Control of ventilation in running birds: effects of hypoxia, hyperoxia, and CO2.

Minute volume (V), tidal volume (VT), respiratory frequency (f), venous lactate, and clavicular air sac gas composition were measured in domestic fowl at rest and during exercise, breathing hypoxic, hyperoxic, or hypercapnic gas. Hyperoxia produced no significant change in ventilation, CO2 inhalation produced increases in V and VT, but the changes in f appeared to be related to the stage of exercise at which CO2 was administered. The sensitivity of the hypercapnic response was similar in resting and exercising birds. Compared with the effects of CO2, hypoxia elicited only a weak ventilatory response in rest and exercise conditions despite severe tissue anaerobiosis.