I've just come back from a VO2max test - part of my comparative physio of exercise class we get to take a real (not an estimated) test -
I have my data (FIO2, FEO2, FECO2, FICO2, VE, VE02, HR) for the test interval - but we have not been handed the data sheet yet on how to make our calculations … but I'm anxious -
anyone have the calculations/formulae for VO2max from the measurements?
Lisa
| QUOTE (LisaS @ Oct 24 2002, 12:39 AM) |
| I've just come back from a VO2max test - part of my comparative physio of exercise class we get to take a real (not an estimated) test - I have my data (FIO2, FEO2, FECO2, FICO2, VE, VE02, HR) for the test interval - but we have not been handed the data sheet yet on how to make our calculations ... but I'm anxious - anyone have the calculations/formulae for VO2max from the measurements? Lisa |
Hey Lisa,
I went to my Critical Care book and found a formula for VO2 (oxygen consumption). I am thinking that VO2 max must be maximum oxygen consumption which is the equation for VO2 applied under conditions of maximum exercise capacity.
Here goes: VO2 = C(a-v)O2 X CO X10 which translates to
Oxygen consumption equals arterial oxygen content minus venous oxygen content multiplied by cardiac output multiplied by 10. The factor of ten is used to get the units correct at the end.
You have to take your data and calculate the oxygen content of arterial blood and venous blood along with your cardiac output. You probably use an extraction ratio to calculate both. Those equations I don't have but I know that the extraction ration stays the same unless there is something happening that affects oxygen delivery like a huge drop in Hgb or cardiac output. Under those conditions, the extraction ratio increases and you see it reflected in changed in your expired O2 content. Since my oxygen delivery experience is under conditions totally opposite yours ( my patients sick; you healthy), the equations and equipment that I use (Swan-Ganz catheter to determine cardiac output) might not apply but some food for thought.
Natalie
thanks Natalie -
I don’t know what he’ll want us to use for Q-dot (cardiac output/min) - maybe we’ll just approximate by HR*[Hb] and assume some normal value for [Hb] - I think that’s what I’ll use for now until I get my “official” instructions.
Lisa
Lisa,
Given the expired gas data that you have you need to use a derivation of the Fick equation given by Natalie. Check out any exercise physiology text for the derivation and more detail than I could ever provide. A couple of suggestions are a classic text “The textbook of work physiology” by Astrand or Fundamental Principles of Exercise Physiology by Rob Robergs (an old teacher of mine). The equations are:
VO2 (BTPS)=VE BTPS * ((FIO2 (1-FECO2) - FEO2 (1 - FICO2))/ (1 - FIO2 - FICO2)
you then calculate VO2 STPD by:
VO2 BTPS * (273/310) * (PB - 47 mm Hg/760)
I’m pretty sure that is it. I’m glad to know that my exercise physiology degrees weren’t a complete waste of time.
Good Luck.
cool, thanks for the info - I'm heading to the Sci Library tomorrow - I'll see if they have those texts and get a better look.