Feasibility of expiratory flow limitation detected by negative expiratory pressure for airway hyperreactivity in children with asthma

Abstract

Objective To detect expiratory flow limitation (EFL)before and after histamine bronchoprovocation test in children with asthma,and compared with the most commonly used lung function parameter FEV1, so that to examine the feasibility of EFL in the assessment of bronchoprovocation test.Methods Thirty stable asthmatic children were included. EFL was measured by applying negative expiration pressure(NEP) at the mouth before and after histamine bronchoprovocation test. Results Histamine bronchoprovocation test was positive in 19 (BPT-positive group) cases and negative in 11 (BPT-negative group) cases of 30 asthmatic children. In BPT-positive group, the mean FEV1 before and after bronchoprovocation test was (1.71±0. 52) L and (1.21±0. 34) L respectively, the mean descending rate was (29.04±7.49)% after histamine provocation. EFL was detected only in 1 case and 3 cases of the 19 asthmatic children with positive, bronchoprovocation test before and after histamine provocation. The difference in three-point EFL(EFL-3) or five-point EFL(EFL-5) before.and after bronchoprovocation test was not significant (EFL-3:1. 05±0.23 vs 1. 16±0. 37, t=1.455, P =0. 163;EFL-5:0. 05±0. 22 vs 0. 26± 0. 65, t = 1. 714, P = 0. 104). In BPT-negative group, the mean FEV1 before and after bronehoprovocation test was (1.89±0.80) L and (1.79±0. 78)L respectively,the mean descending rate was (6. 09±5.29)%.None of the 11 asthmatic children in BPT-negative group presented EFL before and after histamine bronchoprovocation test. Conclusions EFL detected by NEP does not sensitively reflect the positive criteria (FEV1 falling ≥20% ) for bronehoprovoeation test. The feasibility and criterion of EFL detected by NEP in the assessment of bronchoprovocation test await further studies. Key words: Children; Bronchial asthma; Bronchoprovoeation test; Negative expiratory pressure; Expiratory flow limitation