Ventilatory stability to co2 disturbances in wakefulness and quiet
sleep.
Modarreszadeh, Mohammad, Eugene N. Bruce, Herbert Hamilton, and David
W. Hudgel.
Departments of Biomedical Engineering and Medicine, Case Western
Reserve University, Cleveland Ohio, 44106; Pulmonary Division,
MetroHealth Medical Center, Cleveland Ohio, 44109; and Center for
Biomedical Engineering, University of Kentucky, Lexington, KY
40506
APStracts 2:0218A, 1995.
Oscillatory ventilatory pattern occurs more frequently in sleep
despite the stabilizing factor of sleep-induced reduction in CO2
chemosensitivity. In nine young normal humans we have tested the
hypothesis that despite a sleep-induced reduction in
chemosensitivity, the transient, central-chemoreceptor mediated
change in inspiratory ventilation caused by a standardized
disturbance to chemoreflex ventilatory control is similar in quiet
sleep (QS) and wakefulness (AW). The equivalent response to a single
-breath hyperoxic hypercapnic stimulus (i.e., inhaling a single breath
of 0.01 liters of CO2 in O2 - a direct measure of "closed
-loop" dynamical response) was determined using pseudorandom
binary CO2 stimulation and the prediction-error-method of transfer
function estimation. From these data also the response of to a
single-breath increase of 1 Torr in end-tidal CO2 partial pressure
was derived, from which "dynamic" central chemosensitivity
was calculated. Despite a 43% reduction in dynamic central
chemosensitivity, the peak and the area under the closed-loop
response are similar in AW and QS while sleep increases the duration
of the response by 48%. Thus hyperoxic ventilatory stability is not
reduced in QS relative to AW. We propose that changes in dynamics of
pulmonary gas exchange in sleep substantially offset the decreased
chemosensitivity, thereby maintaining the gains and time constants of
the central-chemoreceptor mediated component of the closed-loop
ventilatory control system similar to those during wakefulness.
Received 6 February 1995; accepted in final form 8 May 1995.
APS Manuscript Number A135-4.
Article publication pending Journal of Applied Physiology.
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 30 May 1995.