The effect of nebulized epinephrine on respiratory mechanics and gas exchange in bronchiolitis

Nebulized epinephrine has been advocated as a treatment for airway obstruct ion in infants with bronchiolitis; however, its effect on respiratory mecha nics and gas exchange has been poorly documented to date. We performed a pr einterventional and postinterventional study with primary outcome measures of mechanics (measured by single-breath occlusion passive deflation) and ox ygenation and ventilation indices in order to measure the effects of nebuli zed epinephrine in infants requiring mechanical ventilation for RSV-positiv e bronchiolitis. A two-compartment model was used to describe respiratory m echanics in patients with nonlinear flow-volume curves. Nebulized epinephri ne (0.5 mg/kg) was administered to 15 patients (median age, 0.19 yr; weight , 4.4 kg). Resistance decreased significantly in slow and fast compartments in 87 and 70% of patients, respectively. Median resistance in the slow com partment decreased from 0.427 to 0.198 cm H2O/ml/s (p = 0.0015) and in the fast compartment from 0.167 to 0.116 cm H2O/ml/s (p = 0.018). Compliance, o xygenation index, and ventilation index were not significantly changed afte r administration of epinephrine. We conclude that nebulized epinephrine sub stantially improves respiratory system resistance but not oxygenation or ve ntilation indices. This may be because of the effects of epinephrine on oxy gen consumption or ventilation-perfusion matching.