hypoxia and pulmonary vessels

Q: Hypoxia causes pulmonary? - select one

A) vasoconstriction

B) vasodilatation

Answer: A

The proper term is hypoxic pulmonary vasoconstriction (HPVC). It is considered a normal regulatory mechanism. When pulmonary or peripheral vessels sense hypoxia, the HPVC mechanism limits blood flow to hypoxic alveoli and preserves ventilation-perfusion matching. 

The learning objective of this question is to understand that both alveolar hypoxia as well as peripheral arterial hypoxemia may cause HPVC. It is time-dependent, i.e., either acute or chronic.

Short-term hypoxia, which occurs over hours or a few days, is reversible with return to normal oxygen level or with oxygen administration.

Chronic hypoxia, which occurs over weeks, is often only partially reversible and leads to Group-3 pulmonary hypertension.

#pulmonary

References:

1. Dunham-Snary KJ, Wu D, Sykes EA, Thakrar A, Parlow LRG, Mewburn JD, Parlow JL, Archer SL. Hypoxic Pulmonary Vasoconstriction: From Molecular Mechanisms to Medicine. Chest. 2017 Jan;151(1):181-192. doi: 10.1016/j.chest.2016.09.001. Epub 2016 Sep 16. PMID: 27645688; PMCID: PMC5310129.

2. Sylvester JT, Shimoda LA, Aaronson PI, Ward JP. Hypoxic pulmonary vasoconstriction. Physiol Rev. 2012 Jan;92(1):367-520. doi: 10.1152/physrev.00041.2010. Erratum in: Physiol Rev. 2014 Jul;94(3):989. PMID: 22298659; PMCID: PMC9469196.