Increased resistance of the peripheral airways in patients with unexplained chronic cough

Introduction Troublesome coughing that persists for more than 8 weeks without evident aetiology or effective therapy is termed unexplained chronic cough (UCC). Using impulse oscillometry (IOS) and spirometry, we assessed the functionalities of the large and small airways, respectively, in patients with UCC and in healthy control subjects. Methods On a single occasion, 50 patients with UCC (mean age, 61 years; 82% women) and 23 subjectively healthy controls (mean age, 58.9 years; 95.7% women) underwent IOS and spirometry. Patients with UCC were also subjected to fractional exhaled nitric oxide (FeNO) measurement, and they answered a local questionnaire, a visual analogue scale (VAS) for cough and cough-related symptoms, and a health-related quality of life questionnaire. Results Forty-nine (98%) patients with UCC reported cough symptoms from exposure to chemicals, 39 (78%) had problems with cold air, and 38 (76%) had cough symptoms following exercise. The mean VAS cough score was 62 mm in the patient group. FeNO was measured in 25 patients, showing a mean value of 16.6 ppb. Women with UCC had significantly greater airway resistance and reactance than men with UCC. The UCC group showed significantly increased peripheral airway resistance and reactance, and lower FEV1 % predicted values (albeit within the normal range), as compared with the healthy control group. Conclusion Patients with UCC show increased peripheral airway resistance and significantly lower FEV1 % predicted values compared with healthy control subjects. Routine measurements of lung function with both IOS and spirometry could have added value in the diagnosis of UCC.