Pulmonary hemodynamic responses to acute and chronic hypoxia in two waterfowl species

Abstract

1. 1 Two waterfowl species, the Bar-headed goose, Anser indicus, and the Pekin duck, Anas platyrhyncos forma domestica, were studied first at sea level, and subsequently, after they had acclimated to a simulated altitude of 5450 m (0.5 atm) for 4 weeks. 2. 2. Cardiac output (.Q) and right ventricular pressures were measured in response to graded hypoxia in the sea level (SL) and high altitude acclimated (HA) birds. 3. 3. Mean values obtained from six birds of each species indicated: in the SL condition right ventricular systolic pressures (RVSP) began to increase at arterial P O 2 ( P aO 2 ) of 40 torr in both species; in the duck Q also increased at P aO 2 = 40 torr and to same extent as RVSP, but in the goose Q increased only when P aO 2 reached 30 torr. 4. 4. In the HA birds, under normoxic conditions, Q was above SL control in the goose but slightly below in the duck. RVSP followed the same pattern as .Q. 5. 5. When made hypoxic, the contours of the .Q and RVSP response curves were similar to those seen in the SL control state in both species. 6. 6. The rise of RVSP proportional with the rise of .Q in hypoxia suggests that the major cause of the pulmonary hypertensive response to hypoxia in these species is mechanical in origin.