BRONCHODILATOR RESPONSIVENESS IN INFANTS WITH BRONCHIOLITIS

We evaluated 34 infants with bronchiolitis, (17 of both genders; mean age, 4.6 mos; ranges, 0.7-14.5 mos). The 20 inpatients were significantly younger than the 14 outpatients (2.6 vs. 8.2 months, P < 0.05), and more females were inpatients. Forced expiratory flows at functional residual capacity (V-maxFRC were obtained at baseline, after aerosolized normal saline (NS), and metaproterenol (0.025 mL/kg in 2 mt NS). Flows were expressed as Z-scores, the difference between the measured and predicted flows, divided by the standard deviation for the predicted value. At baseline, outpatients were more obstructed than inpatients (-1.64 vs. -0.95, P < 0.05), infants > 2 months old were more obstructed than infants less than or equal to 2 months old (-1.54 vs. -0.80, P < 0.05), and males more than females(-1.45 vs. -1.02, P < 0.05). Following NS the whole group had a small but significant decrease in Z-scores (-1.23 to -1.31, P < 0.05). Following metaproterenol, the younger infants had significantly (P < 0.05) higher Z-scores compared to baseline and NS (-0.80 vs. -0.86 vs. -0.59). However, no significant changes occurred in order infants. Females also had an increased flow after metaproterenol and were less obstructed than after NS (-1.11 vs. -0.86, P < 0.015). in males no increased flows occurred after metaproterenol (-1.45 vs. -1.48). Bronchodilator responsiveness did not relate to severity of airway obstruction, history of family asthma, allergy, or passive smoke exposure. We conclude that inhaled metaproterenol improves airway,ay function in a subgroup of infants with bronchiolitis, but the subgroup could not clearly be identified because age and gender were confounding factors. (C) 1994 Wiley-Liss, Inc.