Six-minute walk test distance does not reflect oxygen uptake in patients undergoing maintenance hemodialysis

By evaluating the exercise capacity of patients on maintenance hemodialysis (MHD), this study aimed to determine the representability of a 6-minute walk test (6MWT) distance for the cardiopulmonary endurance capacity of patients on MHD. The volume of oxygen uptake (VO ) at a respiratory exchange ratio equal to 1 (VO ) was measured during a graded cycling test, and the 6MWT distance was tested in 27 Chinese patients on MHD and 44 age-matched non-MHD subjects (CON). VO in MHD was lower than the levels of CON (834.44 ± 232.73 and 1,255.08 ± 340.49 mL/min, respectively (t = 5.65, p < 0.001)). The 6MWT distance of MHD was ~ 92 m shorter than that of CON (t = 7.58, p < 0.001). Additionally, a positive linear correlation between 6MWT distance and VO during the graded cycling test was found in CON (r = 0.57, p < 0.001) but was absent in MHD (r = 0.12, p = 0.582). Results indicate a significantly reduced cardiopulmonary endurance capacity and functional walk ability among Chinese patients on MHD. Moreover, 6MWT may not be a proper method to evaluate the cardiopulmonary endurance capacity of patients on MHD due to the absence of a correlation between 6MWT distance and oxygen uptake during exercise.