| Background Previous studies have found that the ratio of the maximal mid-expiratory flow（MMEF）to the forced vital capacity（FVC）can reflect the function of the small airway in patients with chronic obstructive pulmonary disease（COPD）.However,the value of MMEF/FVC in the diagnosis of COPD patients is unclear,and the correlation and significance of MMEF/FVC with exhaled nitric oxide（Fe NO）and serum biomarkers are unclear.ObjectiveTo explore the value of the ratio of maximum mid-expiratory flow（MMEF）to forced vital capacity（FVC）in chronic obstructive pulmonary disease（COPD）risk group,and to analyze the correlation and significance of MMEF/FVC,Fe NO and serum biomarkers in COPD patients.MethodsPart Ⅰ A total of 328 subjects who received pulmonary function tests in in the Sixth Medical Center of PLA General Hospital from January 2016 to January 2020 were retrospectively recruited.There were 115 cases in the control group,104 cases in the COPD risk group,and109 cases in the COPD group（mainly mild to moderate obstructive ventilation dysfunction）.Statistical body mass index（BMI）,vital capacity（VC）,forced vital capacity（FVC）,predicted forced expiratory volume in one second（FEV1%pred）,one-second rate（FEV1/FVC）,forced expiratory 25%～75 % average flow rate at vital capacity（MEF 25%to 75%）,predicted instantaneous flow rate at 50% forced vital force（MEF50%pred）,predicted instantaneous flow rate at 25% forced vital force（MEF25%pred）equal value and analyze.Part Ⅱ From January 2020 to January 2021,149 subjects in the Sixth Medical Center of PLA General Hospital were enrolled.There were 58 cases in the COPD group,44 cases in the COPD risk group,and 47 cases in the healthy control group.The values of MMEF/FVC,Fe NO,interleukin-6（IL-6）,C-reactive protein（CRP）,and surface protein D（SP-D）among the three groups were compared,and then the correlation among them and the predictive value of MMEF/FVC were analyzed.ResultsPart Ⅰ The proportion of small airway dysfunction in the control group was 31%,and that in the COPD risk group was 41%.Then,the receiver operating characteristic curve（ROC）of MMEF/FVC for the diagnosis of small airway dysfunction was analyzed,the area under the curve was 0.867（95% confidence interval was 0.816-0.917,P<0.05）,and the cutoff value was 0.79,showed that MMEF/FVC has diagnostic significance for small airway dysfunction.One-way analysis of variance among the three groups found that（F=130.61,P<0.05）,the difference between the three groups was statistically significant.Spearman correlation analysis found that the progression of COPD was negatively correlated with MMEF/FVC（r=-0.679,P<0.05）,indicating that MMEF/FVC had a high correlation with the development of COPD.Part Ⅱ The value of MMEF/FVC was the highest in the healthy control group,followed by the COPD risk group,and the lowest in the COPD group（P < 0.05）,while the Fe NO level was the highest in the COPD group,followed by the COPD risk group,and the lowest in the healthy control group（P < 0.05）.The levels of serum IL-6 and SP-D in the COPD group were higher than those in the COPD risk group and healthy control group（P < 0.05）.Fe NO,serum biomarkers（IL-6,CRP,SP-D）,and MMEF/FVC were all lowly negatively correlated in the three groups of subjects.The results were Fe NO（r=-0.289,P=0.000）,IL-6（r=-0.296,P=0.000）,CRP（r=-0.255,P=0.002）,SP-D（r=-0.177,P=0.031）;Serum biomarkers（IL-6,CRP）were moderately positively correlated with Fe NO,and the results were CRP（r=0.434,P=0.000）and IL-6（r=0.323,P=0.000）.The area under the receiver operating characteristic curve of diagnosing COPD risk group by combing MMEF/FVC with Fe NO and serum biomarkers was0.696,and the 95% confidence interval was 0.588-0.804.ConclusionsMMEF/FVC value can be used for early screening of COPD,the incidence of small airway dysfunction is higher in healthy people.There is a certain correlation between MMEF/FVC,Fe NO and serum markers,which can be used as indicators to reflect the severity of COPD patients.Combined screening of MMEF/FVC,Fe NO,and serum markers can improve the ability to identify individuals at high risk of COPD. |
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