Hypoxic Pulmonary Vasoconstriction and the Ratio of Hypoxic Lung to Perfused Normoxic Lung

Hypoxic Pulmonary Vasoconstriction

“…Finally, as noted in section IIA1, diversion of blood flow from hypoxic to nonhypoxic lung will be diminished and the HPV-dependent augmentation of P PA enhanced as the size of the hypoxic region becomes larger (1191,1192,1717). In the limit where 100% of the lung is hypoxic at the same P A O 2 , HPV increases P PA , but causes no diversion of blood flow, and therefore plays no role in V A /Q matching.…”

Effect of one-lung ventilation on oxygen delivery in anesthetized dogs with an open thoracic cavity

“…The net effect was that the value for PVRI did not change when calculated in accordance with the standard equation derived from Ohm' s law. Transmural pressure at the capillaries, [37][38][39][40] recruitment of capillaries with increases in CO, 41,42 and hypoxic vasoconstriction 36,[43][44][45] are important factors that will affect pulmonary vascular resistance. Transmural pressure is affected by one-lung ventilation, because the entire end V T is redistributed to only 1 lung.…”

Cardiopulmonary changes induced during one-lung ventilation in anesthetized dogs with a closed thoracic cavity

“…Hypoxemic pulmonary vasoconstriction (HPV) is an active vasoconstrictor mechanism that redistributes blood flow away from nonventilated alveoli to ventilated alveoli. [16][17][18][19][20] During OLV, the amount of shunting is decreased by HPV. 21 Response to HPV in dogs is predictable and continuous depending on the size of the hypoxic segment and FIO 2 .…”

“…22 It has been reported 23 that HPV can induce a 58% reduction of blood flow in a hypoxemic lung. Hypoxemic pulmonary vasoconstriction can be inhibited by a number of factors, including high or low pulmonary vascular pressure, 17,18,24 high or low PvO 2 , 25,26 hypocapnia, 17,27 vasodilating agents, 28,29 vasoconstricting agents, 30,31 and anesthetic agents. 5,22 Isoflurane was used during our study, and it may have substantially reduced the response to hypoxemia, which resulted in major shunting of blood in the nonventilated lung.…”

“…The net effect was a nonsignificant augmentation of the calculated PVRI, as determined in accordance with the standard equation derived from Ohm' s law. Transmural pressure at the level of the capillaries, [35][36][37] recruitment of capillaries with increases in CO, 38,39 and hypoxemic vasoconstriction [16][17][18][19] are important variables that will affect pulmonary vascular resistance. Hypoxemic pulmonary vasoconstriction was probably abolished in this study by the use of isoflurane.…”