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: This study compared the perceived psychophysiologic changes during histamine- and methacholine-induced bronchoconstriction using verbal as well as nonverbal assessment techniques.

Methods: Perception of dyspnea was studied during induced bronchoconstriction in 40 atopic subjects randomly ascribed to either histamine (n = 20) or methacholine (n = 20) bronchial challenge. A 100% increase in specific airway resistance (sR(aw)) indicated airway hyperresponsiveness (AHR). Dyspnea was verbally assessed by the Borg Scale (BS) and the Asthma Symptom Checklist (ASL). A hand dynamometer (HD) served for nonverbal assessment. Both challenge groups did not differ significantly with respect to age, anthropometric data, smoking and lung function before challenge.

Results: AHR did not differ between groups but groups differed significantly with respect to the number of symptoms and to symptom intensity reported after challenge. Subjects who underwent the histamine challenge scored significantly higher on both measures derived from the ASL. BS ratings and HD scores correlated significantly but were not significantly related to the degree of AHR. Accurate and poor perceivers could be discriminated by analysis of the relationship between BS and sR(aw).

Conclusions: These findings suggest that perception of induced dyspnea differs between histamine and methacholine when assessed by a symptom report.