Journal of Applied Physiology, Vol 53, Issue 6 1371-1377, Copyright © 1982 by American Physiological Society
Rapid ventilatory responses to changes in insufflated CO2 in awake roosters
T. L. Clanton, G. O. Ballam, R. K. Moore and A. L. Kunz
The ventilatory responses to pulses or steps in the fraction of CO2 in the
insufflated gas stream (FICO2) in awake, unidirectionally ventilated White
Leghorn roosters (Gallus domesticus) were studied. Within 0.2-0.5 s of the
change in FICO2 at the syrinx, a change in inspiratory or expiratory flow
occurred. Increases in FICO2 increased flow and tidal volume (VT), whereas
decreases in FICO2 decreased flow and VT. Expiratory duration (TE) was
markedly prolonged by decreases in FICO2 and shortened by increases.
Inspiratory duration was affected little by FICO2 changes. The TE response
to pulses of FICO2 (0.2-0.4 s duration) revealed a time dependency such
that a maximum effect occurred when the pulses arrived at the syrinx at
approximately midexpiration. The magnitudes of the responses were
approximately proportional to the amplitude and duration of the FICO2
changes, but decreases in FICO2 had greater effects than increases. A
likely receptor site for these responses is the intrapulmonary
chemoreceptors, which appear to function in a reflex controlling airflow
and timing of the ongoing breath.
