Sleep and maturation of eucapnic ventilation and CO2 sensitivity in the premature primate

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Abstract
Effects of sleep state and postnatal maturation on steady-state CO2 sensitivity, inspiratory drive (VT/TI), and the inspiratory duty cycle (TI/Ttot) were examined in 9 unanesthetized premature Macaca nemestrina in the first 3 wk of life. Minute volume (.ovrhdot.VE) in room air was less in NREM [non-rapid eye movement] sleep than in the awake state but there were no differences in .ovrhdot.VE, VT/TI, or TI/Ttot between REM [rapid eye movement] and NREM sleep. .ovrhdot.VE and VT/TI corrected for body weight increased in REM and NREM sleep with postnatal maturation; TI/Ttot did not vary. Concomitant with this increase in room air .ovrhdot.VE and VT/TI, an increase in CO2 sensitivity (.DELTA..ovrhdot.VE/.DELTA.PaCO2) with postnatal maturation was documented in NREM sleep. CO2 sensitivity was similar between REM and NREM states at each postnatal age. The increase in .ovrhdot.VE following inhalation of 2-5% CO2 was mediated by an increase in VT/TI; TI/Ttot remained constant. The differences in the effect of sleep on CO2 sensitivity between neonates and adults are discussed and possible mechanisms for the observed developmental increase in CO2 sensitivity are proposed.