MATURATION OF VENTILATION AND VENTILATORY PATTERN IN NORMAL SLEEPING INFANTS

Noninvasive studies of ventilation and ventilatory pattern were performed serially in 15 normal infants in the first 4 mth of life during REM and quiet sleep with the barometric method. We measured tidal volume (VT), total respiratory cycle time (Ttot), inspiratory time (TI), expiratory time (TE), mean inspiratory flow (VT/TI), and respiratory 'duty cycle' (TI/Ttot). VT, Ttot, TI, TE, VT/TI, and VT/Ttot but not TI/Ttot increased with age. In all age groups, Ttot, TI, and TE but not VT/TI were greater in quiet than in REM sleep. In the first 2 mth of life, VT was greater in quiet than in REM sleep; in the older infants, VT/Ttot was smaller in quiet than in REM sleep. TI/Ttot was not dependent on sleep state. Thus, because VT/Ttot = VT/TI x TI/Ttot, the increase in VT/Ttot with age results from an increase in mean inspiratory flow rather than from changes in respiratory 'duty cycle'. Further, the 'on-switching' as well as the 'off-switching' of inspiratory activity depends on sleep state.