Application Of Impulse Oscillometry Technique And Spirometry In The Evaluation Of Small Airway Function

Objective:to explore the application of Impulse oscillometry（IOS）and spirometry in small airway function,to specify the value of IOS in the diagnosis of small airway dysfunction（SAD）.To explore SAD and characteristics of airway resistance in chronic obstructive pulmonary disease（COPD）and asthma patients.Methods:Patients who were examined by IOS and spirometry in the Department of Respiratory and Critical Care of the second Xiangya Hospital of Central South University from August 2020 to December2021 were enrolled.Paired chi-square test and spirometry were used to analyze the ability of IOS and spirometry to diagnose SAD in all subjects,COPD and asthma patients.T-test or nonparametric test was used to compare the characteristics of airway resistance among COPD,asthma patients and healthy controls.IOS and spirometry were used in COPD patients to evaluate the severity of airway obstruction and consistency analysis.Results:1.（1）A total of 326 subjects were included in this study,including 62 patients with COPD,49 patients with asthma,41healthy controls and 174 other patients.Among all the subjects,218cases（66.87%）were diagnosed with SAD based on spirometry and 272 cases（83.44%）were diagnosed with SAD based on IOS.There was significant difference between the two methods（P<0.05）.（2）79 patients with SAD were diagnosed by IOS with normal spirometry,compared with the healthy control group.There was significant difference in resistance difference（R5-R20）,resonance frequency（Fres）,structural parameters of peripheral airway resistance（Rp）,ratio of forced expiratory volume in the first second to forced vital capacity（FEV₁/FVC）,maximum mid-expiratory flow(FEF_25%-75%),instantaneous expiratory flow when forced exhalation of 50%vital capacity(FEF_50%),instantaneous expiratory flow at forced exhalation of 75%vital capacity(FEF_75%)（P<0.05）.2.Among the patients with asthma,43 cases（87.75%）were diagnosed with SAD based on spirometry,and 42 cases（85.71%）were diagnosed with SAD by IOS.There was no significant difference between the two methods by Mc Nemar test.3.（1）Among the patients with chronic obstructive pulmonary disease,59（95.16%）were diagnosed with SAD based on spirometry and 52（83.87%）with SAD diagnosed by IOS.There was no significant difference between the two methods.（2）Smith grade was used to evaluate the degree of airway obstruction by IOS,which was significantly different from the traditional GOLD grade used to evaluate airway obstruction.Conclusion:1.IOS is more sensitive than spirometry,it can detect SAD patients normal spirometry.2.IOS is an effective supplement to spirometry to examine SAD in patients with chronic obstructive pulmonary disease and asthma which is more convenient and requires low matching degree for patients than spirometry.3.There is a difference between IOS and traditional GOLD classification in evaluating the severity of airway obstruction,while IOS is more serious in evaluating the severity of airway obstruction.