If one were to consider humidified air (with less oxygen), then the ideal v/q ratio would be in the vicinity of 1.0, thus leading to concept of ventilation-perfusion equality or ventilation-perfusion matching. Therefore, under these conditions, the ideal ventilation perfusion ratio would be about 0.95. In the typical adult, 1 litre of blood can hold about 200 mL of oxygen 1 litre of dry air has about 210 mL of oxygen. Ideally, the oxygen provided via ventilation would be just enough to saturate the blood fully. The V/Q ratio can be measured with a ventilation/perfusion scan.Ī V/Q mismatch can cause Type 1 respiratory failure. These two variables, V and Q, constitute the main determinants of the blood oxygen (O 2) and carbon dioxide (CO 2) concentration.

The V/Q ratio can therefore be defined as the ratio of the amount of air reaching the alveoli per minute to the amount of blood reaching the alveoli per minute-a ratio of volumetric flow rates.

Q – perfusion – the blood that reaches the alveoli via the capillaries.

V – ventilation – the air that reaches the alveoli.

In respiratory physiology, the ventilation/perfusion ratio ( V/Q ratio) is a ratio used to assess the efficiency and adequacy of the matching of two variables:

Shunt vs dead space oxygen