Response to inhaled bronchodilators and nonspecific airway hyperreactivity in children with cystic fibrosis.

We tested the hypothesis that children with CF who have a significant response to bronchodilator (BD) would respond positively to standard methacholine (Mch) challenge. Our objective was to correlate the response to BD with the concentration that produced a 20% fall (PC20) in forced expiratory volume in 1 second (FEV1). We studied 22 patients (12 males), aged 10.5 +/- 0.7 years (mean +/- SE), with a Shwachman-Kulczycki score 82 +/- 2.6 and baseline FEV1 of 80 +/- 4.5% predicted. Baseline expiratory flows, static lung volumes, and airway resistance were measured before and 30 min after inhaled salbutamol. On a separate day, within 2 weeks, a Mch challenge was given, with doubling concentrations from 0.03 to 8.0 mg/mL. A positive challenge was defined as a PC20 less than or equal to 2.0 mg/mL, and a positive response to BD as a greater than 6% of FEV1 increase. Mch challenge yielded 17 responders (R) with a PC20 of 0.5 +/- 0.1 mg/mL, and 5 nonresponders (NR) with a PC20 of 8.8 +/- 2.9 mg/mL. Baseline FEV1 was 77 +/- 5.3% predicted in R compared to 89 +/- 6.3% in NR (P = less than 0.001). History of springtime rhinitis was positive in 9/17 R and 2/5 NR. No significant correlation was found between baseline FEV1 and PC20, or between change in FEV1 post-BD and PC20. A greater than 6% increase in FEV1 was seen in 14/17 R (83% sensitivity) and in none of the 5 NR (100% specificity). In R, 8/17 patients had baseline FEV1 less than 80% predicted, compared to 1/5 in NR.(ABSTRACT TRUNCATED AT 250 WORDS)