The current environmental control device in the shuttle uses lithium hydroxide (LiOH) filter canisters to remove carbon dioxide (CO2) from the cabin air, requiring several bulky filter canisters that can only be used once and must be changed frequently. To alleviate a stowage problem and decrease launch weight, the Crew and Thermal Systems Division (CTSD) at the NASA Johnson Space Center has been researching a system to be used on future shuttle missions. This system uses two beds of solid amine material to absorb CO2 and water, later desorbing them to space vacuum. In this way the air scrubbing medium is regenerable and reusable. To identify the efficacy of this regenerable CO2 removal system (RCRS), CTSD began investigations in the shuttle mockup. The purpose of this investigation was to support the CTSD program by determining mean levels of carbon dioxide and water vapor production in normal, healthy males and females age-matched with the astronaut corps. Subjects' responses were measured at rest and during exercise at intensity levels equivalent to normal shuttle operation activities. The results were used to assess the adjustments made to RCRS and are reported as a reference for future investigations in shuttle environmental control

Lee, Stuart M. C.

Siconolfi, Steven F.

English

NASA Technical Reports Server

NASA
Technical
Paper
3500
August 1994
National Aeronautics and
Space Administration
Carbon Dioxide and Water
Vapor Production at Rest
and During Exercise: A
Report on Data Collection
for the Crew and Thermal
Systems Division
Stuart M. C. Lee
KRUG Life Sciences
Houston, Texas
Steven F. Siconolfi
Lyndon B. Johnson Space Center
Houston, Texas
https://ntrs.nasa.gov/search.jsp?R=19950005398 2020-06-16T10:08:53+00:00Z
This publication is available from the NASA Center for AeroSpace Information,
800 Elkridge Landing Road, Linthicum Heights, MD 21090-2934
(301) 621-0390.
CONTENTS
Introduction 1
Methods 1
Results .................................................................................................................................. 3
iii
Table1.
Table2.
Table3.
Table4.
Table5.
Table6.
Figure 1.
Figure2.
Figure3.
Figure4.
Figure5.
Figure6.
Figure7.
Figure8.
TABLES
SubjectCharacteristics(Mean+SE) ....................................................................... 1
Mean (+SE) Responses for All Subjects ................................................................ 3
Mean (+SE) Responses for All Male Subjects ....................................................... 4
Mean (+SE) Responses for All Female Subjects .................................................... 4
Mean (+SE) Results Relative to Body Weight (kg) Across Gender and
Conditions .............................................................................................................. 8
Observed Mean (+SE) Versus Expected Results Relative to Body Weight (kg)
Across Conditions .................................................................................................. 8
FIGURES
Mean responses of all subjects across resting conditions ....................................... 3
Mean responses of all subjects across exercising conditions .................................. 4
Gender comparisons of _'o2 response across resting conditions ........................... 5
Gender comparisons of "_o2 response across exercising conditions ...................... 5
Gender comparisons of "v'co2 response across resting conditions ......................... 6
Gender comparisons of "v'CO2 response across exercising conditions .................... 6
Gender comparisons of 1Vie response across resting conditions ............................. 7
Gender comparisons of/_e response across exercising conditions ........................ 7
iv
INTRODUCTION
The current cabin environment control system used in the Space Shuttle program uses lithium
hydroxide (LiOH) filter canisters to remove carbon dioxide (CO2) and respiratory water from the
cabin air. Although this system has been effective, it requires several filter canisters that can only
be used once and must be changed frequently. These filtration units are bulky and occupy a
significant portion of locker stowage. The amount of locker storage required for such canisters
will be magnified as the extended duration orbiter (EDO) mission lengths increase up to 18 days
[6].
To alleviate this stowage problem and decrease launch weight, the Crew and Thermal Systems
Division (CTSD) at the NASA Johnson Space Center has been researching an environmental
control system to be used on future Space Shuttle missions. This system, based on technology
used in the Skylab missions, uses two beds of solid amine material to absorb CO2 and respiratory
water and later desorb them to space vacuum. In this way the air scrubbing medium is regenerable
and reusable so that stowage and weight concerns are reduced, and crew time is not impacted to
frequently change filters [6]. To identify the efficacy of this regenerable CO2 removal system
(RCRS), CTSD began isolation investigations in the Shuttle mockup.
The CTSD approached the Exercise Physiology Laboratory of the NASA Johnson Space Center
requestinlg support of these isolation investigations by evaluating each subject's rate of carbon
dioxide (VCO2) and respiratory water (I(/Ie) production. The activities chosen represented the daily
energy expenditures thought to be similar to the activities of Shuttle crew members [3] and a range
of energy expenditures similar to those used in the isolation study. All 23 subjects were evaluated
in the Exercise Physiology Laboratory while resting (i.e., both supine and seated), walking on a
treadmill, and stair stepping. Their data are presented in this report.
METHODS
The CTSD required _QCO 2 and 1VIe for each of the activities evaluated. The activity levels included
supine and seated rest, treadmill walking at a rate equivalent to 540 kJ/h, and stair stepping at
1230, 1845, and 2460 kJ/h. Metabolic rates were provided by CTSD to determine the appropriate
treadmill speed and stepping rates [1].
Selection of subjects by the Human Test Subject Facility was based upon characteristics of the
astronaut corps. Subject characteristics are presented in Table 1.
Table 1. Subject Characteristics (Mean +SE)
Males Females Mean
Age (yr) 36.4 _+2.9 36.9 _+1.2 36.6 +1.6
Height (cm) 180.1 +2.2 165.9 _+1.2 173.9 -+3.5
Weight (kg) 79.0 _+4.6 65.3 _+4.5 72.6 _+3.5
SubjectscompletedaNASA informedconsentform andwereprovidedwith asubjectinformation
sheetspecific to this study. Thesewerereadand subjectswere given the opportunity to have
questionsansweredto their satisfaction,thentheformsweresignedto indicatethattheyhadbeen
understood.
Prior to the isolation studies,the metabolic responsesof all subjectsfor the four different
conditionswereevaluatedin onetestingsession.All subjectsbreathedthrougha Hans-Rudolph
one-way rebreathingvalve. Expired gaseswere analyzedby the Quinton Q-Plex® (Quinton
Industries, Seattle,WA) metabolic cart. The subject'selectrocardiogramwas continuously
monitored by a three-leadEKG configuration (Quinton Q5000 StressTest System) for the
determinationof heartrate.
Datacollection beganwith a 20-minutesupine-restingperiodthat wasfollowed by a 10-minute
seatedrest. Subjectsthenwalkedon the Quinton Q65treadmill at 2.4 km/h (1.5 mi/h), zero-
percent gradefor 5 minutes. At thecompletionof thetreadmillwalking, thesubjectsrestedfor
approximately5 minutes.Thefinal phaseof testingconsistedof benchsteppingon a 22.9cm(9
in) bench at ratesof 16,24, and 32 stepsper minute in 3-minutestageswithout rest between
stages.At thecompletionof thebenchsteppingactivity, subjectswalkedin placefor at least1
minute to avoid venouspooling and possiblesyncopebeforebeing allowed to rest. Subjects
remainedattachedto theEKG monitoring systemuntil their heartratehadreturnedto under100
beatsper minute. Subjectswere allowed to removethe mouthpieceand noseclip assemblies
betweendatacollection for eachactivity. The metabolicgasanalyzerwascalibratedbeforeand
aftereachcondition.
All data,exceptl_e, werecollectedin 30-secondintervalsandstoredon the Q-Plex®. _'O2and
'v'co2werecalculatedbytheQ-Plex® usingthefollowingequations:
"v'02 = VESTPDo(FIO2o [1-FEO2-FECO2])/( [1-FIO2-FICO2]-FEO2)
VC02 = VESTPD'(FECO2-FICO2)
where VESTPD is the volume of expired air at standard temperature and pressure, dry (0 °C, 760
mmHg, zero-percent H20), FIO2 is the fractional concentration of inspired oxygen, FEO2 is the
fractional concentration of expired oxygen, FICO2 is the fractional concentration of inspired carbon
dioxide, and FECO2 is the fractional concentration of expired carbon dioxide [4, 7].
The calculations to predict 1Viewere made after the test using the following equation:
NIe = 0.019oVO2(44-Pa)
where/k_I e is the rate of evaporative water loss in the expired air (g/min), _rO 2 is the oxygen uptake
(L/min STPD) of the subject, and Pa is the ambient water vapor pressure (mmHg)[5].
The CTSD requested that the data for each subject be expressed as a mean response to each
condition. The data were derived in the following manner. Supine-resting mean data were
calculated from the last 10 minutes of the 20-minute supine-resting time interval. The seated-
resting mean data were taken from the last 5 minutes of the 10-minute seated-resting period. The
means for treadmill walking were averaged from the last 2 minutes of the 5-minute walk and for
stair stepping from the last 1 minute of each 3-minute stage.
2
RESULTS
Meanabsoluteresultsfor all subjectsacrossall variablesandconditionsarepresentedin table2,
andgraphically in figures2 and3. Meanresultsby genderarepresentedin tables3 and4, and
graphicallyin figures4 through9.
For thepredictionof expectedresponsesfor future subjects,theresultsarepresentedrelativeto
bodyweight in table5. Nosignificantdifferencesarepresentbetweengenderwhenviewedin this
manner. Observedmeanresultsfor all subjectsrelativeto body weightandexpectedvaluesfor
9o2, VCO2,andIVIederivedfrom othersources[1,4, 5] arealsopresentedin table6.
Table 2. Mean (+SE) Absolute Responses for All Subjects, n=23
902 VC02 1Vie
(L/min) (L/min) (g/min)
Supine Rest 0.21 +0.02 0.19 +0.01 0.12 _+0.01
Seated Rest 0.25 +0.02 0.22 _+0.02 0.14 _+0.01
Treadmill (2.4 km/h) 0.68 _+0.05 0.58 +0.05 0.39 _+0.03
16 steps/min 1.12 _+0.06 0.90 +0.06 0.72 _+0.05
24 steps/min 1.50 _+0.09 1.44 _+0.10 0.97 _+0.07
32 steps/min 1.99 _+0.11 2.21 +0.14 1.29 _+0.10
Figure
0.3
t0.25 • .,'_
[:s" .".."....
. . ...'.".."..".."..-"
_!_!i_i_-i_ .::;;_;:_:.;:
_i_ " ....
O. 1 _':_""*_"4////2
:.'..'.::;::jr.:
..... :..:..::.::::.::
".'..'."] .[.
0 1 ....................."..0<:;'5:."
Vo2
(L/min)
1. Mean responses of all subjects
[] Supine
[] Seated
2"/:.4¢/,.:.
,."/..."//.:9
_N_J_ ::,':.-'.5.,:,',
.7-'Z-.Z-.Z:Z-'Z-"
.......... ,,',.':,%G,'//
(g/min)
across resting conditions.
3
0
VO2
(L/min)
Vco2
(L/min)
Figure 2. Mean responses of all
[] Treadmill 24 km/h
[] 16 Steps/min
[] 24 Steps/min
[] 32 Steps/min
(gJmin)
subjects across exercising conditions.
Table 3. Mean (+SE) Absolute Responses for All Male Subjects, n=12
qco2 Me
(L/min) (L/min) (g/min)
Supine Rest 0.21 +0.02 0.21 +0.02 0.12 _+0.01
Seated Rest 0.27 +0.02 0.24 +0.02 0.15 +0.01
Treadmill (2.4 km/h) 0.75 +0.05 0.64 +0.04 0.43 +0.02
16 steps/min 1.22 +0.06 0.98 +0.07 0.80 +0.06
24 steps/min 1.66 +0.09 1.59 +0.10 1.08 +0.09
32 steps/min 2.24 +0.13 2.45 +0.18 1.46 +0.11
Table 4. Mean (+SE) Absolute Responses for All Female Subjects, n=ll
'QO 2 "QCO 2 ]k_e
(L/min) (L/min) (g/min)
Supine Rest 0.20 +0.01 0.18 +0.01 0.11 +0.01
Seated Rest 0.24 +0.03 0.20 +0.02 0.13 +0.01
Treadmill (2.4 km/h) 0.62 +0.06 0.51 _+0.06 0.35 +0.04
16 steps/min 1.01 +0.06 0.81 +0.06 0.65 +0.05
24 steps/min 1.34 +0.08 1.30 +0.09 0.87 +0.06
32 steps/min 1.74 +0.09 1.98 +0.11 1.12 +0.09
4
Vo2
(L/min)
0.3 7 [] Male
/ [] Female
0.2
0.1
0
Supine Seated
::::::::iitii
;d
'":; 9::
';:::;;::
:_,.',.
ii:ii!:::.q
.'4
• ," "/yl
i.'.!!_
,'d: ,-,-,
Figure 3. Gender comparisons of _ro 2 response across resting conditions.
'_/O2
(L/min)
2.5--
_
1.5--
_
0.5--
[] Male
[] Female
Treadmill 16 24 32
2.4 km/h steps/min steps/min steps/min
Figure 4. Gender comparisons of ¢¢o2 response across exercising conditions.
0.3 1 [] Male
0.25 [] Female
0.2
"QCK)2
(L/rain) O. 15
Figure 5.
0
Supine Seated
Gender comparisons of _/COz response across resting conditions.
Vco2
(ldmin)
3 7 [_l Male
[] Female
Figure 6.
0
Treadmill 16 24 32
2.4 kin& steps/rain steps/min steps/min
Gender comparisons of VCOz response across exercising conditions.
6
Figure 7.
0.2
0.15
(g/min) 0.1
0.05
0
[] Male
[] Female
Gender comparisons of 1VIe
Seated
response across resting conditions.
Figure 8.
(g/min)
1.5
0.5-
0
[] Male
[] Female
Ii ii[
Treadmill
2.4 km/h
16
steps/min
!
24 32
steps/min steps/min
Gender comparisons of _I e response across exercising conditions.
7
Table 5. Mean (+SE) Results Relative to Body Weight (kg)
Across Gender and Conditions
_rO 2 _/CO 2 _¢I e
(mL 02/kg/min) (mL C02/kg/min) (mg/kg/min)
Males
Supine 2.71 +0.26 2.52 +0.23 1.56 +0.15
Sitting 3.14 _+0.30 2.86 _+0.27 1.84 _+0.19
Treadmill (2.4 kin/h) 9.9 _+0.49 8.39 _+0.59 5.82 _+0.27
16 steps/min 15.19 _+0.65 12.74 _+0.68 8.94 _+0.47
24 steps/min 20.69 +_0.86 20.07 _+0.83 12.17 +_0.59
32 steps/min 28.05 _+1.26 30.98 +_1.43 16.49 _+0.82
Females
Supine 2.96 _+0.22 2.62 4- 0.19 1.75 _+0.14
Sitting 3.24 _+0.27 2.84 _+0.22 1.92 _+0.17
Treadmill (2.4 kin/h) 9.37 _+0.50 7.75 +0.48 5.52 _+0.29
16 steps/min 15.53 _+0.64 12.84 +-0.52 9.18 _+0.38
24 steps/min 20.37 +-0.91 20.47 _+0.83 12.26 _+0.53
32 steps/min 26.35 _+0.83 30.92 _+0.95 15.64 _+0.48
Table 6. Observed Mean (+SE) Versus Expected Results Relative to
Body Weight Across Conditions
"002  co2
(mL O2/kg/min) (mL CO2/kg/min) (mg/kg/min)
Observed Expected Observed Expected Observed Expected
Supine 2.83 +-0.17 4.69 2.57 _+0.15 4.26 1.65 +_0.10 2.73
Sitting 3.24 _+0.20 4.47 2.85 +_0.18 3.93 1.87 +-0.13 2.61
Treadmill (2.4 km/h) 9.65 _+0.35 9.21 8.09 _+0.38 7.72 5.68 _+0.19 5.37
16 steps/min 15.35 _+0.45 14.00 12.79 _+0.42 11.67 9.04 _+0.30 8.17
24 steps/min 20.54 _+0.61 21.00 20.26 +0.57 20.71 12.21 _+0.39 12.25
32 steps/min 27.48 _+0.79 28.00 31.18 +0.86 31.77 16.13 +0.49 16.33
DISCUSSION
This technical paper documents the levels of _'c02 and iVle that represent the metabolic expenditure
of normal daily crew tasks in response to different activities. The results of this investigation will
8
serve as a reference for future investigations in the evaluation of the RCRS and other
environmental control systems.
The validity, of mean "QO 2 values during each of the conditions is important to examine because the
values for Me are calculated from VO2 and not reported elsewhere. The mean values for the resting
conditions and treadmill walking are approximately 25 percent lower than those reported in the
literature [2, 4]. This may have resulted from the low breath volumes during these conditions to
which the Q-Plex ® may not be sensitive because it is intended to measure air volumes exchanged
during moderate to heavy exercise. Mean values of VCO2 are similarly depressed at rest and
during treadmill walking. The mean results from the stair-stepping activity for all variables are
well within expected values as calculated from accepted equations [1, 5].
REFERENCES
[1] American College of Sports Medicine. Guidelines for Exercise Testing and Prescription.
Philadelphia, PA: Lea & Febiger, 1991.
[2] Brooks, G. A. and T. D. Fahey. Exercise Physiology: Human Bioenergetics and Its
Applications. New York, NY: MacMillan Publishing Company, 1985.
[3] Jeng, F. Performance evaluation tests of HS-C/RCRS in the ETA chamber, manned and
unmanned. NASA Contractor Report NAS 9-17900, 1993. (In review)
[4] McArdle, W.D., F. I. Katch, and V. L. Katch. Exercise Physiology: Energy, Nutrition,
and Human Performance. Philadelphia, PA: Lea & Febiger, 1986.
[5] Mitchell, J. W., E. R. Nadel, and J. A. J. Stolwijk. "Respiratory weight losses during
exercise." J. Appl. Physiol. 32(4):474-476, 1972.
[6] Ouellette, F. A., H. E. Winkler, and G. S. Smith. "The extended duration orbiter
regenerable CO2 removal system." 20th Intersociety Conference on Environmental Systems,
Williamsburg, VA, July, 1990.
[7] Quinton Instrument Company. Q-Plex®Cardiopulmonary Exercise System Operator
Manual. Seattle, WA: A. H. Robbins Company, 1988.
9
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Carbon Dioxide and Water Vapor Production at Rest and During Exercise:
A Report on Data Collection for the Crew and Thermal Systems Division
6. AUTHOR(S)
Stuart M. C. Lee* and Steven F. Siconolfi
7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES)
Lyndon B. Johnson Space Center
Medical Sciences Division
Houston, Texas 77058
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*KRUG Life Sciences, Houston, Texas
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13. ABSTRACT (Maximum 200 words)
The current environmental control device in the Shuttle uses lithium hydroxide (LiOH) filter canisters to remove carbon
dioxide (CO2) from the cabin air, requiring several bulky filter canisters that can only be used once and must be changed
frequently. To alleviate a stowage problem and decrease launch weight, the Crew and Thermal Systems Division (CTSD) at
the NASA Johnson Space Center has been researching a system to be used on future Shuttle missions. This system uses two
beds of solid amine material to absorb CO2 and water, later desorbing them to space vacuum. In this way the air scrubbing
medium is regenerable and reusable. To identify the efficacy of this regenerable CO2 removal system (RCRS), CTSD began
investigations in the Shuttle mockup. The purpose of this investigation was to support the CTSD program by determining
mean levels of carbon dioxide and water vapor production in normal, healthy males and females age-matched with the
astronaut corps. Subjects' responses were measured at rest and during exercise at intensity levels equivalent to normal Shuttle
operation activities. The results were used to assess the adjustments made to RCRS and are reported as a reference for future
investigations in Shuttle environmental control.
14. SUBJECT TERMS
Carbon dioxide production, water vapor production, regenerable carbon dioxide removal
system (RCRS)
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Carbon dioxide and water vapor production at rest and during exercise. A report on data collection for the Crew and Thermal Systems Division

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