BACKGROUNDPatients with a poor perception of their symptoms of asthma seem to have an increased risk of an asthma attack. The influence of factors such as airway calibre, bronchial hyperresponsiveness, age and sex on the "perceptiveness" of a patient are poorly understood. It is of clinical importance to identify patients who are likely to have a poor perception of their symptoms. We have studied the perception of bronchoconstriction by asthmatic patients during a histamine provocation test and analysed the influence of bronchial obstruction, hyperresponsiveness, sex, and age. We were particularly interested to establish whether there was any difference in perception between subjects with a greater or lesser severity of asthma (expressed as bronchial obstruction, hyperresponsiveness).
METHODSOne hundred and thirty four patients with allergic asthma underwent a histamine provocation test. The FEV₁ was measured after each inhalation of histamine. Subjects were asked to rate subjective quantification of the sensation of breathlessness on a visual analogue scale (VAS). The relationship between changes in VAS values and the reduction in FEV₁ as a percentage of the baseline value was analysed by determining the linear regression slope () between the two parameters and indicates the perception of airway obstruction. Multiple regression analysis was performed to investigate the effect of baseline FEV₁, bronchial hyperresponsiveness, sex and age on the "perceptiveness" for bronchoconstriction.
RESULTSThe median value of the slope  (indicating the perception of airway obstruction) was 0.91 (25-75th percentile: 0.48-1.45). Age and sex had no influence on the perception of bronchoconstriction. Both initial bronchial tone (baseline FEV₁) and bronchial hyperresponsiveness (PC₂₀) showed a significant correlation with the perception of bronchoconstriction. The regression coefficients for FEV₁ and 2log PC₂₀ in the multiple regression model were 0.20 and 0.10. Patients who had a low baseline FEV₁ and/or a high bronchial responsiveness to histamine were more likely to show a low perceptiveness for bronchoconstriction during the challenge test.
CONCLUSIONSLow baseline FEV₁ and high bronchial responsiveness are associated with a low degree of "perceptiveness" for bronchoconstriction. This suggests that patients with a more severe degree of asthma either show adaptation of "perceptiveness" for airway obstruction or that low perceptiveness leads to more severe asthma.

Keywords: perception; airway obstruction; asthma