Characteristics Of Airflow And Impedance And Responsiveness To Different Bronchodilators In Asthmatic Patients On Relief Of Methacholine-induced Bronchospasm

Objective:To investigate the characteristics of pulmonary ventilation function and airway impedance in asthmatic patients with methacholine-induced bronchospasm before and after inhaling bronchodilators,and to compare the short-term effect and recovery time of salbuterol,ipratropium bromide and beclomethasone formoterol on spasmodic airway.Methods:Patients with asthma who visited the outpatient department of Zhujiang Hospital,Southern Medical University from September 2021 to January 2022 were included.Asthmatic patients who were positive for bronchial provocation test and met the inclusion criteria inhaled bronchodilators(200μg salbutamol or 80μg ipratropium bromide or 200/12μg beclomethasone formoterol)immediately after IOS examination and received IOS and spirometry tests at 5,20 and 30 minutes respectively since inhalation.ANOVA or Kruskal-Wallis test was used to compare the indexes of three groups.Repeated measures of analysis of variance was used to compare the effects of different bronchodilators at different time points on the indexes of large and small airways.Kaplan-Meier method was used to describe the probablility of recovery of FEV1,MMEF,R5,and AX within 30 minutes.Mean recovery time of FEV1,MMEF,R5 and AX in beclomethasone formoterol group was compared with that in the salbutamol and ipratropium groups,respectively,in a non-inferiority way.Log-rank test was implemented to compare time-unrecovered probability curves among groups when performing subgroup analysis..Results:1.A total of 120 asthmatic patients were enrolled in this study,including 44 in salbutamol group,37 in ipratropium group,and 39 in beclomethasone formoterol group.Constriction of Large and small airways occurs when a positive bronchial provocation test is obtained.Changes in airflow and impedance of small airways may be important manifestation of a positive provocation test.2.Inhaling bronchodilators can improve airflow and impedance of both large and small airways.Within 5 minutes,spirometry and IOS indexes except FEV3/FVC were improved after inhaling 200μg salbutamol or 80μg ipratropium bromide or 200/12μg beclomethasone formoterol.And there was no difference in improvements of all spirometry and IOS indexes at all time points within 30 min among three groups.3.FEF50 and MMEF declined most notably when a bronchial provocation test was positive.After 30 minutes of inhaling bronchodilators,the spirometry parameters with the greatest degree of improvement were FEF50 and MMEF,and the IOS parameters with the greatest degree of improvement were AX and R5-R20.4.Inhaling 200/12 μg beclomethasone dipropionate/formoterol was not inferior to 200μg salbutamol or 80μg ipratropium in reversing bronchospasm in asthmatic patients.5.After inhaling bronchodilators,small airway indexes,MMEF and AX,recovered slower than large airway indexes,FEV1 and R5.Recovery time of small airway index MMEF was slightly longer than that of AX..Conclusions:Changes in small airway airflow and impedance may be important manifestation of a positive bronchial provocation test.Inhaling beclomethasone formoterol can relieve constriction of large and small airways in the short term just as inhaling salbutamol or ipratropium bromide,so it can be used to rapidly relieve the bronchospasm during acute attacks in asthmatic patients.