physiology of volume fluctuations
Donnie Priest
Description
Collection
Title:
physiology of volume fluctuations
Creator:
Donnie Priest
Date:
10/31/2002
Text:
Dear list,
In reply to the questions about the mechanisms of volume fluctuation in
amputees (and in reference to the VASS system), I would like to state my
opinions as to the main causes of volume fluctuation. I have broken it down
into post surgery, physiological mechanisms, and relationship to overall
body weight.
The amputee just after surgery has considerable adema due to the trauma
and healing caused by the surgery. The body realizes that there are cut
tissues that are healing and increases bloodflow to the areas by increasing
arteriole diameter. This is also combined with non-atrophied muscles since
they were used prior to amputation. The cut muscles will atrophy more than
non-cut muscles, and thus the fit will become asymetrical. (When shrinkage
occurs at this stage, the volume change here is due to a decrease is muscle
tissue as well as a decrease in water concentration).
The second stage is due to physiology and capillary pressure. The
prosthetic socket creates an external pressure on the limb. However, the
blood pressure inside the capillaries remains constant. Thus, less fluids
are able to pass from the capillaries into the cells and more fluids and
wastes leave the cells than enter. This creates shrinkage of volume. This
concept applies to anytime an increased pressure is added. Thus, a new
socket or changing from a sock fit to a gel liner and pin will cause
shrinkage...no matter how long since amputation or if the amputee states he
or she will not shrink.
The third stage is in relationship to the persons body weight. This is a
little more complicated to describe since many mechnaisms are in play. It
can be generalized by stating that if the amputee gains weight, the volume
size of the residual limb increases. The converse is true also.
For volume fluctuations throughout the day, I would state that in my
experience, this is related to all of the above in combination with activity
level. When an amputee walks, some muscles contract inside the socket.
This creates increased venus return, which causes shrinkage.
Hope this helps to understand why atrophy is occuring. Remember that
atrophy is a loss of volume and not just a loss of muscle tissue from non
use. Most of the atrophy in amputees is solely a water loss.
Sincerely,
Donnie Priest
_________________________________________________________________
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In reply to the questions about the mechanisms of volume fluctuation in
amputees (and in reference to the VASS system), I would like to state my
opinions as to the main causes of volume fluctuation. I have broken it down
into post surgery, physiological mechanisms, and relationship to overall
body weight.
The amputee just after surgery has considerable adema due to the trauma
and healing caused by the surgery. The body realizes that there are cut
tissues that are healing and increases bloodflow to the areas by increasing
arteriole diameter. This is also combined with non-atrophied muscles since
they were used prior to amputation. The cut muscles will atrophy more than
non-cut muscles, and thus the fit will become asymetrical. (When shrinkage
occurs at this stage, the volume change here is due to a decrease is muscle
tissue as well as a decrease in water concentration).
The second stage is due to physiology and capillary pressure. The
prosthetic socket creates an external pressure on the limb. However, the
blood pressure inside the capillaries remains constant. Thus, less fluids
are able to pass from the capillaries into the cells and more fluids and
wastes leave the cells than enter. This creates shrinkage of volume. This
concept applies to anytime an increased pressure is added. Thus, a new
socket or changing from a sock fit to a gel liner and pin will cause
shrinkage...no matter how long since amputation or if the amputee states he
or she will not shrink.
The third stage is in relationship to the persons body weight. This is a
little more complicated to describe since many mechnaisms are in play. It
can be generalized by stating that if the amputee gains weight, the volume
size of the residual limb increases. The converse is true also.
For volume fluctuations throughout the day, I would state that in my
experience, this is related to all of the above in combination with activity
level. When an amputee walks, some muscles contract inside the socket.
This creates increased venus return, which causes shrinkage.
Hope this helps to understand why atrophy is occuring. Remember that
atrophy is a loss of volume and not just a loss of muscle tissue from non
use. Most of the atrophy in amputees is solely a water loss.
Sincerely,
Donnie Priest
_________________________________________________________________
Get a speedy connection with MSN Broadband. Join now!
<URL Redacted>
Citation
Donnie Priest, “physiology of volume fluctuations,” Digital Resource Foundation for Orthotics and Prosthetics, accessed November 28, 2024, https://library.drfop.org/items/show/219864.
