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Bronchodilator effects of exercise hyperpnea and albuterol in mild-to-moderate asthma

¹S.C. Pneumologia, Ospedale S. Corona, Pietra Ligure; ²Dipartimento di Medicina Interna, Università di Genova, Genova; and ³Centro di Fisiopatologia Respiratoria e dello Studio della Dispnea, Azienda Ospedaliera S. Croce e Carle, Cuneo, Italy

Submitted 20 March 2009 ; accepted in final form 12 June 2009

In asthmatic patients, either bronchodilatation or bronchoconstriction may develop during exercise. In 18 patients with mild-to-moderate asthma, we conducted two studies with the aims to 1) quantify the bronchodilator effect of hyperpnea induced by incremental-load maximum exercise compared with effects of inhaled albuterol (study 1, n = 10) and 2) determine the time course of changes in airway caliber during prolonged constant-load exercise (study 2, n = 8). In both studies, it was also investigated whether the bronchodilator effects of exercise hyperpnea and albuterol are additive. Changes in airway caliber were measured by changes in partial forced expiratory flow. In study 1, incremental-load exercise was associated with a bronchodilatation that was 60% of the maximal bronchodilatation obtainable with 1,500 µg of albuterol. In study 2, constant-load exercise was associated with an initial moderate bronchodilatation and a late airway renarrowing. In both studies, premedication with inhaled albuterol (400 µg) promoted sustained bronchodilatation during exercise, which was additive to that caused by exercise hyperpnea. In conclusion, in mild-to-moderate asthmatic individuals, hyperpnea at peak exercise was associated with a potent yet not complete bronchodilatation. During constant-load exercise, a transient bronchodilatation was followed by airway renarrowing, suggesting prevalence of constrictor over dilator effects of hyperpnea. Finally, the bronchodilator effect of hyperpnea was additive to that of albuterol.

exercise induced bronchoconstriction; incremental-load exercise; constant-load exercise; lung function