Intrapulmonary co2-rise time and ventilation in ducks.
Furilla, Robert A., and Marvin. H. Bernstein.
Department of Physiology, University of Puerto Rico, School of
Medicine, San Juan, PR 00936-5067 and Department of Biology, New
Mexico State University, Las Cruces, NM 88003
APStracts 2:0284A, 1995.
Many investigators have reported finding intrapulmonary chemoreceptors
(IPCs) in several species of birds and reptiles; however, the role of
IPCs in ventilatory control in birds has not been identified. This
study was undertaken to assess the role of intrapulmonary CO2
dynamics on the control of breathing. Ducks were unidirectionally
ventilated, and their breathing was monitored with a pneumotachograph
connected to a personal computer. A gas-mixing system controlled by
the computer adjusted the rate of rise of airway CO2 concentration
[CO2]. On inspiration, the computer removed CO2 from the ventilating
gas for 1.5 s, followed by a controlled [CO2] rise. Breathing
frequency was directly related to the rate of rise of airway [CO2].
Tidal volume, however, was not correlated with CO2-rise time, but was
related to the peak concentration of airway CO2. This response is
likely mediated by IPCs, because preventing airway [CO2] from falling
during inspiration immediately altered that breath. An increase in
CO2 production (as in exercise) will lead to an increase in the rate
of CO2 excretion into the lung. The resulting alteration of breathing
frequency would thus maintain acid-base balance. The observed
response, therefore, may represent a link between ventilation and
metabolism.
Received 6 September 1994; accepted in final form 5 May 1995.
APS Manuscript Number A930-4.
Article publication pending Journal of Applied Physiology.
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 11 July 1995.