WordNet
respiratory quotient
n. the ratio of the volume of carbon dioxide expired to the volume of oxygen consumed by an organism or cell in a given period of time
Wikipedia
Respiratory quotient
The respiratory quotient (or RQ or respiratory coefficient), is a dimensionless number used in calculations of basal metabolic rate (BMR) when estimated from carbon dioxide production. Such measurements, like measurements of oxygen uptake, are forms of indirect calorimetry. It is measured using a respirometer.
It can be used in the alveolar gas equation.