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NBME 21 Answers

nbme21/Block 1/Question#13

A 25-year-old man develops shortness of breath ...

Decreased alveolar Po2

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 +2  upvote downvote
submitted by alexb(10),

Hypoxic pulmonary vasoconstriction (HPV), also known as the Euler-Liljestrand mechanism, is a physiological phenomenon in which small pulmonary arteries constrict in the presence of alveolar hypoxia (low oxygen levels).

While the maintenance of ventilation/perfusion ratio during regional obstruction of airflow is beneficial, HPV can be detrimental during global alveolar hypoxia which occurs with exposure to high altitude, where HPV causes a significant increase in total pulmonary vascular resistance, and pulmonary arterial pressure, potentially leading to pulmonary hypertension and pulmonary edema.

https://en.wikipedia.org/wiki/Hypoxic_pulmonary_vasoconstriction


 +1  upvote downvote
submitted by haliburton(74),

FA 2017: Chronic hypoxic pulmonary vasoconstriction results in pulmonary hypertension and RVH.

yotsubato  Yeah but in a chronic case this guy would produce more RBC and not be hypoxic anymore. +1