Correlation Between PM_2.5 Concentration Of Exhaled Air And Airway Function And Airway Remodeling In Patients With Bronchial Asthma

BackgroundBronchial asthma is a heterogeneous disease characterized by chronic airway inflammation,airway hyperresponsiveness,and variable expiratory airflow limitation.Exhaled air of human body mainly includes gas,water vapor and suspended particles,and its composition comes from the external environment,airway,alveoli and other parts of the cells and microbial metabolism.Studies have shown that most of the particles in human exhaled air are fine particles with the size of less than 2.5μm.In this paper,we analyzed the correlation between PM_2.5concentration of exhaled air and lung function,airway inflammation level and airway wall structure in patients with bronchial asthma,and preliminarily explored the role of PM_2.5in the lung on the occurrence and development of bronchial asthma.Objective1.To analyze the difference of PM_2.5concentration of exhaled air between asthma patients and healthy people,and to study the correlation between exhaled PM_2.5level and lung function,induced sputum cytology,Fe NO,peripheral blood neutrophil count and percentage,eosinophil count and percentage in asthma patients.To explore the correlation between exhaled PM_2.5level and airway function and airway inflammation level in asthma patients.2.Chest CT of asthma patients was post-processed by digital lung ^TMimage analysis system to objectively quantify the airway wall characteristics（such as lumen area LA,wall thickness/outer diameter percentage T/D%）of the SⅨof the right lung.Then we investigated the correlation between exhaled PM_2.5level and airway remodeling in patients with bronchial asthma.Methods1.Patients with chronic persistent asthma and healthy subjects in the same period who were admitted to the hospital from June to September 2019 were selected as the study subjects.All patients underwent exhaled PM_2.5detection and pulmonary function tests.PM_2.5concentration of exhaled air and pulmonary function parameters were recorded in the two groups for statistical analysis.Age,BMI,gender,smoking history,allergy history,family history,small airway dysfunction and PM_2.5concentration of exhaled air were recorded.Differences between groups were statistically analyzed.2.Among the included patients with bronchial asthma,17 patients assessed with partial control level were selected for chest CT（64 row）examination,exhaled nitric oxide Fe NO,induced sputum cytology and blood routine examination.The PM_2.5concentration of exhaled air,forced expiratory flow at 25%of forced vital capacity of predicted value（FEF25%pred）,forced expiratory flow at 50%of forced vital capacity of predicted value（FEF50%pred）,forced expiratory flow at 75%of forced vital capacity of predicted value（FEF75%pred）,maximum mid-expiratory flow of predicted value（MMEF%pred）,forced expiratory volume in one second of predicted value（FEV₁%pred）,peak expiratory flow of predicted value（PEF%pred）,forced vital capacity of predicted value（FVC%pred）,forced expiratory volume in one second/forced vital capacity（FEV₁/FVC）,the improvement rate of FEV₁and the absolute value change of FEV₁before and after bronchodilation test,Fe NO values,sputum macrophage percentage,sputum lymphocyte percentage,sputum eosinophil percentage,sputum neutrophil percentage,peripheral blood eosinophil count and percentage,and peripheral blood neutrophil count and percentage were recorded.We analyzed the correlation between exhaled PM_2.5concentrations and the above indexes.3.Three-dimensional reconstruction of bronchial trees in chest CT of patients were performed by digital lung^TMimage analysis system.We choose the SⅨthe right lung as the research object to mark and quantify the characteristics（such as lumen area LA,wall thickness/outer diameter percentage T/D%）of the airway from the third generation to the seventh generation.We analyzed the correlation between exhaled PM_2.5concentrations and the above indexes.Results1.A total of 45 patients with chronic persistent asthma were included in the first part,including 13 males and 32 females,aged 26-54 years old.There were 49 healthy controls,including 24 males and 25 females,aged 23-71 years old.There was no significant difference in age,sex and BMI between the asthma group and the control group（P>0.05）.The exhaled PM_2.5concentration of asthma patients[48.00（25.50,70.00）,μg/m3]were significantly lower than that in the control group（P<0.001）.Asthma group was prone to have small airway dysfunction,allergy history and family history of asthma（P<0.001）.2.17 patients assessed with partial control level were selected for chest CT（64row）examination,exhaled nitric oxide Fe NO,induced sputum cytology and blood routine examination,including 4 males and 13 females,aged 26-62 years old.The results indicated that PM_2.5of exhaled air was positively correlated with PEF%pred,FVC%pred and FEV₁%pred（r=0.498,P=0.042;r=0.535,P=0.027;r=0.518,P=0.033）,but had no correlation with FEF 25%pred,FEF 50%pred,FEF 75%pred,MMEF%pred,FEV₁/FVC,FEV₁improvement rate before and after bronchodilation test and absolute value change of FEV₁（P>0.05）.Exhaled PM_2.5concentration was negatively correlated with the percentage of neutrophils in induced sputum and the neutrophils count in peripheral blood（r=-0.596,P=0.012;r=-0.568,P=0.017）,but there were no correlations between exhaled PM_2.5concentrations and Fe NO,sputum macrophage percentage,lymphocyte percentage,eosinophil percentage and peripheral blood eosinophil count and percentage（P>0.05）.Exhaled PM_2.5was positively correlated with the bronchial lumen area（LA/BSA）of the fourth to sixth generations in SⅨof patients with bronchial asthma（r=0.641,P=0.006;r=0.698,P=0.002;r=0.865,P<0.001）,was negatively correlated with the sixth generation bronchial wall thickness/outer diameter percentage（r=-0.503,P=0.040）,and had no correlation with the remaining indexes（P>0.05）.The fourth generation bronchial lumen area（LA/BSA）was positively correlated with PEF%pred and FVC%pred in patients with bronchial asthma（r=0.610,P=0.009;R=0.549,P=0.022）.Conclusion1.The PM_2.5concentration of exhaled air in patients with chronic persistent asthma was significantly lower than that in healthy controls,and it was correlated with lung function,suggesting that the level of PM_2.5in the exhaled air may has certain value in evaluating the airway function of patients with bronchial asthma.2.There was a significant negative correlation between the PM_2.5concentration of exhaled air and the percentage of neutrophils in sputum and neutrophils counts in peripheral blood of asthmatic patients,suggesting that PM_2.5level of exhaled air may be an indicator of neutrophil-mediated airway inflammation.3.The PM_2.5concentration of exhaled air was correlated with the airway remodeling indexes,such as bronchial lumen area and bronchial wall thickness/outer diameter percentage.