PURPOSE:Upper airway cough syndrome (UACS) is the most frequent cause of chronic cough. It is due to a variety of upper respiratory diseases, that are supposed to sensitize pharyngolaryngeal receptors. The aim of this study was to evaluate the characteristics of UACS as compared to other nonasthmatic causes of chronic cough (no-UACS).
METHODS:Questionnaire data, lung function tests, exhaled nitric oxide (FeNO) and cough and airway responsiveness to histamine of 209 UACS patients, were compared with those of 117 nonasthmatic patients with chronic no-UACS cough. Forty five patients with wheeze but without cough and 109 asymptomatic subjects served as controls. The patients underwent: spirometry, histamine responsiveness of the extrathoracic airway (PC25MIF50) and of the bronchi (PC20FEV1), and histamine cough threshold (PCcough). Hyperresponsiveness (HR) was diagnosed when PC25MIF50, PC20FEV1 and PCcough were ≤; 8 mg/ml, and labelled EAHR, BHR and cough-HR.
RESULTS:The UACS group included 87 patients with non allergic rhinosinusitis and 122 with perennial allergic rhinitis; the no-UACS group included 54 patients with gastroesophageal reflux, 15 with ACE-inhibitors cough and 45 with idiopatic cough. UACS patients had higher prevalence of atopy, PND, EAHR and BHR. No-UACS patients were older and had higher prevalence of women and of pharyngitis. Mean values of histamine thresholds and FeNO in UACS, no-UACS and wheeze patients are shown in the figure. UACS patients, as compared to no-UACS, had significantly higher FeNO and lower EA and bronchial thresholds, but similar PCcough. Wheeze without cough was associated with highest FeNO, lowest PC20FEV1 and highest PC25MIF50.
CONCLUSION:These findings indicate that UACS is associated with increased NO production and more severe airway dysfunction, as compared with other causes of chronic nonasthmatic coughs. We may suppose that cough receptors stimulation in UACS is the consequence of airway inflammation, while in no-UACS conditions may simply be due to irritation.
CLINICAL IMPLICATIONS:Treatment of UACS should be targeted at upper airway inflammation, while other chronic coughs could benefit from inhibitors of afferent nerve activity.
DISCLOSURE:Caterina Bucca, No Financial Disclosure Information; No Product/Research Disclosure Information