by means of the following equation:
V°2 = I V - Vl) - (V , * VE 10 minutes where V02 = Oxygen consumption in ml. per minute.
F Iq 2 = Fraction of the inspired oxygen.
V_ = Volume of inspired gas collected for ten 1 minutes (STPD).
F E q 2 = Fraction of expired oxygen.
VE = Volume of expired gas collected for ten minutes (STPD).
Oxygen concentration of Inspired and expired gases was determined by duplicate analysis on the Haldane Q-as
Analyzer. Measurement and storage of inspired and expired gas volumes was managed by use of 120 liter spirometers.
Carbon dioxide production. Carbon dioxide elimi nation was determined by use of the following equation:
VC02 = (F«00 x \ 10 minutes where ^C02 = Minute volume of expired carbon dioxide.
F E q q = Fraction of carbon dioxide in expired air.
V-, = Volume of expired air collected for ten minutes (STPD). 13 Carbon dioxide concentrations in expired air were also determined by duplicate analysis on the Haldane Gas Analyzer.
Skin temperature. Six thermistors were attached to the surface of the skin on the left medial thigh, left lateral thigh, left lateral upper arm, mldllne of the chest, left cheek, and left upper back. The thermistors were connected to a switch box which was in turn attached to a read-out unit. The temperature of any one of the thermistors could be read to the nearest 0.1° F. by turning the control dial on the switch box to the appropriate position. Figure 3 is a representation of the temperature reading system.
FIGURE 3 ILLUSTRATION OF SKIN TEMPERATURE RECORDING SYSTEM
SKIN THERMISTORS
SWITCH TEMPERATURE BOX READ-OUT
Rectal temperature. A thermiBtor was Inserted by the subject five inches into the rectum and attached to a temper ature read-out box separate from the switch box. Temperatures were read to the nearest 0.1° F. 14
Heart rate. Electrode leads from a transmitter unit were placed on the rib cage of the subject. Heart rates were then determined from signals transmitted to a receiver unit connected to a Sanborn Vlsocardlette (Model 51) electro cardiograph.
Calculation of mean Bkin temperature. Mean skin temperature was calculated at ten minute Intervals by modi fication of the method of Teichner (26). The modification
Involves dividing the sum of the weighted factors in his equation by 0.67 to compensate for weighted factors which
Teichner omitted from his final equation. The equation as used in this study is:
(0.1 XT,) + (0.07) (T2) + (0.125)(T,+T4+T.+T6 ) MST = ------— -— ---- 0.67 where MST = Mean skin temperature.
T| = Left cheek temperature.
T2 = Left lateral upper arm temperature.
T^ = Left upper back temperature.
T4 = Left lateral thigh temperature.
T^ = Left medial thigh temperature.
Tg = Chest temperature.
Calculation of mean body temperature. The method of
Hardy and DuBois (17) was utilized to calculate mean body temperature. Computations were made by meanB of the follow ing equation:
MBT = (0.8) (T ^ + (0.2) (T2) 15 where MBT = Mean body temperature. Tj = Rectal temperature. T2 = Mean Bkin temperature.
Procedures
All experiments were performed between 5:00 and 8:00
A.M. on post-absorptive subjects dressed in shorts. Prepa ration outside the isolator Included attaching patch ECO electrodes to the lateral rib cage and fitting a breast plate support for the Douglas directional breathing valve.
After the subject entered the isolator the port was sealed and the chamber was inflated with room air to a pres sure of 1-2 cm. of water. The subject then proceeded to position the skin and rectal thermistors, adjust the nose clip and Douglas valve-mouthpiece assembly, and assume a comfortable sitting position. The entire process required approximately fifteen minutes, during which time isolator temperature and relative humidity were established.
For experiments in which helium-oxygen was the immersion gas, a wash-out procedure requiring the cooper ation of the subject was necessary. The pump in the iso lator could be maneuvered in such a way that the isolator could be inflated or evacuated. The first step in filling the isolator with helium-oxygen was to lower the supporting framework and collapse the Isolator around the subject.
Cylinder gas was then fed into the isolator until it was one-fourth filled. The isolator was again collapsed and then filled completely. The concentration of helium within 16 the isolator was above 70 per cent while oxygen and nitrogen concentrations were approximately 20 and 10 per cent, re spectively.
After obtaining initial readings of skin temperature, rectal temperature, Isolator temperature, relative humidity, and heart rate, a timer was started and these parameters were recorded thereafter every ten minutes for two hours. The time required to read and record all values was two minutes.
Two ten-minute gas collections were made during the experi ment: The first after one hour of exposure (fifty-five to sixty-five minutes) and the second after two hours of ex posure (115 minutes to 125 minutes). At the conclusion of the Becond gaB collection the experiment was terminated.
All measurements of inspired and expired gas volumes. were made with two 120 liter chain-compensated spirometers.
Just before collection a tracing pen was placed on the re volving kymograph of each spirometer. With one aide giving a count-down, a second aide turned both spirometers on simultaneously. A similar procedure was followed at the conclusion of each ten minute collection period. Just be fore the collection period started and Just as it ended, the subject was Instructed to take an inspiration and then exhale and hold his breath until the spirometers had been turned on or off. At the end of the ten minute collection period, valves were manipulated so that the subject breathed from reservoir spirometers. Twenty minutes after the collection period, samples of both Inspired and expired gases were collected over mercury in 125 ml* gas collecting tubes and stored for analysis of oxygen and carbon dioxide concentrations. In spired and expired gas samples were also collected separately
In two one-liter rubber collecting bags and immediately ana lyzed for helium concentration. CHAPTER III
RESULTS
The primary problem under investigation was to determine if a catalytic effect, physical effect, or a
combined catalytic-physical effect of the possible combi nations of environmental and breathing components of hellum- oxygen exists in man.
Internal analysis utilizing the analysis of vari
ance was completed for oxygen consumption, mean skin temper
ature, rectal temperature, and mean body temperature. Graphs were also presented for oxygen consumption, mean skin temper
ature, rectal temperature, mean body temperature, and heart rate.
Oxygen consumption. Although individual differences
in oxygen consumption among the subjects occurred (Tables 2
and 3 in Appendix), imposition of the experimental conditions had no effect on resting oxygen consumption (Figure 4).
In all cases, oxygen consumption was lower the second hour than it was the first (Figure 4). Although the subjects
were post-absorptive and rested, they were presumably not
completely relaxed at the beginning of the experiments. How
ever, as the experiment progressed and as the subjects became
18 V
V
II . Ill IV 3 6 0 — (Air:Air) (He-02:Alr) (Air:He-02) (He-02:He-02)
3 2 0 -
- 2 8 0 - g 240- f—1 280 294 Second ±18 i ifi Hour
£■_!20_—
MEANS-AND S.E. (N=10) OF OXYGEN COMSUMPTION EXPRESSED IN ML OXYGEN PER MINUTE FOR ALL EXPERIMENTS
vo 20 accustomed to the respiratory apparatus they apparently be came more relaxed. Some indication that relaxation did occur is offered upon examination of the decreasing heart rates from 60 minutes to 120 minutes (Figure 11 in Appendix).
Subject-condition interaction was shown for all cases from the first hour to the second. One possible interpre tation of this interaction is that the differences in the surface area of the subjects were responsible. Since a larger subject would have a larger surface area exposed to the environment he would have a greater potential for heat loss.
Treating the oxygen consumption data by examining the effect of breathing gases independent of surrounding gases and surrounding gases independent of breathing gases further shows the lack of any effect by a variable other than time on oxygen consumption. This comparison is illustrated in
Figure 5 where air environments, Conditions I and II, and helium-oxygen environments, Conditions III and IV, were practically identical in terms of oxygen consumption. Air breathing, Conditions I and III, and helium-oxygen breathing experiments, Conditions II and IV, also were observed to have no differences in oxygen consumption. Mean skin temperature. As shown in Figure 6, there was, in general, an initial rise in MST and then a gradual decline to the termination of the experiment. Appreciable individual differences among the subjects existed at the 0 - r Environment Independent Breathing Gases Independent of Breathing Gases of Environment -320-4-
1240 271 29 1 2 B ‘ t io Air
He-0 t+
_: 4o —
r o - First Hour Second Hour Hour Second HourFirst
FIGURE 5
COMPARISON OF THE MEANS AND S.E. (N=20) OF OXYGEN CONSUMPTION FOR ENVIRONMENTS INDEPENDENT OF BREATHING GASES AND BREATHING GASES INDEPENDENT OF ENVIRONMENT, 02 CONSUMPTION EXPRESSED AS ML PER MINUTE Ml SAN SKIN T3 CMPERATURE ( °F AND S.E (N=1 0) FOI: ALL EXPERIMENTS | Air :Alr Moans and 3 =10) ifor M S T __ 1 He-Oo:Ai:? TIME IN MINUTES f---- «► Air: He-0 CONDITION 30 6 0 1 9 0 120 T --- 1 He-0o:Heii /AIR 90.77t0.33!90.8l t 0.27 90.631 0.28AIR 90.79 ± 0.25 91.041 0.22 AIR/HE-0: 90.84 i 0.39 90.81 to . 19 90.41 ±0.13 90.29 i 0.02 OH-2 90.62t 0.22 90.88 ± 0.10 90.201 0.19;90.IO±-0.1 & .
- -O-
c+
H*
20 3 0 5 0 GO 7 0 8 0 100 110 igo Tine in Minuses 23 beginning of the experiment b u b -were not evident at the end of the experiments (Table 4 I n -Appendix).
One somewhat puzzling zfT inding resulted when the ex periment was repeated. For t h e first trial significance was obtained for subjects, c o n d i t i o n s , and time; while for trial two significance was not shown if*or these items. This dis parity between trials one and. "fc-wo in no way affects the conclusion that helium-oxygen d i d affect mean skin temper ature . Upon examination of F i g u r e 6 again, it is seen that the plots for (He-02:He-02) a r e "below plots for all other conditions. Concition III ( a i r i H e ^ ) plots also fall into this pattern. When the t-tesb w a s applied to the final MST no significance was shown a m o n g bhe four conditions. How ever, there does appear to be a "biological difference among
the conditions.
Assuming that b r e a t h i n g neither air nor helium-oxygen has any effect on skin tempera*fc.-«j.re, the mean skin temperature
values for all experiments in w l n i c h the subjects were sur rounded by air, Conditions I aricL II, were compared with the mean skin temperatures in the lieHum-oxygen surrounding Conditions III and IV. Table 3 (see Appendix) summarizes the results of'the t-test b e t w e e n the two variables., Mean
skin temperatures at the starb a n d after ten minutes in the experiment showed no slgnificaru*fc. differences while thereafter, 24 except for readings at 70 minutes, MST was significantly different (Figure 7).
Rectal temperature. Figure 8 shows the course of rectal temperature throughout all experiments. Again, the heterogeneity of the subjects was shown at the beginning and end of the experiments (Table 6 in Appendix). Subject- condition interaction was obtained for final rectal temper ature indicating the individuality of the subjects in re sponding to the conditions. Mean body temperature. MBT decreased in every experiment and there was a significant separation after two hours exposure (Table 7 in Appendix). Study of Figure 9 shows that there appears to be a separation of the record ings for conditions III (air:He-02) and IV (He-02:He-02) from the air surrounding conditions. Since MBT is computed’ using the values for MST and rectal temperature one might expect, after analysis of MST and RT, a separation among the environments. Heart rate. Except for initial readings for Con dition I (air:air) heart rates were very similar throughout the entire study (Figure 11 in Appendix). In all conditions except Condition II (He-02:air) heart rate was less at the end of the experiment than at the beginning. Values for mean and S.E. are shown in Table 1. . i ..... o o MEM S AND S .E • (N=lb) OP MST j’OR A jL a i * ENV ER0NM1SNTS ( I a n i i i ) &ED 1flT H
1 A LL Hej-Og E JVIRO.tMENT 3 ( I I [ a n d IV) SXPREL3SED :n ° f ... . m
I i . > Me in a n 1 S .E , (N = 0 ) f( >r i j ■ l i r e] lv ir o ]im en t j 1 J - fli- I [jegen , . 9 1 .4 - i Me m an< 1 S .E . (N = 0 ) f< >r l e —Og e n v i]’onme] i t s 9l;£ P
• r At n ■ ( »-3 rr \ (D X.x. •• B \ x \ © SO rd-( \ 4 ' \ P> r* * e+ V \ N ^ I £ 1/ ■ \ ... ^ "W.« 1 \ a> < i \ H* P' . 1 } o r •*1 • 4 9U*cAf\ O j
90*0nn ft N i
0 9 .8 <> ~ 1D 20 30 4 0 . 5 o e 0 7 0 8 3 9 O K >o w O \ i o _
T i ne i n M in u tes
- ro VJ1 V
FIGUJ
MEiJJS MD S.E. fN=:10) EOR RECTAL TEMPERATURE EXIRES3E D IN 'P. FOR ALT. 4 Air:Air Moans ;.nd 3, for LT •° He- OotAfr TIME IN M1NUTEV
CONDITION 3 0 6 0 9 0 120 ~ AIR/AIR 98-701 0.20 98.62i 0.18
98.30 i 0.13 98.211 0.14 98.6610.13 98.49+ 0.14 98.17+ 0.U98.05+ 0.14
H-
20 4 0 9 0 O .J. T3me ir. Mlnttes i _ a a .a \ u o\ FIG-U1
ME. LNS A] ro s.i !. (N: :10) ]’OR MIM _B(IDY T1 -3 £ Kl FOI I ALL EYPEl tTMEW 'R ’ Air :Air MeJms a]tLd S.I :. 1N: :10) :'or MIIT — » He-i )? :Ai' V TIME IN MINUTES _ >.. -< : O 30 GO * Air :He-0 > CONDITION 90 120 ’ K---H 9702 ±0.15 J 3 6.67± 0.10 H g ** >«sHe- ■Op AIR/AIR 38.97 ±0.13 96.B0±0.I1 96.75±O.IO "C ' cl HE-Oa/AIR 97.11 ±0.18 <37.IO± 0.16 96.96±0.)4 96.88 ±0.14!36.84 ±0.14 air/m e o 297.14 ±0.12 37303± 0.13 9Gj85±0-I4 96.65± O-l 2!36.52 *0J0 HE •Og/to-Qj, 97.05±0.l 3 3 6,93 ±0.12 96.75iO.14 96.57 ± 0.14 36.46*0.14
3A7 1 m A
H3 0 7 f% CD 7T« fc € CD Jfc, ^ w. | 0j 7* *y n 1 L*V \ C+ N\ *“--- - £ y ►-— CD or o t ( ---- L< - ---- i 90,0 . H* 1 y ► o •— — ■< 73 • • -■i » y
ro -0 28
TABLE 1
MEAN AND S.E. (N=10) OP INITIAL AND PINAL HEART RATES FOR EACH CONDITION Condition Tims I II III IV
Initial 64.9 + 3 59.6 + 1.9 60.8 + 2.1 60.8 + 2.6 Final 57.6 + 2.1 59.6 ± 2.1 56.8 + 2.0 56.8 + 2.7
The pattern of heart rate responses Indicated, as did the patterns for oxygen consumption and rectal temperature, that the subjects became more quiescent as the experiment progressed.
Respiratory exchange ratio. Table 8 (see Appendix) shows values for R. Because the subjects were more than 85 per cent' saturated with helium after two hours exposure (1) comparisons were made between the second hour values of the combination of air breathing experiments, Conditions I and
III, and the combination of helium-oxygen breathing experi ments, Conditions II and IV. The combined mean value of R for Conditions I and III was 0.85 + 0.02 while that for Conditions II and IV was 0.82 + 0.02. Ventilation volume. Values for Vg are presented in
Table 9 (see Appendix). There are no indications of devi ation from normal values. The range of mean values over the entire study was 6.03 liters per minute to 6.91 liters per minute• CHAPTER IV
DISCUSSION
The thermal comfort zone for man ranges from 82.4 to
87.8° P. (15, 16, 18, 23). In this zone the thermal condi tions of the environment with a relative humidity of 30 per cent are such as to provide a natural escape for the body heat at exactly the rate of its production (15)* On either side of the thermal neutral zone, heat loss is increased either by sweating or by Increased radiation and conduction as skin temperature drops (15, 19). In either case heat production or oxygen consumption may be altered. In this study, the isolator temperature of 85° F., which falls in the middle of man's thermal neutral zone, was selected in order to reduce the possibility of pilo-erection or shiver ing in any of the four conditions. Although It is recognized that shivering usually does not occur until an external temperature of 73*4° P. is reached, heat production may be increased with the onset of pilo-erection at a higher temper ature (23)» In a preliminary study, it was found that a subject experienced pilo-erection and felt cold when exposed to an air temperature of 80° P. for one hour. Dianov (8) has suggested that the thermal comfort zone in a helium-oxygen
29 30 environment is shifted upward and narrowed even when subjects are clad in cotton jersey underwear and athletic training clothes.
If the subjects were to react differently in the three experimental conditions when compared with the control, one must conclude the causative factors to be either breath
ing and/or being surrounded by a helium-oxygen mixture. If the subjects showed no differences in reacting to the environ ments, then one must conclude that the helium-oxygen had no effect on the subjects under the conditions of this study.
Both temperature and relative humidity of the isolator were the same in all conditions (Figures 12 and 13 in Appendix).
Because of differences in thermal conductivity, vis
cosity, and density (14, 19, 24) between helium and nitrogen, heat loss via conductlon-convection (21) would be 3*2 times more in helium-oxygen than in air. This would be true only
if there were no physiological adjustments by the subjects.
Although conductive and convective heat loss make up only
about 15 per cent of the heat loss in resting man (13), ap parently the presence of helium-oxygen in the environment had an effect on the subjects. There was a separation in
MST between air surrounding and helium-oxygen surrounding environments. The greater MST decreases in helium substanti
ates the findings of Fox (10), Dianov (S), and Raeke (22). 31 Any time heat loss is greater than heat production in' the body, one of several responses may he seen: (1) peripteral vasoconstriction, (2) a slight drop in rectal temperature, and (3) a drop in rectal temperature followed by a compensa tory increase in oxygen consumption as a result of Increased metabolism. Rectal temperature changes may be accounted for by the light activity of the subjects in preparing for the experiments. If the decrease in rectal temperature had been a reflection of the different environments there would have been a separation in the rate of decrease among the con ditions. This separation did not occur although it appears that during the last half of the experiment, the rate of decrease for helium-oxygen environments may have begun to increase (Figure 8).
Even though the experiment was conducted in the thermal neutral zone, there was a greater decrease in MST in helium-oxygen compared to air. The most plausible reason for the MST separation is that peripheral vasoconstriction took place, thus conserving internal heat. By studying Figure 10, one would predict a greater heat loss in helium-oxygen, but the extent of heat loss could not be predicted because of the homeostatic nature of man. The lack of predictability is reflected in the comments of the subjects as they reacted to the air and helium-oxygen environments. Typical comments after the air surrounding experiments were, ". . . no sense of heat or cold, felt very 32
THEORETICAL HEAT LOSS (Cal./Hr.) BY CONDUCTION-CONVECTION IN A HELIUM-OXYGEN ENVIRONMENT UTILIZING DATA OF DuBOIS (29) Assuming conductive heat loss to he 3 per cent and convective heat loss to be 12 per cent of total heat loss, heat loss via conduction-convection would be increased 3«2 times in a helium-for-nltrogen environment. Values for heat loss are relative since theoretical values for time and equation constants were utilized in the conduction and convection equations (21). ■ 9 He-Ct, Environment — — If heat loss were great enough, there would be a compensatory increase in heat production which would have been reflected in oxygen consumption increases. The results of the F-test showed no differences among the conditions with respect to oxygen consumption. When oxygen consumption data are compared by environments only, I.e., surrounding gas, there is still no difference. In like fashion, air breathing and helium-oxygen breathing experiments were compared and found to be the same. Further evidence that oxygen consumption is not altered in the experiment by the presence of helium Is available upon examination of the changes in oxygen con sumption at the end of the' first hour compared with changes at the end of the second hour. If there were to be a cellu lar effect of helium after two hours exposure, one might expect to see altered oxygen consumption results for Con ditions II (He-Ogiair) and IV (He-0 2 :He-0 2 ) compared with air breathing experiments. In all cases, except Condition IV (He-02 !He-0 2 ) of trial two, oxygen consumption waB lower the second hour. At the time of the second hour collection in the He-02 breathing experiments, the body was more than 85 per cent saturated with helium (1 ), yet oxygen consumption 35 had decreased as though there were no helium present* The observation that oxygen consumption was not altered under any circumstance, except time, leads to the conclusion that.-' heat production was not measurably affected in any of the experimental conditions* Although no alteration in oxygen consumption was noted, there may have been some change in intermediary meta bolism affecting C02 elimination* A change in the respira tory exchange ratio would have been seen in this case* How ever, since R'was not altered there is no evidence available that any metabolic pathway underwent modification. Although Dlanov (8 ) exposed his subjects to an environment in which they were surrounded by and breathing helium-oxygen for several days, he found no effects on rest ing oxygen consumption above those of air environments, in man, under closely controlled conditions of temperature and relative humidity* Raeke (22) reported a 7*9 per cent in crease in oxygen consumption over a six hour period in human " subjects who were clothed in light weight flying suits. It was felt by Raeke that the accelerated metabolism was due to greater body heat loss in helium-oxygen than in air. This observation seems reasonable in light of the fact that the chamber temperature was 75 + 2° P. This temperature is on the lower edge of the thermal comfort zone as suggested by Dianov (8 ). Upon examination of Raeke*s data for the first two hours of his experiment, there was found to be very 3 6 little difference between air control and helium-oxygen ex periments, even at 75° F. (0.56 cubic feet oxygen per half- hour or 264 ml. per minute in air and 0.55 cubic feet oxygen per half-hour or 259 ml. per minute in helium-oxygen). The reason for the reported increases in oxygen consumption in small mammals and tissue samples of small mammals has not been resolved, but whatever the causative mechanism it apparently is not operative in man in a com fortable environment after two hours exposure. CHAPTER V SUMMARY AND CONCLUSIONS Summary The purpose of this study was to determine if there were any catalytic or physical effects on resting man of various combinations of helium-oxygen and air gas mixtures. All experiments were conducted at an environmental temper ature of 85° F. and a relative humidity of 33 to 38 per cent. Each experiment lasted two hours and five minutes and was conducted in a sealed polyvinyl isolator at a pressure of 1-2 cm. of water. Physiological variables measured at ten minute intervals were: skin temperature, rectal temperature, and heart rate. Oxygen consumption was measured after one and two hours of exposure. Mean skin temperature and mean body temperature were calculated. Isolator temperature, relative humidity, and concentration of helium were, measured as well as inspired and expired concentrations of oxygen, carbon dioxide, and helium. Conelusions Analysis of variance showed that resting oxygen con sumption and rectal temperature were not significantly altered in any of the experimental conditions. Mean skin temperature 37 was significantly lowered when subjects were exposed to a helium-oxygen encironment. A temperature gradient of 6° F. (skin to environment) was apparently sufficient to cause a greater heat loss via conduction and convection. The measured lower MST values in helium-oxygen were apparently the result of peripheral vasoconstriction which had the effect of mini mizing or preventing internal heat loss. It must be concluded that the effect, considered to be environmental, which was present was small and produced no alteration in metabolic rate in an environment of 85° F. and low relative humidity during a two hour period. APPENDIX V APPENDIX TABLE 2 SUMMARY OF THE ANALYSIS OF VARIANCE OF OXYGEN CONSUMPTION F Value Main Effect Interaction Analysis of Variance (df=4) (df=3) (df=1) (df=12) (df=4) (df=3) „ in * i Subject- Subject- Condition- Subject Condition Trial CondJltlon °ViaI Trial First hour for trials one and two 4.22a 0.37 1.96 0.87 0.29 ■0.69 o Second hour for trials one and two 6A9h 1.03 2.01 0.34 0.61 0.14 Trial one for first and second hour 15.52b 2.31 5.58a 3.55a 0.69 0.60 Trial two for first and second hour 8.5 6b 1.13 3.68 1.59 0.05 0.76 F(1,12) 0.05 4.75 F(4,12) 0.05 - 3.26 0.01 9.33 0.01 = 5.41 F(3» 1 2) 0.05 3.59 F(12,12) 0.05 = 2.69 0.01 6.22 . 0.01 = 4.16 a p <■ 0.05 b p < 0.01 V \. 41 TABLE 3 OXYGEN CONSUMPTION (Ml./Mln./M2) FOR ALL EXPERIMENTS Trial One Condition Sub I II III IV ject 1 2 1 2 1 2 1 2 W.E. 140.0 151.6 142.2 121.1 136.1 113.9 214.4 148.9 G.K. 135.1 138.8 167.0 168.1 166.0 155.3 142.0 146.8 Boo. 186.6 177.8 118.0 136.1 156.7 129.9 118.4 164.4 £ 00 Bar. 162.6 150.4 131.5 137.8 • 144.1 155.5 131.9 O C D.H. 156.5 133.5 162.9 • 160.0 153.5 132.9 136.5 X 156.2 150.4 144.3 139.0 152.1 139.3 164.6 145.7 Trial Two W.E. 142.8 136.7 132.2 126.1 152.2 143.9 146.7 121.7 G.K. 163.3 149.5 149.5 130.3 158.0 150.0 137.8 153.2 Boc. 163.9 119.1 131.4 "118.0 133.5 120.1 125.3 146.9 Bar. 119.3 132.8 168.1 140.8 137.4 102.9 129.4 145.4 D.H. 172.4 140.6 138.8 148.8 128.8 109.4 158.8 134.7 X 152.3 135.7 144.0 132.8 142.0 125.3 139.6 1 40.4 TABLE 4 SUMMARY OF THE ANALYSIS OF VARIANCE OF MEAN SKIN TEMPERATURE F Value Main Effect Interaction Analysis of Variance (df=12 ) (df=4) (df=3) (df=4) (df=3) (df=1) Subj e c t- Subj e c t- Condition- Subject Condition Trial Condition Trial Trial Beginning MST for trials one and two 3-97 0.22 0.74 0.40 2.03 0.84 Final MST for trials one and two 1.45 2.52 7 .00* 0.42 . 1.45 1.30 Trial one for initial and final MST 18.9113 6.91b I9.73b 3.27 6.45 0.81 Trial two for initial and final MST 1.38 0.96 1.13 2.25 1.29 0.38 F(1,12) 0.05=4.73 F(4,12) 0.05 = 3.26 . 0.01 = 9.33 . 0.01 = 5.41 F(3»12) 0.05 = 3.59 F(12,12) 0.05 = 2.69 0.01 = 6.22 . 0.01 = 4.16 a p < 0.05 b p< 0.01 ro TABLE 5 MST SUMMARY OF t-TEST BETWEEN AIR AND He-Og SURROUNDING- ENVIRONMENTS Time t P Start 0.83 N.S. 10 0.56 N.S. 20 3.44 0.05 30 2.68 0.05 40 3.33 0.05 50 2.75 0.05 60 5.87 0.01 70 1.91 N.S. 80 3.07 0.05 90 7.67 0.01 100 4.31 0.01 110 3.08 0.05 120 5.28 0.01 TABLE 6 SUMMARY OF ANALYSIS OF VARIANCE OF RECTAL TEMPERATURE F Value Main Effect Interaction Analysis of Variance (df=12) (df=4) (df=3) (df=4) (df=3) (df=1) Subject- Subject- Condition- Subject Condition Trial Condition Trial Trial Initial rectal temperature for trials one and two 47.33b 1.33 27.00b 1.66 1..33 3.00 Final rectal temperature for trials one and two 5.44a 2.33 15.44b 9.89b 1.00 1.44 Trial one for initial and final rectal temperature 19.33b 3.33 93.67b 3.67a 50.33b 5.33a Trial two for initial and final rectal temperature 38.00b 9 .00b 107.00b 4.50b 19.00b 0.15 F(1,12) 0.05=4.75 F(4,12) 0.05=3.26 0.01=9.33 0.01=5.41 F(3*12) 0.05=3.59 F(12,12) 0.05-2.69 0.01=6.22 . 0.01=4.16 a p < 0.05 b p < 0.01 \ TABLE 7 SUMMARY OP THE ANALYSIS OF VARIANCE FOR MEAN BODY TEMPERATURE F Value Main Effect Interaction Analysis Subject Condition Time Subject Subject Condition Condition Time Time All Experiments For one hour and two hours 7 1 .00b 11.00b 42.00b 6.00b 7.00b 3.00 F(1,12) 0.05=4.75 F(4,1 2) 0.05 = 3.26 . 0.01 = 9.33 . 0.01 = 5.41 F(3,12) 0.05=3.59 F(12,12) 0.05 = 2.69 0.01 = 6.22 . 0.01 = 4.16 a p < 0.05 b p < 0.01 •J*- VJl 46 TABLE. 8 RESPIRATORY EXCHANGE RATIOS (R) FOR ALL EXPERIMENTS Trial One ' Condition Sub I II III IV ject 1 2 1 2 1 2 1 2 ro CD W. E. .837 .575 .754 .771 .841 .722 . 6 9 4 • G.K. .874 .889 .844 .889 .872 .846 . 8 5 8 .844 Boc. .765 .922 .764 .746 .977 .893 .81 5 .922 Bar. .801 .860 .911 .765 1.018 .822 . 7 3 2 .637 D.H. .808 .824 .776 .799 .813 .782 .801 .789 X .817 .814 .810 .794 .904 ..813 . 7 8 0 .784 .020 .060 .030 .020 .040 .030 . 0 3 0 .050 Trial Two . VO W.E. .907 .882 .794 .775 V>J .834 .8-45 .877 -3- 00 G.K. .889 .893 . .935 .872 .826 . 8 5 7 .833 Boc. .780 .965 .929 .895 .842 .833 . 7 7 8 .744 Bar. .944 .937 .708 .797 .875 1.041 . 9 8 3 .864 • D.H. .919 .816 .818 -3 VO .900 .903 . 8 0 0 .952 X .868 .899 .818 .839 .884 .887 . 8 3 5 .854 tf* .070 .060 .080 .080 .030 .100 . 0 4 0 .090 .030 .030 .040 .040 .010 .040 . 0 2 0 .040 47 TABLE 9 EXPIRED GAS VOLUMES EXPRESSED IN LITERS/MIN. (STPD) Trial One Condition Sub I II III IV ject 1 2 1 2 1 2 1 2 W.E. 5.96 5.10 5.59 4.73 5.13 4.65 5.75 5.01 G.K. 6.69 6.17 8.07 8,33 6.88 6.93 6.55 6.13 Boc. 8.01 6.46 5.19 5.25 6.41 5.82 6.05 6.34 Bar. 7.61 7.56 8.02 7.32 8.32 7.87 7.37 7.42 D.H. 6.28 5.51 6.63 5.67 6.43 5.52 5.35 5.27 X 6.91 6.16 6.70 6.26 6.63 6.16 6.22 6.03 Trial Two W.E. 5.90 5.19 4.96 5.3 6 5.49 5.25 5.17 5.01 G.K. 7.27 6.58 6.83 6.39 7.41 6.50 6.83 7.20 Boc. 6.16 5.79 6.96 5.65 6.06 5.39 5.65 6.12 Bar. 8.06 8.86 8.01 8.09 7.12 8.19 7.82 9.08 D.H. 6.53 6.3 6 6.25 6.16 6.30 5.48 6.89 6.49 X 6.79 6.55 6.60 6.33 6.48 6.16 6.47 6.78 FIGU5 E 11 \ --- \ m e ;NS 'AllD S.E . (N= 10) 5OR HE ART PiATE IN BE; TS PE R MIN UTE EOR AI L EXP ERIME »-3 03 -S3 1.. " • Ail :Air tfean m d S >'E, ClN O ) for ^eart Rate K — ——H> He- 0o :AI r TIME IN MINUTES. > CONDITION O so GO 90 120 ..." > Ail :He-C 2 H--— < ► He- 02 :He-°2 AIR/AIR 64.9 t. 3.3 S3.2 t 3.6 61.G 59.6 t 2.6 57,6 1 2.2" - vA. oA . HE-Oj/AIR 59.a t 2.1 53.2 ± 2.7 GO,8 12.1 58.8 ± 2.1 59.6 12.2: AIR/ME-Oa GO. 8 t 2.2 SO.O i 2.5 GO.8 t 2.9 5,4.51 2.2 56.812.1 WVft ft 5f w © he-o 2/Ue-o 2G0.3 1 2.7 SO. 2 t 2.5 58.8 i 3 .cT 58.81 2 3 56 . 8 12j8 P ^ 4 ‘ J. r I w \ / \ p i \ / \ / \\ / \ fTV CPVC * ' \ \ * . ✓ H* ^ T1 - \ ^ ' T X P S v . \ t► -—? \> i s— \ p NA \ / td . Vw _ r * V k a> / S k ; P d* »{ C --- ( '' ' > /S > CQ \ N V t H a a - VV ' \ * w // OO _ r •tJ \ \^ CD >> ft f-- H* ©w _ >1111 “ MI CO E. (I =10) FOR ] SOLA! OR TEMPER/TURE SANS i ■5 IN °B ALL EXPEHIMEN1S < 1------j> A ll *:Air Mean and £*E» :n= io ) for Iso ls to r T enmei ature 1------? He- ■0o:A3 ,r TIME IN MINUTE* . ►------f Ai3*: He- CONDITION O 30 > 0 | 90 ! 120 °2 ! h---^ He.0o :He !—O2 AIR /AIR 84.5 ±0.11 84.8 ±0.06ja4.9 i 0.03:84.8 ±0.08!85.0±0.04 he-o 2/air 84.4 4 1.16 34.8 ±0.12 j84.8tO.ogja4.9i 0.10 \34.9 ±0.02 air/he-o * - 85.0 ±0.38 34.8 tO.ll 84.8 ±0.11 1!85.0±0.04 S34.9±0.08 HE<52/UE-Os 84.9 ±0.18 85.1 ±0.10 *85.0 ±0.09j85.O±0.18 35.1 ±0.11 i 1 ' \ AC.© fl £ 1 X ! h3 © k T------H k\ e j > / ; ^ \1 / v / \ / 1 tj / / VN. \ / \ A \ . i ' / Y - o4.ZClA 4 <> i > 20 3D 4 3 5 0 GC> 7'0 80 90 IC0 11O 120 _ t Tin e in Minut es -F^ vo i FICHtfjE 13 CO a o m IMS lND s ,E. (1 =10) FOR ] 'OR riIl a t ia E HU* IDOT EXPB ESSE I IN IER CENT > ■ * Ail *:Air I Mian ar.d S.I • (N= 10) 1or Re latir e Hun iditv >_— ’ He-■Og:AJ.V TIME IN MINUTES 11 > ■<► Ail*:He-C CONDITION ^ Q 30 60 9 0 120 *2 ► He-■0o :H€l—Op AIR AIR 38,2 + 0.96 33.910.25 34.3 t 0.64 33.9 - 0.95 33.2 1 0.53 HE>02 air 38.3 ± U 9 35.31 0.53 34.4 to.3*j 33.8 10.29 53.5 10.30 AIR HE-Oi 36.7 i 1.41 54.6 ± 0.56 34.9 - 0.4£1 33.9 ±0.42 34.0 1 0.4.4 UE-O* HEOa 94.3 i 1.02 34.0 t0.67j 34.4 t0.4<2 34.2 1 0.36 34.2 1 0.24 1I Art97 < td \x 0 N\ H - V P 37 c+ hj H* 0 <1 4 © . ^3 O h 99 -4 < r J j ^ . . - 3 E ^ c l l ------?B §c+ 1--- H H* — P*- — .33— f---- H* c+ 31a t : t) 1'5 25 30 4'3 5O 60 7D 8O 9 0 1CO IID 12o - Tilie in Minul es Ul o REFERENCES REFERENCES 1. Behnke, A. R., and Wlllmon, T. L., "Gaseous Nitrogen and Helium Elimination from the Body During Rest and Exercise," American Journal of Physiology. 131: 619, 1941. ------*----- “* 2. 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South, F. E., and Cook, S. F., "Effect of Helium on the Respiration and Glycolysis of Mouse Liver Slices," Journal of General Physiology. 36: 513, 1953. 26. Teichner, W. H., "Assessment of Mean Body Surface Temperature," Journal of Applied Physiology. 12: 169, 1 9 5 8 . ------ 27. Trexler, P. C., "Germ-Free Isolators," Scientific American. 211 (1): 7 8 , 1964. 28. Weiss, H. S., Wright, R. A., and Hiatt, E. P., "Embryo Development and Chick Growth in a Helium-Oxygen Atmosphere," Aerospace Medicine. 36 (3): 311, 1965. 29. Winslow, C. E. A., Herrington, L. P., and Gagge, A. P., "Physiological Reactions of the Human Body to Various Atmospheric Humidities," American Journal of Physiology. 120: 288, 193?^ 30. Young D. R., and Cook, S. F., "The Effect of Helium on the Gas Exchange of Mice as Modified by Body Size and Thyroid Activity," Joumal of Cellular and Com parative Physiology. 42 (2 J: 31^7 1955.