Perception of dyspnea in asthmatics with normal lung function.

UNLABELLED

The perception of dyspnea varies widely among asthmatics and it is influenced by many factors. The aims of our study were to investigate the perception of dyspnea during methacholine-induced bronchoconstriction in asthmatics with normal lung function and to evaluate the influence of bronchial responsiveness, age and gender to dyspnea perception in these patients. A total of 192 outpatients (aged 16-77 years) with stable asthma and normal lung function were examined. Methacholine challenge test was performed to each patient. The provocative dose of methacholine that reduces forced expiratory volume in 1 sec. (FEV1) by 20% (PD20) was estimated. Dyspnea perception of bronchoconstriction was evaluated using a Borg Scale and calculating the perception score corresponding to a fall in FEV1 of 20% (PS20). According to PS20+/-1 standard deviation subjects were divided into three groups: hypoperceivers, normoperceivers and hyperperceivers. From the hypoperceivers group we set up asthmatics with PS20=0 and defined them as nonperceivers. We found out that 43 (22.4%) patients were hypoperceivers, 116 (60.4%)--normoperceivers and 33 (17.2%)--hyperperceivers. The nonperceivers presented 6.3% (n=12) of all subjects. PD20 positively correlated with PS20 (r=0.252, p<0.001). Hypoperceivers showed significantly higher bronchial hyperesponsiveness (PD20=174+/-28 microg) comparing with hyperperceivers (PD20=323+/-50 microg, p=0.013). Bronchial responsiveness to methacholine of nonperceivers (PD20= 106+/-31 microg, range 15-253 microg) was the highest and PD20 was significantly lower comparing with normoperceivers (p=0.005) and hyperperceivers (p=0.001). Age and gender had no significant effect on the perception of bronchoconstriction.

CONCLUSION

The part of asthmatics with normal lung function has impaired perception of dyspnea. Dyspnea perception depends on bronchial responsiveness, but not on age and gender of these patients.