Objective Partial expiratory flow-volume curves have the potential to detect mild bronchoconstriction because they are not affected by the modulatory effects of deep inspiration. The aim of this study was to investigate the relationship between the efficacy of bronchodilator therapy (BDT) in treating the cough and to assess 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 nonproductive cough.
Methods We measured the reversibility of PEF₄₀ caused by a SABA in 42 patients with chronic nonproductive 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.