Effects of Hypoxia on Pulmonary Vascular Reactivity in Pneumonectomized Puppies and Minipigs

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Abstract
Pneumonectomy was performed on 25 1-month old beagle puppies and 13 2-month old minipigs. Three weeks or more later, pulmonary blood flow and pulmonary artery pressure were measured in the survivors and total pulmonary vascular resistance was calculated in each animal. These measurements were made at normal arterial Po 2 and at an arterial Po 2 of 31 ± 5 mm Hg produced by ventilating the animals with 10% oxygen in nitrogen. Seven normal puppies and seven normal minipigs of ages comparable to the pneumonectomized animals were studied as controls. The mean pulmonary artery pressure in the pneumonectomized puppies was not significantly different from that of the normal puppies. There was no significant pulmonary vascular response to hypoxia in the pneumonectomized puppies. The pneumonectomized minipigs had a significantly higher resting mean pulmonary artery pressure than the normals ( P < 0.005). They did not, however, show a greater reactivity to hypoxia than did their normal litter mates. Both pneumonectomized and normal minipigs were more reactive to hypoxia than puppies. The minipigs were restudied approximately 16 weeks after the initial study. Four out of five animals showed a further rise in resting pulmonary artery pressure. Histological studies showed arteriolar medial hypertrophy in the minipig lungs.

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