The Significance Of Fractional Exhaled Nitric Oxide And Small Airway Function In The Diagnosis And Therapeutic Evaluation Of Bronchial Asthma

BackgroundThe essence of bronchial asthma(or asthma)is the chronic airway inflammation,which can affect both central and peripheral airways.The current asthma control guidelines mostly use the indicators reflecting central airway function(FEV1,PEF)as the main indicators for diagnosing and assessing the severity and therapeutic effectiveness of asthma,and rarely assess small airway function.There are increasing evidences that small airway dysfunction is associated with airway hyperresponsiveness and is a key factor in poor asthma control.Fractional exhaled nitric oxide(FeNO)as a marker of airway eosinophilic inflammation can be used to diagnose eosinophilic asthma but has no diagnostic value for non-eosinophilic asthma.The small airway,as an important site of asthma pathology,and its dysfunction is associated with increased airway responsiveness.Its dysfunction occurs at all stages of asthma and does not depend on specific airway inflammation types.Therefore,combined detection of FeNO and small airway function can more fully reflect the characteristics of asthma.Whether combined FeNO and small airway function can improve the diagnostic value of asthma is still not clear.The correlation between Fe NO and lung function parameters,different studies draw different conclusions,and is still controversial.Therefore,this article will explore whether combined FeNO and small airway function have diagnostic value for asthma and their correlation.ObjectiveTo explore the diagnostic value of FeNO and small airway function in asthma and itssignificance in efficacy evaluation.MethodsChoose outpatients with suspected asthma due to cough,chest tightness,wheezing,etc during January and December 2016,and they received bronchial provocation test or bronchodilation test,lung function,FeNO,peripheral blood eosinophil count.They were diagnosed with bronchial asthma according to GINA and bronchial asthma guidelines.A total of 80 patients in the newly diagnosed asthma were selected as asthma group,and 80 healthy persons during the same period were selected as the healthy control group.The healthy control group also received FeNO,lung function,and blood tests.According to lung function,patients was divided into mild asthma group(EFV1% ? 80% pred)66patients and moderate-severe asthma group(FEV1%<80%pred)14patients.Correlation analysis of FeNO and pulmonary function parameters(FEV1%,FEF50%,MMEF%,FEF75%)were conducted for all patients.They were divided into mild asthma group and moderate-severe asthma group for subgroup analysis.The ROC curve was used to assess the diagnostic value of FeNO,MMEF%,and the combination of FeNO and MMEF% for asthma.All patients underwent standardized treatment according to the asthma prevention guidelines.The patients were reviewed once a month for the first 3 months,and then FeNO,pulmonary function,blood routine,and ACT were reviewed every 3 months for a period of one year.All selected patients had informed consent and signed informed consent Results1.Comparison of basic data between two groups of asthma patients and healthy peopleThere was no significant difference in age,gender,BMI,FEV1%,and FVC%between the two groups(p>0.05).The asthma group had higher FeNO,EOS% than the healthy group,lower FEV1/FVC,FEF50%pred,MMEF%pred,FEF75%pred,the difference was statistically significant(p<0.05).The incidence of small airway dysfunction in newly diagnosed asthma patients(55/80)was higher than that of healthy group(15/80)(p<0.05).2.The correlation between FeNO and lung function indicators.The association analysis of FeNO and lung function indexes(small and large airway function indexes)in newly diagnosed asthma patients showed that there was no correlation between FeNO and FEV1%(r=-0.256,P=0.237),and negative correlations were observed between FEF50%pred,FEF75%pred,and MMEF%pred(They were r=-0.159,P<0.05,r=-0.214,P<0.05,r=-0.338,P<0.05,respective).Subgroup analysis between mild asthma and moderate-severe asthma in newly diagnosed asthma showed that there was no correlation between FeNO and FEV1%(P>0.05)and negative correlation with FEF50%,FEF75% and MMEF%(P<0.05).After treatment,FeNO had no correlation with airway function(P>0.05)3.The predictive value of FeNO,MMEF% and combined FeNO,MMEF% in the diagnosis of asthmaFeNO predicts an optimal threshold of asthma diagnosis of 38 ppb,AUC(area under the curve)is 0.787,with a sensitivity and specificity of 83.47% and 58.63%,respectively;MMEF% predicts an optimal threshold of asthma diagnosis of 76.8%,and AUC(area under the curve)is 0.713,with a sensitivity and specificity of 81.53% and 56.93%respectively.Combined detection of FeNO and MMEF% predicted the area under the curve of asthma diagnosis 0.826,sensitivity 86.59%,specificity 59.89%4.After treatment,the recovery time of FEV1 were(4.3±2.6)months,FeNO(6.3±3.2)months,small airways(11.2±3.2)months,and the differences were statistically significant(P<0.05).Even in 1 year,there were still 4 patients with small airway dysfunction and their recovery time was treated as one year.There were 2 patients with small airway dysfunction and 3 patients with normal small airway function due to complete relief of asthma symptoms and normal FeNO,who respectively did not come to hospital for review after 9months and 6 months,and their recovery time was treated as one year.5.Compared with normal small airway function group,small airway dysfunctiongroup had a higher FeNO value(t=2.31,P<0.05),more ICS dosage(t=9.45,P<0.05),and higher recurrence rate(t=7.98,P<0.05)ConclusionSmall airway dysfunction and increased FeNO contribute to the diagnosis of asthma,but the combined Fe NO and MMEF% have higher diagnostic value than a single index,both of which can be used as indicators to assess asthma control and thus indirectly assess the efficacy of treatment.