Respiration during Hyperthermia in the Chicken as Influenced by an Increase in Inhaled CO2

Respiratory rate was measured in unanesthetized, adult hens when abruptly exposed to 1.5% CO2 as they were responding to an environmental temperature of 38 C. Inhalation of 1.5% CO2 greatly depressed respiratory rate at high panting rates, but produced only slight changes during the lower, but sharply increasing, rates of respiration. The initial portion of the panting response appears to be mostly controlled by the respiratory drive initiated by thermoreceptors while higher respiratory rates seem to be more affected by chemical changes.