<unk>  is the<unk> imum capacity to transport and utilize oxygen during incremental exercise. (The derivation is V̇ - volume per time, O2 - oxygen,<unk>  -<unk> imum). It is also called<unk> imal oxygen consumption or<unk> imal oxygen uptake. It is also known as aerobic capacity, which reflects the physical fitness of a person.
It is the<unk> imal intake of oxygen that a person can take in at the moment of exhaustion, which is determined according to that person's age, height, weight, fitness level and basal metabolic rate.
Expressed either as an absolute rate in litres of oxygen per minute (l/min) or as a relative rate in millilitres of oxygen per kilogram of bodyweight per minute (ml/kg/min), the latter expression is often used to compare the performance of endurance sports athletes. A less size-biased measure is to divide by 
m
a
s
s
2
3
{\displaystyle {\sqrt[{3}]{mass^{2}}}}
 rather than mass.
It has become a standard testing method for athletes, athletic and sportive people and even for airplane pilots, car race drivers, and individuals with jobs demanding them to be fit, in good shape and health. It is a part of cardiac and pulmonary screenings too.
VO2 max
DLCO
Ventilation/perfusion ratio
Saturation 
Arteriovenous oxygen difference
Diffusion capacity
FEV1/FVC ratio
Oxygen Enhancement Ratio