Hypoxic pulmonary vasoconstriction due to: (A) Irreversible pulmonary vasocontriction hypoxia, (B) Reversible pulmonary vasoconstriction due to hypoxia, (C) Direct blood to poorly ventilated areas, (D) Occurs hours after pulmonary vasoconstriction
Answer is B. Hypoxic pulmonary vasoconstriction (HPV), also known as the Euler-Liljestrand mechanism, is a physiological phenomenon in which small pulmonary aeries constrict in the presence of alveolar hypoxia (low oxygen levels). Ref Harrison20th edition pg 2334