Do inhaled corticosteroids affect perception of dyspnea during bronchoconstriction in asthma?

Background: Some of the disagreements on the perception of dyspnea (PD) dur ing bronchoconstriction in asthma patients could depend on the interrelatio nships among the following: (1) the influence of baseline airflow obstructi on on the patient's ability to detect any further increase in airway resist ance; (2) the effect of eosinophilic inflammation on the airway; (3) bronch ial hyperresponsiveness (BHR); and (4) the effect of inhaled corticosteroid s (ICSs). Objective: We hypothesized that if the inflammation of the airway wall infl uences to some extent and in some way the PD in asthma patients, ICSs rever se the effect of airway inflammation on the PD. Methods: We studied 100 asthma patients who were divided into the following four groups: patients with obstruction who were either ICS-naive (group I) or were treated with ICSs (group II); and nonobstructed patients who were either ICS-naive (group III) or were treated with ICSs (group IV). PD on th e visual analog scale (VAS) was assessed during a metbacholine-induced FEV1 decrease and specifically was quantified as the VAS slope and score at an FEV1 decrease of 5 to 20%. BHR was assessed in terms of the provocative con centration of methacholine causing a 20% fall in FEV1 (PC20). Eosinophil co unts in induced sputum samples also were performed. Regression analysis, un ivariate analysis of variance, and factor analysis were applied for statist ical evaluation. Results: For a 5 to 20% fall in FEV1 from the lowest point after saline sol ution induction, VAS score was lowest in group II, slightly higher in group I, slightly higher still in group IV, and the highest in group III. In the patients as a whole, BHR related to PD, but age, clinical score, duration of the disease, and presence of baseline airway obstruction did not. In pat ients with obstruction who were treated with ICSs, eosinophil counts relate d to PD negatively. Factor analysis yielded the following four factors that accounted for 70% of the variance in the data: ICS; eosinophil counts; FEV 1; and PC20 loaded on separated factors with PD loading on the same factors as PC20. The post hoc analysis carried out dividing the patients into ICS- treated and ICS-naive, showed that in the former group eosinophil counts an d BHR proved to be factors negatively associated with PD, while in the latt er group eosinophil counts were positively associated with PD. Conclusions: We have shown that eosinophilic inflammation of the airway wal l may increase PD and that the association of eosinophil counts with ICSs m ay result in lessening the PD.