During test sessions of resting, standing and walking activities, standing induced the highest residual limb fluid volume loss in transtibial amputees, according to study results.
“We were trying to figure out during what postures and activities people lost the most fluid volume and to compare the volume changes during different postures and activities,” Joan E. Sanders, PhD, professor of the department of bioengineering at the University of Washington, told O&P Business News. “We thought that was important because if we could identify postures and activities that reduced volume loss or maybe even induced volume gain then that would be important information to patients and practitioners to help advise their patients on when their volume was expected to change and what they could do to help reduce volume loss.”
Fluid volume changes
Sanders and colleagues measured residual limb extracellular fluid volume using a modified commercial bioimpedance analyzer in 24 transtibial amputees who wore a prosthetic limb at least 5 hours a day. Participants had to be capable of 90 seconds of continuous treadmill walking at a self-selected walking speed and 90 seconds of continuous standing.
According to study results, all participants lost fluid volume during standing with equal weight-bearing, whereas 16 participants gained limb fluid volume during walking and 15 gained fluid volume during rest. Researchers found a strong correlation between walk and rest fluid volume changes.
“While participants were sitting down, resting, some of them gained fluid volume and some lost,” Sanders said. “We were surprised because we thought resting would be a time of recovery, fluid would go back in and that didn’t happen. So that got us thinking maybe rest is causing more trouble than it is facilitating recovery.”
The researchers analyzed whether participants with common transition, sit, walk fluid volume change patterns had common characteristics, and found participants with peripheral artery disease (PAD) experienced a relatively high fluid volume gain during sitting. Although minimal changes or losses were seen during sit-to-stand and stand-to-sit transitioning in participants with PAD, healthy female participants experienced high fluid volume changes during sit-to-stand and stand-to-sit transitioning, according to study results.
“We found participants had different times they lost fluid volume while they were resting. Some participants changed volume quite a bit when they went from standing to sitting or sitting to standing and some just changed while they were sitting down,” Sanders said. “That led us to categorize participants differently according to their volume profile. Participants fells into four groups and we thought maybe that means the treatment they should get should be different depending on what category they are in. For example, some groups may be better with vacuum assists, some may be better with doffing their prosthesis periodically throughout the day, but that was just at the end point, so it sets the stage for the next step.”
Sanders and colleagues are in the process of testing and evaluating a portable version of their device. When complete, the device will be used to monitor fluid volume changes and activity in individuals for several days at a time to see if the results are similar to those found in this study.
“We are not really sure what we are going to get, which is kind of exciting. Are people going to show the same results when they sit down? Are they going to gain a lot of fluid?” Sanders said. “I think it is an exciting time for prosthetics. I hope clinicians see this emerging area and I hope they participate a lot. Linking clinical insight to the data is the key to everything.”
According to Sanders, research on fluid volume can lead to the development of technologies that may help adjust the prosthesis when fluid volume changes.
“I think the potential to put instruments into a prosthesis and measure features related to fluid volume is very strong. The computer microelectronic industries are just zooming in terms of sensors and the prosthesis is such a good platform for measurement,” Sanders said. “I think where we are going to end up is with technologies that use that information clinically to adjust the prosthesis. What is missing in that arena is the knowledge and the insight on how to use the data effectively to manage fluid volume or to make decisions about componentry or to adjust the prosthesis or make a new socket. All of those things are unknown at this point.” — by Casey Tingle
Disclosure: Sanders has no relevant financial disclosures.