Effects of overnight electrical stimulation on local oxygenation and muscle thickness in people with spinal cord injury

One of the most prominent secondary problems following SCI is the occurrence of
pressure ulcers. Computer models show that the highest stress and strain
values can be found in the gluteal muscles during sitting, causing tissue
damage. Furthermore, amount of affected tissue seems to increase with muscle
atrophy. Changes in local blood flow characteristics also occur in persons with
SCI. For example, research has shown decreased post-occlusion blood flow in
persons with SCI. Atrophy of gluteal muscles, decreased blood flow and
oxygenation in combination with prolonged periods of sitting cause the area
right beneath the ischial tuberosities to be of high risk for developing
pressure ulcers. To prevent pressure ulcers electrical stimulation might be a
useful tool. Activation of glutes and muscles in upper leg could preserve or
improve muscle mass and improve oxygenation of stimulated tissue.

There are several ways to apply electrical stimulation. In this study we focus
on feasability of overnight electrical stimulation using electrical stimulation
shorts. Overnight electrical stimulation could be a favoured method in using
electrical stimulation because daily activities are not disturbed. In
addition, getting in and out of the shorts can easily be done when the subject
is in bed. Therefore setting up electrical stimulation for overnight electrical
stimulation has the advantage that no extra transfers are required.

We expect overnight electrical stimulation to be a feasible and convenient way
of applying electrical stimulation which does not disturb spinal cord injury
patients in any way. Furthermore, we expect overnight electrical stimulation to
increase muscle mass of stimulated muscles and improve oxygenation in
stimulated area.

For a more detailed description we refere to the introduction of the research
proposal

The study will excist of two experiments. The first experiment is a two week
overnight electrical stimulation program and in the second experiment subjects
will be stimulated for 4 months.With these two experiments we wish to answer
the following research question.

Is overnight electrical stimulation a useful method to reduce the risk on
pressure ulcers?

Specific aims of the two experiments are listed below

Experiment 1: Two week overnight stimulation program
1) Evaluate if electrical stimulation can be applied overnight without
disturbing sleep
2) Determine oxygenation in the stimulated area in different conditions.
3) Determine effect of 2 weeks of overnight electrical stimulation on
oxygenation in stimulated areas.


Experiment 2: Four months overnight stimulation program
1) Deteremine effects of 4 months of overnight stimulation on muscle mass in
stimulated area
2) Determine effect of 4 months of overnight stimulation on pressure
distribution, during sitting.
3) Establish the effects of 4 months of overnight electrical stimulation on
oxygenation in stimulated area.

Desing for both experiments will be a "one group pretest - posttest" design.

Experiment 1:
will be determined prior to and directly after 2 weeks of electrical
stimulation. Quality of sleep will be measured every week using questionnaires.
Tissue saturation in gluteus maximus muscle, oxygen uptake and blood flow in
vastus lateralis muscle, energy expenditure, muscle fatigue and interface
pressure will be measured prior to the intervention, a day before onset of
electrical stimulation, after two weeks of electrical stimulation and 2 weeks
after ending the stimulation program.

Experiment 2:
Thickness of gluteus maximus muscle will be measured prior to and directly
after the intervention. Measurements of tissue saturation in gluteus maximus
muscle, oxygen uptake and blood flow in vastus lateralis muscle and energy
expenditure will take place prior to the study, a day before onset of
stimulation, after 2 and 4 months of overnight electrical stimulation and 2
months after ending electrical stimulation.Quality of sleep will be tested,
using questionnaires, weekly for the first 4 weeks and once every 4 weeks
after the first month of the program. Interface pressure and buttock dimensions
will be measured weekly throughout the intervention.

Subjects will be stimulated every night throughout the experiments (2 weeks or
4 months). The subjects will take their ES shorts and neuromuscular electrical
stimulators home and subjects are asked to put on the ES shorts every night
before going to bed and start electrical stimulation as they lie in bed.
Stimulation program will end 8 hours after starting, however subjects are
allowed to stop electrical stimulation before program is ended. Biphasic
stimulation will be applied at 35Hz to achieve tetanic muscle contraction, with
amplitudes of current stimulation established during setup. In this test, the
subject will wear the ES-shorts and be placed in bed in a supine position. The
electrical stimulation amplitude for the program is determined as the highest
amplitude, with a maximum of 150 mA, which subjects do not find unpleasant or
disturbing and where a muscle contraction is visible. In the second experiment
every two weeks amplitude will be adjusted if needed.

Subjects will visit the lab 4 and 5 times for the short and long experiment
respectively. Each visit will take approximatily 3 hours except for the first
visit where shorts will be fitted an stimulation program is set as well, first
visit will take 4 hours.

In these visits the oxygenation in gluteal area will be determined, therefore a
small probe will be attached under the buttocks. In addition, to determine
oxygenation in vastus lateralis a cuff will be placed around the upper leg for
small periods. Measurements of energy expenditure will be performed by putting
on a mask. Subjects are able to breath normally during this measurement.
In the short experiment subjects will have to fill out questionnaires every
week. Ïn the long experiment a researcher will visit the subjects every week in
order to measure interface pressure and buttock dimensions. These visits will
take about 30 minutes each. In addition, in the long experiment subjects will
go to the Jan van Bremen Institute twice for CT scans.


Electrical stimulation will be applied every night. Electrical stimulation
cause muscle contractions, as a result of the contractions there could be
movement in the limbs. In addition, electrical stimulation could be percepted
as unpleasant. Therefore, electrical stimulation could disturb sleep.
However, we expect overnight electrical stimulation not to be disturbing sleep.
Movement of limbs will be fairly little, because stimulation parameters are not
maximal. Furthermore, because of the loss of sensory in the lower limbs it is
not likely that electrical stimulation will disturb the subjects. Using the
electrical stimulator is safe, the stimulator will stop stimulation over a
channel if contact between electrode and skin or electrode and stimulator is
lost.