Similar Airway Function after Volitional Hyperpnea in Mild-Moderate Asthmatics and Healthy Controls

Background: The beneficial effects of exercise training for asthmatics might relate to repetitive airway stretching. Thus, a training with more pronounced airway stretch using isolated, volitional hyperpnea (HYP) might be similarly or more effective. However, in healthy subjects, a bout of HYP training is known to cause an acute FEV decline. Objective: The aim of the present study was therefore to test whether these changes are more pronounced in asthmatics, possibly putting them at risk with HYP training. Methods: Nine subjects with mild-moderate asthma (confirmed by mannitol challenge) and 11 healthy subjects performed six 5-min bouts (with 6-min breaks; HYP) and one 30-min bout (HYP) of normocapnic HYP at 60% of maximal voluntary ventilation using warm and humid air. FEV and airway resistance (R5) were measured before, in breaks (HYP), and immediately after HYP, and during 60 min of recovery. Results: In both groups, a significant and similar decrease in FEV during HYP (asthmatics: -3 +/- 3%; healthy subjects: -2 +/- 3%), after HYP (asthmatics: -2 +/- 5%; healthy subjects: -1 +/- 4%), and after HYP (asthmatics: -4 +/- 5%; healthy subjects: -3 +/- 3%), and an increase in R5 during and after both HYPs were observed. Maximal changes in FEV and R5 did not correlate with baseline lung function or responsiveness to mannitol. Conclusions: A bout of HYP does not lead to relevant bronchoconstriction and the observed changes in lung function and airway resistance are neither of the magnitude of clinical relevance, nor do they differ from responses in healthy individuals. Thus, HYP training can safely be tested as an airway-specific exercise training alternative (or add-on) modality to regular aerobic exercise training.