PULMONARY MECHANICS OF NORMAL VERY-LOW-BIRTH-WEIGHT INFANTS AT 40 WEEKS POSTCONCEPTION - A COMPARISON WITH NORMAL TERM INFANTS

We evaluated pulmonary function status in healthy, nonventilated very- low-birth-weight (VLBW) infants at 40 weeks postconception because lit tle is known about the pulmonary function status of these infants at t he time of discharge. Seven normal VLBW infants were evaluated at 40 w eeks postconception, and five normal term infants were examined as a c ontrol. The neonates were placed supine with their heads in the neutra l position. Data were obtained while the infant was resting quietly an d breathing spontaneously prior to feeding. Pulmonary mechanics and en ergetics were measured with a CP-100 pulmonary monitor (Bicore Co. Ltd .). Pulmonary mechanics and energetics were determined by the least me an square technique. Dynamic compliance (Cdyn), resistance (Rtot, Re), and work of breathing (WOE) were calculated for the total breath, and tidal volume, minute ventilation, ratio of inspiratory time to respir atory period (Ti/Ttot), and respiratory rate were measured. There were no significant differences between normal VLBW infants and term infan ts in regard to ventilation, mechanics, or energetics. Although the re spiratory system of normal VLBW infants is immature at birth, its deve lopment caught up to term infants by the time of discharge.