how to calc metabolic rate

Question 1

principles of calculating metabolic rate
- how to work out the consumed O2
- how to work out the produced co2
- what 2 things are required to work out metabolic rate
- what is required to measure these 2 things

Answer 1

• the difference between the volume of O2 in inspired air and the volume of O2 in expired air.
• the difference between the volume of CO2 in expired air and the volume of CO2 in inspired air
• knowledge of how much oxygen the body consumes and how much carbon dioxide it produces at any given time
• knowledge of the inspired and expired volumes of these gases

Question 2

what is required to calculate o2 consumption and co2 production
- what are douglas bags
- each thing known and measured

Answer 2

• collect air, then can take a sample, and put through gas analyser to take the measurements needed
  *Percentage of oxygen in inspired air - Known: 20.9%
  *Percentage of carbon dioxide in inspired air - Known: 0.03%
  *Percentage of oxygen in expired air - Measured
  *Percentage of carbon dioxide in expired air - Measured
  *Expired volume - Measured
  *Inspired volume - Measured, or assumed to be the same as expired air (in reality they aren’t always same)

Question 3

using the measurements collected and known figures to work out o2 consumption and co2 production

Answer 3

O2consumption = (volume of inspired O2) - (volume of expired O2) (normal 250ml/min at rest)
- Vol of insp o2= vol of inspired air x percentage of inspired o2
- Vol of exp o2= vol of expired air x percentage of expired o2
CO2production = (volume of expired CO2) - (volume of inspired CO2) (normal 200ml/min at rest)
- Vol of expired co2= volume of expired air x percentage of
expired CO2
- Vol of insp co2= volume of inspired air x percentage of inspired
CO2