[Study on negative expiratory pressure technique in children with bronchial asthma].

OBJECTIVE: To investigate the clinical significance of children bronchial asthma detection by using negative expiratory pressure (NEP) technique.

METHODS: The children with bronchial asthma admitted to Department of Pediatrics of Zhejiang Provincial Integrated Traditional Chinese and Western Medicine Hospital from March 2016 to March 2018 were enrolled. They were divided into mild group (0-4 scores) and severe group (5-12 scores) according to asthma clinical scoring criteria. The children undergoing physical examination at the same period were served as healthy control group. NEP technique and tidal volume (VT) were detected by the pulmonary function instrument. Respiratory flow-volume curves (F-V curves) without NEP were compared with tidal F-V curves after NEP application to assess expiratory flow limitation (EFL). EFL index was calculated according to the percentage of expiratory VT after EFL and expiratory VT when NEP was not used. Pearson correlation method was used to analyze the relationship between EFL index and severity of bronchial asthma. Receiver operating characteristic (ROC) curve was plotted to analyze the value of EFL index in evaluating the severity of bronchial asthma in children.

RESULTS: A total of 86 children with bronchial asthma were enrolled in the study, and 84 patients completed the test and 2 children withdrew due to other diseases. Finally, 84 patients were included in the final analysis, including 41 mild and 43 severe children. Forty-two healthy children in the same period were served as healthy control group. There was no significant difference in gender or age among the groups, and no adverse reactions occurred during the test. The EFL index of children with bronchial asthma was significantly higher than that of the healthy control group, and it was increased with the severity of the disease [mild group compared with healthy control group: (30.60±6.03)% vs. (6.64±2.37)%, severe group compared with healthy control group: (33.70±5.41)% vs. (6.64±2.37)%, both P < 0.05]. There was no significant difference in respiratory rate (RR) or VT between mild group or severe group and healthy control group [RR (times/min): 31.45±4.18, 32.81±4.07 vs. 31.97±4.01, VT (mL/kg): 6.29±1.14, 5.96±0.90 vs. 6.30±1.20, all P > 0.05]. It was shown by the correlation analysis that EFL index was positively correlated with the severity of asthma (r = 0.836, P = 0.000). It was shown by ROC curve analysis that the area under ROC curve (AUC) of EFL index for predicting the severity of bronchial asthma in children was 0.801 [95% confidence interval (95%CI) = 0.725-0.878]; when the best cut-off value of EFL index was 29.21%, the sensitivity was 85.7%, the specificity was 69.2%, the positive predictive value was 75.1%, and the negative predictive value was 60.2%.

CONCLUSIONS: The EFL index measured by NEP technology was closely related to the severity of bronchial asthma. The higher the EFL index, the more serious of the condition. The severity of bronchial asthma could be early judged by EFL index, which provided a basis for the evaluation and treatment of bronchial asthma.