Journal of Applied Physiology, Vol 54, Issue 6 1482-1488, Copyright © 1983 by American Physiological Society
Transient ventilatory response to CO2 as a function of sleep state in full-term infants
J. V. Anderson Jr, R. J. Martin, E. F. Abboud, I. Z. Dyme and E. N. Bruce
The influence of sleep state on the transient (i.e., initial 60 s) and
steady-state ventilatory responses to 2% CO2 inhalation was studied in 19
healthy full-term infants. A nasal mask pneumotachometer was used to
measure ventilation and end-tidal CO2 partial pressure (PCO2) and enabled
abrupt changes in the inspired gas concentration to be made. The magnitude
of the change in minute ventilation for both the transient and steady-state
responses to CO2 was not statistically different between active (AS) and
quiet (QS) sleep. Nonetheless the greater variability in minute ventilation
during AS compared with QS continued throughout the period of CO2
inhalation and was associated with a more variable change in ventilation in
the individual infants during AS. There was a greater increase in end-tidal
PCO2 over the first 60 s during AS (3.3 +/- 0.3 vs. 2.6 +/- 0.2 Torr, in AS
and QS, respectively, P less than 0.03). This may indicate a smaller
initial increase in alveolar ventilation, relative to CO2 delivery to the
lungs, in response to CO2 inhalation during AS. Asynchronous chest wall
movements were more common during AS than QS (P less than 0.005) and did
not change with CO2. The inconsistent transient ventilatory response to CO2
during AS compared with QS may be important in the behavior of infants to
spontaneous episodes of hypercapnia occurring during AS.
