Air hunger induced by acute increase in pco2 adapts to chronic
elevation of pco2 in ventilator-dependent subjects.
Bloch-Salisbury, Elisabeth, Steven A. Shea, Robert Brown, Karleyton
Evans, and Robert B. Banzett.
Physiology Program, Harvard School of Public Health, Boston, MA
02115 and Pulmonary Division, West Roxbury Veterans Administration
Medical Center, West Roxbury, MA 02132
APStracts 3:0215A, 1996.
Brief increases in PaCO2 (lasting several minutes) produce a sensation
of respiratory discomfort (`air hunger'). It is not known if air
hunger adapts to chronic changes in PaCO2. This study tested whether
the level of PETCO2 required to evoke air hunger would increase with
chronic elevation of PETCO2 (lasting several days). Four ventilator
-dependent subjects participated in a two-week study during which they
were ventilated with air (placebo) or air rich in CO2 (CO2 exposure).
Average resting PETCO2 during control periods was 25 mmHg (typical
for such patients); PETCO2 was 15 mmHg higher during CO2 exposure.
Ventilation and PaO2 did not differ between conditions. Periodically,
we performed tests in which subjects rated the intensity of air
hunger induced by brief increases in PETCO2. The increase in PETCO2
required to elicit a given air hunger rating during CO2 exposure also
increased by about 15 mmHg. That is, subjects' sensation of air
hunger fully adapted to the chronic increase in PETCO2. Arterial pH
did not fully return to control values during CO2 exposure.
Accommodation in the chemoreceptors and neural pathways which
subserve air hunger sensation may explain the adaptation of air
hunger.
Received 30 August 1995; accepted in final form 25 March 1996.
APS Manuscript Number A948-5.
Article publication pending Journal of Applied Physiology.
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 1 May 96