Effects of hypoxic pulmonary vasoconstriction on pulmonary gas exchange

Brimioulle, Serge, Philippe Lejeune, and Robert Naeije.Effects of hypoxic pulmonary vasoconstriction on pulmonary gasexchange. J. Appl. Physiol. 81(4):1535-1543, 1996.Several reports have suggested that hypoxicpulmonary vasoconstriction (HPV) might result in deterioration ofpulmonary gas exchange in severe hypoxia. We therefore investigated theeffects of HPV on gas exchange in normal and diseased lungs. Weincorporated a biphasic HPV stimulus-response curve observed in intactdogs (S. Brimioulle, P. Lejeune, J. L. Vachièry, M. Delcroix, R. Hallemans, and R. Naeije, J. Appl.Physiol. 77: 476-480, 1994) into a 50-compartment lung model (J. B. West, Respir.Physiol. 7: 88-110, 1969) to control the amount ofblood flow directed to each lung compartment according to the localhypoxic stimulus. The resulting model accurately reproduced the bloodgas modifications caused by HPV changes in dogs with acute lung injury.In single lung units, HPV had a moderate protective effect on alveolaroxygenation, which was maximal at near-normal alveolarPO₂ (75-80 Torr), mixed venousPO₂ (35 Torr), andPO₂ at which hemoglobin is 50%saturated (24 Torr). In simulated diseased lungs associated with40-60 Torr arterial PO₂,however, HPV increased arterial PO₂ by 15-20 Torr. We conclude that HPV can improve arterialoxygenation substantially in respiratory failure.