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STUDY OBJECTIVES: Little is known about the normal ranges and repeatability of cough reflex sensitivity measurements, or the relationship of cough reflex sensitivity to other upper airway reflexes in subjects with chronic dry cough. We set out to define the normal range of cough reflex sensitivity and its repeatability in health and disease, and to assess its relationship to the glottic-stop reflex. DESIGN: Prospective, cross-sectional study. SUBJECTS AND METHODS: We measured capsaicin cough reflex sensitivity in 134 healthy subjects and 88 patients with respiratory disease, and assessed the repeatability over 2 weeks in a subgroup of individuals (healthy subjects, 15; chronic cough patients, 15). In another subgroup (healthy patients, 16; chronic cough patients, 14), we measured the sensitivity of the glottic-stop reflex (using inhaled ammonia). RESULTS: Capsaicin cough sensitivity varied widely in the population of healthy subjects, and there was considerable overlap of cough reflex sensitivity between healthy control subjects and patients with cough. The intraclass correlation coefficients for repeatability of cough sensitivity (concentration of capsaicin that causes two coughs, and concentration of capsaicin that causes five coughs) were 0.89 and 0.88, respectively. Patients with chronic cough had a significantly more sensitive glottic-stop reflex than healthy subjects (glottic-stop sensitivity threshold, 483 ppm vs 1,029 ppm, respectively; p = 0.01), and there was a significant positive correlation between glottic-stop and cough reflex sensitivity (r = 0.5; p < 0.01). CONCLUSIONS: We have shown a wide variation of cough reflex sensitivity in healthy subjects, although the measurement does have good 2-week repeatability. There was a reasonably close relationship between cough sensitivity and glottic-stop reflex sensitivity, indicating either that the cough reflex and the glottic-stop reflex share a common pathway or that subjects who have a chronic cough have a global abnormality of upper airway reflexes.

Original publication

DOI

10.1378/chest.127.2.550

Type

Journal article

Journal

Chest

Publication Date

02/2005

Volume

127

Pages

550 - 557

Keywords

Ammonia, Asthma, Bronchitis, Capsaicin, Chronic Disease, Cough, Cross-Sectional Studies, Dose-Response Relationship, Drug, Eosinophilia, Female, Gastroesophageal Reflux, Glottis, Humans, Lung Diseases, Male, Middle Aged, Reference Values, Reflex, Sensitivity and Specificity, Sensory Thresholds, Sex Factors, Statistics as Topic