C. Jensen, C. Bech
Apr 1, 1992
The Journal of Experimental Biology
Ventilatory control of the composition of the gases in the air sacs was studied during entry into fasting-induced, shallow, nocturnal hypothermia in the domestic pigeon ( Columba livia ). Respiratory frequency ( f ), tidal volume ( V T ) and oxygen uptake ( V O O2 were recorded simultaneously in six pigeons; partial pressures of CO 2 and O 2 in the abdominal and interclavicular air sacs were measured in seven pigeons. Ambient temperature was 25°C (thermoneutral) and the body temperature (Tb) was recorded in all experiments. A reduction in T b from 40.5 to 37.5°C paralleled decreases in f and V T from 13.3 min −1 and 15.2 ml BTPSkg −1 to 10.7 min −1 and 12.4ml BTPSkg −1 , respectively. There was a minor, but non-significant, simultaneous decrease in the ventilatory requirement (total ventilation/O 2 uptake) from 0.38 to O.35 ml BTPSmmol −1 . However, in both air sacs the partial pressure of CO 2 increased when T b decreased, indicating an effective parabronchial hypoventilation. The results support the idea of a gradually developing respiratory acidosis during hypothermia.