The Relationship Between Chest Wall Muscle Thickness, Pulmonary Function, and Prognostic Markers in Idiopathic Pulmonary Fibrosis

Abstract

Background and Objectives: Idiopathic pulmonary fibrosis (IPF) is a specific form of chronic, progressive interstitial lung disease with an unknown etiology. It is often accompanied by skeletal muscle mass loss. Chest wall muscles play a crucial role in respiratory movements and form part of the skeletal muscles. The aim of this study is to evaluate the relationship between chest wall muscle thickness and pulmonary function test (PFT) results, as well as other prognostic markers, in patients with IPF. Materials and Methods: A retrospective analysis was conducted on 108 patients diagnosed with IPF and 53 control subjects. Chest wall muscle thickness was measured on thoracic computed tomography (CT) images at specific anatomical levels. PFT parameters, the Gender-Age-Physiology (GAP) index, number of acute exacerbations, and mortality data were evaluated in relation to muscle thickness. Results: IPF patients had significantly reduced thickness in the bilateral external scapular muscles at both the aortic and pulmonary trunk levels compared to controls. Bilateral pectoral muscle thickness at the aortic level was positively correlated with forced vital capacity (FVC) and negatively correlated with the number of exacerbations. Internal scapular muscle thickness at the aortic level showed a significant positive correlation with diffusion capacity of the lung for carbon monoxide (DLCO) and a negative correlation with both GAP scores and exacerbation frequency. External scapular muscle thickness at the pulmonary trunk level was positively associated with PFT parameters and inversely correlated with the GAP index, exacerbations, and mortality. Conclusions: In patients with IPF, the bilateral external scapular muscle thickness at the aortic and pulmonary trunk levels was significantly reduced compared to controls. Significant associations were found between some chest wall muscle thicknesses and the GAP index, pulmonary function, acute exacerbations, and mortality, underscoring the prognostic value of baseline muscle measurements. Measurement of chest wall muscle thickness using routine thoracic CT scans may offer additional prognostic value in IPF. Incorporating this parameter into clinical evaluation may help identify patients who could benefit from supportive interventions, such as nutritional therapy or pulmonary rehabilitation.

Keywords: chest wall muscle mass; idiopathic pulmonary fibrosis; prognosis.

Figure 1

Flow diagram of subjects in this study. Abbreviations; IPF, idiopathic pulmonary fibrosis; ILD, interstitial lung disease; CT, computed tomography.

Figure 2

Representative CT slices showing chest wall muscle thickness measurements in IPF patients and controls. Muscle thickness was measured on axial CT images. Arrows indicate measurement points: (A,B) at the level of the aortic arch; (C,D) at the level of the pulmonary trunk. Abbreviations; IPF, idiopathic pulmonary fibrosis; CT, computed tomography.