title: Reproducibility and validity of a Yan-style portable citric acid cough challenge.
abstract: Although many different methods of measuring cough reflex sensitivity have been published, few are simple enough to use outside of a hospital or laboratory environment. The aim of this study was to develop a simple, quick, and portable cough challenge, assess its reproducibility, and compare its results with those measured by an existing established hospital protocol. Twenty-five volunteers performed cough challenges based on an established hospital dosimeter protocol, and, on a separate occasion, by a protocol inhaling citric acid from DeVilbiss 40 hand-held nebulisers (citric acid concentrations of 10-3000 mM). Reproducibility of the hand-held cough challenge was assessed in 11 volunteers. Cough thresholds were consistently higher by the hand-held method than by the hospital dosimeter method. The geometric mean citric acid concentrations causing two coughs (threshold D2) were 3.14 and 2.77 log mM, respectively (p<0.001). The geometric mean (95% CI) difference between the tests was 0.51 log mM (0.18-0.83) of the average of the two values. Cough D2 thresholds attained by the two techniques did, however, show significant correlation (r=0.95, p<0.0001). The coefficient of repeatability for the hand-held method was 0.40 log mM. Administering citric acid from DeVilbiss 40 hand-held nebulisers offers a rapid, portable, and reproducible cough challenge in healthy volunteers. The results correlate well with an existing Mefar dosimeter challenge, but give two to three times greater cough thresholds.
authors.affiliation: Sheffield Occupational and Environmental Lung Injury Centre, Royal Hallamshire Hospital, Glossop Road, Sheffield S10 2JF, UK. chris@chrisandrachael.freeserve.co.uk
authors.forename: Chris Michael
authors.initials: CM
authors.lastname: Barber
authors.forename: Andrew D
authors.initials: AD
authors.lastname: Curran
authors.forename: Lisa M
authors.initials: LM
authors.lastname: Bradshaw
authors.forename: Alyn H
authors.initials: AH
authors.lastname: Morice
authors.forename: Roger
authors.initials: R
authors.lastname: Rawbone
authors.forename: David
authors.initials: D
authors.lastname: Fishwick
mesh_terms: D000925:Anticoagulants / Q000494:pharmacology*; D019343:Citric Acid / Q000494:pharmacology*; D003371:Cough / Q000139:chemically induced*; D005260:Female; D006801:Humans; D008297:Male; D009330:Nebulizers and Vaporizers; D012018:Reflex / Q000187:drug effects*; D015203:Reproducibility of Results
chemical_list: D000925:Anticoagulants; D019343:Citric Acid