Gas exchange during exercise in hypoxic ducks

We quantitatively assessed pulmonary gas exchange in Pekin ducks (Anas platyrhynchos) during running exercise (1.44 km X h-1 at 3 degrees incline) while the ducks spontaneously breathed either air (FIO2 = 0.21) or a hypoxic gas mixture (FIO2 = 0.12). During exercise, oxygen consumption increased 3 times above the resting value in normoxia and 3.6 times above rest in hypoxia. The convection requirement rose 34% and 20% in running normoxic and hypoxic ducks, respectively. The O2 extraction coefficient was the same in resting normoxic and hypoxic ducks (0.19 vs 0.18) and decreased by the same amount under exercise conditions (0.14 vs 0.15). Arterial PO2 was maintained during exercise in normoxia but increased slightly during exercise in hypoxia. Cardiac output increased by 73% and 111% during exercise in normoxic and hypoxic ducks, respectively. Calculations indicate that both the O2-diffusing capacity and the total conductance for O2 of the gas exchange system increased markedly during exercise in normoxia and hypoxia. We conclude that at this level of exercise, there was no apparent limitation to gas exchange in either the normoxic or hypoxic Pekin duck.