Measuring metabolic energy expenditure for individuals with lower limb amputation

1. A two-minute walk test is less robust in measuring the stead state metabolic expenditure in lower leg amputee patients compared to total oxygen uptake analysis and minute interval analysis over 6 minutes, but it can still be accurately used if these tests are not tolerated. 

Evidence Rating Level: 2 (Good) 

When comparing prosthetic devices, interventions or populations, assessing the energy expenditure through metabolic demand during a six-minute walk test is the current standard. For patients with lower-limb amputations, this test can be very difficult or impossible. Additionally, an analysis of healthy adults showed that 96.8% of walking sessions lasted less than three minutes, further making a six-minute test less representative of real-world conditions. The challenge with shorter walking assessments is they do not allow participants to reach a steady state (SS) of energy expenditure, though recent studies have shown health adults can reach SS in 2 minutes. Additionally, other metrics such as oxygen uptake analysis and slope analysis of metabolic measures have been shown to correlate well with longer walking tests. Together, this makes the two-minute walk test (2MWT) a promising option for metabolic testing in lower-limb amputee populations. This study aimed to validate the 2MWT in these patients. They included individuals with transfemoral amputation (TF group), transtibial amputation (TT group), or no amputation (NoAmp group). Participants were assessed for a 2-minute total oxygen uptake, minute intervals over 6 minutes, and the 2MWT. All participants had amputations due to non-dysvascular causes. In total oxygen use testing, there were significant correlations between total oxygen consumption and steady state oxygen consumption for all three groups (p <0.05). During the minute interval analysis, SS was significantly correlated with nearly all metabolic measures including O2 consumption, O2, cost, and heart rate. Finally, the 2MWT showed fewer correlations with the SS and significant outcomes were also weaker compared to total oxygen uptake or minute interval analyses. Therefore, the 2MWT is an inferior test for SS in lower leg amputee patients than total oxygen uptake analysis and minute interval analysis. However, since there is some correlation, in the instance a longer walk test cannot be tolerated, a 2MWT can be used. 

Click to read the study in PLOSONE

Image: PD

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