Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
CA 02620288 2008-02-01
Mitigation of Pressure Ulcers Using Electrical Stimulation
FIELD OF THE INVENTION
[0001] This invention relates to the mitigation treatment of pressure ulcers
and, in
particular, the mitigation of treatment of pressure ulcers through electrical
stimulation.
BACKGROUND OF THE INVENTION
[0002] Pressure ulcers are typically associated with individuals of
compromised
mobility, namely the infirm, the elderly, and people with spinal cord injury
(see
references 10, 12, 31, 49, 60, 61). A pressure ulcer is any lesion caused by
unrelieved
pressure resulting in damage of underlying tissue (see reference 1), involving
any one of,
or any combination of, skin, fat, fascia, muscle, or bone. Pressure ulcers
develop
following a prolonged period of compression of the tissue between a bony
prominence
and a surface (see references 13, 24, 48, 53, 60) which causes the occlusion
of capillaries
and leads to ischemia. Ischemia, therefore, has historically been considered a
major
factor leading to pressure ulcer formation (see references 27-29).
Paradoxically, the
restoration of blood flow, vital to preserving tissue viability, has also been
identified to
cause extended damage of the tissue (see references 20, 23, 41, 55). In
instances where
the ischemic state has been maintained for extended periods, the influx of
oxygen-rich
blood causes the activation of free radicals, further damaging the cells in
the tissue (see
references 20, 23, 41, 55). In addition to the injury caused by biochemical
changes
occurring during tissue ischemia and ensuing reperfusion, high stress levels
at the bone-
muscle interface and the duration of their application, have also been
reported as direct
causes of tissue injury (see references 7, 8, 11, 35-37). Furthermore, injury
to the muscle
results in the formation of scar tissue; thus, creating more foci for
increased stress, and
leading to injury of adjacent previously healthy tissue (see references 18,
36). It is the
combined effects of these processes that cause the edema, inflammation and
necrosis that
ultimately lead to formation of a pressure ulcer (see references 14, 19, 20,
47, 56, 57).
[0003] Pressure ulcers can be initiated at the dermis, usually in the presence
of
excessive friction and/or compromised dermal integrity and progress towards
the deeper
1
CA 02620288 2008-02-01
layers of tissue. Muscle is considered to be more susceptible to tissue
degradation from
mechanical loading and oxygen deprivation (see references 7, 31) than dermis,
consequently injury can also be induced in the deep tissue and progress
outwards (see
reference 11), evolving into a severe full-thickness pressure ulcer. This type
of pressure-
related injury to the deep tissue under intact skin has been defined by the
National
Pressure Ulcer Advisory Panel as deep tissue injury (DTI) (see references 2,
3). Deep
tissue injury can be extremely perilous, as it can evolve undetected until a
significant
destruction of the tissue has occurred. Presently, pressure ulcers are
detected by visual
inspection of the skin (see reference 45), which often belies existing
extensive damage to
deeper tissue (see reference 11).
[0004] At the present time, techniques employed to prevent ulcer formation
include frequent repositioning (see reference 12) as well as the use of
specialized
cushions and mattresses that provide either static or dynamic pressure relief
of the tissues
at risk (see reference 22, 46). Recognizing the absence of a significant
reduction in the
incidence of pressure ulcers (see references 10, 15, 16, 30, 42, 49, 50, 54),
new
preventative interventions are needed, especially for DTI.
SUMMARY OF THE INVENTION
[0005] In one aspect, there is provided a method for mitigating or preventing
formation of pressure ulcers in a patient by transmitting an electrical
stimulus to a skin
portion of a patient sufficient to effect contraction of a muscle, wherein the
method
includes a first mode of operation and a second mode of operation, comprising:
over a
period of at least about one hour, continuously switching between the first
mode of
operation and the second mode of operation, wherein, for each instance of the
first mode
of operation, the first mode of operation lasts a respective predetermined
stimulus time
duration, and a respective operative electrical stimulus, sufficient to effect
contraction of
a muscle, is transmitted to the skin portion, thereby effecting contraction of
the muscle,
during the entire, or substantially the entire, respective predetermined
stimulus time
duration. and wherein, for each instance of the second mode of operation, the
second
mode of operation lasts a respective predetermined relaxation time duration,
and the
2
CA 02620288 2008-02-01
muscle is relaxed during the entire, or substantially the entire, respective
predetermined
relaxation time duration.
[0006] In another aspect, there is provided a method for mitigating or
preventing
formation of pressure ulcers in a patient, comprising over a period of at
least about one
hour, transmitting a plurality of intermittent transmissions of an electrical
stimulus, each
one of the plurality of intermittent transmissions sufficient to effect
contraction of a
muscle, to a skin portion of the patient, thereby effecting contraction of the
muscle
wherein a respective time interval is provided between each pair of successive
intermittent transmissions of the plurality of intermittent transmissions,
such that there is
a plurality of respective time intervals, and wherein the muscle is relaxed
during the
entirety, or the substantial entirety, of each one of the plurality of
respective time
intervals.
[0007] In another aspect, there is provided use of a plurality of intermittent
transmissions of an operative electrical stimulus, sufficient to effect
contraction of a
muscle, to a skin portion of a patient, thereby effecting contraction of the
muscle, for
mitigating or preventing formation of pressure ulcers in the patient, wherein
the plurality
of intermittent transmissions is transmitted over a period of at least about
one hour, and
wherein a respective time interval is provided between each pair of successive
intermittent transmissions of the plurality of intermittent transmissions,
such that there is
a plurality of respective time intervals, and wherein the muscle is relaxed
during the
entirety, or the substantial entirety, of each one of the plurality of
respective time
intervals.
[0008] In another aspect, there is provided a method for mitigating or
preventing
formation of pressure ulcers in a patient by transmitting an electrical
stimulus to a skin
portion of a patient sufficient to effect contraction of a muscle, wherein the
method
includes a first mode of operation and a second mode of operation, comprising
continuously switching between the first mode of operation and the second mode
of
operation, wherein for each instance of the first mode of operation, the first
mode of
operation lasts a respective predetermined stimulus time duration, and a
respective
3
CA 02620288 2008-02-01
operative electrical stimulus, sufficient to effect contraction of a muscle,
is transmitted to
the skin portion, thereby effecting contraction of the muscle, during the
entire, or
substantially the entire, respective predetermined stimulus time duration and
wherein, for
each instance of the second mode of operation, the second mode of operation
lasts a
respective predetermined relaxation time duration, and the muscle is relaxed
during the
entire, or substantially the entire, respective predetermined relaxation time
duration, and
wherein the respective predetermined relaxation time duration of each instance
of the
second mode of operation is at least five (5) minutes.
[0009] In another aspect, there is provided a method for mitigating or
preventing
formation of pressure ulcers in a patient, comprising transmitting a plurality
of
intermittent transmissions of an electrical stimulus, each one of the
plurality of
intermittent transmissions sufficient to effect contraction of a muscle, to a
skin portion of
a patient, thereby effecting contraction of the muscle, wherein a respective
time interval
is provided between each pair of successive intermittent transmissions of the
plurality of
intermittent transmissions, such that there is a plurality of respective time
intervals, and
wherein the muscle is relaxed during the entirety, or the substantial
entirety, of each one
of the plurality of respective time intervals, and wherein each one of the
plurality of
respective time intervals is at least five (5) minutes.
[0010] In another aspect, there is provided use of a plurality of intermittent
transmissions of an operative electrical stimulus, sufficient to effect
contraction of a
muscle, to a skin portion of a patient, thereby effecting contraction of the
muscle, for
mitigating or preventing formation of pressure ulcers in the patient, wherein
a respective
time interval is provided between each pair of successive intermittent
transmissions of the
plurality of intermittent transmissions, such that there is a plurality of
respective time
intervals, and wherein the muscle is relaxed during the entirety, or the
substantial
entirety, of each one of the plurality of respective time intervals, and
wherein each one of
the plurality of respective time intervals is at least five (5) minutes.
[0011] In another aspect, there is provided a method for mitigating or
preventing
formation of pressure ulcers in a patient by transmitting an electrical
stimulus to a skin
4
CA 02620288 2008-02-01
portion of a patient sufficient to effect contraction of a muscle, wherein the
method
includes a first mode of operation and a second mode of operation, comprising
over a
period of at least about one hour, continuously switching between the first
mode of
operation and the second mode of operation, wherein, for each instance of the
first mode
of operation, the first mode of operation lasts a respective predetermined
stimulus time
duration, and a respective operative electrical stimulus, sufficient to effect
contraction of
a muscle, is transmitted to a skin portion by an electrode, in contact with
the skin portion,
thereby effecting contraction of the muscle, during the entire, or
substantially the entire,
respective predetermined stimulus time duration, and wherein, for each
instance of the
second mode of operation, the second mode of operation lasts a respective
predetermined
relaxation time duration, and no electrical stimulus, or substantially no
electrical
stimulus, is transmitted to the skin portion by the electrode during the
entire, or
substantially the entire, respective predetermined relaxation time duration.
[0012] In another aspect, there is provided a method for mitigating or
preventing
formation of pressure ulcers in a patient, comprising over a period of at
least about one
hour, and by way of an electrode in contact with a skin portion of the
patient, transmitting
a plurality of intermittent transmissions of an electrical stimulus, each one
of the plurality
of intermittent transmissions sufficient to effect contraction of a muscle, to
the skin
portion of the patient, thereby effecting contraction of the muscle, wherein a
respective
time interval is provided between each pair of successive intermittent
transmissions of the
plurality of intermittent transmissions, such that there is a plurality of
respective time
intervals, and wherein no electrical stimulus, or substantially no electrical
stimulus, is
transmitted to the skin portion by the electrode during the entirety, or the
substantial
entirety, of each one of the plurality of respective time intervals.
[0013] In another aspect, there is provided use of a plurality of intermittent
transmissions of an operative electrical stimulus, sufficient to effect
contraction of a
muscle, to a skin portion of a patient, thereby effecting contraction of the
muscle, for
mitigating or preventing formation of pressure ulcers in the patient, wherein
the plurality
of intermittent transmissions is transmitted over a period of at least about
one hour by an
electrode in contact with the skin portion, and wherein a respective time
interval is
CA 02620288 2008-02-01
provided between each pair of successive intermittent transmissions of the
plurality of
intermittent transmissions, such that there is a plurality of respective time
intervals, and
wherein no electrical stimulus, or substantially no electrical stimulus, is
transmitted to the
skin portion by the electrode during the entirety, or the substantial
entirety, of each one of
the plurality of respective time intervals.
[0014] In another aspect, there is provided a method for mitigating or
preventing
formation of pressure ulcers in a patient by transmitting an electrical
stimulus to a skin
portion of a patient sufficient to effect contraction of a muscle, wherein the
method
includes a first mode of operation and a second mode of operation, comprising
continuously switching between the first mode of operation and the second mode
of
operation, wherein, for each instance of the first mode of operation, the
first mode of
operation lasts a respective predetermined stimulus time duration, and a
respective
operative electrical stimulus, sufficient to effect contraction of a muscle,
is transmitted to
the skin portion by an electrode, in contact with the skin portion, thereby
effecting
contraction of the muscle, during the entire, or substantially the entire,
respective
predetermined stimulus time duration, and wherein, for each instance of the
second mode
of operation, the second mode of operation lasts a respective predetermined
relaxation
time duration, and the muscle is relaxed during the entire, or substantially
the entire,
respective predetermined relaxation time duration, and wherein the respective
predetermined relaxation time duration of each instance of the second mode of
operation
is at least five (5) minutes.
[0015] In another aspect, there is provided a method for mitigating or
preventing
formation of pressure ulcers in a patient, comprising transmitting a plurality
of
intermittent transmissions of an electrical stimulus with an electrode in
contact with a
skin portion of the patient, each one of the plurality of intermittent
transmissions
sufficient to effect contraction of a muscle, to the skin portion, thereby
effecting
contraction of the muscle, wherein a respective time interval is provided
between each
pair of successive intermittent transmissions of the plurality of intermittent
transmissions,
such that there is a plurality of respective time intervals, and wherein no
electrical
stimulus, or substantially no electrical stimulus, is transmitted to the skin
portion by the
6
CA 02620288 2008-02-01
electrode during the entirety, or the substantial entirety, of each one of the
plurality of
respective time intervals, and wherein each one of the plurality of respective
time
intervals is at least five (5) minutes.
[0016] In another aspect, there is provided use of a plurality of intermittent
transmissions of an operative electrical stimulus, sufficient to effect
contraction of a
muscle, to a skin portion of a patient, thereby effecting contraction of the
muscle, for
mitigating or preventing formation of pressure ulcers in the patient, wherein
the plurality
of intermittent transmissions is transmitted by an electrode in contact with
the skin
portion, and wherein a respective time interval is provided between each pair
of
successive intermittent transmissions of the plurality of intermittent
transmissions, such
that there is a plurality of respective time intervals, and wherein no
electrical stimulus, or
substantially no electrical stimulus, is transmitted to the skin portion by
the electrode
during the entirety, or the substantial entirety, of each one of the plurality
of respective
time intervals, and wherein each one of the plurality of respective time
intervals is at least
five (5) minutes.
[0017] In another aspect, there is provided a method for mitigating or
preventing
formation of pressure ulcers in a patient comprising effecting a treatment,
wherein the
treatment is intermittently transmitting an electrical stimulus to a skin
portion of a patient
sufficient to effect contraction of a muscle, and thereby effecting
contraction of the
muscle, wherein the muscle being contracted is not pre-conditioned immediately
prior to
the treatment
[0018] In another aspect, there is provided use of an intermittent electrical
stimulus being transmitted to a skin portion of a patient and sufficient to
effect
contraction of a muscle, and thereby effecting contraction of the muscle to
effect a
treatment for mitigating or preventing formation of pressure ulcers in the
patient, wherein
the muscle being contracted is not pre-conditioned immediately prior to the
treatment.
[0019] In another aspect, there is provided a method for mitigating or
preventing
formation of pressure ulcers in a patient comprising intermittently
transmitting an
electrical stimulus to a skin portion of a patient sufficient to effect
contraction of a
7
CA 02620288 2008-02-01
muscle, and thereby effecting contraction of the muscle, wherein the
electrical stimulus
being transmitted is insufficient to effect lifting of the patient or movement
of the limbs.
[0020] In another aspect, there is provided use of an intermittent electrical
stimulus being transmitted to a skin portion of a patient and sufficient to
effect
contraction of a muscle, and thereby effecting contraction of the muscle in
order to
mitigate or prevent formation of pressure ulcers in the patient, wherein the
electrical
stimulus being transmitted is insufficient to effect lifting of the patient or
movement of
the limbs.
[0021] In another aspect, there is provided, a method for mitigating or
preventing
formation of pressure ulcers in a patient comprising intermittently
transmitting an
electrical stimulus to a skin portion of a patient sufficient to effect
contraction of a
muscle, and thereby effecting contraction of the muscle, wherein the patient
is disposed
in a supine position or in a recumbence position when the skin portion is
receiving the
electrical stimulus.
[0022] In another aspect, there is provided Use of an electrical stimulus
being
transmitted to a skin portion of a patient sufficient to effect contraction of
a muscle, and
thereby effecting contraction of the muscle in order to mitigate or prevent
formation of
pressure ulcers in the patient, wherein the patient is disposed in a supine
position or in a
recumbence position when the skin portion is receiving the electrical
stimulus.
BRIEF DESCRIPTION OF DRAWINGS
[0023] The invention will better be understood when consideration is given to
the
following detailed description thereof. Such description makes reference to
the annexed
drawings wherein:
[0024] Figure 1 is a top schematic view of the experimental set-up using a rat
as
the experimental subject, illustrating how constant pressure was applied to
the quadriceps
muscle of the right hind limb of a rat;
8
CA 02620288 2008-02-01
[0025] Figure lb is a graph illustrating a 50-minute record of the force
applied to
the quadriceps muscle of a rat; the sharp increases in force corresponding to
the
contraction of muscle due to intermittent electrical stimulation (IES);
[0026] Figures 1 c and 1 d are top and side views of experimental set up for
the rat
experiments, illustrating the locations of the electrode and leads for
electrical stimulation
(input) and the force transducer for measuring the force (output) generated by
the
contraction of the muscles are demonstrated, and also is shown the indenter
that was used
to apply external force to the body in order to load the muscle and
surrounding tissue to
levels that mimic the loading levels experienced by individuals sitting in a
wheelchair or
lying down in a bed;
[0027] Figure 1 e illustrates the force generated by contraction of muscle in
response to the intermittent electrical stimulation treatment applied to
quadriceps muscles
in the rats during two hours of treatment having relaxation periods of: (i) 5
minutes, and
(ii) 10 minutes;
[0028] Figure 2 is magnetic resonance imaging scans of one animal,
illustrating
sequential T2-weighted spin echo magnetic resonance images (MRI's) of a rat's
thigh
ranging from the rostral extent of the quadriceps muscle (a) to its caudal end
(j), obtained
24 hours after the application of external pressure, with approximate
placement of
indenter indicated in slice (f).
[0029] Figure 3a is a T2-weighted spin-echo magnetic resonance image of rat
hind limbs 24 hours after the application of pressure; Figure 3b are magnetic
resonance
images of the quadriceps muscle. Figure 3c are magnetic resonance images of
the
quadriceps muscle in both hind limbs, the signal intensity of pixels within
the region of
the left and right quadriceps muscles; was obtained, and the signal intensity
from pixels
in the experimental limb was compared to the average + 2*standard deviation
intensity of
those in the contralateral limb, pixels with higher intensity in the
experimental limb were
marked with red and considered to contain increased water content, pixels with
higher
intensity than threshold in the contralateral limb were marked with blue as a
control; Cnt
9
CA 02620288 2008-02-01
Grp = control group; Exp Grp 1-3 = experimental groups 1-3; Contra Cnt Grp =
contralateral control group;
[0030] Figure 4 are images of sample hematoxylin and eosin-stained cross
sections from different animals in each group; Cnt Grp = control group; Exp
Grp 1-3 =
experimental groups 1-3;
[0031] Figure 5 is summary of magnetic resonance imaging and histology
results;
Left Axis: individual data points (filled circles) and mean SD (filled
triangles)
representing the percent of muscle volume with increased water content (edema)
in the
quadriceps muscle in all rat groups; right axis: Individual data points (empty
circles) and
mean SD (empty triangles) representing the necrosis score from the
quadriceps muscle
in all rat groups, and scoring for quantifying muscle necrosis (per 4.9 mm2 of
muscle
area) is: 0 = no necrosis in region analyzed; 1= 0-10% of region analyzed
exhibited
necrosis; 2 = 10-25%; 3 = 25-50%; 4> 50%. (*represents statistically
significant
difference, PCT.05);
[0032] Figure 6 illustrates changes in levels of oxygenation and surface
pressure
due to loading and IES (a) quantitative T2* imaging following 6, 30-sec bouts
of
electrical stimulation applied to medial gastrocnemius, persistent regional
increases in
blood oxygenation were seen with IES; (b) quantitative T2* imaging of the
gluteus
maximus muscles under different conditions, a persistent decrease in blood
oxygenation
was seen when the muscles were loaded, a persistent increase was obtained with
IES; (c)
surface-skin interface pressure map of the gluteus muscles under different
conditions, and
highest point of pressure with loading was observed around the sacrum
(arrows); with
IES, pressure became more evenly distributed, eliminating the previous
concentrations of
high pressure; ROI 1-4 = region of interest 1-4; pre-stim = before electrical
stimulation;
post 1-6 = after 1-6 bouts of electrical stimulation;
[0033] Figure 7 illustrates the experimental set-up for human volunteers;
[0034] Figure 8 shows an MRI of the left and right gluteus muscles
demonstrating
the changes in muscle shape during contractions induced by electrical
stimulation (top)
CA 02620288 2008-02-01
and also shows the redistribution of surface pressure (middle) and the
increase in tissue
oxygenation (bottom) during electrical stimulation;
[0035] Figure 9 shows the locations of the electrodes for delivering the
intermittent electrical stimulation treatment in the various positions in
which a patient
would be disposed;
[0036] Figure 10 is a schematic illustration of a system for effecting the
mitigation or prevention of formation of pressure ulcers by transmitting an
electrical
stimulus to the skin of a human patient, and;
[0037] Figures 11 and 11 a, b, c, and d illustrate examples of intermittent
electrical
stimulation pattern.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0038] Unless otherwise indicated, all numbers expressing quantities of
ingredients, properties such as distance, operating conditions, and so forth
used in the
specification and claims are to be understood as being modified in all
instances by the
term "about." Accordingly, unless indicated to the contrary, the numerical
parameters set
forth in the following specification and attached claims are approximations
that may vary
depending upon the desired properties sought to be obtained by the present
invention. At
the very least, and not as an attempt to limit the application of the doctrine
of equivalents
to the scope of the claims, each numerical parameter should at least be
construed in light
of the number of reported significant digits and by applying ordinary rounding
techniques.
[0039] Notwithstanding that the numerical ranges and parameters setting forth
the
broad scope of the invention are approximations, the numerical values set
forth in the
specific examples are reported as precisely as possible. Any numerical value,
however,
inherently contain errors necessarily resulting from the standard deviation
found in their
respective testing measurements.
11
CA 02620288 2008-02-01
[0040] There is provided a method for mitigating or preventing formation of
pressure ulcers in a patient by transmitting an electrical stimulus to a skin
portion of a
patient sufficient to effect contraction of a muscle. There is also provided a
use of an
electrical stimulation of a skin portion of a patient sufficient to effect
contraction of a
muscle of a patient for mitigating or preventing formation of pressure ulcers
in the
patient. An example of a system for effecting this use or method is
illustrated in Figure
10. The system includes a stimulator 12 which is electrically coupled to each
of an anode
14 and a cathode 16 with a respective one of the leads 18, 20. Each one of the
anode 14
and the cathode 16 is in contact with a skin portion of the patient. For
example, each one
of the anode 14 and the cathode 16 may be embedded in clothing worn by the
patient.
For example, skin burns may be mitigated by measuring the impedance of the
electrode-
tissue interface and limiting the amount of voltage that can be applied by the
stimulator
across the interface. For example, the stimulator is battery operated.
[0041] As mentioned above, a pressure ulcer is any lesion caused by unrelieved
pressure resulting in damage of underlying tissue, involving any one of or any
combination of skin, fat, fascia, muscle, or bone, and a pressure ulcer
develops following
a prolonged period of compression of the tissue between a bony prominence and
a
surface.
[0042] For example, the pressure ulcer is a deep tissue injury, as explained
above.
[0043] For example, with respect to the transmission of the electrical
stimulus, the
electrode stimulus is transmitted to the skin portion by an electrode in
contact with the
skin portion. For example, the electrical stimulus is an electrical signal.
For example, the
electrical signal is a discrete signal (eg. pulsatile waveform), a continuous
signal (eg.
sustained sinusoidal waveform, rectangular waveform), or a combination of a
discrete
signal and a continuous signal. For example, with respect to the electrical
signal, the
electrical signal includes a characteristic frequency of 20 Hz to 60 Hz. For
example the
electrical signal includes a characteristic frequency of 40 Hz.
[0044] Figures 11 a, b, c, d illustrate examples of intermittent electrical
stimulation patterns. Figure 11 a illustrates a basic intermittent electrical
stimulation
12
CA 02620288 2008-02-01
pattern. Figure 1 lb illustrates an example of intermittent electrical
stimulation pattern for
bilateral stimulation. Bilateral stimulation refers to the application of the
basic
intermittent electrical stimulation pattern, which includes an ON mode (also
described
below as a "first mode of operation") and an OFF mode (also described below as
a
"second mode of operation"), to the muscles on both sides of the body (eg.
left and right
gluteus maximus muscles). The ON mode of pattern to the muscles on both sides
of the
the body can occur simultaneously (i.e. stimulation of the muscles take place
at the same
time). Or, the ON mode of stimulation to the muscles on both sides of the body
can be
staggered. For example, the ON mode to one side can occur at the end of the ON
mode to
the other side, or up to 15 minutes from the end of the ON mode to the other
side. Figure
11 c illustrates continuous (or "sustained") and pulsatile applications during
the ON mode
of the pattern. Figure l 1 d illustrates the general waveforms of each
stimulus pulse.
[0045] For example, with respect to the skin portion, the skin portion is a
skin
portion underneath which lies the nerve controlling the contractions of a
muscle, and
which is supported by a support surface. For example, the skin portion, to
which the
electrical signal is transmitted, is a skin portion proximate to the tissue
for which the
pressure ulcer is intended to be mitigated. For example, the force exerted by
the support
surface, as the support surface is supporting the skin portion, effects
compression of
tissue disposed between the skin portion and a bony prominence. For example,
the skin
portion is provided on the buttocks of the patient. In this respect, for
example, the
support surface is a seating surface.
[0046] For example, with respect to the effect of the transmission of the
electrical
signal to the skin portion, the electrical stimulation effects contraction of
the muscle,
thereby reshaping the form of the muscle and redistributing pressure away from
the tissue
for which the pressure ulcer is intended to be mitigated, and also increasing
oxygenation
of tissue which may have suffered from ischemia.
[0047] In one aspect, there is provided a method for mitigating or preventing
formation of pressure ulcers in a patient comprising effecting a treatment,
wherein the
treatment is intermittently transmitting an electrical stimulus to a skin
portion of a patient
13
CA 02620288 2008-02-01
sufficient to effect contraction of a muscle, and thereby effecting
contraction of the
muscle, wherein the muscle being contracted is not pre-conditioned immediately
prior to
the treatment. In a related aspect, there is provided a use of an intermittent
electrical
stimulus being transmitted to a skin portion of a patient and sufficient to
effect
contraction of a muscle, and thereby effecting contraction of the muscle and
effecting a
treatment for mitigating or preventing formation of pressure ulcers in the
patient, wherein
the muscle being contracted is not pre-conditioned immediately prior to the
treatment.
Pre-conditioning of the muscles means applying electrical stimulation to the
muscle for a
period of time (for example, several hours) each day, for a number of days
immediately
prior to the treatment (for example, several months, and usually at least
three months).
During the initial phases of the pre-conditioning period, stimulation is
applied for a
minimum of one (1) hour per day. This period is increased to several hours,
with some
people having the stimulation applied for 12 hours or more. The purpose of the
pre-
conditioning is for the purpose of increasing muscle mass and improving muscle
endurance (fatigue resistance). For example, in the 60 day period immediately
prior to
the treatment, the mass of the muscle intended to be contracted during the
treatment does
not significantly increase. In this respect, for example, during the 60 day
period
immediately prior to the treatment, the mass of the muscle intended to be
contracted
during the treatment increases less than 5%. As a further example, during the
60 day
period immediately prior to the treatment, the endurance of the muscle
intended to be
contracted during the treatment does not significantly increase. In this
respect, for
example, during the 60 day period immediately prior to the treatment, the
endurance of
the muscle intended to be contract increases less than 5%. In this context,
changes in
endurance are measured in accordance with the endurance (fatigue) test
provided in R.B.
Stein, T. Gordon, J. Jefferson, A. Sharfenberger, J.F. Yang, J.T. de Zepetnek,
and M.
Belanger (1992), "Optimal stimulation of paralyzed muscle after human spinal
cord
injury". Journal of Applied Physiology 72(4):1393-400, which is incorporated
in its
entirety herein by reference, and more particularly, is provided in the last
paragraph on
page 1394 of that article, at the passage beginning with: "Fatigue was
measured by...".
[0048] In another aspect, there is provided a method for mitigating or
preventing
formation of pressure ulcers in a patient comprising intermittently
transmitting an
14
CA 02620288 2008-02-01
electrical stimulus to a skin portion of a patient sufficient to effect
contraction of a
muscle, and thereby effecting contraction of the muscle, wherein the
electrical stimulus
being transmitted is insufficient to effect lifting of the patient or movement
of the limbs.
In this respect, the electrical stimulus being transmitted is configured to
effect minimal
joint movement. In a related aspect, there is provided a use of an
intermittent electrical
stimulus being transmitted to a skin portion of a patient and sufficient to
effect
contraction of a muscle, and thereby effecting contraction of the muscle in
order to
mitigate or prevent formation of pressure ulcers in the patient, wherein the
electrical
stimulus being transmitted is insufficient to effect lifting of the patient or
movement of
the limbs. For example, with respect to the lifting, the lifting is of at
least a portion of the
patient's body relative to a support surface supporting the patient (eg. the
buttocks region
lifting above the wheelchair seat). For example, the electrical stimulus being
transmitted
effects isometric contraction of the muscle. For example, the electrical
stimulus effects a
change in the angle between two bones defining each and every joint of the
patient by
less than 10 degrees (ie. upon application of the electrical stimulus, none of
the joints of
the patient change by 10 degrees or more). For example, when the patient is in
the sitting
position, stimulation of the gluteus maximus would cause an isometric
contraction of the
muscle with less than 10 degrees change in the hip joint angle. For example,
when the
patient is in the supine position, stimulation of the gluteus maximus would
cause an
isometric contraction of the muscles with less than 10 degrees change in the
hip joint
angle and lumbar spine. As a further example of when the patient is in the
supine
position, stimulation of trapezius would cause an isomeric contraction of the
muscle with
less than 10 degrees change in the shoulder joint angle. As a further example
of when the
patient is in the supine position, stimulation of the muscles of the back of
the head would
cause an isometric contraction of the muscles with less than 10 degrees change
in the
angle of the neck relative to the head. For example, when the patient is in
the lateral
recumbence position, stimulation of the deltoid would cause an isometric
contraction of
the muscle with less than 10 degrees change in the shoulder angle. As a
further example
of when the patient is in the lateral recumbence position, stimulation of the
gluteus
medius muscle would cause an isometric contraction of the muscle with less
than 10
degrees change in the hip angles. As a further example of when the patient is
in the
CA 02620288 2008-02-01
lateral recumbence position, stimulation of tensor fascia latae would cause an
isometric
contraction of the muscle with less than 10 degrees change in the hip joint
angle or knee
angle.
[0049] In another aspect, there is provided a method for mitigating or
preventing
formation of pressure ulcers in a patient comprising intermittently
transmitting an
electrical stimulus to a skin portion of a patient sufficient to effect
contraction of a
muscle, and thereby effecting contraction of the muscle, wherein the patient
is disposed
in a supine position or in a recumbence position when the skin portion is
receiving the
electrical stimulus. In a related aspect, there is provided a use of an
electrical stimulus
being transmitted to a skin portion of a patient sufficient to effect
contraction of a muscle,
and thereby effecting contraction of the muscle in order to mitigate or
prevent formation
of pressure ulcers in the patient, wherein the patient is disposed in a supine
position or in
a recumbence position when the skin portion is receiving the electrical
stimulus. For
example, when the patient is disposed in a supine position, the muscle is any
one of a
gluteus muscle, a muscle at least partially surrounding the shoulder blades of
the patient,
or a muscle disposed in proximity to the back of the head of the patent. For
example,
when the patient is disposed in a lateral recumbence position, the muscle is a
muscle of
the hip (eg, gluteus medius and tensor fascia latae muscles) or the side
muscles
surrounding the shoulder (eg, deltoid muscle).
[0050] In another aspect, there is provided a method for mitigating or
preventing
formation of pressure ulcers in a patient, including a first mode of operation
and a second
mode of operation. The method comprises, over a period of at least one hour,
continuously switching between the first mode of operation and the second mode
of
operation. For each instance of the first mode of operation, the first mode of
operation
lasts a respective predetermined stimulus time duration, and a respective
operative
electrical stimulus, sufficient to effect contraction of a muscle, is
transmitted to a skin
portion of a patient, thereby effecting contraction of the muscle, during the
entire, or
substantially the entire, respective predetermined stimulus time duration. For
each
instance of the second mode of operation, the second mode of operation lasts a
respective
predetermined relaxation time duration, and the muscle is relaxed during the
entire, or
16
CA 02620288 2008-02-01
substantially the entire, respective predetermined relaxation time duration.
The switching
from an instance of the first mode of operation to an instance of the second
mode of
operation is effected when the respective predetermined stimulus time duration
of the
respective instance of the first mode of operation is completed. As well,
switching from
an instance of the second mode of operation to an instance of the first mode
of operation
is effected when the respective predetermined relaxation time duration of the
respective
instance of the second mode of operation is completed. For example, the
respective
predetermined stimulus time duration of each instance of the first mode of
operation is at
least seven (7) seconds. As a further example, the respective predetermined
stimulus
time duration of each instance of the first mode of operation is greater than
seven (7)
seconds and less than (30) seconds. As a further example, the respective
predetermined
stimulus time duration of each instance of the first mode of operation is ten
(10) seconds.
For example, the respective predetermined relaxation time duration of each
instance of
the second mode of operation is at least five (5) minutes. As a further
example, with
respect to the respective predetermined relaxation time duration, the
respective
predetermined relaxation time duration of each instance of the second mode of
operation
is at least ten (10) minutes. As a further example, with respect to the
respective
predetermined relaxation time duration, the respective predetermined
relaxation time
duration of each instance of the second mode of operation is ten (10) minutes.
For
example, the continuous switching between the first mode of operation and the
second
mode of operation is effected over a period of at least two hours.
[0051] In a related aspect, there is provided a method of mitigating or
preventing
formation of pressure ulcers in a patient, comprising, over a period of at
least one hour,
transmitting a plurality of intermittent transmissions of an electrical
stimulus, each one of
the plurality of intermittent transmissions being sufficient to effect
contraction of a
muscle, to a skin portion of a patient, thereby effecting contraction of the
muscle. A
respective time interval is provided between each pair of successive
intermittent
transmissions of the plurality of intermittent transmissions of an electrical
stimulus, such
that there is a plurality of respective time intervals. The muscle is relaxed
during the
entirety, or the substantial entirety, of each one of the plurality of
respective time
intervals. For example, each one of the plurality of intermittent
transmissions is at least
17
CA 02620288 2008-02-01
seven (7) seconds. As a further example, each one of the plurality of
intermittent
transmissions is greater than seven (7) seconds and less than (30) seconds. As
a further
example, each one of the plurality of intermittent transmissions is ten (10)
seconds. For
example, each one of the plurality of respective time intervals is at least
five (5) minutes.
As a further example, each one of the plurality of respective time intervals
is at least ten
(10) minutes. As a further example, each one of the plurality of respective
time intervals
is ten (10) minutes. For example, the plurality of intermittent transmissions
is effected
over a period of at least two hours.
[0052] In a further related aspect, there is provided use of a plurality of
intermittent transmissions of an operative electrical stimulus, sufficient to
effect
contraction of a muscle, to a skin portion of a patient, thereby effecting
contraction of the
muscle, for mitigating or preventing formation of pressure ulcers in the
patient, wherein
the plurality of intermittent transmissions of an operative electrical
stimulus is transmitted
over a period of at least one hour. A respective time interval is provided
between each
pair of successive intermittent transmissions of the plurality of intermittent
transmissions
of an electrical stimulus, such that there is a plurality of respective time
intervals. The
muscle is relaxed during the entirety, or the substantial entirety, of each
one of the
plurality of respective time intervals. For example, each one of the plurality
of
intermittent transmissions is at least seven (7) seconds. As a further
example, each one of
the plurality of intermittent transmissions is greater than seven (7) seconds
and less than
(30) seconds. As a further example, each one of the plurality of intermittent
transmissions is ten (10) seconds. For example, each one of the plurality of
respective
time intervals is at least five (5) minutes. As a further example, each one of
the plurality
of respective time intervals is at least ten (10) minutes. As a further
example, each one of
the plurality of respective time intervals is ten (10) minutes. For example,
the plurality of
intermittent transmissions is effected over a period of at least two hours.
[0053] In another aspect, there is provided a method for mitigating or
preventing
formation of pressure ulcers in a patient, including a first mode of operation
and a second
mode of operation. The method comprises continuously switching between the
first
mode operation and the second mode of operation. For each instance of the
first mode of
18
CA 02620288 2008-02-01
operation, the first mode of operation lasts a respective predetermined
stimulus time
duration, and a respective operative electrical stimulus, sufficient to effect
contraction of
a muscle, is transmitted to a skin portion of a patient, thereby effecting
contraction of the
muscle, during the entire, or substantially the entire, respective
predetermined stimulus
time duration. For each instance of the second mode of operation, the second
mode of
operation lasts a respective predetermined relaxation time duration, and the
muscle is
relaxed during the entire, or substantially the entire, respective
predetermined relaxation
time duration. The switching from an instance of the first mode of operation
to an
instance of the second mode of operation is effected when the respective
predetermined
stimulus time duration of the respective instance of the first mode of
operation is
completed. As well, switching from an instance of the second mode of operation
to an
instance of the first mode of operation is effected when the respective
predetermined
relaxation time duration of the respective instance of the second mode of
operation is
completed. The respective predetermined relaxation time duration of each
instance of the
second mode of operation is at least five (5) minutes. For example, the
respective
predetermined relaxation time duration of each instance of the second mode of
operation
is at least ten (10) minutes. For example, the respective predetermined
relaxation time
duration of each instance of the second mode of operation is ten (10) minutes.
For
example, the respective predetermined stimulus time duration of each instance
of the first
mode of operation is at least seven (7) seconds. As a further example, the
respective
predetermined stimulus time duration of each instance of the first mode of
operation is
greater than seven (7) seconds and less than (30) seconds. As a further
example, the
respective predetermined stimulus time duration of each instance of the first
mode of
operation is ten (10) seconds.
[0054] In a related aspect, there is provided a method of mitigating or
preventing
formation of pressure ulcers in a patient, comprising transmitting a plurality
of
intermittent transmissions of an electrical stimulus, sufficient to effect
contraction of a
muscle, to a skin portion of a patient, thereby effecting contraction of the
muscle. A
respective time interval is provided between each pair of successive
intermittent
transmissions of the plurality of intermittent transmissions of an electrical
stimulus such
that there is a plurality of respective time intervals. The muscle is relaxed
during the
19
CA 02620288 2008-02-01
entirety, or the substantial entirety, of each one of the plurality of
respective time
intervals. Each one of the plurality of respective time intervals is at least
five (5)
minutes. For example, each one of the plurality of respective time intervals
is at least ten
(10) minutes. For example, each one of the plurality of respective time
intervals is ten
(10) minutes. For example, each one of the plurality of intermittent
transmissions is at
least seven (7) seconds. As a further example, each one of the plurality of
intermittent
transmissions is greater than seven (7) seconds and less than (30) seconds. As
a further
example, each one of the plurality of intermittent transmissions is ten (10)
seconds.
[0055] In a further related aspect, there is provided use of a plurality of
intermittent transmissions of an operative electrical stimulus, sufficient to
effect
contraction of a muscle, to a skin portion of a patient, thereby effecting
contraction of the
muscle, for mitigating or preventing formation of pressure ulcers in the
patient. A
respective time interval is provided between each pair of successive
intermittent
transmissions of the plurality of intermittent transmissions of an electrical
stimulus such
that there is a plurality of respective time intervals. The muscle is relaxed
during the
entirety or the substantial entirety of each one of the plurality of
respective time intervals.
Each one of the plurality of respective time intervals is at least five (5)
minutes. As a
further example, each one of the plurality of respective time intervals is at
least ten (10)
minutes. As a further example, each one of the plurality of respective time
intervals is
ten (10) minutes. For example, each one of the plurality of intermittent
transmissions is
at least seven (7) seconds. As a further example, each one of the plurality of
intermittent
transmissions is greater than seven (7) seconds and less than (30) seconds. As
a further
example, each one of the plurality of intermittent transmissions is ten (10)
seconds.
[0056] The term "relaxed", when used above to describe the muscle, mean that
the muscle is not being induced to contract by an electrical stimulus.
[0057] For example, with respect to the second mode of operation, the
respective
relaxation time duration of each instance of the second mode of operation is
provided to
provide sufficient rest for the muscle in between the transmissions of the
electrical stimuli
during successive instances of the first mode of operation. Without providing
this
CA 02620288 2008-02-01
relaxation time duration, the muscle may become fatigued much earlier during
the
method or use of the intermittent transmissions, and require an unacceptable
early
termination of the treatment or the use of the intermittent transmissions.
[0058] In another aspect, there is provided a method for mitigating or
preventing
formation of pressure ulcers in a patient, including a first mode of operation
and a second
mode of operation. The method comprises, over a period of at least one hour,
continuously switching between the first mode of operation and the second mode
of
operation. For each instance of the first mode of operation, the first mode of
operation
lasts a respective predetermined stimulus time duration, and a respective
operative
electrical stimulus, sufficient to effect contraction of a muscle, is
transmitted to a skin
portion of a patient by an electrode, thereby effecting contraction of the
muscle, during
the entire, or substantially the entire, respective predetermined stimulus
time duration,
wherein the electrode is in contact with the skin portion. For each instance
of the second
mode of operation, the second mode of operation lasts a respective
predetermined
relaxation time duration, and no electrical stimulus, or substantially no
electrical
stimulus, is transmitted to the skin portion by the electrode during the
entire, or
substantially the entire, respective predetermined relaxation time duration.
The switching
from an instance of the first mode of operation to an instance of the second
mode of
operation is effected when the respective predetermined stimulus time duration
of the
respective instance of the first mode of operation is completed. As well,
switching from
an instance of the second mode of operation to an instance of the first mode
of operation
is effected when the respective predetermined relaxation time duration of the
respective
instance of the second mode of operation is completed. For example, the
respective
predetermined stimulus time duration of each instance of the first mode of
operation is at
least seven (7) seconds. As a further example, the respective predetermined
stimulus
time duration of each instance of the first mode of operation is greater than
seven (7)
seconds and less than (30) seconds. As a further example, the respective
predetermined
stimulus time duration of each instance of the first mode of operation is ten
(10) seconds.
For example, the respective predetermined relaxation time duration of each
instance of
the second mode of operation is at least five (5) minutes. As a further
example, with
respect to the respective predetermined relaxation time duration, the
respective
21
CA 02620288 2008-02-01
predetermined relaxation time duration of each instance of the second mode of
operation
is at least ten (10) minutes. As a further example, with respect to the
respective
predetermined relaxation time duration, the respective predetermined
relaxation time
duration of each instance of the second mode of operation is ten (10) minutes.
For
example, the continuous switching between the first mode of operation and the
second
mode of operation is effected over a period of at least two hours.
[0059] In a related aspect, there is provided a method of mitigating or
preventing
formation of pressure ulcers in a patient, comprising, over a period of at
least one hour,
and by way of an electrode in contact with a skin portion of a patient,
transmitting a
plurality of intermittent transmissions of an electrical stimulus, sufficient
to effect
contraction of a muscle, to the skin portion of a patient, thereby effecting
contraction of
the muscle. A respective time interval is provided between each pair of
successive
intermittent transmissions of the plurality of intermittent transmissions of
an electrical
stimulus such that there is a plurality of respective time intervals. No
electrical stimulus,
or substantially no electrical stimulus, is transmitted to the skin portion by
the electrode
during the entirety, or the substantial entirety, of each one of the plurality
of respective
time intervals. For example, each one of the plurality of intermittent
transmissions is at
least seven (7) seconds. As a further example, each one of the plurality of
intermittent
transmissions is greater than seven (7) seconds and less than (30) seconds. As
a further
example, each one of the plurality of intermittent transmissions is ten (10)
seconds. For
example, each one of the plurality of respective time intervals is at least
five (5) minutes.
As a further example, each one of the plurality of respective time intervals
is at least ten
(10) minutes. As a further example, each one of the plurality of respective
time intervals
is ten (10) minutes. For example, the plurality of intermittent transmissions
is effected
over a period of at least two hours.
[0060] In a further related aspect, there is provided use of a plurality of
intermittent transmissions of an operative electrical stimulus, sufficient to
effect
contraction of a muscle, to a skin portion of the patient, thereby effecting
contraction of
the muscle, for mitigating or preventing formation of pressure ulcers in the
patient,
wherein the plurality of intermittent transmissions of an operative electrical
stimulus is
22
CA 02620288 2008-02-01
transmitted over a period of at least one hour by an electrode in contact with
the skin
portion. A respective time interval is provided between each pair of
successive
intermittent transmissions of the plurality of intermittent transmissions of
an electrical
stimulus such that there is a plurality of respective time intervals. No
electrical stimulus,
or substantially no electrical stimulus, is transmitted to the skin portion by
the electrode
during the entirety, or the substantial entirety, of each one of the plurality
of respective
time intervals. For example, each one of the plurality of intermittent
transmissions is at
least seven (7) seconds. As a further example, each one of the plurality of
intermittent
transmissions is greater than seven (7) seconds and less than (30) seconds. As
a further
example, each one of the plurality of intermittent transmissions is ten (10)
seconds. For
example, each one of the plurality of respective time intervals is at least
five (5) minutes.
As a further example, each one of the plurality of respective time intervals
is at least ten
(10) minutes. As a further example, each one of the plurality of respective
time intervals
is ten (10) minutes. For example, the plurality of intermittent transmissions
is effected
over a period of at least two hours.
[0061] In another aspect, there is provided a method for mitigating or
preventing
formation of pressure ulcers in a first mode of operation and a second mode of
operation.
The method comprises continuously switching between the first mode of
operation and
the second mode of operation. For each instance of the first mode of
operation, the first
mode of operation lasts a respective predetermined stimulus time duration, and
a
respective operative electrical stimulus, sufficient to effect contraction of
a muscle, is
transmitted to a skin portion of a patient by an electrode, thereby effecting
contraction of
the muscle, during the entire, or substantially the entire, respective
predetermined
stimulus time duration, wherein the electrode is in contact with the muscle.
For each
instance of the second mode of operation, the second mode of operation lasts a
respective
predetermined relaxation time duration, and no electrical stimulus, or
substantially no
electrical stimulus, is transmitted to the skin portion by the electrode
during the entire, or
substantially the entire, respective predetermined relaxation time duration.
The switching
from an instance of the first mode of operation to an instance of the second
mode of
operation is effected when the respective predetermined stimulus time duration
of the
respective instance of the first mode of operation is completed. As well,
switching from
23
CA 02620288 2008-02-01
an instance of the second mode of operation to an instance of the first mode
of operation
is effected when the respective predetermined relaxation time duration of the
respective
instance of the second mode of operation is completed. The respective
predetermined
relaxation time duration of each instance of the second mode of operation is
at least five
(5) minutes. For example, the respective predetermined relaxation time
duration of each
instance of the second mode of operation is at least ten (10) minutes. For
example, the
respective predetermined relaxation time duration of each instance of the
second mode of
operation is ten (10) minutes. For example, the respective predetermined
stimulus time
duration of each instance of the first mode of operation is at least seven (7)
seconds. As a
further example, the respective predetermined stimulus time duration of each
instance of
the first mode of operation is greater than seven (7) seconds and less than
(30) seconds.
As a further example, the respective predetermined stimulus time duration of
each
instance of the first mode of operation is ten (10) seconds.
[0062] In a related aspect, there is provided a method of mitigating or
preventing
formation of pressure ulcers in a patient, comprising, by way of an electrode
in contact
with a skin portion of a patient, transmitting a plurality of intermittent
transmissions of an
electrical stimulus, sufficient to effect contraction of a muscle, to the skin
portion of a
patient, thereby effecting contraction of the muscle. A respective time
interval is
provided between each pair of successive intermittent transmissions of the
plurality of
intermittent transmissions of an electrical stimulus such that there is a
plurality of
respective time intervals. No electrical stimulus, or substantially no
electrical stimulus, is
transmitted to the skin portion by the electrode during the entirety, or the
substantial
entirety, of each one of the plurality of respective time intervals. Each one
of the
plurality of respective time intervals is at least five (5) minutes. For
example, each one of
the plurality of respective time intervals is at least ten (10) minutes. For
example, each
one of the plurality of respective time intervals is ten (10) minutes. For
example, each
one of the plurality of intermittent transmissions is at least seven (7)
seconds. As a
further example, each one of the plurality of intermittent transmissions is
greater than
seven (7) seconds and less than (30) seconds. As a further example, each one
of the
plurality of intermittent transmissions is ten (10) seconds.
24
CA 02620288 2008-02-01
[0063] In a further related aspect, there is provided use of a plurality of
intermittent transmissions of an operative electrical stimulus, sufficient to
effect
contraction of a muscle, to a skin portion of a patient, thereby effecting
contraction of the
muscle, for mitigating or preventing formation of pressure ulcers in the
patient, wherein
the plurality of intermittent transmissions of an operative electrical
stimulus is transmitted
by an electrode in contact with the skin portion. A respective time interval
is provided
between each pair of successive intermittent transmissions of the plurality of
intermittent
transmissions of an electrical stimulus such that there is a plurality of
respective time
intervals. No electrical stimulus, or substantially no electrical stimulus, is
transmitted to
the skin portion by the electrode during the entirety, or the substantial
entirety, of each
one of the plurality of respective time intervals. Each one of the plurality
of respective
time intervals is at least five (5) minutes. As a further example, each one of
the plurality
of respective time intervals is at least ten (10) minutes. As a fiart.her
example, each one of
the plurality of respective time intervals is ten (10) minutes. For example,
each one of
the plurality of intermittent transmissions is at least seven (7) seconds. As
a further
example, each one of the plurality of intermittent transmissions is greater
than seven (7)
seconds and less than (30) seconds. As a further example, each one of the
plurality of
intermittent transmissions is ten (10) seconds.
[0064] Embodiments of the present invention will be described in further
detail
with reference to the following non-limitative examples.
EXAMPLES
[0065] Experiments have been conducted to investigate the effectiveness of
applying intermittent electrical stimulation (IES) to reduce muscle injury due
to the
presence of persistent external pressure. We hypothesized that the IES-induced
muscle
contractions would prevent the formation of DTI. These periodically-induced
contractions may parallel the effects of voluntary or assisted repositioning,
which is the
standard method for preventing the formation of DTI. We suggested that the
mechanism
of action of IES is twofold: 1) IES-induced contractions would reshape the
underlying
muscle, thereby reducing the high stress levels experienced at the muscle-bone
interface,
CA 02620288 2008-02-01
minimizing the amount of damage caused by the mechanical deformation and
compression of the tissue. 2) Each contraction would also periodically restore
blood flow
and increase the oxygenation of the compressed tissue, reducing the amount of
damage
caused by long periods of ischemia and subsequent reperfusion.
[0066] Intermittent electrical stimulation may be a useful medical
intervention
that allows immobilized individuals to remain seated or supine for prolonged
periods of
time, reducing the frequency of assisted repositioning, and, most importantly,
reducing
the development of DTI.
Overview of Experimental Procedures
[0067] To investigate the effectiveness of IES in the prevention of DTI, a
series
of experiments were conducted in four groups of rats. The Control Group
received 2
hours of external load applied to the quadriceps muscle of one hind limb.
Experimental
Groups 1 and 2 received the load application as well as IES at either 10-
minute or 5-
minute intervals. Experimental Group 3 received the application of IES at 5-
minute
intervals but no load application. Deep tissue injury was quantified 24 hours
later by in-
vivo T2-weighted magnetic resonance imaging (MRI) and post mortem histological
assessment of the extracted quadriceps muscles. The untreated contralateral
legs of all
animals served as healthy controls (Contralateral Control Group).
[0068] To obtain an insight into the mechanisms of action of IES, the effect
of
IES on tissue oxygenation was measured in two experiments with able-bodied
human
volunteers. Tissue oxygenation measurements were obtained from an able-bodied
volunteer by means of T2* MRI quantification in muscles in both unloaded and
loaded
conditions, respectively. A single experiment in an able-bodied volunteer was
also
performed to measure changes in the surface (bed-buttocks interface) pressure
profiles
generated by the IES-elicited contractions. All volunteers provided written
consent. All
experimental protocols were approved by the Animal Care and Welfare Committee
and
the Health Research Ethics Board at the University of Alberta.
Effectiveness of IES in preventing DTI
26
CA 02620288 2008-02-01
[0069] Pressure application and electrical stimulation setup
Eighteen adult female, Sprague-Dawley rats (weight = 320 36 g) were
anesthetized
with isoflurane (2-3% isoflurane in 500 ml/min oxygen) and a nerve-cuff was
implanted
around the femoral nerve of each hind limb. Following implantation the rat was
placed
on a flat surface with a restraining device (Figure 1 a). Both hind limbs were
fully
extended and a padded strap was placed around each ankle to tether the legs in
place.
The knee and upper calf in the experimental leg were also restrained using a
padded
clamp to prevent any off-sagittal movement of the leg.
[0070] Pressure was applied to the quadriceps muscle of the experimental leg
using a 3-mm diameter indenter. The contralateral leg served as an internal
control. Rats
were randomly assigned to 3 groups of 6 animals each (Control Group,
Experimental
Group 1, Experimental Group 2). Rats in Experimental Group 1 received the
application
of pressure and simultaneous application of a 10-s stimulus bout (biphasic,
charge-
balanced, constant current, 10 - 40 mA, 250 s, 50 pulses/s) to the femoral
nerve of the
experimental leg every 10 minutes throughout the duration of pressure
application. Rats
in Experimental Group 2 received pressure and simultaneous electrical
stimulation to the
treated leg (10-s bouts) every 5 minutes (see Figure ld). Rats in the Control
Group
received the pressure application but no electrical stimulation. In all
animals, pressure
was applied for a period of 2 hours. The load applied was normalized to 38% of
the body
weight of each rat, which is the expected unilateral amount of loading in the
buttocks and
thighs in seated individuals (see reference 9). Loads were measured with a
miniature
beam force transducer (Interface, Scottsdale, Arizona, U.S.A.). The force was
recorded
at a sampling rate of 100 samples/s using a CED Power 1401 A/D board
(Cambridge
Equipment Design, Cambridge, UK) and SIGNAL 2 software (Cambridge Equipment
Design, Cambridge, UK) throughout the duration of the experiment (Figure lb).
The
indenter was adjusted as required using a micromanipulator (Narishige, Japan)
to
maintain the desired level of applied force (Figure lb). Throughout the
experiments, the
pressure applied to each group was 164 6.7 kPa for the Control Group, 167
26.6 kPa
for Experimental Group 1, and 165.2 25.1 kPa for Experimental Group 2.
Following
the period of pressure application, the leg was unloaded, the nerve-cuffs from
both limbs
27
CA 02620288 2008-02-01
were removed and the skin was sutured. Post-operatively, buprenorphine (0.05
mg/kg)
was administered subcutaneously, to alleviate any discomfort.
[0071] To test the effect IES alone may have on the stimulated muscles,
experiments were conducted in a fourth group of six rats (285 6 g),
designated
Experimental Group 3 (see Figure 1 e). The experimental procedures previously
described were maintained with the exception of no pressure application. The
stimulation
paradigm utilized was that of Experimental Group 2, with IES being applied to
one hind
limb of the animal every 5 minutes for a period of 2 hours.
[0072] Figure 1 e illustrates the force generated by contraction of muscle in
rates
in response to intermittent electrical stimulation treatment during 2 hours of
treatment.
The mean and standard deviation of the force generated by the contraction of
the muscle
in response to the electrical stimulus during each bout of electrical
stimulation over a two
hour period are shown for 6 rats (top plot) and 5 rats (bottom plot). Bouts of
10 seconds
of stimulation (stimulation ON period) delivered every 5 minutes resulted in
force
reduction of -25% after 2 hours (top plot). This reduction was not significant
and did not
significantly affect the effectiveness of the treatment. Bouts of 10 seconds
of stimulation
(stimulation ON period) delivered every 10 minutes resulted in no force
reduction after 2
hours (bottom plot).
B. Assessment of Deep Tissue Health using MRI
[0073] Magnetic resonance imaging was used to obtain an in-vivo assessment of
DTI following pressure application and to quantify the effectiveness of IES in
preventing
such injury (see references 6, 52). Twenty-four hours after the removal of
pressure each
rat was anesthetized with an intraperitoneal injection of sodium pentobarbital
(40 mg/kg).
The rat's hind limbs were secured inside a 7-cm diameter birdcage coil and
placed inside
a 3.0 Tesla magnet (Magnex Scientific PCL). A T2-weighted spin-echo sequence
(echo
time (TE) = 80 ms, relaxation time (TR) = 2000 ms) was employed to detect the
presence
of edema (as indicated by increased water content) within the quadriceps
muscles in both
hind limbs of each rat. Data were collected during a 30-minute scanning
session and
twenty MRI slices (images) were acquired from each rat, with slice thickness
of 2 mm
28
CA 02620288 2008-02-01
and slice separation of 1 mm (every other slice shown in Figure 2). The
acquisition
matrix size was 256 pixel x 256 pixel within a field of view (FOV) of 120 mm x
120 mm,
resulting in an in-plane resolution of 0.47 mm x 0.47 mm. Both hind legs were
imaged in
the same slice. MRI slices were obtained in the sagittal, coronal and
transverse planes in
relation to the rat's femur.
[0074] All MRI data were imported to MATLAB 7Ø1 (Mathworks, Natick,
Massachusetts, U.S.A.) for analysis using custom-written routines. The left
and right
quadriceps muscles were manually selected from every slice and all analyses
were
restricted to the pixels inside these two regions (Figure 3a). To quantify the
amount of
increased water content present within the experimental leg from each slice,
the signal
intensity of each pixel in that leg was compared to a threshold intensity
level obtained
from the contralateral leg (Figure 3b). The mean + 2*standard deviation in the
signal
intensity from the quadriceps muscle of the contralateral leg was chosen as
the threshold
intensity level. If the signal intensity of a pixel in the experimental leg
was higher than
the threshold, the pixel was considered to have increased water content, or
edema (Figure
3c). A percentage of the affected area relative to the total area of the
muscle was
obtained from each slice and the total affected volume was calculated for each
rat by
summing the results from all slices. The threshold was also applied to each
control
(contralateral) limb from each rat to quantify the amount of increased water
content that
could be attributed to factors other than the application of pressure or IES,
such as the
electrode cuff implantation or normal variation in the signal intensity.
Results from the
untreated contralateral limbs of all 24 rats were designated as the
Contralateral Control
Group. For measured comparisons between groups both one-way ANOVA and Tukey
post-hoc tests were used. All P values less than 0.05 were considered
statistically
significant.
C. Histological assessment
[0075] To corroborate the extent of injury in the muscle from the MRI
assessment, histological evaluation of the tissue was also performed. Under
deep
anesthesia (sodium pentobarbital, 40 mg/kg), the animal was transcardially
perfused with
29
CA 02620288 2008-02-01
a formaldehyde (1%) /gluteraldehyde (2.25%) fixative and the quadriceps
muscles from
both hind limbs were removed. The muscles were photographed, weighed and their
volume calculated. The muscle tissue was stored in the same fixative, and
subsequently
dehydrated through washing in a graded series of ethanol dilutions and
embedded in
paraffin.
[0076] Muscle sections obtained from the region identified by the MR images as
containing edema were longitudinally bisected. A 2 - 3 mm thick longitudinal
section
was obtained, as well as five 2 - 3 mm thick transverse sections. A 5 gm slice
was
obtained from each section and stained with hematoxylin and eosin (H&E).
[0077] A veterinary pathologist blinded to the experimental groups performed
all
histological analyses. A 4.9 mm2 area from each slice was assessed to identify
muscle
fiber necrosis, inflammatory cell infiltration, hemorrhage and tissue
mineralization. A
necrosis score (0 - 4) was assigned to each longitudinal slice based on the
approximate
area exhibiting necrosis out of the slice total area. Subsequently, the
transverse slices
from each animal were used to confirm the extension of necrosis throughout the
muscle.
The estimated volume of the muscle affected by necrosis from the histological
assessment was compared against the estimated volume of the corresponding
muscle
affected by edema as calculated from MRI slices. Scoring of histological
muscle sections
between groups was assessed by a Kruskal-Wallis non-parametric test. All P
values less
than 0.05 were considered statistically significant. All results are expressed
as mean ~
standard deviation.
Mechanisms of action of IES in human subjects
A. Muscle oxygenation measurements in human subjects
[0078] In addition to testing the effectiveness of IES in preventing DTI, we
sought to understand the mechanisms of action of IES. An initial experiment
was
conducted in an able-bodied volunteer (male, 22 yr) to assess changes in
tissue
oxygenation associated with contractions elicited by IES in an unloaded
muscle. The
experimental setup is illustrated in Figure 7. Electrodes were placed on the
body and
CA 02620288 2008-02-01
electrical stimulation was delivered to induce muscle contractions. The change
in the
shape of the muscle during contraction, redistribution of surface pressure and
changes in
tissue oxygenation were measured using magnetic resonance imaginging (MRI)
techniques and surface pressure mats. Surface, non-magnetic electrodes were
placed over
the motor point of the medial gastrocnemius (MG) muscle of one leg. Tissue
oxygenation levels were estimated by quantifying changes in the T2* signal in
MR scans
of the muscle in which an increase in the T2* signal is attributed to an
influx of
oxygenated hemoglobin to the tissue (see references 26, 39). MR scans were
acquired
with a 1.5 Tesla whole body Siemens Sonata scanner (Siemens Medical Solution,
Malvern, Pennsylvania) and a 27-cm diameter transmit/receive knee coil
circumscribing
the lower leg. A custom-prepared multi-gradient-echo sequence (TR = 51.8 ms, 8
TEs
ranging from 3.6 ms to 47 ms, single slice, 6 mm slice thickness, flip angle =
20 , FOV =
208 mm x 205 mm, readout matrix = 160 pixel x 158 pixel, in-plane resolution =
1.3 mm
x 1.3 mm) was utilized for all data acquisitions. Baseline levels of
oxygenation in MG
were obtained as well as simultaneous measurements from the lateral
gastrocnemius
(LG), medial soleus (MS), and lateral soleus (LS) muscles for comparison.
Following the
acquisition of baseline scans, successive scans were acquired immediately
after 30-s
bouts of electrical stimulation delivered through the surface electrodes
(biphasic, charge-
balanced, constant current, 70 mA, 250 s, 50 pulses/s).
[0079] To mimic a simulated sitting position in which muscles are compressed,
albeit around the ischial tuberosities, a second experiment was performed on
the gluteus
maximus muscles to assess changes in oxygenation levels induced by IES.
Surface, non-
magnetic electrodes were placed over the motor points of the left and right
gluteus
maximus muscles of an able-bodied volunteer (male, 26 yr). Due to space
limitations
within the MRI scanner, which prohibits volunteers from sitting upright,
muscle
compression during sitting was simulated by adding weight over the pelvis of
the person
lying supine inside a 1.5 Tesla whole-body scanner. Oxygenation measurements
were
obtained at: 1) rest, 2) with a 20 kg (30% of body weight) load applied over
the pelvis,
and 3) with a 20 kg load and IES applied simultaneously.
31
CA 02620288 2008-02-01
[0080] Surface coils placed below the subject and a multi-gradient-echo
sequence
(TR = 90.3 ms, 20 TEs ranging from 3.8 to 89.6 ms, single slice, 8 mm slice
thickness,
flip angle = 30, FOV = 223 mm x 397 mm, readout matrix = 72 pixel x 128 pixel,
in-
plane resolution = 3.1 mm x 3.1 mm) were utilized for imaging the gluteus in
the
transverse plane. Three successive 31-s scans were acquired at rest to obtain
baseline
levels of oxygenation in the left and right gluteus maximus muscles. A 20 kg
load was
placed over the pelvic region to compress the gluteus muscles and 10 31-s
scans were
acquired over a 10-minute period of loading. Subsequently, 6 31-s scans were
obtained
each immediately following a 10-s stimulus bout (biphasic, charge-balanced,
constant
current, 70 mA, 250 gs, 50 pulses/s, 3-s ramp-up, 3-s ramp-down) applied every
minute
to the gluteus muscles with the load in place. The stimulation parameters
utilized did not
cause pain or discomfort to the volunteer.
[0081] Magnetic resonance data were imported into MATLAB 7Ø1 (Mathworks,
Natick, Massachusetts, U.S.A.) to measure changes in the T2* signal in each
muscle
using a mono-exponential non-negative least squares fit routine (see reference
59). A
region of interest (ROI) was selected around each target muscle (MG, LG, SM,
and SL,
or right gluteus maximus, and left gluteus maximus) in each MR slice, and the
T2* levels
in each ROI were determined. The T2* values were normalized to their
corresponding
baseline levels obtained at rest.
B. Surface pressure measurements
[0082] In addition to injury due to ischemic changes, high stress levels and
cell
deformation have also been associated with tissue damage (see references 7, 8,
11, 35,
36). Ideally, stress levels should be measured at the bone-muscle interface,
the place of
origin for DTI. However, due to the lack of non-invasive measuring techniques
at this
deep level, an alternative and commonly used technique is to measure
superficial pressure
levels at the support surface-skin interface (see reference 5). In order to
obtain insight
into the effects of IES in reshaping the gluteus maximus muscles, and
modifying the
surface pressure profiles with each contraction, a single experiment was
performed. The
experiment was conducted in the same able-bodied volunteer (male, 26 yr),
using the
32
CA 02620288 2008-02-01
same testing conditions as those utilized to assess oxygenation levels in the
gluteus
maximus muscles: 1) rest, 2) weight, and 3) weight + IES. To elicit
contractions in the
left and right gluteus maximus muscles, surface electrodes were placed over
the motor
point of each muscle. The volunteer was placed in a supine position with the
buttocks
over an X-3 System pressure sensitive mattress (XSensor, Calgary, AB, Canada).
Measurements of surface pressure in the sacral region of the buttocks were
obtained over
a 1-minute period of rest. A 20-kg load, equivalent to 30% of the body weight
of the
volunteer, was applied over the pelvis to compress the tissue of the buttocks.
Surface
pressure measurements were acquired for 1 minute under this condition.
Electrical
stimulation was then applied simultaneously to both gluteus maximus muscles. A
series
of 3 15-s stimulus bouts (biphasic, charge-balanced, constant current, 70 mA,
250 s, 50
pulses/s) were applied with the load in place. Changes in surface pressure
associated
with IES were measured during each bout of stimulation.
Results
Effectiveness of IES in preventing the formation of DTI
[0083] The main objective of this investigation was to determine whether IES
is
an effective technique for preventing DTI. Our results show that edema and
tissue injury
can develop after a 2-hour application of constant pressure. In all test
groups and at the
completion of the study, the skin under the pressure indenter did not exhibit
any
indication of inflammation or injury, underscoring the difficulty of
identifying DTI by
visual inspection of the skin.
[0084] In the Control Group (pressure, No IES), the application of external
pressure for 2 hours generated edema in 60 15% of the muscle. In contrast
(Figure 5,
left axis, filled circles), Experimental Groups 1(pressure + IES every 10min)
and 2
(pressure + IES every 5min) exhibited a significantly reduced region of edema
in the
muscle, (16 f 16% for Experimental Group 1 and 25 13% for Experimental Group
2).
Experimental Group 3 (No pressure, IES every 5min) and Contralateral Control
Group
(untreated contralateral limbs) exhibited a 5+ 4% and a 5+ 4% respectively.
The extent
of increased water content in all three experimental groups was significantly
different
33
CA 02620288 2008-02-01
from that in the Control Group (one-way ANOVA test, p = 0.0001), but was not
significantly different from each other (Tukey post-hoc test, Exp 1 vs Exp 2,
p = 0.59;
Exp 1 vs Exp 3, p = 0.45; Exp 2 vs Exp 3, p = 0.06 ).
[0085] Histological assessment of the quadriceps muscle tissue (Figure 4;
note:
the amount of edema observed with MRI correlated well with the amount of
necrotic
fibers assessed from the histological slides, and all histological sections
were viewed at
100x magnification) showed that the severity of muscle injury varied between
the control
and experimental groups. In general, the lesions within the muscle were
characterized by
swelling, loss of striations, and fragmentation of muscle fibers. The
connective tissue
surrounding affected muscle fibers was often infiltrated by numerous
neutrophils
admixed with smaller numbers of macrophages. Hemorrhage into muscle bundles
was
most apparent in severely affected tissue. Figure 5 (right axis, open circles)
summarizes
the extent of tissue necrosis in the control and experimental groups. The
Control Group
had the largest extension of necrotic fibers in the tissue with a score of 3.2
0.8. This
score represented a necrotic area occupying 25 to 50% of the area analyzed.
The extent
of tissue necrosis was significantly larger in the Control Group than that in
Experimental
Group 1, which had a score of 1.0 0.9 (Kruskal-Wallis non-parametric test, p
= 0.01),
representing a necrotic area of less than 10%. Experimental Group 2 also
exhibited a
significantly smaller area of muscle necrosis than the Control Group (Kruskal-
Wallis
non-parametric test, p = 0.03), with a score of 1.2 1.5, equivalent to a
necrotic area
between 10% and 20%. The necrosis score was also significantly smaller in
Experimental Group 3 (Kruskal-Wallis non-parametric test, p=0.004), with a
score of 0.5
0.6. There was no significant difference between all three experimental groups
in the
amount of necrosis assessed. The infiltration of neutrophils and macrophages,
as well as
the presence of red blood cells and mineralization of the tissue, were not
significantly
different between the control and experimental groups.
Increases in tissue oxygenation due to IES-elicited contractions
[0086] Two experiments were performed with the goal of measuring the changes
in tissue oxygenation levels associated with the use of IES. The effects of
IES-elicited
34
CA 02620288 2008-02-01
contractions on muscle oxygenation were first tested in a condition where the
muscle was
at rest and unloaded. Figure 6a summarizes the effect of IES on the level of
oxygenation
in the muscles of the lower leg. Normalized T2* levels in MG, LG, LS, and MS
are
shown. Interestingly, IES selectively increased the T2* level of MG, the
stimulated
muscle. This increase in oxygenation was maintained throughout the experiment.
Oxygenation levels in LG, LS, and MS did not show any change when compared to
baseline measurements.
[0087] The second experiment measured the increase in tissue oxygenation
following IES-elicited contractions of loaded muscles. These loaded muscles
had a
corresponding reduction in oxygen supply, a situation that represents the
state of tissue
around the ischial tuberosities in a seated individual. Figure 6b summarizes
the effect of
IES on the level of tissue oxygenation in the gluteus maximus muscles in the
presence of
an external pressure. Normalized T2* levels in the right and left gluteus
maximus
muscles are shown for each condition tested (rest, weight, weight + IES). The
oxygenation levels in both muscles decreased immediately by -4% after the load
application; oxygenation remained at this lower level throughout the 10
minutes in which
this condition was maintained. Following IES, the oxygenation levels in the
muscles
increased above the initial baseline levels by -6%.
Changes in surface pressure profiles due to IES-elicited contractions
[0088] In a third experiment (Figure 6c) surface pressure measurements of the
buttocks were obtained under the same three conditions previously tested
(rest, weight,
weight + IES). The average pressure throughout the buttocks at rest was 10.9
kPa,
distributed over a 487 mm2 area. As expected, the region of highest pressure
was that
surrounding the bony prominence (the sacrum in this case), and exhibited an
average
pressure of 21.7 kPa.
[0089] Following the loading of the pelvis, the average pressure throughout
the
buttocks increased to 13.9 kPa and was distributed over a 511 mm2 area. The
average
pressure in the region around the sacrum increased to 25.8 kPa. Simultaneous
bilateral
application of IES to the loaded (compressed) gluteus maximus muscles induced
CA 02620288 2008-02-01
contractions which reconfigured the shape of the muscles. The average pressure
throughout the buttocks became 14.3 kPa distributed over an area of 424 mm2.
However,
the average pressure around the sacrum was reduced to 19.5 kPa, a level lower
than that
seen even during the rest condition.
[0090] Figure 8 illustrates an MRI of the left and right gluteus muscles
demonstrating the changes in muscle shape during contractions induced by
electrical
stimulation (top). It also shows the redistribution of surface pressure
(middle) and the
increase in tissue oxygenation (bottom) during electrical stimulation.
Discussion
Effectiveness of IES in preventing the formation ofDTI
[0091] Several studies have reported the beneficial effects of both
alternating and
direct current electrical stimulation for healing chronic wounds, including
pressure ulcers
(see references 4, 17, 21, 25, 43, 51, 58). The consensus is that when
combined with
traditional treatments, electrical stimulation improves wound healing. Very
few studies
however, have investigated electrical stimulation alone as a method for
preventing the
formation of pressure ulcers.
[0092] Levine et al. first proposed using electrical stimulation to prevent
pressure
ulcers and measured the effect of electrical muscle stimulation on 1) pressure
at the
seating interface (see reference 32), 2) muscle shape (see reference 33), and
3) blood flow
(see reference 34). Their results indicated that during each contraction of
the gluteus
muscles 1) the superficial pressure surrounding the ischial tuberosities was
reduced; 2)
the shape of the compressed muscle was modified; and 3) blood flow increased
in the
stimulated muscle. Based on these observations, it was suggested that
electrical
stimulation might be an effective technique to prevent pressure ulcers.
[0093] Following the seminal study of Levine et al., Rischbieth et al (see
reference 44) and Bogie et al (see reference 4) reported that an increase in
muscle mass
was achieved through long-term electrical stimulation. The increase in muscle
mass was
suggested to provide individuals with improved cushioning, which in turn,
could prolong
36
CA 02620288 2008-02-01
the time they can remain seated. Recently, Bogie et al (see reference 5)
analyzed the
long-term effects of electrical stimulation of the gluteus muscles in one
individual with
spinal cord injury. Measurements of surface interface pressure, transcutaneus
oxygen
levels, and muscle thickness were similar to observations previously reported
by Levine
(see references 32-34), Rischbieth (see reference 44), and Bogie (see
reference 4). It was
also determined that any benefits gained during the period of electrical
stimulation were
abolished once the electrical stimulation was discontinued. While the evidence
from
these studies suggested the potential effectiveness of IES in preventing the
formation of
pressure ulcers, heretofore no study had investigated the effects of IES on
the integrity of
deep muscle exposed to constant pressure.
[0094] The present study examined the efficacy of IES in preventing DTI in a
rat
model and its mechanism of action in human volunteers. Our results show, that
within
defined parameters of electrical stimulation, a considerable reduction in DTI
was
observed. Traditionally, tissue injury generated by ischemia following long
periods of
tissue compression, has been considered the principal etiological factor
behind pressure
ulcers (see references 27-29). Within this precept, more frequent stimulation
should
restore tissue oxygenation in the tissue to normal or near-normal levels,
potentially
eliminating tissue injury caused by ischemia. The finding that there was no
significant
difference between our experimental groups (IES every 10 minutes vs. 5
minutes) could
indicate that the beneficial effects of an increase in oxygenation to the
tissue may have
reached their threshold when stimulation occurred every 10 minutes. It is
possible that
the amount of damage observed in both experimental groups could be attributed
to
damage generated directly by the high stress levels at the bone-muscle
interface and
excessive cell deformation, a factor that was further exaggerated in our
experimental set
up due to the fixation of the hind limb which led to an increase, rather than
a decrease, in
focal pressure during the IES-induced contractions (evident in the increases
in recorded
force in Figure lb). Although the application of pressure to the rats' limbs
was done
outside the MRI scanner, utmost care was taken in the placement of the
indenter, such
that it was as centered as possible over the QM and the femur.
37
CA 02620288 2008-02-01
[0095] Comparison of Experimental Group 3 and the Contralateral Control Group
demonstrated that the use of IES as frequently as every 5 minutes does not
cause an
increase in the water content of the muscle. The minimal amount of water
content
identified in the Contralateral Control Group, as calculated in this study,
indicates that
-5% of the tissue water content quantified in the Control Group and
Experimental
Groups 1 and 2 was not caused by the load application.
[0096] It has been suggested that high stress levels at the bone-muscle
interface is
a primary factor in the development of pressure ulcers (see references 7, 8,
11, 35, 36),
but the extent of tissue injury that is associated with these mechanical
forces (shear and
stress) has yet to be determined. Although complete elimination of DTI has not
been
achieved, our results suggest that IES delivered every 10 minutes is
sufficient to reduce
greatly the extent of damage in deep tissue exposed to constant external
pressure.
[0097] None of the rats in this study showing indications of DTI displayed
injury
to the overlying skin. This emphasizes that skin appearance is a poor
indicator of deep
tissue health, and supports the need for other alternative methods to detect
DTI. The
results of this study, as well as those reported previously by Bosboom et al
(see reference
6) and Stekelenburg et al (see reference 52), show that MRI is an effective
tool for the
detection of muscle edema associated with the presence of DTI, even when
injury occurs
in muscles as small as those in the rat hind limbs (Figure 3a). Although MRI
currently
may not be ideal for screening patients with DTI due to cost and availability,
in situations
where an individual is considered to be at high risk of developing an ulcer or
has a long
history of ulcer development, it might be necessary to perform periodic
screenings.
Identifying DTI before it fully evolves into a pressure ulcer would not only
have a
significant beneficial impact on the health and quality of life of the
individual, but could
greatly reduce costs associated with further medical and surgical treatments.
Mechanisms ofAction of IES
[0098] Our results demonstrated that the levels of available oxygen in the
tissue
of gluteus maximus were reduced immediately after compressing the muscles
(Figure 6).
However, instantly following the first IES-induced contraction of the muscles,
the levels
38
CA 02620288 2008-02-01
of tissue oxygen increased. This increase was greater than baseline levels,
and was most
likely caused by reactive hyperemia, a process in which there is an increase
in blood flow
into the capillaries after brief periods of occlusion (see reference 38). This
increase in
oxygenation was maintained after each of the 6 IES-induced contractions. While
oxygenation levels in the unloaded medial gastrocnemius muscle also increased
with IES,
the increase was less than that in the gluteal measurements. This may be due
to the fact
that blood flow to the medial gastrocnemius muscle was not altered, and
consequently
oxygenation levels were already at normal levels.
[0099] While periodical increases in tissue oxygenation should have the
beneficial effect of negating tissue injury associated with ischemia-
reperfusion, pressure
relief is still needed to prevent further damage from persistent high stress
levels of muscle
cells. Our results demonstrated that IES of the compressed gluteus muscles
reconfigured
the shape of the muscles and distributed the pressure laterally in the
buttocks. The net
result was a periodical relief of the superficial pressure around the bony
prominence and
reduction in the overall pressure throughout the buttocks. The use of
superficial pressure
measurements combined with recently developed finite element models (see
references
37, 40) of the gluteal muscles which can estimate the stress levels at the
bone-muscle
interface, could provide a more accurate tool for predicting the risk of
developing DTI.
[00100] Although the disclosure describes and illustrates various embodiments
of
the invention, it is to be understood that the invention is not limited to
these particular
embodiments. Many variations and modifications will now occur to those skilled
in the
art of headwear. For full definition of the scope of the invention, reference
is to be made
to the appended claims.
39
CA 02620288 2008-02-01
References
1. Agency for Health Care Policy & Research PfPUT. Clinical Practice Guideline
Number 15. Treatment of Pressure Ulcers. US Department of Health & Human
Services, Public Health Service AHCPR Publication No 95-0652, 1994.
2. Ankrom MA, Bennett RG, Sprigle S, Langemo D, Black JM, Berlowitz DR,
Lyder CH, and Panel. NPUA. Pressure-related deep tissue injury under intact
skin and the current pressure ulcer staging systems. Advances in Skin and
Wound
Care 18: 35-42, 2005.
3. Black JM and Panel. NPUA. Moving toward consensus on deep tissue injury
and pressure ulcer staging. Advances in Skin and Wound Care 18: 415-421, 2005.
4. Bogie KM, Reger SI, Levine SP, and Sahgal V. Electrical stimulation for
pressure sore prevention and wound healing. Assistive Technology 12: 50-66,
2000.
5. Bogie KM, Wang X, and Triolo RJ. Long-term prevention of pressure ulcers in
high-risk patients: a single case study of the use of gluteal neuromuscular
electric
stimulation. Archives of Physical Medicine & Rehabilitation 87: 585-591, 2006.
6. Bosboom EMH, Bouten CV, Oomens CW, Baaijens FP, and Nicolay K.
Quantifying pressure sore-related muscle damage using high resolution MRI.
Journal ofApplied Physiology 95: 2235-2240, 2003.
CA 02620288 2008-02-01
7. Bouten CV, Oomens CW, Baaijens FP, and Bader DL. The etiology of
pressure ulcers: skin deep or muscle bound? Archives of Physical Medicine and
Rehabilitation 84: 616-619, 2003.
8. Breuls RGM, Bouten CV, Oomens CW, Bader DL, and Baaijens FP. A
theoretical analysis of damage evolution in skeletal muscle tissue with
reference
to pressure ulcer development. Journal of Biomedical Engineering 125: 902-909,
2003.
9. Collins F. Sitting: pressure ulcer development. Nursing Standard 15: 54-58,
2001.
10. Conine TA, Choi AK, and Lim R. The user-friendliness of protective support
surfaces in prevention of pressure sores. Rehabilitation Nursing 14: 261-263,
1989.
11. Daniel RK, Priest DL, and Wheatley DC. Etiologic factors in pressure
sores: an
experimental model. Archives of Physical Medicine & Rehabilitation 62: 492-
498,
1981.
12. Edlich RF, Winters KL, Woodard CR, Buschbacher RM, Long WB, Gebhart
JH, and Ma EK. Pressure ulcer prevention. Journal of Long-term Effects of
Medical Implants 14: 285-304, 2004.
13. Fennegan D. Positive living or negative existence? Nursing Times 15: 51-
54,
1983.
14. Finestone HM, Levine SP, Carlson GA, Chizinsky KA, and Kett RL.
Erythema and skin temperature following continuous sitting in spinal cord
injured
individuals. Journal of Rehabilitation Research & Development 28: 27-32, 1991.
15. Garber SL and Dyerly LR. Wheelchair cushions for persons with spinal cord
injury: an update. American Journal of Occupational Therapy 45: 550-554, 1991.
41
CA 02620288 2008-02-01
16. Garber SL and Krouskop TA. Body build and its relationship to pressure
distribution in the seated wheelchair patient. Archives of Physical Medicine &
Rehabilitation 63: 17-20, 1982.
17. Gardner SE, Frantz RA, and Schmidt FL. Effect of electrical stimulation on
chronic wound healing: a meta-analysis. Wound Repair and Regeneration 7: 495-
503, 1999.
18. Gefen A, Gefen N, Linder-Ganz E, and Margulies SS. In vivo muscle
stiffening under bone compression promotes deep pressure sores. Journal of
Biomechanical Engineering 127: 512-524, 2005.
19. Gilsdorf P, Patterson R, and Fisher S. Thirty-minute continuous sitting
force
measurements with different support surfaces in the spinal cord injured and
able-
bodied. Journal of Rehabilitation Research & Development 28: 33-38, 1991.
20. Grace PA. Ischaemia-reperfusion injury. British Journal of Surgery 81: 637-
647,
1994.
21. Griffin JW, Tooms RE, Mendius RA, Clifft JK, Vander Zwaag R, and el-
Zeky F. Efficacy of high voltage pulsed current for healing of pressure ulcers
in
patients with spinal cord injury. Physical Therapy 71: 433-442, 1991.
22. Gunningberg L, Lindholm C, Carlsson M, and Sjoden P. Effect of visco-
elastic foam mattresses on the development of pressure ulcers in patients with
hip
fractures. Journal of Wound Care 9: 455-460, 2000.
23. Gute DC, Ishida T, Yarimizu K, and Korthuis RJ. Inflammatory responses to
ischemia and reperfusion in skeletal muscle. Molecular & Cellular Biochemistry
179: 169-187, 1998.
24. Guthrie RH and Goulian D. Decubitus ulcers: Prevention and Treatment.
Geriatrics: 67-71, 1973.
42
CA 02620288 2008-02-01
25. Houghton PE, Kincaid CB, Lovell M, Campbell KE, Keast DH, Woodbury
MG, and Harris KA. Effect of electrical stimulation on chronic leg ulcer size
and appearance. Physical Therapy 83: 17-28, 2003.
26. Jordan BF, Kimpalou JZ, Beghein N, Dessy C, Feron 0, and Gallez B.
Contribution of oxygenation to BOLD contrast in exercising muscle. Magnetic
Resonance in Medicine 52: 391-396, 2004.
27. Kosiak M. Etiology and pathology of ischemic ulcers. Archives of Physical
Medicine & Rehabilitation 40: 62-69, 1959.
28. Kosiak M. Etiology of decubitus ulcers. Archives of Physical Medicine &
Rehabilitation 42: 19-29, 1961.
29. Kosiak M, Kubicek WG, Olson M, Danz JN, and Kottke FJ. Evaluation of
pressure as factor in production of ischial ulcers. Archives of Physical
Medicine &
Rehabilitation 39: 623-629, 1958.
30. Krause JS and Broderick L. Patterns of recurrent pressure ulcers after
spinal
cord injury: identification of risk and protective factors 5 or more years
after
onset. Archives of Physical Medicine & Rehabilitation 85: 1257-1267, 2004.
31. Labbe R, Lindsay T, and Walker PM. The extent and distribution of skeletal
muscle necrosis after graded periods of complete ischemia. Journal of Vascular
Surgery 6: 152-157, 1987.
32. Levine SP, Kett RL, Cederna PS, Bowers LD, and Brooks SV. Electrical
muscle stimulation for pressure variation at the seating interface. Journal of
Rehabilitation Research & Development 26: 1-8, 1989.
33. Levine SP, Kett RL, Cederna PS, and Brooks SV. Electric muscle stimulation
for pressure sore prevention: tissue shape variation. Archives of Physical
Medicine
& Rehabilitation 71: 210-215, 1990.
43
CA 02620288 2008-02-01
34. Levine SP, Kett RL, Gross MD, Wilson BA, Cederna PS, and Juni JE. Blood
flow in the gluteus maximus of seated individuals during electrical muscle
stimulation. Archives of Physical Medicine & Rehabilitation 71: 682-686, 1990.
35. Linder-Ganz E, Engelberg S, Scheinowitz M, and Gefen A. Pressure-time cell
death threshold for albino rat skeletal muscles as related to pressure sore
biomechanics. Journal of Biomechanics 39: 2725-2732, 2006.
36. Linder-Ganz E and Gefen A. Mechanical compression-induced pressure sores
in
rat hindlimb: muscle stiffness, histology, and computational models. Journal
of
Applied Physiology 96: 2034-2039, 2004.
37. Linder-Ganz E, Shabshin N, Itzchak Y, and Gefen A. Assessment of
mechanical conditions in sub-dermal tissues during sitting: A combined
experimental-MRI and finite element approach. Journal of Biomechanics, 2006.
38. Mollison HL, McKay WP, Patel RH, Kriegler S, and Negraeff OE. Reactive
hyperemia increases forearm vein area. Canadian Journal ofAnaesthesia 53: 759-
763, 2006.
39. Noseworthy MD, Bulte DP, and Alfonsi J. BOLD magnetic resonance imaging
of skeletal muscle. Seminars in Musculoskeletal Radiology 7: 307-315, 2003.
40. Oomens CW, Bressers OF, Bosboom EM, Bouten CV, and Bader DL. Can
loaded interface characteristics influence strain distributions in muscle
adjacent to
bony prominences? Computer Methods in Biomechanic & Biomedical
Engineering 6: 171-180, 2003.
41. Peirce SM, Skalak TC, and Rodeheaver GT. Ischemia-reperfusion injury in
chronic pressure ulcer formation: a skin model in the rat. Wound Repair and
Regeneration 8: 68-76, 2000.
42. Raghavan P, Raza WA, Ahmed YS, and Chamberlain MA. Prevalence of
pressure sores in a community sample of spinal injury patients. Clinical
Rehabilitation 17: 879-884, 2003.
44
CA 02620288 2008-02-01
43. Reger SI, Hyodo A, Negami S, Kambic HE, and Sahgal V. Experimental
wound healing with electrical stimulation. Artificial Organs 23: 460-462,
1999.
44. Rischbieth H, Jelbart M, and Marshall R. Neuromuscular electrical
stimulation
keeps a tetraplegic subject in his chair: a case study. Spinal Cord 36: 443-
445,
1998.
45. Russell L. Pressure ulcer classification: defining early skin damage.
British
Journal ofNursing 11: S33-34, S36, S38, S40-41, 2002.
46. Russell LJ, Reynolds TM, Park C, Rithalia S, Gonsalkorale M, Birch J,
Torgerson D, Iglesias C, and Group. P-S. Randomized clinical trial comparing
2 support surfaces: results of the Prevention of Pressure Ulcers Study.
Advances
in Skin and Wound Care 16: 317-327, 2003.
47. Sagach VF, Kindybalyuk AM, and Kovalenko TN. Functional hyperemia of
skeletal muscle: role of endothelium. Journal of Cardiovascular Pharmacology
20: S 170-S 175, 1992.
48. Salcido R, Fisher SB, Donofrio JC, Bieschke M, Knapp C, Liang R, LeGrand
EK, and Carney JM. An animal model and computer-controlled surface pressure
delivery system for the production of pressure ulcers. Journal of
Rehabilitation
Research & Development 32: 149-161, 1995.
49. Salzberg CA, Byrne DW, Cayten CG, van Niewerburgh P, Murphy JG, and
Viehbeck M. A new pressure ulcer risk assessment scale for individuals with
spinal cord injury. American Journal of Physical Medicine & Rehabilitation 75:
96-104, 1996.
50. Seymour RJ and Lacefield WE. Wheelchair cushion effect on pressure and
skin
temperature. Archives ofPhysical Medicine & Rehabilitation 66: 103-108, 1985.
51. Stefanovska A, Vodovnik L, Benko H, and Turk R. Treatment of chronic
wounds by means of electric and electromagnetic fields. Part 2. Value of FES
CA 02620288 2008-02-01
parameters for pressure sore treatment. Medical and Biological Engineering and
Computing 31: 213-220, 1993.
52. Stekelenburg A, Oomens CW, Strijkers GJ, Nicolay K, and Bader DL.
Compression-induced deep tissue injury examined with magnetic resonance
imaging and histology. Journal ofApplied Physiology 100: 1946-1954, 2006.
53. Swarts AE, Krouskop TA, and Smith DR. Tissue pressure management in the
vocational setting. Archives of Physical Medicine & Rehabilitation 69: 1988,
1988.
54. Thomas DR. Are all pressure ulcers avoidable? Journal of the American
Medical
Directors Association 4: S43-S48, 2003.
55. Tsuji S, Ichioka S, Sekiya N, and Nakatsuka T. Analysis of ischemia-
reperfusion injury in a microcirculatory model of pressure ulcers. Wound
Repair
and Regeneration 13: 209-215, 2005.
56. Tupling R, Green H, Senisterra G, Lepock J, and McKee N. Effects of
ischemia on sarcoplasmic reticulum Ca(2+) uptake and Ca(2+) release in rat
skeletal muscle. American Journal of Physiology Endocrinology & Metabolism
281: E224-E232, 2001.
57. Tupling R, Green H, Senisterra G, Lepock J, and McKee N. Ischemia-induced
structural change in SR Ca2+-ATPase is associated with reduced enzyme activity
in rat muscle. American Journal of Physiology Regulatory Integrative &
Comparative Physiology 281: R1681-R1688, 2001.
58. Vodovnik L and Karba R. Treatment of chronic wounds by means of electric
and electromagnetic fields. Part 1. Literature review. Medical and Biological
Engineering and Computing 30: 257-266, 1992.
59. Whittall KP and Mackay AL. Quantitative interpretation of NMR relaxation
data. Journal of Magnetic Resonance 84: 134-152, 1989.
46
CA 02620288 2008-02-01
60. Woolsey RM and McGarry JD. The cause, prevention, and treatment of
pressure sores. Neurologic Clinics 9: 797-808, 1991.
61. Zanca JM, Brienza DM, Berlowitz D, Bennett RG, Lyder CH, and
N.P.U.A.P. Pressure ulcer research funding in America: creation and analysis
of
an on-line database. Advances in Skin and Wound Care 16: 190-197, 2003.
47
