Objective: To evaluate the relationship between expiratory flow limitation (EFL) and chronic dyspnea and the effect of bronchodilator on EFL in patients with bronchial asthma.
Methods: Sixty-five patients with bronchial asthma were treated for pre- and post-bronchodilation of 400 microg salbutamol.
Results: EFL was detected in 26 (40%) of the 65 bronchial asthma patients, 11 only in supine position and 15 in both sitting and supine positions. There was a significant difference in FEV(1) percentage of the predicted value (FEV(1)% pred) between patients with and without EFL (t = 5.822, P < 0.01); the mean values of FEV(1)% pred in non-EFL group and EFL group was (77 +/- 18)% and (52 +/- 15)% respectively, and the value was lowest in patients who showed EFL both in seated and supine positions [(43 +/- 12)%]; the mean values of FEV(1)% pred in those showing EFL only in sitting position (S-EFL) and both in sitting and supine position (SS-EFL) were (64 +/- 10)% and (43 +/- 12)% respectively (t = 2.283, 6.694 respectively, P < 0.01, < 0.05). Both three-point EFL and five-point EFL were significantly correlated with FEV(1) (r = -0.637, -0.630 respectively, all P < 0.01). There was a significant negative correlation between as proposed by the Canadian Medical Research Council (MRC) dyspnea scale and FEV(1) (r = -0.501, P < 0.01), and a significant positive correlation between dyspnea scale and 3-point EFL and five-point EFL (r = 0.627, 0.636 respectively, all P < 0.01). After salbutamol, of the 17 patients having EFL and < 70% pre FEV(1) at baseline, EFL completely reversed in 9, and changed from SS-EFL to S-EFL in 5, with significant improvements in 3-point and 5-point EFL as compared with before salbutamol (t = 6.769, 6.010 respectively, all P < 0.01).
Conclusions: EFL as measured by NEP (negative expiratory pressure) technique may be more useful in the evaluation of dyspnea in bronchial asthma patients than routine lung function measurements. The EFL in bronchial asthma patients is reversible after bronchodilator administration.