The severity of breathlessness during challenges with inhaled methacholine and hypertonic saline in atopic asthmatic subjects. The relationship with deep breath-induced bronchodilation

The severity of breathlessness at given degrees of airway obstruction varies between patients with asthma. It has been postulated that the symptoms during bronchoconstriction are determined in part by involvement of airway inflammation. We compared the severity of breathlessness at various degrees of acute airway obstruction between a direct stimulus of airway smooth muscle, methacholine, and an indirectly acting stimulus, hypertonic saline. Twelve atopic asthmatic adults (mean +/- SD; age 25.3 +/- 3.4 yr; baseline FEV1 91.2 +/- 10.4% pred; PC20 1.0 mg/ml methacholine +/- 1.7 doubling dose) entered a methacholine and a hypertonic saline period in random order. In each period doubling doses of either methacholine (0.03 to 256 mg/ml) or hypertonic saline (0.9 to 14.4% NaCl) were inhaled on two occasions 7 d apart, using standardized tidal breathing methods. The response was obtained by FEV1 and, in order to assess volume history effects on airway caliber, by the ratio of flows obtained from volume history standardized maximal and partial expiratory flow-volume curves (M/P ratio). Breathlessness was measured by a visual analogue scale (VAS), which ranged from 0 (none) to 100% (most severe experienced). The subjects were blinded to the response in lung function. The changes from baseline in VAS scores at intervals of 5% fall in FEV1 (delta VAS) and the changes in M/P ratios (delta M/P ratio) were calculated by linear interpolation. The results were analyzed by MANOVA. There were no differences in baseline FEV1 or baseline VAS scores between the methacholine and hypertonic saline periods (p > 0.40).(ABSTRACT TRUNCATED AT 250 WORDS)