Clinical Significance Of Alveolar Exhaled Nitric Oxide Combined With Open Source CT In The Diagnosis And Treatment Of Common Small Airway Dysfunction

Objective:This study aims to assess the diagnostic value of alveolar nitric oxide concentration（Ca NO）in small airway dysfunctions（SAD）.To investigate the potential correlation between Ca NO,and small airway indexes of pulmonary function and some lung volume parameters detected by open-source CT in SAD patients.Moreover,to explore the clinical significance of post-processing techniques of open-source CT in diagnosing and treating SAD.Methods:A total of 132 patients with suspected SAD for clinical symptoms of chronic cough and short breath,and initially treated in the Department of Respiratory and Critical Care Medicine of Baotou Central Hospital from October 2019 to December 2020 were recruited in this study.They were examined for Ca NO,pulmonary function and paired inspiratory and expiratory CT scans.Recruited patients were categorized into five groups,including 66asthma patients in typical bronchial asthma group（group 1,n=53）and cough variant asthma group（group 2,n=13）.Patients with chronic obstructive pulmonary disease（COPD）were assigned to group 3（n=24）,and those with SAD except for asthma and COPD were included in group 4（n=21）.Healthy volunteers were included in group 5 as controls（n=21）.Ca NO,pulmonary function indexes and lung volume parameters detected by CT were recorded and compared.These indexes were reexamined after 1-month standard treatment in patients with asthma and COPD,aiming to assess the improvement rates.In addition,recruited patients were divided to group A and B based on the presence or absence of SAD,and the diagnostic potentials of Ca NO and pulmonary function indexes in SAD.SPSS 22.0 was used for data processing.Normality test was performed using the Shapiro-Wilk test,and normally distributed measurement data were expressed as±s;Otherwise,they were expressed as M（Q3-Q1）.Categorical data were expressed as numbers（n）and percentage（%）.Normally distributed measurement data with homogeneity of variance among three or more groups were compared by analysis of variance.Differences between and after treatment in the group were compared by paired Student’s t test.Kruskal-Wallis test was used to compare data that were not normally distributed or variance unequal.Their differences between groups were analyzed using Bonferroni correction,and differences between and after treatment in the group were compared using Wilcoxon test.Enumeration data were compared using Chi-square test.Spearman’s correlation test was performed to analyze correlation between two indexes.Diagnostic potential was assessed by depicting receiver operating characteristic（ROC）curves.Graph Pad Prism 8.0 was used for figure formatting.A significant difference was set at p<0.05.Results:（1）There were no significant differences in sex,age,body weight,height and smoking history among five groups（P>0.05）.（2）Ca NO,pulmonary function indexes and lung volume parameters detected by CT were significantly different among five groups（P<0.05）.Briefly,fractional exhaled nitric oxide（Fe NO）and Ca No in group 5 were significantly higher in group 5 than those of the other groups.Forced expiratory volume in one second（FEV₁%）was detected the highest in group 5,and lowest in group3.Forced expiratory volume in one second/forced vital capacity ratio（FEV₁/FVC%）in group 5 was higher than that of group 1,3 and 4,and it was higher in group 2 and 4 than that of group 1and 3.Maximal expiratory flow at 75%(MEF₇₅%)was lower in group 3 than that of the other groups.MEF₅₀%,MEF₂₅%and maximal mid-expiratory flow curve（MMEF%）were all higher in group 5 than those of group 1,3 and 4,and they were higher in group 2 than those of group 1 and 3,meanwhile,they were higher in group 4 than those of group 3.The spatial distribution of low attenuation areas（LAA%）on CT was lower in group 5 than that of the other groups,which was higher in group 3 than that of group 4.Excitation/inhibition ratio（E/I）was higher in group 3 than that of group 1 and 2,which was the lowest in group 5.（3）Ca NO,pulmonary function indexes and lung volume parameters detected by CT were significantly different before and after treatment in group 1,2 and 3（P<0.05）.In particular,Fe NO,Ca NO,LAA%and E/I were reduced after treatment,whilst FEV₁%,FEV₁/FVC%,MEF₇₅%,MEF₅₀%,MEF₂₅%and MMEF%were elevated.The improvement rates of FEV₁%,MEF50%and MMEF%were higher in group 3 than those of group 2,and the improvement rate of LAA%in group 2 was higher than that of group 1 and 3.（4）Correlation analysis in 5 groups showed that Ca NO was negatively correlated to FEV₁%,FEV₁/FVC%,MEF₇₅%,MEF₅₀%,MEF₂₅%and MMEF%（r<0,P<0.05）,which was positively correlated to LAA%and E/I（r>0,P<0.05）.FEV₁%,FEV₁/FVC%,MEF₇₅%,MEF₅₀%,MEF₂₅%,MMEF%are positively correlated with each other（r>0,P<0.05）,and negatively correlated with LAA%and E/I（r<0,P<0.05）;LAA%was positively correlated to E/I（r>0,P<0.05）.（5）There were significant differences in Ca NO and lung volume indexes between group A and B（P<0.05）,and LAA%,Ca NO and E/I in group A were all significantly higher than those of group B.（6）Area under ROC（AUC）of Ca NO combined with lung volume index was 0.785（95%CI,0.703-0.868）,and that of LAA%was 0.730（95%CI,0.639-0.820）.Conclusion:（1）Both asthma and COPD patients have large and small airway inflammation,which is more frequently involved in small airways of COPD patients.（2）Ca NO has a certain correlation with small airway indexes of lung function and lung volume parameters of open-source CT.（3）A single detection of Ca NO in diagnosing SAD has a poor outcome.（4）Post-processing techniques of open-source CT is superb in identifying SAD prior to the development of pulmonary dysfunction,and LAA%is a good diagnostic biomarker of SAD.