DIRECT CURRENT [D.C]INTERRUPTED (PULSED)
DIRECT CURRENT [I.D.C]
RHPT 353 – 1435-1436-1ST SEMESTER
Lecture outlines
2
This lecture deals about the interrupted direct current in
following categories;

Basic terminologies & Definition of IDC

Physiological & therapeutic effects of IDC

Indications & Contra indication of IDC

Selective impulse & technique of application of IDC
3rd Lecture 353 RHPT
7/1/2016
Lecture objectives
3
At the end of lecture the student is able to

Define and outline the principle of IDC current.

List the physiological effects, therapeutic effects, indication,
& contraindication of IDC

Select the appropriate IDC dose

Demonstrate & apply galvanic current on her/ his
colleague
3rd Lecture 353 RHPT
7/1/2016
Typical nomenclature + the appropriate units of
measurement used to describe waveform characteristics
4

Amplitude = intensity (mA)

Frequency = pulse rate or pulses per second (Hz)

Phase duration = pulse width (μsec)
3rd Lecture 353 RHPT
7/1/2016
Define rise time, fall time, and duty cycle
5



Rise time is the time that it takes the wave to travel from
zero to its peak amplitude.
Fall time is the time that it takes the wave to travel from its
peak amplitude to zero.
Duty cycle is the relative proportion of time between the
stimulation period and the rest period.
3rd Lecture 353 RHPT
7/1/2016
Self Questions: Pulse Attributes
F
A
B
D
C




6

B
A = Amplitude
B = Phase Duration
C = Pulse Duration
D= Inter-pulse Interval
F=Pulse period 3rd Lecture 353 RHPT
7/1/2016
Electrical Circuits in the Human Body
Current enters the body through a SERIES circuit (skin &fat).
Once the current enters the tissues, it takes many different
3rd Lecture 353 RHPT 7/1/2016
7
PARALLEL paths
Electrically excitable and non-excitable
tissues.
8
3rd Lecture 353 RHPT
7/1/2016
What factors typically alter skin resistance?
9
Increases Skin Resistance





Decreases Skin Resistance
Increasing electrode
surface(Cross section area)
 Removing excess hair
 Warming skin
 Washing skin
 Decrease distance between
electrodes (length)
 Minimize air-electrode
3rd Lecture interface
353 RHPT 7/1/2016
Cooler skin
temperature
Electrode type/surface
factors
Hair and oil present
Increased skin dryness
Increased skin
thickness

DEFINITION – Direct Current.
10

DC is a unidirectional current in where the flow of current is one
direction

It is also called modified DC or long duration current as pulse duration
between 10 ms (milliseconds) to 300 ms (maximum of 600 ms) and
frequency about 30 Hz or less.

These long duration currents are used to stimulate DENERVATED
MUSCLES
3rd Lecture 353 RHPT
7/1/2016
Direct current
11

Direct (galvanic) wave form
 Pure
DC current, used for iontophoresis
3rd Lecture 353 RHPT
7/1/2016
I.D.C / Modified Direct Current
12

Interrupted DC wave form
 Unidirectional
flow caused by rapid and repeated turning on
and off of the current
 Similar
to modified square wave
3rd Lecture 353 RHPT
7/1/2016
What criteria are used to describe
direct current (DC)?
13
A current is considered DC if it meets the following criteria:

The flow of electrons is unidirectional.

The polarity is constant.

The current produces a twitch response only at the time of
make (when the circuit is closed).

The membrane is hyperpolarized as long as the current is on.

The duration of current flow is3rd>1
second.
Lecture 353 RHPT 7/1/2016
I.D.C - Effects
POLAR
+ Acid
oxygen
coagulates
vasoconstriction
sedates
______________________________________________________________
- Alkaline
hydrogen
liquefies
vasodilation
stimulates
Effects
Interpolar
1.Increases in superficial blood circulation
2. Temperature increase
3. Stimulates cell metabolism due to iron
movement between cells regeneration
14
3rd Lecture 353 RHPT
7/1/2016
Direct currents produce polar effects. What polar effects are
produced by the anode and the cathode?
15
Positive (Anode)






Hyperpolarizes nerve
fibers
Repels bases
Hardens tissues
Stops hemorrhage
Sedates, calms
Reduces pain in acute
situations
Negative (Cathode)






Depolarizes nerve
fibers
Attracts bases
Softens tissues
Increases hemorrhage
Stimulates
Reduces pain in chronic
situations
3rd Lecture 353 RHPT
7/1/2016
IMPORTANT POINTS
16

The duration and frequency of the impulse/pulse can be
adjusted, duration of 100 ms and frequency of 30 Hz is
being commonly used.

Current intensity may rise and fall rapid as in rectangular
impulses or gradual as in triangular , trapezoid & saw
tooth type.(Accommodation Pulses / Selective pulses)
3rd Lecture 353 RHPT
7/1/2016
Modified types of impulses
17
Rectangular
Trapezoidal
Triangular
3rd Lecture 353 RHPT
7/1/2016
Saw-tooth
Physiological effects of Galvanic current
18
Stimulation of motor nerve
Stimulation of denervated muscle
Stimulation of the sensory nerve
3rd Lecture 353 RHPT
7/1/2016
1. Stimulation of motor nerve
19


Stimulation of motor nerve with interrupted direct current
produces contraction of the muscles supplied.
The stimuli are frequently repeated, so each stimuli
produce a brisk muscle twitch followed by immediate
relaxation.
3rd Lecture 353 RHPT
7/1/2016
2. Stimulation of the sensory nerve
20
This will lead to

Stabbing and burning sensation

Reflex vasodilatation lead to erythema
3rd Lecture 353 RHPT
7/1/2016
3. Stimulation of denervated muscle
21

Provided that the intensity of current and duration of
impulses are adequate, a contraction of denervated
muscle can be initiated (Sluggish worm like
contraction)

An impulse of 100 ms is generally considered
satisfactory for the treatment
of denervated muscle.
3rd Lecture 353 RHPT 7/1/2016
Importance of stimulating denervated
muscle
22

When a muscle is deprived of its nerve supply, changes in
its structure and properties tend to occur.

There is marked wasting of the muscle fibers and, if
degeneration is of long-standing, they tend to become
fibrosed and to lose their properties of irritability,
contractibility, extensibility and elasticity.

Electrical stimulation of the muscle fibers may SLOW
these changes.
3rd Lecture 353 RHPT
7/1/2016
Therapeutic effects and uses of the IDC
23
Denervated muscle : aiming to maintain the muscle in a
healthy state until re-innervation

N.B: when the muscle is denervated:

it loss voluntary and reflex activity

Atrophy , degeneration and fibroses


Fibrillation
Galvanic stimulation retard(slowdown) muscle atrophy and
degeneration but not prevent it
3rd Lecture 353 RHPT
7/1/2016
Therapeutic effects and uses of the IDC
24
1- Treatment of Axonotemesis
2- Treatment of Neurotemesis


Ninety(90) contraction is usually regarded as the
minimum number of contraction for the treatment to be
effective.
IDC should be stopped when nerve recovery obtained and
faradic should be started
3rd Lecture 353 RHPT
7/1/2016
Contraindication and precaution to use
IDC
25
Contraindications:

Cardiac pacemaker

Unconscious patients

Recent radiotherapy

Cardiac sinus
3rd Lecture 353 RHPT
7/1/2016
26

Early tendon transfer

Malignancy

Infected wound
 Hemorrhage
Areas of venous and arterial thrombosis
and thrombophlebitis
 Pregnancy
3rd Lecture 353 RHPT
7/1/2016
Precautions
27

Cardiac disease

Anesthetic /hypothetic skin

Small children and subjects with impaired mentation

If the patient has undergone iontophoresis /
Phonophoresis.
3rd Lecture 353 RHPT
7/1/2016
Selective impulses
28
Definition

It is the impulses in which the current rises gradually.

It is also called triangular or accommodation pulses

Muscle tissue can be stimulated by this type.
3rd Lecture 353 RHPT
7/1/2016
Selection of impulses type
29

The slow rise of intensity of
the selective impulses has
advantage to contract the denervated muscle with less sensory
stimulation than the rectangular current.

To stimulate denervated muscle a triangular current waveform
of 50 ms or 100ms is suitable.

For denervated muscle ,it is best to use more than 100 ms,
300, or 500 ms triangular pulses (Or) square wave pulses of
30ms or more
3rd Lecture 353 RHPT
7/1/2016
Methods of application
30
There are two methods in application
1) Labile technique
2) Stabile technique
1)Labile technique
This is using one small pen electrode in the muscle belly as
active electrode and one disc or surface electrode is fixed
over nerve trunk (below the level of lesion) or origin of the
muscle as inactive electrode.
2)Stabile technique
3rd Lecture 353 RHPT 7/1/2016
This is using two disc electrode fixed on the muscle.
The practical and clinical implications for frequency
31
Frequency (Hz)
Type of Contraction produced in
MUSCLE

1-10

Twitch contraction

>30

Tetanic contraction

30-70


100-1000

Non-fatiguing tetanic
contraction
Fatiguing tetanic
contraction
3rd Lecture 353 RHPT
7/1/2016
The practical and clinical implications for
phase duration
32



Phase duration contributes to the comfort of the
stimulation.
The amount of chemical change that occurs in the
tissues, and nerve discrimination.
A duration of 50 to 100 μsec typically is used for
sensory stimulation, and 200 to 300 μsec is
typically used for motor stimulation.
3rd Lecture 353 RHPT
7/1/2016
The practical and clinical implications for
amplitude
33

Greater intensity yields greater depths of penetration
(generally speaking)

Low intensities used for sensory stimulation

High intensities used for motor stimulation
3rd Lecture 353 RHPT
7/1/2016
General Points to note – Lab Activity
34

1. Preparation of apparatus
1.a. Assembling of the apparatus
1.b. Testing of the machine

2.Preparation of the patient

3.Stimulation of motor points


3rd Lecture 353 RHPT
7/1/2016
Important aspects of Preparation of
Apparatus
35


Selection can also be made of the shape of
the impulse for the muscle stimulation.
The pulse duration is set to – 100ms.
3rd Lecture 353 RHPT
7/1/2016
Important aspects of Testing of Apparatus
36


The placement of electrodes for testing is
same as for the faradic stimulation.
A brisk muscle twitch is followed by an
immediate rest period is expected.
3rd Lecture 353 RHPT
7/1/2016
Important aspects of Patient preparation
37



Tell him about the type of sensation he/she should
feel during the stimulation – stabbing or burning
sensation.
Give them proper instruction & warning about the
treatment.
Reduce the skin resistance by performing the skin
resistance lowering procedure.
3rd Lecture 353 RHPT
7/1/2016
Important aspects of Treatment
38



The muscles to be stimulated remains in a partially
shortened position (Middle range of muscle work)
The Galvanic current may be applied with the muscle in a
partially lengthened position.
This should only be done if the contractions produced are
sufficiently strong to cause shortening of the muscles +
joint movement.
3rd Lecture 353 RHPT
7/1/2016
Important aspects of Treatment
39


A minimum of 90 Contractions of each
muscle is desirable in a session as a general
rule – effective treatment
Fatigue – A weakening of contractions is the
indication for limiting the length of the
treatment.
3rd Lecture 353 RHPT
7/1/2016