Perception of dyspnea during histamine- and methacholine-induced bronchoconstriction

Background: Perception of dyspnea is poorly related to bronchoconstriction and may be influenced by distinct psychophysiologic stimuli. Objective: Thi s study compared the perceived psychophysiologic changes during histamine- and methacholine-induced bronchoconstriction using verbal as well as nonver bal assessment techniques. Methods: Perception of dyspnea was studied durin g induced bronchoconstriction in 40 atopic subjects randomly ascribed to ei ther histamine (n = 20) or methacholine (n = 20) bronchial challenge. A 100 % increase in specific airway resistance (sR(aw)) indicated airway hyperres ponsiveness (AHR), Dyspnea was verbally assessed by the Borg Scale (BS) and the Asthma Symptom Checklist (ASL). A hand dynamometer (HD) served for non verbal assessment. Both challenge groups did not differ significantly with respect to age, anthropometric data, smoking and lung function before chall enge. Results: AHR did not differ between groups but groups differed signif icantly with respect to the number of symptoms and to symptom intensity rep orted after challenge. Subjects who underwent the histamine challenge score d significantly higher on both measures derived from the ASL. BS ratings an d HD scores correlated significantly but were not significantly related to the degree of AHR, Accurate and poor perceivers could be discriminated by a nalysis of the relationship between BS and sR(aw). Conclusions: These findi ngs suggest that perception of induced dyspnea differs between histamine an d methacholine when assessed by a symptom report.