Growth failure in bronchopulmonary dysplasia: elevated metabolic rates and pulmonary mechanics.

Growth failure is a major problem in infants with bronchopulmonary dysplasia (BPD), but the cause is unknown. We studied 13 infants with BPD but without other medical problems that could contribute to growth failure at 6 months' corrected age. We measured resting oxygen consumption (Vo2), Pao2, airway resistance, specific airway conductance, and dynamic pulmonary compliance (Cdyn) by body plethysmography and growth. Growth failure was defined as height and weight less than the tenth percentile of the Babson growth curves. Vo2 in infants with growth failure and BPD was markedly elevated compared with that in control infants and infants with BPD and normal growth. Vo2 showed an inverse correlation with body weight in infants with BPD but not in control infants. Although Vo2 was inversely related to Cdyn, the total work of breathing only partially explained the increased metabolic demands of the growth failure group. We speculate that growth failure in infants with BPD is partially the result of increased metabolic demands from increased work of breathing but that other mechanisms may act to elevate the metabolic expenditure of these infants.