Increased Pulmonary Vascular Pressor Response to Hypoxia in Highland Dogs

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Abstract
Greater pulmonary vascular resistance increases in response to acute hypoxia were observed in the anesthetized dog at 1600-m altitude than in dogs studied at sea level. Consequently, the hemodynamic response to hypoxia was studied in 11 lowland dogs flown to Denver [Colorado, USA] and compared to the response of 11 dogs obtained locally. The local highland dogs had mean increases in pulmonary arterial pressure and pulmonary vascular resistance during hypoxia of +17 .+-. 1 mm Hg and +5.3 .+-. 0.9 mm Hg/l per min, respectively, in contrast to the increases of +12 .+-. 1 mm Hg and +2.8 .+-. 0.2 mm Hg/l per min observed in the lowland dogs. The increase in pulmonary arterial pressure induced by prostaglandin F2.alpha. was not significantly different in the 2 groups. The pulmonary pressor response to hypoxia in 7 lowland dogs restudied after 3-4 wk residence at 1600 m was not altered. The difference in responsiveness of the pulmonary vascular bed to hypoxia in the 2 groups suggests that chronic low-grade hypoxia may alter hypoxic reactivity, and that the resident altitude should be considered when comparing data from various laboratories.

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