Intrauterine Vs Extrauterine Lung Development over the Last Trimester: Comparison of Lung Function at Term

Abstract 1308 Poster Session IV, Tuesday, 5/4 (poster 287)

Objective: Lung development is prominent over the last months of a normal pregnancy. In preterm infants this process takes place ex utero during breathing in contrast to infants born at term. We hypothesized that factors related to preterm breathing affect lung growth and development. We compared lung volume together with indices of elasticity and small and large airway function in healthy fullterm and preterm infants near term.

Subjects and methods: Eighteen preterm infants [median (range) birth weight 1.17(0.84-2.5)kg; gestational age 28.5(25-33)weeks] without respiratory disease (not intubated, spontaneously breathing with <30% F_iO₂ after 2 days of age) were studied at the median(range) postmenstrual age of 40(38-41) weeks and study weight 3.15(2.41-4.25)kg. They were compared to 22 healthy fullterm infants [birth weight 3.46(2.66-4.54)kg; gestational age 40(37-41) weeks] studied at 2(1-3) days postnatal age. Functional residual capacity (FRC;ml) and moment ratios (M1/M0, M2/M0) were measured by a multiple breath nitrogen washout method (Pediatr Pulmonol 1998;25:52). Conductance (Grs;L/s/cmH₂O) and compliance (Crs; ml/cmH₂O) of the respiratory system were assessed by the single-breath airway occlusion technique.

Results: No differences in FRC, conductance and moment ratios were found. Yet, unexpectedly, Crs/FRC was significantly lower in infants born preterm. (Table)

Table 1 No caption available

Conclusion: Preterm breathing does not exert major effects on lung growth and airway function, but might affect lung elasticity in the tidal range of lung volume.