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

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 (SpO(2)) 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 SpO(2) 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 SpO(2) during 6MWT. Early assessment of exercise desaturation using the 6MWT may be more important in patients with IPF compared with patients with other ILDs.