BZ Gas Analysis. VI 
Calculation of Results of Experiments on Respiratory Exchange 
with Spirometer, Douglas Bag, and Small Animal 
Respiration Apparatus. 
Analyze sample of air from the spirometer or bag for percentage of 
oxygen and CO2. The volume of the gasometer is obtained by knowing the 
diameter of the bell, calculating its cross-section in sq. cm. by zr’, and 
reading the distance the bell has risen on the self-winding steel tape meas- 
ure fastened at the top of the bell. If the bag is used, measure contents 
of bag by passing the air through a gas meter and note temperature in the 
meter. Read barometer. By means of Table I reduce the volume of air 
expired in 1 minute to standard pressure and pan get Na (O°C. and 760 
mm.). 
From the CO, percentage subtract the CO: of the inspired air (0.03), 
and multiply by the (reduced) volume of air expired in 1 minute. This 
gives the CO, production per minute. 
‘The volume of oxygen absorbed is less easy to calculate however, as 
the volume of dry air has diminished in the process of respiration because 
more oxygen has been taken up than carbon dioxide has been given off. 
Since nitrogen is neither taken up nor given off in respiration, it is evident 
that for every 100 volumes of expired air there corresponded in the inspired 
air, not 20.93 volumes of oxygen, but ane se or 0.2648, multiplied by the 
percentage of nitrogen in the expired air. By subtracting from the oxygen 
figure so obtained the oxygen percentage found by analysis, the true per 
cent of oxygen consumed is found. Multiplying the volume of air expired 
per minute by this percentage gives the oxygen really consumed, and 
dividing the CO, produced by the oxygen consumed gives the respiratory 
quotient”’ (Haldane, 3). 
Instead of making this Mleulariar the results may be obtained by 
means of Table II. By this table the apparent respiratory quotients [CO, 
per cent found by analysis divided by (20.93 minus oxygen found by analy- 
sis)] can be transformed into true quotients, and the correct intake of 
oxygen obtained by dividing the output of carbon dioxide by the true 
respiratory quotient. 
From Table III for indirect calorimetry the amount of energy produced 
and the character and amounts of the substances oxidized in the body are 
obtained by taking the figure corresponding to the respiratory quotient 
and multiplying it by the oxygen consumption. 
To calculate the respiratory dead space (5) get the tidal volume (?.e., 
total expired air divided by number of breaths) and multiply by 
COs: per cent in mixed expired air 
1:00 — 
CO: per cent in alveolar air 
The dead space for oxygen is obtained similarly. The oxygen pulse (6) 
is the oxygen consumed per minute divided by the pulse rate. 
The external work on the stationary bicycle (7) equals the product of 
the resistance in kilos by the circumference of the wheel in meters by the 
number of revolutions per minute. 
