Association Of Pectoralis Muscle Area And Its Attenuation With Indices Of Disease Severity In Patients With Idiopathic Pulmonary Fibrosis

Objective:Idiopathic pulmonary fibrosis（IPF）is a chronic and progressive fibrosis interstitial lung disease of unknown cause,with poor prognosis and easy to lead to death as the disease progresses.Sarcopenia due to IPF is associated with illness and prognosis,but current methods for assessing sarcopenia are limited.In order to better understand the thoracic skeletal muscle status of IPF patients and the relationship between thoracic skeletal muscle and disease,this study used chest CT to measure the pectoralis muscle area（PMA）and pectoralis muscle attenuation（PMT）to explore the relationship between the thoracic skeletal muscle status of IPF patients and the disease severity index.Methods:This study included 243 subjects,including 138 stable patients with IPF who were followed up in the Department of Respiratory and Critical Care Medicine of the First Affiliated Hospital of China Medical University from January 2017 to July 2022,and 105 healthy controls from the Physical Examination Center of the First Affiliated Hospital of China Medical University.We collected the age,gender,height,weight,body mass index（BMI）,lung function and other basic data of all participants,and selected a single axial slice of the CT scan above the aortic arch to examine the pectoral muscle for PMA and PMT measurement on the clinical work computer reading software IMPAX RIS.After adjusting age,gender,and BMI,we used covariance analysis to determine the differences in PMA and PMT between the IPF group and the healthy control group,and used Pearson correlation analysis and Linear regression analysis to clarify the relationship between PMA and PMT and pulmonary function indicators（FVC,FVC%pred,DLco,DLco%pred）,HRCT lung interstitial fibrosis score（ground-glass opacity,grid shadow,honeycomb shadow and total score）and blood gas analysis indicators（Pa O₂and Pa CO₂）,comparing the diffusion function damage in the IPF group PMA and PMT among different grades,ROC curve was constructed to evaluate the predictive ability of PMA and PMT for respiratory failure in IPF patients.Results:1.After adjusting for age,sex and BMI,the PMA and PMT values of patients in the IPF group were lower than those of healthy controls（P<0.001）.2.In the Pearson correlation analysis,we found that PMA values of patients with IPF were correlated with sex,and that men’s PMA values were higher than women’s（P<0.001）,and PMA values were positively correlated with height,weight,BMI,FVC,DLco,DLco%pred（P<0.001）,Pa O₂（P<0.05）,and negatively correlated with age,honeycomb shadow,and HRCT total score（P<0.05）;PMT values of patients with IPF were correlated with sex,and men’s PMT values were higher than women’s（P<0.05）,and positively correlated with height,FVC,FVC%pred,DLco,DLco%pred,Pa O₂（P<0.05）,and negatively correlated with age,ground-glass opacity,grid shadow,and HRCT total score（P<0.05）.3.According to DLco%pred grouping,the patients with IPF were divided into mild,moderate and severe groups,and the differences in PMA and PMT among groups were statistically significant（P<0.05）.As the damage to lung diffusion worsens,PMA and PMT also gradually decrease.4.After adjusting for gender,age,height and BMI,PMA values of patients with IPF were still significantly correlated with FVC,DLco,DLco%pred,grid shadow,honeycomb shadow,HRCT total score and Pa O₂（P<0.05）,PMT values of patients with IPF were significantly correlated with FVC,FVC%pred,DLco%pred,ground-glass opacity,grid shadow,HRCT total score and Pa O₂（P<0.05）.5.The optimal cut-off value for PMA for predicting respiratory failure in the IPF group was 30.969cm²,with a sensitivity of 0.706 and a specificity of 0.653,while the optimal cut-off value for PMT for predicting respiratory failure in the IPF group was 37.608HU,with a sensitivity of 0.500 and a specificity of 0.853（P<0.05）.Conclusion:1.Pectoralis muscle area（PMA）and pectoralis muscle attenuation（PMT）measured by chest CT were significantly lower in patients with IPF than those in healthy controls,indicating that stable patients with IPF may have sarcopenia.2.The decrease in PMA and PMT in IPF patients is related to the degree of pulmonary function impairment and pulmonary interstitial fibrosis of patients,that is,the more severe the degree of lung function impairment and pulmonary interstitial fibrosis,the lower the PMA and PMT values.3.The measurement of PMA and PMT has a certain predictive power for respiratory failure in IPF patients.