Reversibility of the Pulmonary Function Based on the Partial Flow-volume Curve Predicts the Efficacy of Bronchodilator Therapy for Treating Chronic Cough

Objective Partial expiratory flow-volume curves have the potential to detect mild bronchoconstriction be- cause they are not affected by the modulatory effects of deep inspiration. The aim of this study was to inves- tigate the relationship between the efficacy of bronchodilator therapy (BDT) in treating the cough and to as- sess the increase in the expiratory flow of the partial flow-volume curve at 40% above the residual volume level (PEF40) caused by treatment with a short-acting beta-2 agonist (SABA) in patients with chronic nonpro- ductive cough. Methods We measured the reversibility of PEF40 caused by a SABA in 42 patients with chronic nonproduc- tive cough at visit 1 (day 0). The patients received BDT for six days. The visual analogue scale (VAS) was used to assess the efficacy of BDT in treating coughing at visit 2 (day 7) (0 mm, 'no cough;' 100 mm, 'no change in coughing'). Results Reversibility of the PEF40 was correlated (r=0.690, p<0.001) with the VAS score determined at visit 2 and was higher in the patients with cough variant asthma (CVA) (44.9±18.3%) than in those with atopic cough (13.4±10.4%) (p<0.01). Conclusion Reversibility of the PEF40 predicted the efficacy of BDT in patients with chronic nonproductive cough and helped to identify patients with CVA.