Mechanics and energetics of breathing in newly diagnosed infants with cystic fibrosis: effect of combined bronchodilator and chest physical therapy.

Response to bronchodilator (BD) and chest physical therapy (CPT) was evaluated in newly diagnosed infants with cystic fibrosis (n = 13; age, 6.9 +/- 1.5 SE months) who were asymptomatic for lung disease at the time of the study. Lung function was assessed from the mechanics and energetics of breathing prior to and following combined BD and CPT. After therapy, respiratory rate, tidal volume, minute ventilation, and pulmonary compliance were not statistically different from values under baseline conditions. In contrast, there was a significant decrease in pulmonary resistance (-34%; P less than 0.05) and the resistive work of breathing (-26%; P less than 0.05) following the combined treatment. The effect of combined BD and CPT in decreasing the resistive respiratory load may be related to relief of subclinical bronchospasm, reduction in mucosal edema, and mobilization of mucous secretions.