Airway Tone During Exercise in Healthy Subjects: Effects of Salbutamol and Ipratropium Bromide

Abstract

In healthy subjects changes in airway calibre during exercise are conflicting and smaller than in asthmatics. Methodological differences could explain the discrepancies between the results obtained in healthy subjects. Therefore, our aim was to assess during exercise the changes in airway diameter and the effects of 200 µg salbutamol (SAL) or 40 µg ipratropium bromide (IPR) inhalations versus placebo (PLA), using spirometry and respiratory resistance (Rrs). Eight non-asthmatic subjects exercised 9 min at 70 % of their maximal aerobic power after inhalation of 200 µg SAL, 40 µg IPR, or PLA. Maximal flow-volume curves were obtained before and after inhalations, at 3 (E3) and 6 (E6) minutes of exercise, and during recovery. Rrs were measured by impulse oscillometry before and after inhalation, and immediately at the end of exercise. At rest, FEV₁ increased significantly after inhalation of SAL and IPR. Rrs decreased only after SAL. During exercise FEV₁ increased significantly from rest with SAL and IPR while forced mid expiratory flow (FEF_{25 - 75}) increased significantly for all conditions. At E6 the rise of FEV₁ and FEF_{25 - 75} were greater with SAL compared to PLA and IPR. In all conditions Rrs increased significantly immediately at the end of exercise as compared to rest but less than during flow-matched hyperpnea. It is concluded that a similar bronchodilation was observed during exercise with and without anticholinergic drug which suggests a withdrawal of parasympathetic control of airways during exercise in healthy subjects. Nevertheless, the bronchodilation observed during exercise is not maximal since it can be reinforced by β₂-mimetic drug.

Key words

Respiratory resistance - exercise - bronchodilation - healthy subject - parasympathetic tone

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