The Correlation Analysis Between Small Airway Function And Airway Hyperresponsiveness

ObjectiveTo analyze the relationship between small airway function and airway hyperresponsiveness,and to explore the predictive value of small airway function on airway hyperresponsiveness in patients with chronic cough,expect to get a simple method of diagnosis of airway hyperresponsiveness,so that atypical asthma can be diagnosed and treated as soon as possible.Methods1.A total of 272 cases suspected as asthma patients for the chronic cough were enrolled in the Department of Respiratory of the XX Hospital.The patients’general information was collected,including age,gender,body mass index(BMI).Then conventional pulmonary function tests and bronchial provocation tests(BPT)were performed.2.Diagnostic criteria of small airway lesions:two of FEF50%,FEF75%and MMEF75/25 are lower than 65%predicted value in the conditions that FEV1,FVC and PEF are all normal(higher than 80%predicted)and FEV1/FVC>70%;the positive of BPT diagnostic criteria:the positive of BPT is defined as PD20FEV1(cumulative inhaled histamine dose when FEV1 decreased by 20%or more)less than 7.8μmol(2.2 mg),which suggests the presence of airway hyperresponsiveness.3.According to the results of bronchial provocation tests or the the results of lung function and diagnostic criteria of small airway lesions,All the subjects were divided into bronchial provocation tests positive group and negative group or the abnormal small airway function group and normal group.Compared the differences of the general information,basic pulmonary function or the positive rate of the bronchial provocation tests between the two groups.Used receiver operator characteristic(ROC)curves to examine the abilities of percentage predicted values(%pred)for maximal midexpiratory flow、the forced expiratory flow at 75%、50%、25%of vital capacity and peak expiratory flow(MMEF75/25%pred、FEF75%pred、FEF50%pred、FEF25%pred、PEF%pred)to predict airway AHR.Analyzed the correlation between PD20FEV1 of BPT positive group and the indexes representing small airway function by Spearman correlation analysis in order to explore the relationship between small airway function and severity of airway hyperresponsiveness.Results1.Of 272 suspected as asthma patients,divided by the results of bronchial provocation tests,the cases of the bronchial provocation tests positive group and negative group were 165 and 107.Age,BMI,atmospheric channel function indexes compared with the positive and negative groups there was no statistically significant difference(P>0.05).Small airway function indexes of positive group was obviously lower than negative groups,and the differences between BPT negative group and positive group were statistically significant(P<0.05).2.According to the results of lung function and diagnostic criteria of small airway lesions,the patients of the abnormal small airway function group were 57,in which there were 49 patients performed bronchial provocation tests positive.The positive rate of the bronchial provocation tests of the abnormal small airway function group was obviously higher than that of normal group(86.0%vs54.0%),the difference was statistically significant(χ~2=19.347,P<0.01).3.The area under the receiver operating characteristic curve of percentage predicted values(%pred)for maximal midexpiratory flow、the forced expiratory flow at 75%、50%、25%of vital capacity and peak expiratory flow(MMEF75/25%pred、FEF75%pred、FEF50%pred、FEF25%pred、PEF%pred)was 0.524、0.439、0.540、0.418、0.276 respectively.The index compared with an area of 0.5 the reference line covered,differences were statistically significant(P<0.05).4.The correlation analysis suggested that PD20FEV1 was positively correlated with MMEF75/25%pred、FEF75%pred、FEF50%pred、FEF25%pred、PEF%pred,the correlation coefficient was 0.702(95%CI:0.640~0.764)、0.654(95%CI:0.588~0.720)、0.704(95%CI:0.642~0.765)、0.723(95%CI:0.662~0.784)、0.682(95%CI:0.616~0.749)respectively.Conclusion1.Small airway function of patients with airway hyperresponsiveness was significantly lower than patients with normal airway reactivity.2.Bronchial provocation tests in the patients with abnormal small airway function may be more likely to appear positive results.3.Small airwayfunction,tosome extent,can reflect the severity of airway hyperresponsivenessso,in which atypical asthma can be diagnosed earlier.