The Value Of Femoris Rectus Ultrasound In Skeletal Muscle Function Evaluation In Patients With Chronic Obstructive Pulmonary Disease

Background: Skeletal muscle dysfunction is one of the most common comorbidities of chronic obstructive pulmonary disease(COPD),which directly affects the quality of life,psychological state and social relationships of patients.6-minute walking test(6MWT)is a commonly used tests of skeletal muscle function evaluation,which has been strictly standardized and has a good repeatability.6MWT is also an important test to assess the severity of COPD and to predict patients’ mortality.In addition,the measurements for skeletal muscle function include sit-to-stand test(STST),quadriceps muscle strength,femoral rectus ultrasound and so on.Ultrasound is easier to popularize and operate,greatly increasing its clinical feasibility.Objectives: The purpose of this study is to evaluate the effectiveness of femoris rectus ultrasound applied in skeletal muscle function evaluation in patients with COPD through determining the relationships between femoris rectus cross-sectional area and other parameters including 6-minute walking distance(6MWD),30-seconds sit-to-stand times,quadriceps muscle strength.Methods: 94 patients with COPD were enrolled in our research.We assessed their femoris rectus muscle cross-sectional area with ultrasound,pulmonary function,fat-free mass index(FFMI),BODE index,6MWD,30-second sit-to-stand times and quadriceps muscle strength.Descriptive statistical analysis results were expressed by means of mean± standard deviation.Kolmogorov-Smirnov test was applied to verify whether the data obey normal distribution.Correlation analysis applied Pearson correlation or Spearman rank correlation test according to different types of data.Receiver operating characteristic(ROC)curve was used to determine the predictive value of femoris rectus muscle ultrasound in the decrease of exercise tolerance in different genders.Results: 94 patients with COPD were collected consecutively(age 66.54±8.04 years old,FEV1% 55.24±27.84%).In the correlation analysis,we found out that the 6MWD was positively correlated with the cross-sectional area of the femoris rectus(r=0.327,P=0.003).The 6MWD was positively correlated with the quadriceps muscle strength(r=0.615,P=0.000),and 30-second sit-to-stand times(r=0.480,P=0.000).The thickness of the femoris rectus had a positive correlation with the cross-sectional area of the femoris rectus(r=0.743,P=0.003)and forced vital capacity(FVC)(r=0.247,P=0.021),but there was no correlation between the thickness of the femoris rectus and the other parameters.The cross-sectional area of the femoris rectus was positively correlated with the quadriceps muscle strength(r=0.417,P=0.000)and had no correlation with 30-second sit-to-stand times.There was a linear correlation between 6MWD and the cross-sectional area of femoris rectus,the linear regression equation was ? = 195.291 + 21.76 X.We considered that when the 6MWD was less than 350 m,an event of decrease in exercise tolerance of the subjects happened.The predictive value of the cross-sectional area of the femoris rectus in the exercise tolerance decrease event was calculated.Its area under the ROC curve(AUC)was 0.645,P=0.024<0.05,the sensitivity was 91.9%,and the specificity was 43.2%.At the same time,AUC=0.786,P=0.003 in female COPD patients,with a sensitivity of 100% and a specificity of 52.4%.AUC=0.489,P=0.90 in male patients with COPD,with a sensitivity of 86.2% and a specificity of 31.3%.Conclusions: The cross-sectional area of femoris rectus and 6MWD showed a good correlation,which enables femoris rectus ultrasound to assess skeletal muscle function in COPD patients.For patients with COPD,femoris rectus ultrasound has a high sensitivity in the prediction of decreased exercise tolerance events,especially for female subjects.