Ventilation/perfusion ratio
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In respiratory physiology, the ventilation/perfusion ratio (or V/Q ratio) is a measurement used to the efficiency and adequacy of the matching of two variables:[1]
- "V" - ventilation - the air which reaches the lungs
- "Q" - perfusion - the blood which reaches the lungs
A normal value is approximately 0.8.[2]
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 ratio:[3]
- apex of lung - higher
- base of lung - lower
The V/Q ratio can be measured with a ventilation/perfusion scan.
An area with no ventilation (and thus a V/Q of zero) is termed a shunt.[4]
[edit] References
- ^ MedEd at Loyola Medicine/pulmonar/physio/pf9.htm#q1
- ^ http://www.rnceus.com/abgs/abgvq.html
- ^ http://www.capnography.com/Physiology/Componentsoftime.htm
- ^ http://www.nda.ox.ac.uk/wfsa/html/u12/u1211_02.htm
