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Ventilation/perfusion ratio

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] An area with no perfusion (and thus a V/Q of infinitiy) is termed "dead space"


  1. ^ MedEd at Loyola Medicine/pulmonar/physio/pf9.htm#q1
  2. ^
  3. ^
  4. ^
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Ventilation/perfusion_ratio". A list of authors is available in Wikipedia.
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