Correlation Analysis Between Ultrasonic Assessment Of Diaphragm Function And Clinical Features In Patients With Stable COPD And Its Clinical Significance

Background&Objectives:Diaphragm dysfunction is common in COPD patients.The diaphragmatic morphology and function of patients with stable COPD were evaluated by ultrasound,and the relationship between diaphragm ultrasound indicators and clinical features such as smoking,symptoms,pulmonary function,and blood markers was analyzed.The predictive value of diaphragm ultrasound indicators in the diagnosis of COPD was also evaluated,so as to provide reference for further full assessment of COPD and future diagnosis and treatment.Methods:This is a cross-sectional observation study.A total of 100 patients admitted to the Department of Respiratory and Critical Care Medicine and the Department of Thoracic Surgery of the First Affiliated Hospital of Naval Medical University from November 2021to January 2023 were selected,including 52 patients with stable COPD,24 subjects in healthy control group and 24 subjects in smoking group,all of whom were similar in gender,age and BMI.According to the percentage of FEV₁ in the predicted value,the COPD groups were divided into GOLD1,GOLD2,GOLD3 and GOLD4,with 15,21,14 and 2 cases,respectively.General information and in-hospital examination results of participants were collected,and pulmonary function examination,6-minute walk test,m MRC questionnaire,CAT score were further improved,and BODE index was calculated.The subjects’venous blood samples were collected,and the expressions of molecules and genes related to inflammation,oxidative stress and aging were detected by q PCR and Elisa.The diaphragm thickness and diaphragm excursion during resting and deep breathing were measured by ultrasound,and the function reserve of diaphragm was calculated.The predictive value of diaphragm ultrasound indicators in the diagnosis of COPD was evaluated,and the relationship between diaphragm ultrasound indicators and smoking,symptoms,pulmonary function and blood markers in COPD group was analyzed.Results:Compared with the control group,diaphragm excursion in patients with COPD was significantly increased during resting breathing（P=0.019）,but significantly decreased during deep breathing（P<0.01）.The diaphragm excursion reserve ratio in COPD patients was lower than that in control group and smoking group（P<0.05）,and decreased with the increase of airflow limitation.There was no significant difference in diaphragm thickness between COPD patients and control group at the end of resting expiratory and end of resting inspiratory（P>0.05）.The diaphragm thickening fraction in COPD patients during resting breathing was higher than that in control group（P=0.032）,but the diaphragm thickness at the end of deep inspiratory and diaphragm thickening fraction during deep breathing were both lower than those in control group（P<0.05）.The diaphragm force reserve ratio in COPD patients was significantly decreased compared with that in control group and smoking group（P<0.05）.The more severe COPD was,the lower the diaphragm force reserve ratio was.There was no significant difference in diaphragm ultrasound indicators between smoking group and control group（P>0.05）.In COPD group,the diaphragm force reserve ratio was positively correlated with the maximum voluntary ventilation volume（MVV）and 6-minute walk distance（6MWD）（r=0.30,P<0.05;r=0.57,P<0.01）,was negatively correlated with total bilirubin,cystatin C,m MRC,CAT score and BODE index（r=﹣0.29,P<0.05;r=﹣0.30,P<0.05;r=﹣0.52,P<0.01;r=﹣0.58,P<0.01;r=﹣0.35,P<0.05）.In COPD group,diaphragm excursion reserve ratio was positively correlated with airway obstruction degree（FEV₁）,small airway function(FEF_50%),MVV and 6MWD（r=0.34,P<0.05;r=0.33,P<0.05;r=0.37,P<0.01;r=0.39,P<0.01）,was negatively correlated with m MRC,CAT score and BODE index（r=﹣0.61,P<0.01;r=﹣0.61,P<0.01;r=﹣0.52,P<0.01）.There was no significant correlation between diaphragm ultrasound indicators and smoking index in COPD group（P>0.05）.There were no significant differences in serum inflammatory factors（IL-1β,IL-6,TNF-α）and age-related molecules（CD248,LRRN3,NELL2,LEF1）in stable COPD patients compared with control group（P>0.05）.Serum IL-6 in COPD group was positively correlated with diaphragm thickness at the end of resting expiratory and end of resting inspiratory（r=0.60,P<0.05;r=0.60,P<0.05）,was negatively correlated with diaphragm excursion during deep breathing（r=﹣0.51,P<0.05）.The relative expression level of Nrf2 gene in blood of COPD group was significantly lower than that of control group（P<0.01）,and no correlation was found between the expression level and indicators of diaphragm ultrasound.There were no significant differences in the expression levels of genes related to oxidative stress（SIRT3,PPARG,FOXO1）and aging（FOXO3,LRRN3,NELL2,APOE,LEF1,CD248）in stable COPD patients compared with control group（P>0.05）.Blood APOE gene expression in COPD group was negatively correlated with diaphragm thickening fraction during deep breathing（r=﹣0.59,P<0.05）.Blood NELL2gene expression in COPD group was negatively correlated with diaphragm excursion during resting breathing（r=﹣0.56,P<0.05）,and positively correlated with diaphragm excursion reserve ratio（r=0.58,P<0.05）.The areas under ROC curve of diaphragm excursion during deep breathing,diaphragm excursion reserve ratio and diaphragm force reserve ratio in predicting the diagnosis of COPD were 0.727,0.747 and 0.785,respectively.The cut-off values were 55.25mm,0.659 and 0.661,and the sensitivity were 55.8%,65.4%and 76.9%,and the specificity was 85.4%,81.2%and 81.2%,respectively.Conclusions:Diaphragm ultrasound can evaluate the diaphragm dysfunction and severity in patients with stable COPD well.Diaphragm excursion reserve ratio and diaphragm force reserve ratio are closely related to symptoms of COPD patients,and can be used to better evaluate the symptoms of COPD patients.The diaphragm force reserve ratio has a certain predictive value in the diagnosis of COPD,and is expected to provide a noninvasive,safe and objective evaluation index for patients who cannot complete pulmonary function examination.