Unaltered perception of dyspnoea during treatment with long-acting beta2-agonists

There is the possibility that during treatment with inhaled long-acting beta2-agonists that a loss of perception of dyspnoea might occur and that the forced expiratory volume in one second (FEV1) might fall precipitously during bronchial provocation. This study investigated these possibilities during methacholine provocation, continued until there was > or =30% fall in FEV1, mimicking a moderate asthma attack. Nineteen asthmatic patients were asked to score their dyspnoea as a Borg score during provocation with methacholine. One hour prior to this provocation, the patients used the last morning dose of 14 days treatment with either formoterol (twice daily 24 microg by Turbuhaler), salmeterol (twice daily 100 microg by Diskhaler) and placebo in a double-blind, randomized, double-dummy, cross-over design. The perception of dyspnoea, expressed as the Borg score divided by the change in FEV1 at > or =30% fall in FEV1, was similar on the three test days at 0.067, 0.076 and 0.074%(-1) after formoterol, salmeterol and placebo treatment, respectively (p=0.16). The slope of the methacholine dose response curve did not differ (p=0.52). In conclusion, no suggestion was found for an abnormal perception of dyspnoea or an exaggerated fall in forced expiratory volume in one second during provocation with methacholine under long-acting beta2-agonist treatment.