Relationship between lung volume and endurance in patients with interstitial lung disease

<bold>Background:</bold> Interstitial lung disease (ILD) progression decreases lung volume and respiratory function, leading to dyspnea and decreased endurance, including exercise tolerance. It is routinely evaluated using respiratory function tests and computed tomography (CT). However, respiratory function tests cannot be performed on patients who cannot use a mouthpiece. Although CT requires no patient effort and can be performed in most cases, quantitative evaluation criteria have not yet been established. Moreover, few studies have assessed lung volume in patients with ILD, and its association with clinical symptoms remains unverified. <bold>Objectives:</bold> This study aimed to examine the association between lung volume on CT and clinical symptoms such as endurance in patients with ILD. <bold>Methods:</bold> This study included 38 patients with ILD admitted to our hospital between 2017 and 2019, of whom, 15 and 23 patients had idiopathic and non-idiopathic pulmonary fibrosis, respectively. Lung volume on CT was evaluated using an image-analysis software, and bilateral whole lung field volumes were calculated. Endurance was assessed using the 6-minute walk distance (6MWD). Secondary outcome measures included the forced vital capacity (FVC) and other parameters of the respiratory function test. Pearson's correlation coefficient was used to evaluate the relationship between lung volume and each endpoint. Multiple regression analysis was performed with lung volume as the dependent variable and relevant items as the independent variables. <bold>Results:</bold> FVC(r=0.75) and 6MWD (r=0.43) were significantly associated with lung volume. Multiple regression analysis revealed an association between lung volume and 6MWD (R²=0.48). <bold>Conclusion:</bold> Lung volumes on CT are correlated with endurance in patients with ILD.