Abstract
To determine the effect of sleep state and CO2 inhalation on the control of expiratory time (Te) in neonates we studied 9 preterm (BW 1990±92 g; GA 33±0.5 wks and PNA 12±3 days) and 9 term infants (BW 3420±211 g; GA 40±0.4 wks and PNA 4±1 days). We measured tidal volume (VT), expiratory time (Te), post-inspiratory diaphragmatic activity (Pidi), transpulmonary pressure (PL), expiratory flow (Vexp) and expiratory pulmonary resistance (Re) in both quiet and active sleep. After breathing 21% O2 for 3 mins in each state, infants rebreathed from a bag containing 5% CO2 in 40% O2 for 2 to 3 minutes. We calculated Re using PL and Vexp measured at 0.25 sec after the beginning of expiration and also at the point of maximum expiratory flow. A total of 1538 breaths were analyzed. Vexp was similar in preterm and term infants (30.55 vs 29.32 ml/sec; p=0.5) and greater in active than in quiet sleep (33.7 vs 26.1; p=0.02). Vexp was a highly correlated function of Pidi, the lower the flow the greater the Pidi (r=0.84; p=0.001; n=815). The effect of CO2 was to decrease Pidi (p<0.01). PL and Vexp correlated negatively with Te in such a way that the Re remained the same within the range of Te studied. The observations suggest that the control of expiratory time in the neonate is greatly dependent on Pidi and that Re has no measurable role. This may be a handicap to small infants who cannot depend on expiratory resistance to stabilize Te.
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Reempts, P., Moriette, G., Cates, D. et al. THE EFFECT OF SLEEP STATE AND co2 INHALATIONON THE CONTROL OF EXPIRATORY DURATION IN THE NEWBORN INFANT. Pediatr Res 18 (Suppl 4), 402 (1984). https://doi.org/10.1203/00006450-198404001-01857
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DOI: https://doi.org/10.1203/00006450-198404001-01857