[Application value of surface respiratory muscle electromyography and its ratio to tidal volume in the assessment of airway hyperresponsiveness in bronchial asthma patients].

To explore the application value of surface respiratory muscle electromyography and its ratio to tidal volume in the assessment of airway hyperresponsiveness in bronchial asthma patients. A case-control study was conducted to retrospectively analyze the data of 29 asthma patients who visited the outpatient department of respiratory medicine of the First Affiliated Hospital of Guangzhou Medical University from October 2015 to May 2017 and 27 non-asthmatic subjects who were recruited as the control group.Changes in surface respiratory muscle electromyography (parasternal, EMG, diaphragmatic, EMG), and its ratio to tidal volume (EMG/VT, EMG/VT) before and after the histamine challenge test were compared between the asthma group and the control group; and their receiver operating characteristic (ROC) curves were plotted. The average age of 29 patients in the asthma group was (50±13) years (male: female=14∶15), while that of 27 subjects in the control group was (35±13) years (male: female=11∶16). After the histamine challenge test, EMG, EMG/VT, EMG and EMG/VT in the 29 asthma patients were 16.5 (11.4, 19.7)μV, 1.8 (1.4, 2.3) μV·kg/ml, 11.9 (10.0, 15.0) μV, and 1.3 (1.0, 1.7) μV·kg/ml, respectively, which were significantly higher than those at baseline [12.0 (8.5, 6.0) μV, 0.9 (0.7, 1.3) μV·kg/ml, 9.4 (7.2, 12.8) μV, and 0.8 (0.7, 1.1) μV·kg/ml, all <0.001]. Changes of EMG, EMG/VT, EMG and EMG/VT(ΔEMG, ΔEMG/VT, ΔEMG, and ΔEMG/VT) in the asthma group before and after the provocation test were 37.2% (16.2%, 60.5%), 77.1% (40.3%, 145.9%), 28.9% (15.4%, 50.9%), and 62.2% (36.6%, 109.1%)%, respectively, which were significantly greater than those in the control group [0.9% (-17.2%, 9.0%), 0.7% (-13.3%, 20.1%), 3.9% (-11.0%, 10.0%), and-2.0% (-12.7%, 21.4%), all <0.001]. The sensitivities of ΔEMG, ΔEMG/VT, ΔEMG, and ΔEMG/VT for diagnosing airway hyperresponsiveness were 79.3%, 86.2%, 75.9%, and 79.3%, respectively, while the specificities were 85.2%, 96.3%, 92.6%, and 92.6%, respectively. The areas under ROC curves (AUC) for ΔEMG, ΔEMG/VT, ΔEMG, and ΔEMG/VT were 0.842 (95%: 0.720-0.926), 0.917 (95%: 0.812-0.974), 0.843 (95%: 0.721-0.926), and 0.916 (95%: 0.810-0.973) respectively, with no statistically significant differences among these AUC values (all >0.05). Surface respiratory muscle (parasternal, diaphragmatic) EMG and its ratio to tidal volume can accurately reflect the changes of airway resistance during bronchial provocation test, and differentiate asthma patients from non-asthmatic subjects, which therefore could be an alternative for the asthma diagnosis.