Cough and glottic-stop reflex sensitivity in health and disease.
OBJECTIVE
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.


METHODS
Prospective, cross-sectional study.


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.
Prudon
Benjamin
B
MB ChB, Institute for Lung Health, Department of Respiratory Medicine, Glenfield Hospital, Leicester, LE3 9QP UK.
Birring
Surinder S
SS
Vara
Dhiraj D
DD
Hall
Andrew P
AP
Thompson
Jonathan P
JP
Pavord
Ian D
ID
D000641:Ammonia; D001249:Asthma / Q000175:diagnosis / Q000503:physiopathology; D001991:Bronchitis / Q000175:diagnosis / Q000503:physiopathology; D002211:Capsaicin; D002908:Chronic Disease; D003371:Cough / Q000503:physiopathology*; D003430:Cross-Sectional Studies; D004305:Dose-Response Relationship, Drug; D004802:Eosinophilia / Q000175:diagnosis / Q000503:physiopathology; D005260:Female; D005764:Gastroesophageal Reflux / Q000175:diagnosis / Q000503:physiopathology; D005931:Glottis / Q000503:physiopathology*; D006801:Humans; D008171:Lung Diseases / Q000175:diagnosis / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D012016:Reference Values; D012018:Reflex / Q000502:physiology*; D012680:Sensitivity and Specificity; D012684:Sensory Thresholds / Q000502:physiology; D012737:Sex Factors; D013223:Statistics as Topic
D000641:Ammonia; D002211:Capsaicin