THE EFFECTS OF CAROTID-BODY HYPOCAPNIA ON VENTILATION IN GOATS

This study was designed to examine the influence of carotid body (CB) hypocapnia on ventilation by selectively perfusing the CB through an extracorporeal circuit in 19 goats. When PcbCO was decreased from normocapnic levels in 14 awake goats (ΔPcbCO = 10.9 Torr), PaCO increased 5.6 Torr (P < 0.05) and V̇E decreased 24% (P < 0.001) (mean values). The ventilatory sensitivity to inspired CO2 was not changed by CB hypocapnia in 5 of these goats, but the response was shifted to the right. During CB hypocapnia, ventilatory instability, including apnea, was observed in 4 of 14 goats; this irregular breathing continued at elevated levels of PaCO. In 5 anesthetized goats, CB hypocapnia (ΔPcbCO = 18.0Torr) decreased V̇E by 70% in the intact state, but produced no significant ventilatory depression after CB denervation. We conclude that CB hypocapnia depresses ventillation in both awake and anesthetized goats mostly through CB chemoreceptor effects, and suggest that this hypoventilation may predispose to ventilatory instability in some animals. © 1990.