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Exercise Science 3
 

Section 3

Now we can use these values to calculate VO2, the volume of oxygen removed from the inspired air per min, and VCO2, the volume of carbon dioxide produced per min.

Calculation of VO2 and VCO2

For Oxygen consumption:

VO2 = VIO2 – VEO2

where VIO2 and VEO2 are the volumes of O2 (per min) in the inspired and expired air, respectively.

Now VIO2 = VI x FIO2%/100 = VI x 20.93/100

and VEO2 = VE x FEO2%/100

Hence:

VO2 = (VI x 0.2093) – (VE x FEO2%/100)

For Carbon Dioxide production:

VCO2 = VECO2 – VICO2

and by analagous reasoning to that used above for VO2:

VCO2 = (VE x FECO2%/100) – (VI x 0.0003)

Worked Example

O2 in expired air in the Douglas bag: 16.8%
CO2 in expired air in the Douglas bag: 4.1%
VESTPD: 8.36 litres/min
VISTPD: 8.37 litres/min

VO2 = (VI x 0.2093) – (VE x FEO2%/100)

Here VO2 = (8.37 x 0.2093) – (8.36 x 0.168)
i.e. VO2 = 0.347 litre/min

VCO2 = (VE x FECO2%/100) – (VI x 0.0003)

Here VCO2 = (8.36 x 0.041) – (8.37 x 0.0003)
i.e. VCO2 = 0.340 litre/min


VO2:  (3 DP)
VCO2:  (3 DP)