Characteristic of four exercise tests in patients with idiopathic pulmonary fibrosis

Objective: There are various methods of exercise test, including a 6-minute walk test (6MWT), an incremental shuttle walking test (ISWT), a cardiopulmonary exercise test (CPX) and constant work-rate test (CWRT). The purpose of this study was to compare the hypoxemia and subjective symptoms of 6MWT, ISWT, CPX and CWRT in patients with idiopathic pulmonary fibrosis (IPF). Methods: 6MWT, ISWT, CPX, and CWRT were assessed in the one hundred IPF patients (%FVC 74.4%, %DLco 49.2%). The lowest SpO2 and the Borg scale of the dyspnea and leg fatigue at the end were measured in each test. The results from each test were compared. Results: The lowest SpO2 in 6MWT, ISWT, CPX, CWRT were 81.7 ± 9.5%, 82.5 ± 8.0%, 87.0 ± 6.2%, 86.8 ± 6.7%, respectively. The result of 6MWT and ISWT was significantly lower than that of CPX and CWRT (p <0.05), however, there was no significant difference between 6MWT and ISWT and between CPX and CWRT. Dyspnea and leg fatigue of CWRT was significantly the highest in the four tests (p <0.05). Dyspnea and leg fatigue of 6MWT was significantly the lowest in the four tests (p <0.05). Conclusions: The lowest SpO2 in 6MWT and ISWT were lower than that of the others. CWRT provided the strongest dyspnea and leg fatigue at the end. Understanding the diversity of individual tests are important in selecting appropriate exercise tests in clinical studies of IPF.