Oxygen uptake efficiency slope: A submaximal test evaluation tool that provides cardiopulmonary reserve data in individuals with Parkinson's disease

Abstract

Background: Oxygen uptake efficiency slope (OUES) is a method for investigating cardiorespiratory fitness and is proposed as an alternative to overcome the limitations of traditional measures such as peak oxygen consumption (VO_2peak) for patients who do not achieve a maximum response, such as in Parkinson's disease (PD).

Objective: To assess the performance of individuals with PD during the six-minute walk test (6MWT) using the OUES.

Methods: This is an observational cross-sectional study including 12 individuals with PD and 12 healthy controls. Participants performed the 6MWT along with an analysis of exhaled gas kinetics. The OUES was determined from the last 16 s of the walk test. Multiple linear regression analyses were computed to explore associations between the independent (OUES) and the dependent variables (VO_2peak) controlled by group.

Results: The OUES was associated to VO_2peak on the 6MWT (β=0.24, p<0.01) in individuals with PD. The PD group had low performance on the 6MWT with a shorter distance walked (mean difference: -113.1 m; 95% CI: -203.2, -59.1) and worse cardiopulmonary condition with lower OUES values (mean difference: -0.52 [l/minO₂]/[l/minVE]; 95% CI: -0.83, -0.21) found in this same group.

Conclusions: Our results suggest that OUES is related to VO_2peak during the 6MWT, and therefore it could be used as a submaximal test evaluation tool which provides cardiopulmonary reserve data in individuals with PD.

Keywords: 6-minute walk test; Cardiorespiratory fitness; Central nervous system disease; Physical function; Physical therapy.