Reproducibility and validity of a Yan-style portable citric acid cough challenge.
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.
Barber
Chris Michael
CM
Sheffield Occupational and Environmental Lung Injury Centre, Royal Hallamshire Hospital, Glossop Road, Sheffield S10 2JF, UK. chris@chrisandrachael.freeserve.co.uk
Curran
Andrew D
AD
Bradshaw
Lisa M
LM
Morice
Alyn H
AH
Rawbone
Roger
R
Fishwick
David
D
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
D000925:Anticoagulants; D019343:Citric Acid