Effects of exercise intensity compared to albuterol in individuals with cystic fibrosis

Abstract

Background: Although exercise is a vital component of the therapy prescribed to individuals with cystic fibrosis (CF), it is not a priority due to a finite amount of treatment time and the view that exercise is not as beneficial as pharmacological treatments by many individuals with CF. We sought to compare the therapeutic benefits of exercise and their prescribed bronchodilator albuterol.

Methods: CF (n = 14) and healthy (n = 16) subjects completed three visits, a baseline screening with VO2 max test and two treatment visits. On the two treatment visits, subjects completed spirometry and diffusing capacity of the lungs for nitric oxide (DLNO) maneuvers either at baseline, 60, and 110 min post-albuterol administration, or at baseline and the midway point of three separate 15 min exercise bouts at low, moderate and vigorous intensity (25, 50 and 65% of the maximum workload, respectively).

Results: With moderate exercise the increase in DLNO was double (39 ± 8 vs 15 ± 6% change) and the level of bronchodilation similar (23% change) when compared to 110 min post-albuterol in individuals with CF. During exercise FVC became reduced (-309 ± 66 mL with moderate exercise) and the increase in FEV1 was attenuated (103 ± 39 vs 236 ± 58 mL, exercise vs. albuterol) when compared with the response to albuterol in individuals with CF. Epinephrine (EPI) release increased 39, 72 and 144% change with low, moderate and vigorous intensity exercise respectively for individuals with CF, but this increase was blunted when compared to healthy subjects.

Conclusion: Our results suggest that moderate intensity exercise is the optimal intensity for individuals with CF, as low intensity exercise increases EPI less than 50% and vigorous intensity exercise is over taxing, such that airflow can be restricted. Although the duration of the beneficial effect is uncertain, exercise can promote greater improvements in gas diffusion and comparable bronchodilation when compared to albuterol.

Keywords: Albuterol; Bronchodilation; Catecholamines; Cycle ergometer; Diffusion capacity of the lungs for nitric oxide; Submaximal exercise.

Figure 1

Change in pulmonary function in response to submaximal exercise and albuterol. Panel A: Diffusion Capacity of the Lungs for Nitric Oxide (DLNO) Panel B: Forced Vital Capacity (FVC) Panel C: Forced Expiratory Volume in one second of the FVC (FEV₁) Panel D: Forced Expiratory Flow at 25–75% of FVC (FEF_25–75). The black bars represent healthy subjects and the white bars represent CF subjects. The error bars represent the standard error of the mean. * = p < 0.025 healthy vs. CF and † = p < 0.025 moderate intensity vs. 60-minutes post albuterol.