Encouraging Pulmonary Outcome for Surviving, Neurologically Intact, Extremely Premature Infants in the Postsurfactant Era

Abstract

The aim of this study was to determine the long-term pulmonary outcome of extreme prematurity at a single tertiary-care center from 1997 to 2001 in the postsurfactant era. We assessed symptoms, exhaled nitric oxide, spirometry, methacholine challenge (provocative concentration of methacholine required to decrease FEV₁ by 20% [PC(20)]), lung volumes, diffusion, and cardiopulmonary exercise tolerance. Of 279 infants born, 192 survived to discharge, and 79 of these developed bronchopulmonary dysplasia (BPD) (65 mild, 12 moderate, two severe). We studied a subgroup of 53 neurologically intact preterm subjects aged 10 ± 1.5 years (28 with BPD [born, 26.2 ± 1.4 weeks; birth weight, 821 ± 164 g] and 25 without BPD [born, 27.2 ± 1 weeks; birth weight, 1,050 ± 181 g]) and compared them with 23 term control subjects. Of the BPD cases, 21 were mild, seven were moderate, and none was severe; 77.4% of subjects received antenatal steroids, and 83% received postnatal surfactant. Sixty percent of the preterm subjects wheezed at age < 2 years compared with 13% of the control subjects (P < .001), but only 13% wheezed in the past year compared with 0% of control subjects (not significant). For preterm and control subjects, respectively (mean ± SD), FEV₁ % predicted was 85% ± 10% and 94% ± 10% (P < .001), with limited reversibility; residual volume/total lung capacity was 29.3% ± 5.5% and 25% ± 8% (P < .05); diffusing capacity/alveolar volume was 89.6% ± 9.2% and 97% ± 10% (P < .005); and PC(20) was 6.5 ± 5.8 mg/mL and 11.7 ± 5.5 mg/mL (P < .001). PC(20) was < 4 mg/mL in 49% of preterm subjects despite normal exhaled nitric oxide. Most measurements were similar in premature subjects with and without BPD. Peak oxygen consumption and breathing reserve were normal, but % predicted maximal load (measured in Watts) was 69% ± 15% for subjects with BPD compared with 88% ± 23% for subjects without and 86% ± 20% for control subjects (P < .01). Pulmonary outcome was encouraging at mid-childhood for neurologically intact survivors in the postsurfactant era. Despite mechanical ventilation and oxygen therapy, most had no or mild BPD. Changes found probably reflect the hypoplastic lungs of prematurity.