Hypoxic Vasoconstriction

[MudPhud20XX]

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So one of the clinically important phenomenon in the pulmonary circulation is hypoxic vasoconstriction, defined as: when there is a deceased in PAO2 (alveolar), a local vasoconstriction of pulmonary blood vessels is produced which results in a lowering of blood flow through the lung.

To me this is really counter-intuitive. Can anyone explain how does hypoxic vasoconstrcition help improve decreased in PAO2? What am I missing here?

Many thanks in advance.

 

[AnalisCanalis]

There is really no point in perfusing non-ventilated areas of the lung. Hypoxic vasoconstriction will redirect blood flow to areas which are ventilated, thus optimizing gas exchange.