Table 1.

Nomenclature.

or	rate of oxygen consumption
	rate of carbon dioxide production
Pi	power input
Po	power output
fH	heart rate
VS	cardiac stroke volume
	cardiac output
CIO2	oxygen content in inspired air
CEO2	oxygen content in expired air
CaO2	oxygen content in arterial blood
	oxygen content in mixed venous blood
VT	respiratory tidal volume
fresp	respiratory frequency
	respiratory minute volume
PO2	partial pressure of oxygen
PaO2	partial pressure of oxygen in arterial blood
	Krogh's diffusion constant for oxygen
A	total effective area of the gas exchange surface
D	mean diffusion distance over which the respiratory gases diffuse
Hb	haemoglobin
PaCO2	partial pressure of carbon dioxide in arterial blood
P50	partial pressure at which haemoglobin is 50% saturated