Some Effects of Hyperventilation on Respiratory Patterns

Abstract

Urethanized cats were hyperventilated with a respiration pump during eupnea, panting and gasping. The amount of hyperventilation sufficient to convert eupnea to a prolonged apnea not only failed to inhibit thermal tachypnea but markedly increased the panting rate. The gasping pattern was susceptible to hypocapnic depression for a brief period after severe hyperventilation but returned to the control pattern while the pCO2 was still reduced. Results are interpreted as further evidence for the hypothesis that the respiratory center is functionally separated into a chemosensitive and a reflex zone. It is suggested that panting involves the reflex center which is facilitated by low pCO2 or high pH, whereas eupnea and probably gasping operate through the chemosensitive neurons excited by increases in CO2.