AJP - Regulatory, Integrative and Comparative Physiology, Vol 243, Issue 1 164-R169, Copyright © 1982 by American Physiological Society
Breath-to-breath variations in rate and depth of ventilation in sleeping infants
G. G. Haddad, T. L. Lai, M. A. Epstein, R. A. Epstein, K. F. Yu, H. L. Leistner and R. B. Mellins
Ventilatory measurements were made noninvasively over 2- to 3-h periods
during sleep in each of nine normal infants at 1 mo of age. To assess the
changes that occur in ventilation on a breath-to-breath basis, we 1)
examined the variations of each of tidal volume (VT), respiratory cycle
time (Ttot), expiratory time (TE), and inspiratory time (TI) and 2) studied
their interrelationships. We found that the variations of VT, Ttot, and TE
but not of TI were significantly greater in rapid-eye-movement (REM) than
in quiet sleep. In addition, on a breath-to-breath basis, VT had a positive
linear relationship and strong correlation with TI; however, the
correlation between VT and TE was weak in both sleep states. VT/Ttot was
found to be moderately and negatively correlated with Ttot in both REM and
quiet sleep. VT was weakly correlated with Ttot in REM sleep and was, on
the average, more correlated with Ttot in quiet sleep. We suggest that in
infants 1) on a breath-to-breath basis, VT/Ttot is likely to drop if
respiratory frequency is decreased and 2) VT is nonlinearly related to Ttot
during sleep; this lack of linearity depends on the lack of constancy of
VT/Ttot, which is in turn closely related to the variability of the
"on-switching" of inspiratory activity.
