Factors affecting dyspnea after the 6-minute walk test in idiopathic pulmonary fibrosis patients presenting with exercise-induced hypoxemia

[Purpose] The current study aimed to investigate factors affecting dyspnea after the 6-minute walk test (6MWT) in idiopathic pulmonary fibrosis (IPF) patients presenting with hypoxemia. [Subjects and Methods] The subjects were IPF out-patients with stable symptoms whose percutaneous arterial oxygen saturation fell to 88% during the 6MWT test. Quadriceps force, 6-minute walk distance (6MWD), dyspnea after the 6MWT, and leg fatigue (LF) were evaluated as exercise-related variables. [Results] The subjects were 14 patients (mean age 73.6 ± 6.3 years) classed based on the modified Medical Research Council dyspnea scale as 0 for 2 patients, 1 for 6 patients, and 2 for 6 patients, indicating that the patients were comparatively mild cases. Mean 6MWD was 408.9 ± 102.4 m, and dyspnea after the 6MWT and LF were 3.0 ± 1.4 and 1.5 ± 1.5, respectively. Dyspnea after the 6MWT was correlated with vital capacity (VC), forced vital capacity, and LF. Stepwise multiple regression analysis identified VC and LF as factors significantly affecting dyspnea after the 6MWT. [Conclusion] The results of this study demonstrated that it is necessary to evaluate both pulmonary function and LF in IPF patients presenting with exercise-induced hypoxemia and exertional dyspnea.