Effect of chronic hypoxia on the pulmonary arterial blood pressure of the chicken

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Abstract
Single-comb White Leghorn chickens hatched and living in a high-altitude environment of 12,500-ft elevation, had pulmonary arterial blood pressures approximately twice as great as found in chickens at sea level. The pulmonary arterial blood pressures were highly correlated with the relative right ventricular masses of the individual birds at all altitudes. The proportionality coefficients of this relationship in chickens were double those reported by others in cattle. In the female chicken it appears that each 1 mm Hg increase in the mean pulmonary arterial blood pressure above sea level control values results in a 41 -mg increase in the right ventricular mass (hypertrophy). Inhalation of 95% O2 and 5% CO2 for 10 min had no apparent effect on this pulmonary arterial hypertension at high altitude, although acute hypoxia (asphyxia, by tracheal occlusion) produced a pulmonary arterial hypertension in sea-level birds. The occlusion of 1 major pulmonary artery produced a 67% increase in the pulmonary arterial blood pressure in the unobstructed lung. Chronic hypoxia (12,500-ft elevation) produced a 47% reduction in the arterial O2 tension and no significant changes in the arterial CO2 tension and pH. Anesthesia at the surgical level in chickens results in an acute hypoxia and an acidosis. This hypoxic effect from the anesthesia was much less marked at high altitude. Pulmonary arterial blood pressures reached control values within 2 days after the high altitude-adapted animals were returned to sea level.

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