Exertional Desaturation Is More Severe in Idiopathic Pulmonary Fibrosis Than in Other Interstitial Lung Diseases

Abstract

Objective: Interstitial lung disease (ILD) is classified into several disease groups. Among them, idiopathic pulmonary fibrosis (IPF) has higher incidence and poor prognosis; therefore, it is important to characterize specific IPF symptoms. Exercise desaturation is a strong factor related to mortality in patients with ILD. Thus, the purpose of this study was to compare the degree of oxygen desaturation between IPF and other ILD (non-IPF ILD) patients during exercise, using the 6-minute walk test (6MWT). Methods: This retrospective study included 126 stable patients with ILD who underwent 6MWT in our outpatient department. The 6MWT was used to assess desaturation during exercise, 6-minute walk distance (6MWD), and dyspnea at the end of exercise. In addition, patient characteristics and pulmonary function test results were recorded. Results: Study subjects were divided into 51 IPF patients and 75 non-IPF ILD patients. The IPF group had significantly lower nadir oxygen saturation determined by pulse oximetry (SpO₂) during 6MWT than the non-IPF ILD group (IPF, 86.5 ± 4.6%; non-IPF ILD, 88.7 ± 5.3%; p = 0.02). The significant association between the nadir SpO₂ and IPF or non-IPF ILD grouping remained even after adjusting for gender, age, body mass index, lung function, 6MWD, and dyspnea (β = −1.62; p <0.05). Conclusion: Even after adjusting for confounding factors, IPF patients had lower nadir SpO₂ during 6MWT. Early assessment of exercise desaturation using the 6MWT may be more important in patients with IPF compared with patients with other ILDs.