R = Respiratory Exchange Ratio

When there is no carbon dioxide present in
the inspired gas (which is a good assumption to make since the
concentration of carbon dioxide in the inspired air is often neglible), R
equals the rate of carbon dioxide ouput divided by the rate of oxygen
intake.  The respiratory exchange ratio is also equal to 
PECO2(1-FIO2)/(PIO2-PEO2-(PECO2*FIO2)) where

PECO2= The partial pressure of carbon dioxide in expired air,
PIO2= The partial pressure of oxygen in inpired air,
PEO2= The partial pressure of oxygen in expired air,
FIO2= The fractional concentration of oxygen in inspired dry air.

A sample problem:

Answers:

For more information on this topic, please refer to West , pages 53, 54, 171.

Also, check out the following links that may be helpful:

• University of Arizona: Respiration Lecture #49
• Loyola: Concept of Ventiation/Perfusion Matching
• And, as always, if you have questions, or if you can suggest a helpful link, please e-mail me.

No!
Please don't make me go to any of those pages!
I want to go somewhere completely different!

This page was written by Mary Alice Kalpakian, a student in this course.

BME 403 Pages maintained by the T.A., Douglas Miles.