Unaltered perception of dyspnoea during treatment with long-acting β₂-agonists

Abstract

Unaltered perception of dyspnoea during treatment with long-acting b 2 -agonists. H.J.van der Woude, R. Aalbers. #ERS Journals Ltd 2001. ABSTRACT: There is the possibility that during treatment with inhaled long-acting b 2 -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 ¢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 mg by Turbuhaler1), salmeterol (twice daily 100 mg by Diskhaler TM ) 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 ¢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 b 2 -agonist treatment. In the treatment of asthma, the inhaled long-acting b 2 -agonists formoterol and salmeterol have obtained an important role due to their excellent bronchodilating and bronchoprotective effects [1]. This excellent bronchodilating effect could have a negative influence; patients may be unable to perceive a deterioration of the effects of airway inflammation [2]. It may be possible this is partly a result of a change in perception of dyspnoea due to the b 2 -agonist. Furthermore, the suggestion has been made that after prior administration of a bronchodilator, there may be an exaggerated fall in forced expiratory volume in one second (FEV1) when the bronchial provocation test is continued [3]. Therefore, this study investigated whether poor perception of dyspnoea may be caused by long-acting b 2 -agonist treatment, by assessing dyspnoea scores during a provocation test performed after maximal bronchodilation from inhaled long-acting b 2 -agonists. In addition the slope of the methacholine dose response curve was measured to see if it was increased. Materials and methods PatientsNineteen nonsmoking patients aged 18-50 yrs with a diagnosis of asthma according to the American Thoracic Society Guidelines [4] were invited to participate in the study (table 1). Eligible patients had an FEV1w1.5 L andw60% of predicted [5], a 20% fall in FEV1 after provocation with methacholine ¡4 mg?mL -1 and a fall of ¢30% in FEV1 on continuing the test. Exclusion criteria were: concomitant diseases that might interfere with the study; use of long-acting b 2 -agonists, or...