Gas Transfer and Pulmonary Blood Flow at Rest and during Exercise in Adults 21 Years after Preterm Birth

Rationale: After preterm birth, limited data exist in adulthood regarding alveolar-capillary growth and exercise capacity. Gas transfer at rest through exercise is a noninvasive measure of alveolar-capillary development. Objectives: To determine exercise capacity and gas transfer at rest and during exercise in ex-preterm adults. Methods: Ex-preterm subjects (n = 60; median gestation, 31.5 wk) recruited at birth underwent exercise testing at 21 years of age and were contemporaneously compared with 50 healthy control subjects. Measurements and Main Results: Subjects exercised on a cycle ergometer, and measurements of heart rate (HR), FRC, effective pulmonary blood flow ((Q) over dotpeff), stroke volume (SV), DLCO, (V)over soto(2), arteriovenous oxygen difference (AVO), transit time (TT), respiratory rate (Rf), (V) over dotCO(2), (V) over dotE, VT, and respiratory quotient (RQ) were made using a respiratory mass spectrometer. In the index study group and control subjects, the median DLCO (mmol/min/kPa/m(2)) at rest was 4.33 (95% confidence interval [CI], 4.18-4.62) and 4.75 (95% CI, 4.50-5.10), respectively (P = 0.01), and the median (Q) over dotpeff (L/min/m(2)) at rest was 3.26 (95% CI, 3.16-3.49) and 3.59 (95% CI, 3.43-3.81), respectively (P = 0.04). (Q) over dotpeff and DLCO values normalized during exercise but were reduced and lower than controls after a recovery period. No significant differences were found in exercise capacity between the groups. Conclusions: The data suggest a long-term effect of premature delivery on resting cardiac output and gas transfer, not due to abnormal cardiac or pulmonary function and with no evidence of exercise limitation.