Cough reflex sensitivity to capsaicin in patients with overlap syndrome
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2010-09-18 |
Overlap syndrome is a term, which specifies the existence of both chronic obstructive pulmonary disease (COPD) and obstructive sleep aponea (OSA) in the same patient. Cough is a prevalent symptom in patients with COPD and OSA. The effect of overlap syndrome on cough reflex sensitivity is unknown. Aim of the study was to evaluate cough reflex sensitivity to capsaicin in patients with overlap syndrome and correlation between OSA severity and cough reflex sensitivity. Methods: 34 patients with moderate to severe COPD were enrolled. None of the patients had used inhaled or oral corticosteroids and long-acting bronchodilators at least one month before the study. COPD patients were identified as presenting overlap syndrome (n=18) when apnea-hypopnea index (AHI), obtained from full-night polysomnography, was greater when 15/h. Subjects with AHI lower when 15 were classified as non-OSA COPD patients (n=16). All patients underwent cough reflex provocation test with capsaicin. Capsaicin aerosol was given in order of ascending concentration until the concentration inducing 5 or more coughs (C5) was attained. Results: patients with overlap syndrome and non-OSA COPD patients did not differ in terms of age, body mass index and COPD severity. C5 was significantly higher (i.e., cough reflex sensitivity lower) in patients with overlap syndrome (log C5 2.34±0.18µM mean ± SEM) than in non-OSA COPD patients (log C5 1.70±0.22; p=0.036). A significant positive correlation was obtained between AHI and log C5 (r=0.41, p<0.038). Conclusion: according to our data cough reflex sensitivity to capsaicin is decreased in patients with overlap syndrome and positively correlates with OSA severity.