Study On The Diagnostic Value Of Exhaled Nitric Oxide Combined With Pulmonary Function And Peripheral Blood Eosinophil Ratio In Cough Variant Asthma

Objective:This study through detection of exhaled nitric oxide（FENO）,conventional pulmonary function,pulse oscillation pulmonary function,and peripheral blood routine in patients with chronic cough,to compare and analysis of exhaled nitric oxide,ventilation function index,improvement rate of small airway function index after use of bronchodilators,and peripheral blood eosinophil percentage in patients with cough variant asthma patients（CVA）and non-cough variant asthma patients（NCVA）.analysis of the correlation between FENO values and lung function parameters and peripheral blood eosinophil percentage in patients with CVA,to explore the clinical value of FENO combined with pulmonary function and peripheral blood eosinophil percentage in chronic cough patients Screening out the CVA patients.Methods:Collection of 267 patients with chronic cough diagnosed at the Affiliated Hospital of Northern Sichuan Medical College Department of Respiratory Medicine from March 2016 to November 2017.Collection of 267patients with chronic cough diagnosed at the Affiliated Hospital of Northern Sichuan Medical College Department of Respiratory Medicine from March2016 to November 2017.All patients were detected of FENO,conventional pulmonary function,pulse oscillatory pulmonary function,bronchial dilation test,peripheral blood routine examination,and all chronic cough patients were divided into CVA and NCVA groups according to the examination results.Comparative analysis of FENO values and ventilatory function index（FEV₁pre%,FEV₁/FVC%,PEFpre%,MEF75pre%,MEF50pre%,MEF25pre%,MMEFpre%）,and small airways Functional index（MEF75,MEF50,MEF25,MMEF）improvement rate after use of bronchodilators,pulse oscillation lung function index（Z5,R5pre%,R20pre%,X5,and Fres）,and the proportion of peripheral blood eosinophil.Spearman correlation analysis was used to investigate the correlation between FENO and pulmonary function parameters and the percentage of peripheral blood eosinophils in patients with CVA.Results:（1）The median and interquartile range of FENO values in the CVA and NCVA groups were[45（34.25,74.75）]ppb and[14（10,19）]ppb,respectively,the FENO values in the CVA group were significantly higher than NCVA group,the difference was statistically significant（P<0.001）.The percentage of eosinophil in the CVA group and the NCVA group were（5.93±2.31）%and（2.33±1.63）%,respectively.There was statistical difference between the two groups（P<0.001）.（2）The CVA group ventilation function indicators（FEV₁pre%,FEV₁/FVC%,PEFpre%,MEF75pre%,MEF50pre%,MEF25pre%,MMEFpre%）were significantly lower than NCVA group,the difference was statistically significant（P<0.001）,among them,the MEF75pre%,MEF50pre%,MEF25pre%,and MMEFpre%in the CVA group were significantly lower than normal,PEFpre%,FEV₁pre%,and FEV₁/FVC%is basically within the normal range.（3）The improvement rate of MEF75,MEF50,MEF25 and MMEF after the use of bronchiectasis in CVA group was significantly higher than that in NCVA group,and the difference was statistically significant(P<0.001﹚.（4）There was no significant difference in Z5,R5pre%,X5,Fres between CVA and NCVA patients（P>0.05）.R20pre%in CVA patients was significantly higher than that in NCVA patients,and the difference was statistically significant（P<0.05）.（5）There was a positive correlation between FENO and EOS%in CVA group.The correlation coefficient was（r=0.863）,and the correlation was statistically significant（P<0.001）.The FENO level and lung function parameters MEF50pre%,MEF25pre%,and MMEFpre%in CVA group were negative correlation,correlation coefficients were（r=-0.31,-0.277,-0.27）,and the correlation was statistically significant（P<0.05）.In CVA group FENO levels and pulmonary function parameters FEV₁pre%,FEV₁/FVC%,PEFpre%,and MEF75pre%correlation coefficients were（r=-0.21,-0.02,0.007,-0.101）,respectively,and the correlation was not statistically significant（P>0.05）,In CVA group FENO levels and Z5,X5,R5 pre%,R20 pre%,and Fres correlation coefficients were（r=-0.036,0.004,-0.079,-0.052,-0.128）,respectively,and the correlations were not statistically significant（P>0.05）.Conclusions:（1）In patients with chronic cough,the FENO level and peripheral blood eosinophil percentage in CVA patients were significantly higher than those in NCVA patients.The FENO level in CVA patients was positively correlated with the peripheral blood eosinophil percentage,suggesting that most CVA patients has eosinophilic inflammation of the airway.FeNO can be used to assist in differential diagnosis of CVA and NCVA.（2）In patients with chronic cough,the MEF75pre%,MEF50pre%,MEF25pre%,and MMEFpre%of CVA patients were significantly lower than normal,and were significantly lower than those of NCVA patients.The improvement rate of MEF75,MEF50,MEF25 and MMEF was significantly increased in patients with CVA after using bronchial dilatation agent.It is suggested that the small airway function of CVA patients showed a significant decline,and the small airway obstruction was improved more obvious after using bronchiectasis.Small airway function examination and use of bronchodilators after the improvement of small airway function index in the identification of CVA and NCVA has a greater clinical value.（3）In patients with chronic cough,the R20pre%of CVA patients was significantly higher than that of NCVA patients,suggesting that the central airway viscous resistance of CVA patients was increased compared with NCVA patients,and R20pre%could be used to help identify CVA and NCVA.（4）In patients with chronic cough,only a small proportion of FENO levels and lung function parameters have weak correlation in CVA patients,and the significance of both in CVA patients cannot be replaced by each other.FENO combined with pulmonary function and peripheral blood eosinophil ratio detection has greater clinical value in the identification of CVA and NCVA.