Abstract
Maturational effects on inspiratory timing reflexes have been studied, however little is known about the control of expiratory duration in newborn infants. We studied 5 healthy preterm infants, 28-32 wks gestation, birthweight 1.3±0.2 kg (mean±SD), on day 2-4 of life. Using a one-way valve with resistive manifold (J.Appl.Physiol. 40:177,1976), we presented 3 graded resistive loads during 9-25 single expirations. Airflow and mask pressure were recorded while the infant breathed through a face mask and pneumotachograph and flow was integrated to give volume. Expiratory time (Te) was measured from the flow tracing. Control values were determined from the breath preceding the loaded breath. During resistive loads, expired volume was reduced from 10.7±0.6 ml (mean±SD) by an average of 10.4% (Rl, NS), 20.4% (R2, p<0.005), and 32.2% (R3, p<0.005) and Te was significantly prolonged from 0.47±0.05 sec by 10.0%, 21.9%, and 29.4% for R1, R2, and R3 (p<0.05 or less). For comparable reductions in expired volume, Te was less prolonged than in full term infants previously studied. Our study of expiratory timing modulation agrees with previous studies on inspiratory timing which show that lung inflation reflex activity is decreased in preterm infants. The inability of preterm infants to maintain end-expiratory volume consistently above relaxation volume may depend on the relative weakness of this expiratory timing modulation.
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Stark, A., Frantz, I., Cohlan, B. et al. TIMING RESPONSE TO GRADED EXPIRATORY RESISTIVE LOADING IN PRETERM INFANTS. Pediatr Res 18 (Suppl 4), 406 (1984). https://doi.org/10.1203/00006450-198404001-01878
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DOI: https://doi.org/10.1203/00006450-198404001-01878