Improving pulmonary function does not decrease oxygen consumption in infants with bronchopulmonary dysplasia

To determine whether the high oxygen consumption VO2 in infants with bronchopulmonary dysplasia (BPD) is caused by increased mechanical power of breathing, and if improvement of pulmonary mechanics would reduce mechanical power of breathing and VO2 we gave 16 infants with oxygen-dependent BPD at 19.5 +/- 10.7 (mean +/- SD) weeks of age placebo, theophylline, and orally administered diuretics or theophylline plus diuretics. Pulmonary mechanics, mechanical power of breathing, and VO2 were measured at the beginning and end of each study period. In the placebo group, all infants had elevated VO2 (7.4 +/- 1.4 mL/kg/min) and carbon dioxide production (6.6 +/- 1.2 mL/kg/min), increased airway resistance (59 +/- 30 cm H2O/L/sec), decreased dynamic compliance (0.073 +/- 0.024 mL/cm H2O/cm), increase respiratory rate (52 +/- 11), and increased mechanical power of breathing (2.22 +/- 1.05 kg.cm/kg/min). Treatment with theophylline, diuretics, and theophylline plus diuretics resulted in a significant improvement in pulmonary mechanics and mechanical power of breathing, but not in VO2. These results suggest that the increased VO2 in infants with BPD is not secondary to increased mechanical power of breathing.