Effects of elevated vacuum on in-socket residual limb fluid volume: case study results using bioimpedance analysis

Abstract

Bioimpedance analysis was used to measure the residual limb fluid volume of seven transtibial amputee subjects using elevated vacuum sockets and nonelevated vacuum sockets. Fluid volume changes were assessed during sessions with the subjects sitting, standing, and walking. In general, fluid volume losses during 3 or 5 min walks and losses over the course of the 30 min test session were less for elevated vacuum than for suction. Numerous variables, including the time of day that data were collected, soft tissue consistency, socket-to-limb size and shape differences, and subject health, may have affected the results and had an equivalent or greater effect on limb fluid volume compared with elevated vacuum. Researchers should well consider these variables in the study design of future investigations on the effects of elevated vacuum on residual limb volume.

Figures

FIGURE 1. Electrodes positioned on a subject’s residual limb

Outer electrodes 1 and 4 were current-injecting while inner electrodes 2 and 3 were voltage-sensing. Wires to the electrodes were strain-relieved using Tegaderm.

FIGURE 2. Results from Case #1

The gray line is the original data, and the black line is the 10-point moving mean. 0% represents the baseline at the outset of the session 2 min after sitting quietly with the prosthesis donned. This long term elevated vacuum user showed an increase in limb fluid volume over the session.

FIGURE 3. Switching from suction to elevated vacuum (Harmony)

Results from Case #2 for part of the trial are shown. The vacuum was switched from suction to elevated vacuum at approximately 550s.

FIGURE 4. Results for electronic elevated vacuum users – Cases #5 and #6

Limb fluid volumes at the end of the walks are shown. The numbers immediately above the data lines are the vacuum pressure settings. Limb fluid volume changes are relative to the fluid volume after the first walk at the 1-setting.