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 mL NS). Flows were expressed as 2‐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 s2 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 2‐scores (−1.23 to −1.31, P <: 0.05). Following metaproferenol, 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 older 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 function in a subgroup of infants with bronchiolitis, but the subgroup could not clearly be identified because age and gender were confounding factors. Pediatr Pulmonol. 1994; 17:81–85 . © 1994 Wiley‐Liss, Inc.