Background: It is well documented that the perception of dyspnea (POD), subjectively reported by patients, is an important index used to guide treatment. The severity of dyspnea following methacholine-induced bronchoconstriction and added mechanical loads is increasing in popular. No formal attention has been addressed to the reduction in dyspnea following bronchodilators.
Study objective: To investigate if the magnitude of dyspnea perceived by a subject is independent on the direction (e.g., bronchoconstriction or bronchodilation) of the change in airway resistance.
Methods: The POD was measured in 26 mild moderate asthmatic patients following bronchodilation, using beta2-agonists, and following bronchoconstriction, induced by methacholine challenge, to almost the same magnitude.
Results: The increase in forced expiratory volume in 1 s (FEV1), 30 min after the inhalation of beta2-agonist (mean +/- SEM 22.3 +/- 0.8%), was associated with a statistically significant decrease (P < 0.005) in the POD. The mean decrease in FEV1 following methacoline challenge, was 23 +/- 0.7% and was followed by a statistically significant increase (P < 0.005) in the POD. The magnitude of the decrease in the POD following albuterol was almost identical to the magnitude of the increase in the POD following methacholine.
Conclusions: In stable mild-moderate asthmatic patients, the changes in the magnitude of dyspnea, perceived by a subject, is independent on the direction of the change in the FEV1.