Inhaled beta-agonists improve lung function but not maximal exercise capacity in cystic fibrosis

To investigate the effects of inhaled beta-agonists on sub-maximal and maximal exercise capacity, breathing pattern, dyspnoea, leg-discomfort and spirometry in patients with cystic fibrosis (CF).

Eight patients performed two maximal incremental cycle-ergometry tests on separate days with inhaled placebo or salbutamol (600 microg) administered before each test in a randomized, double-blind, placebo-controlled crossover trial. Primary outcomes were exercise duration (Exdur) in seconds (s) and maximal oxygen uptake (VO2max) in litres/minute (L/min). Forced expiratory volume in 1 s (FEV1) was measured immediately pre-inhaler, post-inhaler and post-exercise. Dyspnoea and leg-discomfort were assessed post-exercise.

Within-day FEV1 comparisons demonstrated that the placebo test day FEV1 improved significantly post-exercise (0.11 L, p<0.05) and the salbutamol test day FEV1 improved significantly post-inhaler (0.22 L, p<0.001) and post-exercise (0.07 L, p<0.01). Between-day FEV1 comparisons demonstrated significant improvements in post-inhaler (0.17 L, p<0.05) and post-exercise (0.13 L, p<0.05) FEV1 following salbutamol. Sub-maximal and maximal exercise showed no significant difference as shown by Exdur (547+/-154 s vs. 529+/-127 s) and VO2max (1.9+/-0.5 L/min vs. 1.9+/-0.6 L/min). No significant change in breathing pattern, dyspnoea or leg-discomfort was detected. The study had a power of 92% to detect a 10% improvement in Exdur.

In adults with CF, salbutamol improves post-exercise FEV1 and is safe when administered immediately before exercise but does not improve exercise capacity, exercise-induced dyspnoea or leg-discomfort.