Electrical stimulation

ELECTRICAL
STIMULATION
By:- Dr. Arjun Patel
M.P.T.(Musculoskeletal and sports
science
1
ELECTRICAL STIMULATION

How movement
is produced?
1
• STIMULUS
(Brain)
2
• TRANSMISSION
(Nervous system)
3
• RESPONSE
(Muscle)
ELECTRICAL STIMULATION 2

VARIANTS OF DIRECT CURRENT
Continuous Direct Current Interrupted Direct Current
Depolarized Direct Current Intermittent Depolarized Direct Current

PARAMETERS OF ALTERNATING CURRENT

PARAMETERS OF ELECTRIC CURRENT
Continuous or uninterrupted alternating current:
• It is bidirectional flow of alternating current without interruption.
Pulsed or pulsatile or interrupted alternating current:
• It is flow of alternating current with periodic ceases for definite
period of time.
Monophasic pulsed current:
• In this type, flow of alternating current is unidirectional.
Biphasic pulsed current:
• In this type, flow of alternating current is bidirectional.

Pulse and Phase:
• It is an isolated electrical event separated by definite time from
next electrical event. Pulse includes flow of electric current on both
directions. Phase is a part of pulse which indicates flow of electric
current in only one direction. One pulse has either one or two
phases.
Pulse duration:
• It is the time between onset of pulse and termination of same pulse
to complete one complete cycle of bidirectional flow of alternating
current.
Phase duration:
• It is the time between onset of phase and termination of same
phase to complete unidirectional flow of alternating current.

Intensity or amplitude or magnitude:
• It is the amount of maximum current reached in one phase.
Rise time:
• It is the time taken by phase to rise from zero intensity to maximum
intensity.
Decay time:
• It is the time taken by pulse to decrease from maximum intensity to
zero intensity.
Interpulse interval:
• It is time between termination of one pulse and onset of next
successive pulse.

Frequency:
• It is number of complete pulses passes through a fixed
point in space in a unit time.
 Unit:
• For general purpose: Hertz (Hz)
• For continuous alternating current: cycles per second (cps)
• For pulsed alternating current: pulses per second (pps)
 Classification of current according to frequency:
• Low frequency current: Up to 1,000 Hz
• Medium frequency current: 1,000 Hz to 10,000 Hz
• High frequency current: More than 10,000 Hz

Waveform: It is geometric shape of the pulse or phase as they
appear on the graph of current or voltage versus time graph.

•Surface electrodes: Electrodes are attached to
skin
•Invasive or indwelling electrodes: Electrodes
are implanted near the nerves or bones
•Internal electrodes: Electrodes are inside the
body cavities
Physiotherapists are using surface electrodes only
so our discussion will be for surface electrodes
only in detail.
CLASSIFICATION OF ELECTRODE ACCORDING TO
ITS PLACEMENT SITE IN BODY
10

In different clinical settings different types of
electrodes are used depending on individual
preference. Each type has its merits and demerits.
Rubber electrodes
Metal electrodes
Vacuum electrodes
Self-adhesive electrodes
TYPES OF SURFACE ELECTRODES
11

RUBBER ELECTRODES
They are made up of carbon and silicone. These electrodes are used most
commonly. Their color is mostly black. They have hole to connect it with
lead on one side. By shape they are rectangular, square or circular
depending on manufacturer.
Advantages:
• They are user friendly.
• They can be adjusted
according to body contour
making firm contact.
Disadvantages:
• They need gel or water to
make contact between skin and
electrode. Without this
conducting medium current
will not enter to patient’s skin.
• They become very dirty and
less flexible to make firm
contact with patients’ body
with more use. They must be
disinfected with sterilizing
material after every use.
• They may crack in between
after sometime.
• They need stabilization with
strap or adhesive tape on the
skin.
12

Advantage:
•They are also easy to use.
•They are not breakable.
•They do not need conducting
gel but lint pad should be dipped
in water.
METAL ELECTRODE
They are made up of metals as the name suggests. They are
used less frequently. Disadvantages:
•They need wet lint pad made
up of cloth that surrounds
electrode on each side as direct
contact of electrode with skin
leads to skin chemical burn.
•They are not flexible to body
contour.
•They also need stabilization
with strap of adhesive tape.
13

VACUUM ELECTRODES
Advantages:
• They do not need
stabilization by strap of tap.
• It can be placed over the
body’s irregular body part.
• They also do not need
conducting gel.
They are cup like structure made up of plastic. Inside this
cup like structure, there will be electrode. Vacuum will be
created by machine between cup and body so electrode will
be held over the body part.
Disadvantages:
• Cost of machine will be
higher because of extra
vacuum component.
14

SELF-ADHESIVE
ELECTRODES
They are adhered to patients’ body by sticky material on
it. These are most recent advance used now-a-days.
Advantages:
•They are very easy to use.
•They do not need any type of
stabilization material.
Disadvantages:
•They tend to wear after
repeated use.
15

TYPES OF STIMULATORS
Constant current or Regulated
current type
• Intensity is in Current.
• Unit:- Ampere
• Accurate
• Mostly used for diagnosis
purpose
Constant voltage or Regulated
voltage type
• Intensity is in Voltage
• Unit:- Volt
• Comfortable
• Mostly used for treatment
purpose

CONTRA-INDICATIONS
 Over thoracic region
 Cardiac pacemakers
 Phrenic nerve
 Urinary bladder
 Carotid sinus
 Hypertensive patients
 Uncooperative patients
 Inflammation
 Tuberculosis
 Superficial metal implant
 Peripheral vascular
disorders
 Neoplasm
 Infection
 Pregnant females
 Proximity to diathermy
 Obese patients
 Thrombosis
 Active infection
 Sensation alteration
N.M.E.S. 17

ACCOMODATION
• When current is applied at constant intensity
nerve declines to response.
• Sudden rise or fall in current is LESS effective
than gradual rise or fall in current.
18

EFFECT OF FREQUENCY OF STIMULATION
0 to 20 Hz – No Tetany (Complete contraction
followed by complete relaxation of muscle)
20 to 60 Hz – Partial Tetany (Complete
contraction followed by incomplete relaxation
of muscle)
More than 60 Hz – Tetany (Complete
contraction without relaxation of muscle)
19

STRENGTH OF CONTRACTION
It depends on…
No. of motor units activated (which depends
on intensity)
Rate of change of current i.e. waveform
e.g. with gradually increasing intensity type of
waveform, intensity needed is more and with
sudden increasing intensity type of waveform,
intensity needed is less.
20

EFFECTS OF ELECTRICAL STIMULATION
• Chemical effects
• Physical effects
• Thermal effects

TYPES OF PULSE DURATION
PULSE
DURATION
Short
(<10 ms)
Long
(>10 ms)

FARADIC CURRENT
• It is short duration interrupted current with a
pulse duration of 0.1-1 ms and a frequency of
50-100 Hz.
• It was produced by faradic coil, type of
induction coil.
• Now faradic coils are replaced by modern
electronic stimulators.
• They both have same physiological effects
though they differ considerably.
23

DIFFERENCE BETWEEN ORIGINAL FARADIC
AND MODERN ELECTRIC STIMULATOR
Original Faradic Current Modern Electric Stimulator
24

MODIFIED FARADIC CURRENTS
• Faradic type currents are surged for treatment
pulse.
• In original faradic coil, current was surged by
hand but now it happens automatically.
• It is desirable that duration of surges and
interval between them should be decided by
separate knobs.

EFFECT OF NERVE STIMULATION
• Bell-Magendie’s law
• Effect on sensory nerves
Prickling sensation and erythema formation
• Effect on motor nerves
Muscle contraction
• Effect on motor nerve trunk
26

PHYSIOLOGICAL EFFECTS
• Body tissue is conductor for electric current as
it contains fluid with ions
• Epidermis has high resistance i.e. 1000 Ω or
more…
• Good conductor has more blood supply (e.g.
Muscle)
• Poor conductor has less blood supply (e.g. Fat)
27

• Stimulation of sensory nerve
• Stimulation of motor nerve
• Effects of muscle contraction
• Stimulation of denervated muscle
• Chemical effects
28

INDICATIONS
• Facilitation of muscle contraction
• Re-education of muscle
• Training a new muscle action
• Neurapraxia of motor nerve
• Severed motor nerve
• Improved venous and lymphatic drainage
• Prevention and loosening of adhesions
29

TECHNIQUE
• STEP 1: Check for contra-indications
• STEP 2: Check the apparatus
• STEP 3: Application
• STEP 4: Wind-up
30

SMART-BRISTOW COIL
• Pulses of electric current as used in faradic treatment
in physiotherapy departments are usually generated by
electronic apparatus with facilities for pulsating the
bursts of electric pulses.
• In older machines a faraday coil is used which
generates the pulses by the interruption of current to
an inductor (similar to a car ignition coil).
• The Smart Bristow faradic coil used in physiotherapy
apparatus has a retractable iron core which is moved in
and out of the coil to change the strength of the
pulses.
31

MODE OF TREATMENT
• Motor point stimulation
For individual muscle
• Group muscle stimulation
For quadriceps, pelvic floor muscles etc.
• Faradic foot-bath
For interrossei, lumbricals and abductor hallucis
• Faradism under pressure
For upper limb and lower limb
32

MOTOR POINTS
Definition:
• Anatomically: It is point where nerve enters
into the muscle.
• Physiologically: It is point where one can get
maximum contraction with minimum intensity
of current.
Location:
• It is situated at junction of proximal 1/3 and
distal 2/3

INTERMITTENT GALVANIC CURRENT
• It is by most usual modification of direct current,
the flow of current commencing and ceasing at
regular intervals.
• Selective impulses – Used for stimulation of
denervated muscles
• Duration may be increased up to 300 to 600 ms.
More the duration, more the effective
contraction.
• If pulse duration increases, frequency must be
decreased.

INTERMITTENT GALVANIC CURRENT
• Mostly depolarized impulses are used so there
are less chances of chemical burns.
• Depending on different knobs adjustment,
definite parameters of electric current may be
availed for treatment purpose.
• Current is always applied to the patient via
potentiometer as this allows the intensity of
current to be turned up from zero.

• Stimulation of denervated muscle (If pulse
duration and intensity are sufficient.)
• Stimulation of sensory nerves
• Stimulation of motor nerves
Contraction with slowly rising current is more
effective than suddenly rising current for
denervated muscle as there is no
accommodation in denervated muscle.

INDICATIONS
MAIN INDICATION IS…
• Stimulation of denervated muscle
• It may slow down process of loss in muscle
properties like irritability, contractibility,
extensibility and elasticity.
• In early stage of regeneration of muscle..
Note:- Stimulation must be strong enough to
produce muscle contraction.

FOR THERAPEUTIC PURPOSE
Intermittent Galvanic Current/
Modified Direct Current
• Pulse duration more than
10 ms (Long duration pulse)
• Frequency 30/min
• It is used for stimulation of
denervated muscle.
• It is variant of direct current
• For electrical stimulation,
cathode or anode can be
active.
• It gives stabbing sensation
Surge Faradic Current
• Pulse duration less than 10
ms (Short duration pulse)
• Frequency 50-100 Hz
• It is used for stimulation of
denervated or innervated
muscle.
• It is variant of alternating
current.
• For electrical stimulation,
cathode is active.
• It gives prickling sensation.

REFERRENCES

QUESTIONS?
41

Electrical stimulation

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