APPLICATION OF THE INFRA-RED GAS ANALYZER TO THE STUDY OF 
HUMAN ENERGY METABOLISM* 
by 
H, J, Spoor, Capt., M.C., and G, C, Davis, Capt., M,C, 
from 
Medical Department Field Research Laboratory 
Fort Knox, Kentucky, 21 August 1947 
*Sub-Project under Studies of Physiological and Psychological Problems 
of Military Personnel in Relation to Equipment, Environment and Military 
Tasks, (M.D.F.H.L.-57). Approved by CG, ASF, 31 May 1946. Project No, 57-4 
MEDEA 
21 August 1947 
ABSTRACT 
APPLICATION OF THE INFRA-RED GAS ANALYZER TO THE STUDY OF 
HUMAN ENERGY METABOLISM 
OBJECT 
The determination of the caloric expenditure of troops during maneu- 
vers has resolved itself into the establishment of a suitable practical 
field method for measurement of respiratory changes in man in such physical 
situations that would not permit the use of existing apparatus. A method 
was desired which would offer 2 advantages over present field techniques: 
(l) graphic continuous analytical record over protracted periods rather 
than period averages for short duration effort, and (2j portable equipment 
which would measure actual expenditure of a particular activity rather 
than an additive effect of the exercise plus apparatus load. 
RESULTS 
A new technique for measurement of caloric expenditure during con- 
tinuous activity has been developed. Both laboratory and field trials 
have proved the adaptability of the Leeds and Northrup selective gas analyz- 
er to the estimation of carbon dioxide in expired air. Caloric expenditure 
studies on men undergoing mountain warfare training have been accomplished. 
The new method offered instantaneous analysis and continuous records over 
protracted periods of activity. 
CONCLUSIONS 
The infra-red analyzer equipped with an adequate pumping system for 
controlled air flow has been adapted to metabolic work and found satisfac- 
tory, both in the laboratory and in the field. 
RECOMMENDATIONS 
The apparatus developed and tested is satisfactory for routine study 
of respiratory exchange. To obtain absolute fidelity, i.e, synchronization 
of recorded response with respiratory excursion, and continuous analytical 
records of oxygen utilization, should be the aim of subsequent investiga- 
tion. 
Submitted by: 
H, J, Spoor, Capt., M.C, 
G. C. Davis, Capt,, M.C, 
Approved^ 
RAY (/ f 
Director *of Research 
Approved, 
FPJ3DSRICK J. KNOBLAUCH 
Lt• Col•y &•G• 
Commanding APPLICATION OF THE INFRA-RED GAS ANALYZER TO THE STUDY OF 
HUMAN ENERGY METABOLISM 
I. INTRODUCTION 
The problem of caloric expenditure studies on troops engaged in 
military maneuvers resolved itself into the establishment of a suitable 
practical field method for determining respiratory changes in man in such 
physical situations that would not permit the use of bulky apparatus. The 
method devised offers two advantages over present field techniques: 
(l) graphic continuous analytical record over protracted periods rather 
than period averages for short duratiop, effort, and (2) portable equipment 
which will measure actual expenditure of particular exertion rather than 
special conditions of simulated exercise plus apparatus load. To obtain 
these objectives: (l) a Leeds and Korthrup infra-red gas analyzer was 
adapted to quantitative detection of carbon dioxide, (2) continuous graphic 
data were recorded by an Esterline-Angus microammeter, and (3) portability 
was simulated by use of the A-13 oxygen demand mask to which was connected 
a long air line carried by cable and pulley rigging extending to the analy- 
sis assembly. The apparatus permitted continuous sampling of air over 
difficult terrain. 
This report concerns itself with (l) the adaptation of the Leeds and 
Korthrup infra-red gas analyzer and associated apparatus to measurement of 
human energy metabolism in the laboratory and (2) application to field 
studies of the energy metabolism of troops engaged in mountain warfare 
training. 
LI. EXPERIMENTAL 
A# Apparatus and Methods 
1, Gas Analyzer. 
The Leeds and Korthrup selective gas analyzer was designed to 
measure small concentrations of carbon monoxide (l). It has been adapted 
to quantitation of water vapor (2), and has been sensitized to carbon 
dioxide (3)• The subject instrument is functionally based upon the selec- 
tive absorption by the gas in question of radiation in the infra-red region 
of the spectrum (CO 4.7* H2O 6.0 and CO2 4#3 microns wave length absorp- 
tion bands). 
A complete technical description of the instrument, with 
detailed operating instructions has been previously reported (3)* A brief 
description follows: Infra-red radiation is emitted by an electrically 
heated nichrome coil. The rays pass across a test chamber which contains 
the gas sample to be analyzed. After leaving the test chamber, the beam 
of radiation is split into 2 parts by an axially divided filter chamber, 
and then falls onto 2 thermopile sections. The instrument achieves its 
selectivity by the fillings of the filter chambers. One of these is filled 
with the gas under analysis (i.e. CO2) and the other with non-absorbent 
gas (i.e. O2). The oxygen side of the cone does not absorb an appreciable 
amount of radiation. The carbon dioxide side of the cone absorbs radiation 
maximally within its absorption bands. Both branches respond identically 
to non-absorbed radiation. Output of the two thermopiles is balanced. 
Then, introduction of carbon dioxide into the test chamber causes a change 
1 in thermopile output because absorption decreases the radiation falling 
upon the oxygen cone thermopile. All foreign components absorb from each 
chamber equally except for those gases with absorption bands overlapping 
those of carbon dioxide. Possible effects of carbon monoxide and water 
vapor are avoided by eliminating these two as contaminants. 
2. Expired Air Collection. 
For the measurement of carbon dioxide concentration of 
expired air to be useful as a measure of metabolic expenditure, one of two 
conditions must be filled. First, the expiratory volume can be measured, 
from which the carbon dioxide concentration will give the per cent by 
volume as in the classical Haldane technique; second, the volume flow from 
the subject can be kept essentially constant by force pumping. Enrichment 
of this constant volume with carbon dioxide from expired air will permit 
expression of carbon dioxide as per cent of a flow. From data of this 
sort carbon dioxide, expelled by the subject for a period, can indicate 
directly his rate of production, regardless of the actual expired volume• 
In this problem, we have utilized the latter principle, 
namely constant flow from the subject by means of force pumping of air 
through a large capacity hose leading from mask to machine. A schematic 
diagram of the assembly is given in Figure 1. An analyzer aliquot was 
drawn from the main flow line by means of a small constant speed rotary 
pump. In practice the only limiting factor on maneuverability of the sub- 
ject in reference to analyzer and recorder was the length of air hose 
between subject and machine. The limit on this length was the ability to 
handle the hose mechanically. By use of cable and pulley rigging 
in the field, up to 400 feet of hose were handled with no more inconvenience 
to the subject than the usual laboratory mask assembly. In the laboratory 
during standardization of the apparatus various flow meters, mixing chambers, 
temperature baths and filtration columns for investigation of factors in- 
fluencing instrument sensitivity and selectivity were inserted between the 
subject and the analyzer. 
3. Air Flow Rates. 
The determination of air flow rates in the main and aliquot 
circuits was very accurately accomplished because subsequent carbon dioxide 
concentrations were interpreted as percentage of a constant volume. These 
flow rates were ascertained in the laboratory by the following standard 
techniques: 
a. Spirometer Calibration. 
The laboratory spirometer, 500 liter capacity, was calibrat- 
ed by filling it from an air compressor through a volumetric gas meter 
(Precision Scientific Co., Chicago, Ill.j recording liters. Direct measure- 
ment of filling volume per centimeter bell rise gave a value of 4.35 liters 
when corrected to standard conditions. 
2 FI6.I. DIAGRAM OF ASSEMBLY 
b. Calibration of Main Circuit* 
The volume flow of air through the large hose circuit from 
the subject depended upon the operating speed of the main line pump Fig. 1), 
The line flow was calibrated by measuring the rate of air flow at various 
motor rate control settings against the previously calibrated 500 liter 
spirometer. Tracings of time against distance (bell elevation) for "variac" 
settings of 20, 40, 50, 60 and 80 volts were obtained. Values from these 
curves (i.e, cm./min,) were converted to liters per minute by use of the STP 
conversion factor for the spirometer, namely 4.35 liters per centimeter 
rise. Line resistance in the system was induced by two distinct major fac- 
tors: (l) the mask and man and (2) an orifice flow diaphragm used in con- 
junction with recording devices. Table 1 summarizes the data obtained. 
These data compare flow rates under the following conditions: (l) with 
neither mask, man nor flow meter; (2) with mask alone, without man or meter; 
(3) with mask and man, but no meter; (4) with meter and mask, without man; 
(5) with mask, man and orifice flow meter. 
TABLE 1 
MAIN LINE FLOW 
Liters per Minute (STP) at Various Variac Settings 
CONDITIONS 
20 V 
40 V 
50 V 
60 V 
80 V 
1 
104 
261 
366 
2 
42.8 
115 
168 
3 
31.8 
108 
164 
211 
4 
91.8 
114 
137 
5 
83*4 
102 
124 
3 Condition 5*—i*e,, with mask, man and orifice flow meter—was that used 
for subsequent metabolic study. Standard conditions were arbitrarily 
established as those prevailing at a main line pump variac setting of 
50 volts, namely, 102 liters per minute (STP). This volume was greatly 
in excess of any expiratory volume later obtained from a subject. Cal- 
culated volume flow based on the orifice formula (4) agreed with the above 
experimental values. 
c. Calibration of Aliquot Circuit* 
The small aliquot circuit leading to the gas analyzer was 
powered by a constant speed motor air pump designed to deliver about 10 
liters of air per minute through the analyzer chamber. To check constancy 
of flow of this pump, the air stream was calibrated against the spirometer. 
Current supplied to the pump was regulated by a variac (P2 Pig. l), and 
tracings of volume versus time at various voltage settings recorded. For 
settings ranging from 40 to 160 volts the flow output varied between 10.02 
and 12,00 liters per minute. The motor was designed to operate most effi- 
ciently at 120 volts. The air flow rate at this setting was 10.8? liters 
per minute. This was used throughout for aliquot line flow. 
Changes in flow of the main line had no effect on the constancy of the 
aliquot flow, , 
4. Standardization of the Selective Gas Analyzer. 
After air volume control was established, standardization of 
the infra-red gas analyzer against known carbon dioxide-oxygen gas mixtures 
was accomplished. An investigation of the factors influencing receptivity 
and interpretation accuracy of the instrument was undertaken. 
a. Standard Carbon Dioxide Mixtures* 
Known mixtures of carbon dioxide and opcygen covering the 
expected range of carbon dioxide concentration (0 - 5%) to be encountered 
were prepared. Analysis by the Haldane technique of different cylinders 
containing gas gave the following compositions: 0.267, 0.549, 1.26, 2.37 
and 4.32 per cent carbon dioxide in oxygen. These, with outside air 
(0.03% CO2) and pure oxygen, comprised the standard series. Air dilution 
at the source to 100 liters per minute was enough in excess over expir- 
atory volume to insure analysis within this standard range. The standard 
gas mixtures were fed directly into the aliquot line to the analyzer.' As 
stated, air flow to the analyzer was supplied at a constant rate of 10.86 
liters per minute. Inserted into the air line between the pump (?2 Fig, 1) 
and the analyzer was a "charcolite" air filter (Fig, 1), This served three 
purposes: (l) mechanical filtration of air, (2) removal of water vapor, and 
(3) removal of charcoal absorbable gases. For testing the effects of water 
vapor the filter was replaced by suitable apparatus. An initial series of 
responses of the gas analyzer to the various carbon dioxide mixtures is 
shown in Figure 2. The Esterline-Angus graphic records read from right to 
left. Tabulation of the results in terms of average and maximum micro- 
volt deflection is given (Table 2). 
4 FIG, 2. STANDARDIZATION CURVES 
The Esterline-AsguS Co. Inc.. mo. u • a. WCH 
Th{ ISC -C » HZ L t » Cr.*PT No. 4SO&-C 
5 TABLE 2 
STANDARD 002 MIXTURES, MICROVOLT DEFLECTION 
Per Cent CO^ 
Average Microvolts 
Maximum Microvolts 
Oxygen (pure) 
0,26? 
0,549 
1.260 
2.370 
4.320 
0,0 (by adjustment) 
6.95 
15.1 
33.5 
51.2 
77.0 
0.0 (by adjustment) 
7.8 
17.0 
37.0 
57.0 
82.0 
Average values were obtained by measuring the area under the curve for the 
entire period during which the test gas was running. This value, divided 
by the length of record, gave the average deflection for the period. 
Averages are lower than the maximum recorded deflections because of time 
lag in absorption and mixing. Ideally, both maximum and average values 
should have been identical; practically, the average value was of greater 
use for application to measurement of expired carbon dioxide. 
b, Oxygen Versus Outside Air (0.03% C02) • 
Operation of the continuous gas analyzer over extended 
periods required repeated standardization of the base line because of elec* 
trical drift in the recording meter. This base line adjustment could have 
been made using cylinder oxygen, but in field work it was more convenient 
to standardize against outside air, a source material of constant carbon 
dioxide content mbre readily accessible than pure oxygen. A series of analy- 
ses was run, first to measure the sensitivity of the machine to the 0.03$ 
CC>2 of air and second, to make direct comparison of standard mixtures using 
oxygen and air base lines. The average deflection produced by 0.03$ CO2 was 
slightly greater than 1 microvolt. The response is recorded in Figure 2. 
Comparison of the response of the machine to the known gas mixtures using 
the two base lines gave the conclusion that deflection response of the 
machine to carbon dioxide versus oxygen was slightly greater than response 
to the same carbon dioxide versus air. The effects were within the antici- 
pated range for pure additive values, that is, 1-2 microvolt increase at 
each level. Curves comparing these responses are given later (Fig, 3), 
c. Flow Change and Pressure Effects, 
The apparatus was designed to give constant air flow to 
the analyzer but, to ascertain just what effects changes in rate of flow 
through the analyzer cell would have on the readings, a series of experiments 
was conducted. The effect of sudden complete cessation of flow and gradual 
decrease in flow were tested at the very low and at relatively high concen- 
trations of carbon dioxide (0.03, 1.26 and 2.37%). Using the lowest con- 
centration of gas (0.03% CO2), the following results were obtained! sudden 
stoppage of flow caused a fall in deflection of 1 microvolt practically 
instantaneously; on return of the flow, there was a reestablishment of the 
original deflection within -J minute; prolonged stoppage of flow (2 minutes) 
produced a decrease in deflection of 1 microvolt within \ minute, then a 
6 gradual fall of 1 microvolt over the succeeding minutes; return of 
flow returned the deflection to its original level within | minute* Simr- 
ilar effects although less marked, were seen with the higher concentrations 
of carbon dioxide; at levels of 1,26% CQ?, stoppage of flow -caused a de- 
crease in deflection of 2 microvolts within 1 minute; restoration of the 
previous level (29 microvolts in this case) required a little longer, 1 
instead of minute. Gradual cessation of air flow was difficult to eval- 
uate because with a constant speed motor variation from 12 to 10 liters per 
minute was the maximum obtainable (160 to 40 volts), Within this range 
no change in deflection toward 2,37% 002 could be shown. At a variac set- 
ting of 20 volts, the motor failed after a short period of 5 liters per 
minute flow. During this period, between 10 to 0 liters per minute flow, 
a fall of 3 microvolts occurred. The fall was probably identical with the 
effect of cessation of flow. All of the preceding data are illustrated in 
the second record of Figure 2, 
d. Temperature Effects, 
Previous work with the infra-red machine, when used for 
analysis of carbon monoxide, indicated that recordings were stable under 
gradual changes of temperature. Warning was implied to avoid sudden tem- 
perature change, although no commitment was made as to the magnitude of 
the error introduced (1), The influence of temperature change on carbon 
dioxide analysis has been investigated, Warrar-up of the machine for lj 
hours as recommended led to an analysis chamber temperature of 30°C, This 
temperature was maintained constantly while operating with ambient air of 
from 26° to 29°C. Preheating ingress air only slowly influenced the 
stabilized chamber temperature. Preheating inflowing air from 26° to 44°0» 
during a period of i hour increased the analysis chamber temperature from 
30° to 33°C. With the 3° rise in chamber temperature (exit air) the records 
showed a maximum upward deflection of 3-4 microvolts. The curve was flat 
between 30°-31°C with a 1 microvolt rise between 31°-31*5°C; a 2 microvolt 
rise between 31«5°-32°C$ 3-4 microvolt rise between 32°-32,5°0| steady be- 
tween 32,5°-33°C, Gradual increase in operating temperature caused positive 
deflection of the recorder pen for both outside air and 1,26% COg, This 
can be attributed to a shift in the base line. Sudden change of inflow gas 
from 44° to 29°C had no effect on the record. The only explanation of this 
fact is a lack of sensitivity of the instrument to sudden temperature change 
because the gas passing through the analyzer was not heated to chamber tem- 
perature. Ssterline-Angus experimental records of these data are given in 
Figure 2. 
e. Effect of Water Vapor, 
The influence of water vapor upon carbon dioxide analysis 
was small, transitory and self-compensating. Air at 2?°C saturated with 
water vapor caused an immediate downward displacement of the base line of 
approximately 2 microvolts. The effect was of 20 seconds duration, then the 
record reassumed its base line. With Cp2 mixtures, a similar but exaggerated 
downward shift occurred, Using a standard mixture containing 1.26$ C02> 
saturation with water vapor caused a downward displacement of 3 microvolts 
which lasted 30 seconds at maximum, then decreased in effect until the 
original deflection was regained after 2 minutes. Dry gas replacing the 
moist which had reached balance caused no shift in deflection. The effects 
are probably not those of interference with flow because the time elapsed in 
7 converting one mixture to another was very short. In addition, the immed- 
iate effects were greater than those produced by even prolonged flow stop- 
page, No flow change effect took place on converting from moist to dry gas. 
Records of these data are given in Figure 2, 
f. Elapsed Time on Response, 
Several factors have been reported as influencing the 
stability of the gas analyzer response to standard gas mixtures. The instru- 
ment has been regarded as satisfactorily stable if precautions have been 
taken to assure: (l) adequate warm-up, (2) well-charged batteries, (3) fre- 
quent zero adjustment of the established base line and (4) occasional stand- 
ardization against a known gas mixture. The most likely factor to account 
for change in response has been stated to be an electrical leakage from 
terminals to ground. In those instances in which there has been a distinct 
loss of sensitivity with elapsed time the fault has been attributed to 
leakage of the filter cone (l), In the subject instrument leakage of gas 
had been minimized by a permanent cement seal of the analysis cell window 
to the filter cone assembly. Sensitivity control of the instrument had 
been incorporated so that one could adjust receptivity to a definite stand- 
ard value. Duplication of standard curves by this means has been the 
practical way of controlling sensitivity loss (3), 
During the accumulation of the following data, the sensi- 
tivity adjustment of the instrument was fixed in order to ascertain the 
absolute magnitude of inherent instrument sensitivity loss, Standardize** 
tion curves taken at different times using both oxygen and air base have 
been run. Comparative curves for each series are given (Fig, 3)• There 
was a loss of sensitivity during the 30 day period studied which was greater 
than casual variation between standardizations. There is insufficient evi- 
dence to attribute this loss to cone leakage on other than presumption 
from earlier reports. The practical method of adjustment of instrument 
sensitivity to a standard deflection with a known calibrating gas mixture 
nullifies the sensitivity loss. 
g. Calibration of Curve, 
The average deflection represented by each point in Figure 
3 was arrived at by measurement, in square millimeters, of the area under 
each tracing during the test period. From this value, average deflection 
in millimeters was calculated. Each 10 microvolt deflection on the record- 
ing paper represented 11.5 millimeters. From these data the equation for 
standardization was obtained. All curves conformed roughly to the general 
equations 
C = Kx log K2/K2-S 
where C is CO2 concentration in per cent, and Kg are empirical constants 
and E is the microvolt deflection. Equation values for the curves of 19 
March are tabulated (Table 3)• 
8 FIG. 3 
STANDARDIZATION CURVES 
OXYGEN - 18 FEB. 
AIR 19 FEB. 
OXYGEN — 19 MAR. 
AIR 19 MAR. TABLE 3 
CALIBRATION DATA FOE CURVES OF 19 MARCH 
Cone. Cpg 
Oxygen 
Air 
% 
Kl 
k2 
Kl 
K2 
0.26? 
7.70 
7.90 
103 
5.76 
11.2 
107 
0.549 
14.7 
8.21 
103 
13.7 
9.21 
107 
1.26 
31.1 
8.08 
103 
29.3 
9.08 
107 
2.37 
50.0 
8.04 
103 
4B.4 
9.07 
107 
4.32 
72.8 
8.10 
103 
71.2 
9.08 
107 
In the above table, constant Kq after establishment of 
K£ should have been unchanged with variation of C and E within the individ- 
ual series. The agreement was not perfect. Values at the higher concen- 
trations of carbon dioxide, 1.26 through 4.32$, closely approached theo- 
retical. The lower values were less predictable. Pure oxygen based 
values agreed more closely in the lower concentrations than did the air 
based values because the influence of the 0.03$ CO2 in air lowered de- 
flection by decreasing the absolute concentration change of CO2 presented 
to the instrument, Lack of coupletely theoretical response with oxygen 
base at low concentrations may have been due to either inaccuracy of 
record interpretation or slight errors in Haldane analysis rather than 
the apparent sensitivity variation of the analyzer. 
In practice during subsequent work, the instrument has 
been standardized frequently and calibration curves have been run in con- 
junction with the metabolic experiments. 
B, Results 
1. Laboratory Tests on Human Subjects. 
After calibration and standardization of the apparatus and 
recording instruments, application of the technique to measurement of 
energy expenditure was undertaken on 3 laboratory subjects. The subjects 
wore an A-13 oxygen demand mask, held in place by a "Juliet type" harness. 
This type of mask was chosen primarily because of its comfort and also for 
its adaptability to field conditions. To the mask was attached a hose 
leading to the analyzer assembly. Through mask and hose, air was drawn 
at a rate of 102 liters per minute. An analyzer aliquot was drawn by the 
punping system previously described. The 3 subjects were used to adapt 
apparatus and technique to human energy study primarily with field appli- 
cation in mind. 
a. Length of Main Line Hose. 
The problem of the optimum length of hose which could 
be led from a subject without adversely influencing analytical accuracy 
was encountered. Initially 20 feet of hose from mask to instrument was 
tried. With this arrangement there was a definite variation of C0£ con- 
tent of the analyzed gases which corresponded with the subject’s respir- 
atory exchange. The volume through the analyzer was constant but, as had 
10 been expected, air passing through the mask was richer in carbon dioxide 
during expiration than during inspiration. No attempts were made to 
synchronize these concentration changes with respiratory excursion during 
this study: first, because of inherent machine lag and second, because 
some line mixing made for distortion of the record. For ease of calcula- 
tion and clarity of record a smooth curve xvas desired. This was obtained 
in two ways: (l) by use of a cyclonic type mixing chamber inserted in 
the analyzer flow line just ahead of the recording instrument, and (2) by 
use of a much longer (400 feet) lead hose from mask to machine. The 
latter method was adapted for field trials, the former for the laboratory 
work, Exercise curves obtained with 20 foot, 400 foot and 20 foot lead 
line with the mixer have been obtained. Each experiment was run on a 
different day and the time duration of each effort was adjusted by the 
subject to his ability rather than to a fixed schedule. There was no 
essential difference in average deflection produced by any type system. 
The variations seen are within the range of individual response to an 
exercise on repetition. A graphic interpretation of these data in terras 
of the average microvolt deflection during periods of rest, treadmill 
activity and recovery is given (Fig, 4), 
b. Comparison of Energy Expenditure. 
To compare energy expenditure between subjects, the 
values obtained for each must be converted into caloric equivalent for a 
unit area of body surface over a definite period of time. Convention 
calls for expenditure per square meter body surface per hour or minute. 
Our subjects had been chosen as representative of the soldier group upon 
whom field studies were made. Their characteristics are tabulated 
(Table L)- 
TABLE 4 
PHYSICAL DATA OF LABORATORY SUBJECTS 
.a 
Subject 
Age 
— 
Weight 
Height 
Body Surface 
R.P. 
19 
135 
5' 10p" 
1.77 K2 
W,H. 
20 
190 
51 8” 
2.02 
J.s. 
19 
158 
5» 11" 
1*90 
Using the laboratory technique of a 20 foot lead line and cyclonic air mix- 
ing chamber, a series of treadmill exercises was obtained on each subject* 
The severity and duration of each phase of the exercise were made strictly 
uniform between subjects. From these data the energy expenditure of the 
3 men for each phase of the activity was compared. 
A representative curve from 1 subject (W.H.) is given in 
Figure 5* Deflection in microvolts on the tracing represents CC£ output 
during rest, level walking and 5 mph), a recovery period, additional 
rest, grade walking (10%, 2g and 3i mph) and recovery. The type curve was 
typical of all, although actual quantity output of carbon dioxide depended 
upon the individual. Equilibration of microvolt deflection to per cent 
carbon dioxide for any point on the curve was obtained from standard values. 
The air flow rate was maintained constant at 102 liters per minute. All 
air passing through the system came through the mask. All CO? recorded was 
that produced by the subject. An outside air base line was used and stand- 
ardization against air had been accomplished. Deflection of the recording pen 
11 FIG. 4 
TREADMILL ACITIVTY 
SUBJECT R.R 
20' LINE 
•320' LINE 
■ 20' LINE-MIXER 
12 FIG. 5 ACTIVITY RECORD SUBJECT W. H. 
m.p. iMu-. A. The Esterline-Angus Co, Inc., .ndianapolis. mo „ a a va,/~ia 
US Co.. INC.. 1NO.ANAPOL1S, ,NQ„ u s *. CHART No. 4305-C 
13 directly measured CO2 output. One gram of CO2 is equivalent to 3 calories 
(5). By calculation, microvolt deflection could be read as calories per 
minute. To compare subjects, values must be made uniform by consideration 
of surface area. Figure 6 graphically compares the average caloric ex- 
penditure for each subject during each phase of the test exercise. The data 
are given as Calories per square meter body surface per minute. The value 
given in the figure as "rest" was evaluated by Haldane analysis in order 
to compare the infra-red method with a standard laborstory procedure. The 
comparison is given in Table 5* 
TABLE 5 
CALORIC EXPENDITURE AT REST, HALDANE AND INFRA-RED ANALYSIS 
Subject 
Calories/M^/Hour 
Haldane 
Infra-Red 
R.P. 
57.5 
55.2 
5 8.h 
W.H. 
58.5 
60.2 
61.2 
J.S. 
59.0 
58.3 
54.4 
True basal rates for men of the age group are 45 there- 
fore, the rest period should be considered pre-exercise. 
2. Field Trials. 
The Medical Department Field Research Laboratory was re- 
quested to determine the caloric expenditure of troops in mountain train- 
ing during the test of operational rations at Camp Carson, Colorado, 
September 1946 (OQMG Ration Test #4631)• Snergy experlditure studies were 
made on representative soldier subjects undergoing prescribed mountain 
warfare training. The opportunity was taken to give the infra-red gas 
analyzer a full field trial. This trial included not only a comparison 
of the new technique with the standard field method of Douglas bag-Haldane 
analysis over terrain on which the latter could be applied (6), but also the 
the adaptation of the new technique to study of soldiers undergoing maneu- 
vers the energy requirements of which had not been previously assessed. 
Technically, the studied climbs were: (l) mountain walk, a climb over a 
marked trail upon which both new and old analysis techniques were practiced? 
(2) scramble, a difficult climb over loose shale rock? (3) belay, free 
climb up a perpendicular rock face utilizing hand and foot holds? and (4) 
tension, or mechanically assisted climbing up an overhanging rock face. 
In addition to these data, direct comparisons have been made between dif- 
ferent men undertaking identical activities, and also an assessment has 
been made of the influence of both confidence and experience on energy 
expenditure during mountain climbing training. 
a* Adaptation of Gas Analyzer, 
The selective gas analyzer and pumping equipment were 
mounted, for maneuverability, on a small trailer. The apparatus differed 
from the laboratory assembly in several respects: (l) a recording gas 
meter replaced the laboratory flow meter for registration of the rate of 
air flow, and (2) the machine had a different thermopile assembly from that 
used in the laboratory. 
14 FIG.6 
TREADMILL ACTIVITY 
CAL/M2/MIN. 
LEVEL 
10% GRADE 
15 b. Lead Line Maneuverability. 
A method for conveying the lead line hose which extend- 
ed between the subject and recorder was developed on the basis of cable 
and pulley rigging. Taut cables were drawn between objectives on the 
particular rock-climbing terrain to be studied. Movable pulleys were 
mounted on the cables and from these pulleys was suspended the raain line 
hose. A short lead of light hose connected the subject to the raain line. 
Practically the entire weight of the hose assembly was supported mechanic- 
ally, while the man on test was allowed maximum freedom. The trailer con- 
taining the analyzer and pumping apparatus was established at the cliff 
base. Four hundred feet of main line hose were arranged to reach each 
face to be studied. 
c. Subjects, 
Two subjects from each of 6 companies were used. The 
test companies were those of the ration study (Test of Operational Rations, 
Type E)(?). The subjects were approximately battalion average age, height 
and weight (Table 6)• 
TABLE 6 
PHYSICAL CHARACTERISTICS OF SUBJECTS 
Subject 
Height 
(inches) 
(pounds) 
Age 
(years) 
Surface Area 
(square meters) 
H-063 
71 
141 
18 
1.86 
H-025 
6aJ 
238 
18 
1.76 
1-080 
70 
142 
18 
1.81 
1-078 
69 
145 
18 
1.81 
K-X03 
69 
155 
18 
1.85 
K-092 
70i 
248 
19 
1*84 
L-032 
70 
194 
19 
2.08 
L-110 
70 
170 
19 
1.96 
M-114 
68^ 
168 
19 
1.91 
M-105 
68 
178 
18 
1.94 
S—O/4.6 
68 
168 
19 
1.88 
S-051 
70 
167 
18 
1.92 
The metabolism study was coordinated with the battalion 
teaching,schedule so that those men chosen were not deprived of their 
training. Each subject reported for energy expenditure studies according 
to a set schedule and was tested 3 times during the 1 month training period 
i.e., the 1st week, 2nd week and 3rd week. The severity of the assigned 
climb was governed by the subjects instruction in climbing technique. 
Early tests were simple mountain walking. Later tests were precision 
climbing, i,e,, scramble, belay and tension. Some of the more difficult 
phases of the study were made only on those members of the group who were 
considered by their military training instructors to be proficient. This 
policy minimized accidents. 
16 d. Analyses 
Two methods of analysis were used: the field adaptation 
of the classical Douglas bag-Haldane analysis technique, and the infra- 
red analyzer. The Haldane values for oxygen and carbon dioxide, with the 
metered respired volume obtained from the Douglas bag, were used to com- 
pute energy expenditure in terms of Calories per minute. The method of 
calculation for the infra-red analysis was identical with that used in the 
laboratory. Standard mixtures of carbon dioxide were used to establish 
calibration curves during the experimental period. The standardization 
curves for the analyzer conformed to the equation previously noted. 
e. Comparison Between Haldane and Infra-red Analyses 
A relatively rugged mountain walk was chosen as a standard 
effort for the subjects in order to compare the caloric expenditure values 
obtained by both the Haldane and the infra-red techniques. This course 
consisted of a 200 foot uphill path, the average grade of which approxi- 
mated 53 per cent. Douglas bag samples were taken at rest, during ascent, 
while recovering after ascent and during descent of the standard grade. 
Over the same course, at a different time, an infra-red analysis was made. 
The energy expenditure for each phase of the standard exertion for each 
subject is given in Table 7* Values obtained with the 2 methods were in 
closest agreement at resting levels. Increased exertion gave outputs 
which were comparable in trend and average only. The discrepancy between 
the 2 methods is best explained as due to individual variation in energy 
expenditure by a subject upon repetition of the same effort. 
f. Comparison of Infra-red Analysis Curves .Between Subjects. 
The analysis curves for output of COg demonstrated rather 
close contour agreement between subjects when taken as initial exposure to 
a particular type of exercise. In Figure 7 the analyzer curves, obtained 
from paired subjects undergoing 3 types of climbing training, are conpared. 
They represents (l) paired subjects undertaking quick time tl20 steps per 
minute) and double time (180 steps per minute) marching; (2) climbing the 
200 foot mountain walk previously described; and (3) ascent and descent of 
a 400 foot course of mountain walk and shale scramble. The curves have 
been superimposed. The elapsed times differ slightly. On both of the 
climbs between ascent and descent there was a five minute "break” or re- 
covery period* 
The 400 foot course was a continuation of the 2X> foot 
standard grade, and consisted of an additional 200 feet of very difficult 
shale rock scramble. The grade was somewhat steeper than that of the 
previous effort. The carbon dioxide output, converted to 
for the total course showed fairly good agreement between men (Table 8)• 
17 Subject 
— - 
Area 
Sq, M, 
1 i 
Rest-before exercise 
Ascent 2001 
■ ■ - ■ * - 
Recovery-post ascent 
Descen 
it 200» 
Haldane 
Infra-Red 
Haldane 
Infra-Red 
Haldane 
Infra-Red 
Haldane 
Infra-Red 
L-032 
2.08 
.891 
.802 
4.86 
5.21 
1.27 
2.58 
2.20 
3.78 
L-110 
1.96 
.832 
.796 
4.26 
4.35 
2.12 
2.61 
2.39 
3.28 
H-025 
1.76 
.768 
1.191 
4.23 
3.64 
1.97 
2.47 
2.12 
2.03 
H-063 
1.86 
.661 
.791 
2.39 
3.06 
1.60 
2.23 
1.66 
3.03 
K-103 
1.85 
1.000 
1.230 
4.38 
4.07 
1.92 
1.99 
2.78 
2.45 
K—092 
1.84 
.952 
.858 
4.04 
3.92 
1.86 
1.38 
2.99 
2.24 
M-105 
1.94 
.944 
1.000 
4.35 
2.94 
1.53 
2.43 
3.12 
2.37 
M-QJL4 
1.91 
.734 
.644 
3*48 
4.02 
1.29 
2.04 
1.94 
2.65 
S-046 
1.88 
.632 
.665 
4.89 
4.33 
1.70 
1.98 
2.49 
2.59 
s-051 
1.92 
.876 
.906 
3.74 
3.34 
1.37 
2.08 
2.73 
2.43 
1-078 
1.81 
1.022 
.951 
3.62 
t 
3.48 
1.41 
1.63 
2.79 
' 2.40 
1-080 
1.81 
1.022 
.813 
< 
4.86 
2.94 
1.82 
1.60 
2.84 
2.36 
TABLE 7 
ENERGY EXPENDITURE CAX./ii2/MIN. 
18 FIG. 7 
maoi in Ur* a The Estfrline-Angus Co., Inc., inoianacolia, inu , u.a a. 
The. Estlrlinf-ANcius Co , Inc., inoianapoi is. >nd.. u s.a Chart No 43G5-C 
Thf Estfrli nf-A nous*Co . Inc., inuianapoi is ini)., u s.a Chart No. 4305-C TABLE 8 
FREE CLIMB AND SCRAMBLE - 400 FEET AND RETURN 
Subject 
Total 
Calories 
Time 
min. 
Cal./min. 
Cal./min/^^ 
L-032 
90.1 
16 
5.64 
2.71 
L-no 
111.2 
20.2 
5.54 
2.82 
H-025 
108.7 
23.3 
4.66 
2.65 
H-063 
99.1 
21.8 
4.54 
2.44 
K—103 
92.4 
25.4 
3.63 
1.96 
K-092 
111.5 
31.0 
3.59 
1.95 
M-105 
87.5 
22.3 
3.93 
2.02 
M-1I4 
87.4 
22.9 
3.82 
2.00 
s-046 
82.1 
23.2 
3.54 
1.88 
s-051 
84.4 
22.7 
3.72 
1.93 
1-078 
107.7 
24.8 
4.34 
2.40 
1-080 
77.8 
19.5 
3.99 
2.20 
g. Terrain Familiarity (confidence) in Belay Climb. 
In the laboratory, repetition of the same exercise by 
a subject did not give identical energy distribution, for he was apparent- 
ly able to govern his energy expenditure in accordance with anticipated 
need. In the field, familiarity with terrain gave the man added confi- 
dence which enabled him to perform an assignment in shorter time, at the 
same rate of caloric expenditure. In practice all comparisons have been 
made when the subjects had the same familiarity with a given terrain. 
Ideally, initial effort would have been preferable. To illustrate this 
point, we chose a difficult, totally unfamiliar climb and called for vol- 
unteers. Five of the 12 subjects agreed to undergo the test. Because of 
the hazard, the men were protected by a belaying line. This was a safety 
"check fall” rope from the manfs body to an assistant above him in climb. 
No actual climbing aid was given by this rope, but its presence prevented 
serious falls. Each of the 5 volunteers made the climb (125 feet of perpen- 
dicular ascent) using only natural hand and foot holds. For all, it was 
avowed to be an initial attempt. Figures 8 and 9 picture the belay climb 
area with a subject and apparatus in ascent. Caloric expenditure and time 
requirements for the men are given in Table 9. 
TABLE 9 
BELAY CLIMB - CALORIC EXPENDITURE 
Subject 
Surface 
Area 
Total 
Calories 
Time 
min. 
Cal/M^/min. 
K-103 
1.85 
106.1 
21.0 
2.72 
K-092 
1.84 
74.6 
14.6 
2.74 
H-029 
1.80 
101.5 
18.0 
3.14 
H-025 
1.76 
84.0 
15.0 
3.18 
1-080 
1.81 
104.5 
17.3 
3.36 
20 FIG. 8. BELAY CLIMB AREA 
21 FIG. 9. BELAY CLIMB 
22 On the second attempt at the same belay climb, required 
time was cut by one third without proportionate rise in energy expenditure. 
This improvement was the result of confidence. The role of experience 
was checked on two men from outside of the test group. One of these was 
a mountain climbing instructor, and the other a presumably inexperienced 
"jeep” driver. Each volunteered to make the climb. The instructor 
attacked the climb immediately, made no false starts and completed the 
course in less than two thirds of the time required by the novice. The 
trained manfs caloric expenditure was less than that of the untrained. 
In Figure 10 are records illustrating the influence of confidence and of 
experience• 
h. Climbing Under Mental Tension* 
The most difficult climb in mountain training was the 
’’tension" climb, so named because the subject was under stress while climb- 
ing. There were no hand holds or foot holds; the climber ascended by driv- 
ing steel pegs into clefts in the cliff face, and drew himself up from peg to 
peg by means of a sling rope. This climb was forbidden to the soldier 
subjects because of the danger, but the instructor who cooperated on the 
belay climb agreed to a demonstration. His energy expenditure was 
relatively low, and ascent very slow. During 10 feet of climbing which 
required 15 minutes, the caloric expenditure was 2.84 Cal/M2/min. 
i. Summary Values for Mountain Training. 
Summary values for energy expenditure of troops engaged 
in mountain training during the field trials are given in Table 10. 
TABLE 10 
MOUNTAIN TRAINING ENERGY EXPENDITURE (AVERAGES) 
Activity 
Cal/tf/Minute 
Rest (before exertion) 
0.39 
Quick Tims March (120 steps/min.) 
- 2.59 
Doable Time Larch (180 steps/min.) 
■ 5.04 
Free Climb and Mountain Walk 
2.04 
(200r course & return) 
Ascent 
3o77 
Descent 
* 2.09 
Recovery (break period) 
- 2.55 
Free Climb and Scramble 
2.25 
(400* course and return) 
Belay Climb 
3.03 
23 FIG. IQ III. DISCUSSION 
A new technique for measurement of caloric expenditure during contin- 
uous activity has been developed. Both laboratory and field trials have 
proved the adaptability of the Leeds and Northrup selective gas analyzer 
to the estimation of carbon dioxide in expired air. Caloric expenditure 
studies on men undergoing mountain warfare training have been accomplished. 
The new method offers instantaneous analysis and continuous records over 
protracted periods of exercise. These criteria have not been met by pre- 
vious methods. 
IV. CONCLUSIONS 
The Leeds and Northrup infra-red gas analyzer sensitized for carbon 
dioxide detection and equipped with an adequate pumping system for con- 
trolled air flow has been adapted to metabolic work and found satisfactory 
both in the laboratory and in the field. The A-13 oxygen demand mask in 
conjunction with long air lines carried by cable and pulley rigging offered 
a light weight, comfortable, non-restraining respirator for field study 
of energy expenditure. Energy output studies on representative soldier 
subjects engaged in mountain warfare training have been recorded. 
V. RECQLH3IDATI0NS 
The apparatus developed and tested is satisfactory for routine study 
of respiratory exchange. To obtain absolute fidelity, i.e. synchro*- 
rdzation of recorded response with respiratory excursions, and continuous 
analytical records of oxygen utilization, should be the aim of subsequent 
investigation. 
VI. BIBLIOGRAPHY 
1* Nelson, N. The N,D,R,C. Infra-red gas analyzer for determination 
of rapidly changing carbon monoxide concentrations, A,M.R,L, 
Project No, T-9, 18 May 1945# 
2, Palmes, E. D. and Park, C. R, A technique of human, calorimetry. 
M.D.F.R.L. Project No. 55-3, 31 March 1947. 
3. Hitchcock, F. A. Summary report infra-red gas detector and gas 
analyzer. O.S.R.D, Report No. 1642, 1 January 1944. 
4. Lange, N. A. Handbook of chemistry, Sandusky, Handbook Publishers, 
Inc., 1941* p. 666, 
5. Carpenter, T.M. Tables, factors and formulas for computing 
respiratory exchange and biological transformations of energy, 
Carnegie Institution of Washington, Publication 303 B, Third 
Edition 1939. 
6. laboratory manual of field methods for biochemical assessment of 
metabolic and nutritional condition. Harvard Fatigue Laboratory, 
p. 93, March 1945. 
7. Johnson, R, E. Test of operational ration, type "E". Medical 
Nutrition Laboratory, Chicago, Illinois, 1 March 1947. 
25