In respiratory physiology, the<unk>  (or V/Q<unk>  is a measurement used to the efficiency and adequacy of the matching of two variables:
"V" -<unk>  - the air which reaches the lungs
"Q" -<unk>  - the blood which reaches the lungs
A normal value is approximately 0.8.
Because the lung is centered vertically around the heart, part of the lung is superior to the heart, and part is inferior. This has a major impact on the V/Q<unk> :
apex of lung - higher
base of lung - lower
The V/Q<unk>  can be measured with a<unk><unk>  scan.
An area with no<unk>  (and thus a V/Q of zero) is termed a shunt.
An area with no<unk>  (and thus a V/Q of infinitiy) is termed "dead space"
Ventilation/perfusion ratio
Alveolar gas equation
Alveolar-arterial gradient
Volumetric flow rate
Arteriovenous oxygen difference
Diffusion capacity
Cardiac output
Pulmonary compliance