Observation Of Exhaled Nitric Oxide Level In Chronic Airway Diseases

Objective To explore the clinical significance of exhaled nitric oxide level in chronic airway diseases by comparing the difference of exhaled nitric oxide level in different chronic airway diseases.Methods A total of 245 persons in The Second Attached Hospital Of Fujian Medical University from October 2019 to November 2020 were selected as participates of this study,including 72 patients with chronic obstructive pulmonary disease(COPD),86 patients with bronchial asthma(asthma),46 patients with non-cough variant asthma(CVA)chronic cough,and 41 healthy volunteers.Fractional exhaled nitric oxide(FeNO),Aveolar nitric oxide(CaNO),lung function,impulse oscillometry,peripheral blood eosinophil count and percentage of peripheral blood eosinophil were measured respectively.The differences of exhaled nitric oxide level in different groups,and the correlation between exhaled nitric oxide level with clinical data was analyzed.Receiver operator characteristic curve(ROC)was used to determine the optimal cut-off value of airway inflammation in the diagnosis of asthma.Results(1)The FeNO value of asthma group was higher than that of COPD group,non-CVA chronic cough group and healthy control group [40.80(37.27)ppb vs.17.85(15.58)ppb,13.80(12.22)ppb,10.10(9.80)ppb,P < 0.05].The level of FeNO in COPD group was higher than that in healthy control group [17.85(15.58)ppb vs.10.10(9.80)ppb,P < 0.05].(2)The level of CaNO in asthma group was higher than that in non-CVA chronic cough group [3.30(4.63)ppb vs.2.50(1.75)ppb,P < 0.05],and there was no significant difference between the other two groups(P>0.05).(3)CaNO was positively correlation with FeNO(r = 0.147,P<0.05).CaNO was positively correlated with peripheral blood eosinophil count(r = 0.170,P < 0.05)and Percentage of peripheral blood eosinophils(r=0.130,P<0.05),ut no correlation between CaNO and smoking index(r = 0.102,P=0.111).(4)FeNO was positively correlated with peripheral blood eosinophil count(r=0.352,P<0.05)and percentage of peripheral blood eosinophils(r=0.296,P<0.05),FeNO was negatively correlated with age(r =-0.130,P <0.05).(5)The value of airway inflammation index in the diagnosis of asthma: The area under ROC curve of FeNO: 0.81,the best critical value: 22.90 ppb,with 76% sensitivity and 77% specificity;The area under the ROC curve of CaNO:0.60,the best critical value: 3.65 ppb,with 43% sensitivity and 82% specificity.(6)The value of distinguishing asthma from non-CVA chronic cough:the area under ROC curve of FeNO: 0.82,the best critical value: 21.15 ppb,with 77% sensitivity and 76%specificity.The area under ROC curve of CaNO: 0.65,the optimal critical value:3.45 ppb,with 45% sensitivity and 85% specificity.(7)FeNO was negatively correlated with FEV1%Pred(r=-0.214,P<0.05).There was no correlation between CaNO and FEV1%Pred(r=-0.058,P=0.366).(8)There was no correlation between airway nitric oxide and airway resistance parameters measured by impulse oscillometry.Conclusion(1)CaNO was positively correlated with FeNO,peripheral blood eosinophil count and percentage of peripheral blood eosinophil.There was no correlation between CaNO and body mass index.FeNO was positively correlated with peripheral blood eosinophil count and peripheral blood eosinophil percentage.(2)The level of FeNO in asthma was higher than that in patients with other chronic airway diseases.The level of CaNO in asthma group was higher than that in non-CVA chronic cough group.(3)FeNO is more sensitive and specific than CaNO and other airway inflammation markers in the diagnosis of asthma.(4)The sensitivity of CaNO in the differential diagnosis of asthma and non-CVA chronic cough is low.(5)There may not be a good correlation between the level of exhaled nitric oxide in airway and the airway resistance parameters of impulse oscillometry.