Electric shock , electrical hazards and its management

-Dr. Rushikesh K. Joshi
(MPT Neuro.)

Sources of Electrical Hazards
Dr. Rushikesh K. Joshi, PT

 Electrical hazards occur when a person comes
into contact with a current-carrying
conductor.
 A current-carrying conductor is usually
thought of as metal wire that supply electrical
power to receptacles, or as the wire within
the power-supply cords to electrical devices.
 Moreover, We should be familiar with the
term ‘Environmental currents’

 Breaks in the insulation on such cables or
wires through misuse, normal wear and tear,
or deterioration with age expose the
conductor.
 The contact of body tissues with such bare
wires may result in shocks with potentially
serious consequences.

 Less obvious types of potential current-
carrying conductors include the metal cases,
or other external conductive components on
line-powered instruments, that can carry
current as a result of contact (electrical short)
with internal conductors, inappropriate
electrical connections within the device, or
other factors.

 Such currents are commonly referred to as
leakage currents.
 Low levels of leakage current (< 1 mA) are
routinely found on most line-powered
instruments.
 Normally this current does not present a
problem because instrument cases are
connected to a wire (safety ground) that
provides a low-resistance pathway to ground.
(fig: A)

 If this path way does not exist, as when using
a line-powered device with a two-prong plug
or if the wire to the safety ground is broken
for any reason, leakage currents can flow to
ground through an individual who is touching
the device, resulting in electrical shock
(Fig: B).

 An additional approach used to protect
against the development of significant
ground faults or leakage currents is the use
of electrical device called a ground fault
interrupter. (GFI; or sometimes ground fault
circuit interrupter).

 A GFI monitors the amount of current going
to and returning from a lined powered device.
 When the amounts of outgoing and returning
currents differ by more than 3 to 5 mA, the
GFI opens a switch and instantly cuts the
current to the device.
 GFIs are designed to trip in 1/40th of a
second.

 There are two types of GFIs in power-supply
circuits a receptacle GFI,
 1) located within a wall outlet and
 2) a circuit breaker GFI, located in a circuit
breaker box.

 This has particular significance in those
situations where line-powered devices are
used for in-home health care.
 Battery-operated stimulators may be an
appropriate alternative for many home
treatment programs unless a receptacle GFI is
properly installed.

 Potential Adverse Effects of DC at
Electrotherapeutic Levels

 Tissue damage, especially to the skin, can be
caused by clinical uses of direct current even
at low amplitudes.
 Skin damage may result from electrolytic
reactions that occur when DC passes through
the skin.

 Acidic reactions can occur beneath the
positive electrode (anode), and alkaline
reactions can occur beneath the negative
electrode (cathode) used in DC treatment
procedures .
 If the buildup of acids or alkaline by-
products is sufficient, skin damage in the
form of blistering burns may result.

 Additionally, coagulation of microcirculation
(capillary circulation) may occur beneath the
anode of a DC circuit and result in tissue
necrosis secondary to ischemia.
 Although DC clinical applications to the skin
have the potential to raise tissue
temperature, adverse skin responses are not
thought to be thermal burns.

 The extent of damage that can result from DC
is determined by the amplitude of current
applied, the time over which the current is
allowed to flow, and the tissue impedance.
 For these reasons, DC electrotherapeutic
procedures are generally limited to
applications of current at 5.0 mA or less for
periods of 15 minutes or less, and steps are
taken to reduce skin impedance before
treatment.

 Electrode sizes are selected so that current
densities do not exceed 0. 1 to 0.5 mA per
cm2 of electrode surface area. For these
treatment parameters, the patient should not
report any sensation beneath the electrodes.
 A report of a tingling sensation as continuous
DC is applied should signal the health care
provider to reduce the amplitude and re-
examine the treatment setup to ensure
uniform electrode contact.

 Close observation of the skin is required in
each patient receiving DC stimulation to avoid
adverse reactions.
 This inspection is particularly important due
to the anesthetic effect that may occur
beneath the electrodes.

 Although some forms of pulsed monophasic
currents have been reported to have chemical
effects similar to those of DC, very short
duration monophasic pulsed currents do not
apparently produce harmful electrochemical
effects on the skin.

Types of Electric Shock

 Electric shocks can be of three types
depending upon the nature and amount of
current flow and can also be classed as two
types depending upon the severity.

A). Depending upon the nature and amount of
current flow electric shocks can be:
(1) Macro-shock,
(2) Micro-shock,
(3) Earth-shock.
B). Depending on the severity of shock: The
shock can be
(1) Mild-shock
(2) Severe-shock

 If the current flow is from the body surface
through the skin into the body, a relatively
large amount of current is needed to produce
a harmful shock, called macro-shock.

 If the current by-passes the surface of the
body and enters the heart by way of
myocardial electrodes or a trans-venous
catheter, a minute current can produce a fatal
shock without the patient experiencing
anything.

 For example, a therapist may be handling a
patient with an electrical monitoring device
on the heart.
 If at the same time he were to connect his
hands to a faulty table lamp, or some device
with a broken ground connection whilst
palpating the patient’s chest, then he could
give the patient a micro-shock, and cause
ventricular fibrillation.

 When the shock is due to a connection
between the live wire the main and the earth,
it is known as earth-shock.
 The patient who is receiving treatment with a
current that is not earth free and if there is no
earth connection between the outer casing of
the apparatus and earth or when the building
does not have a ground connection,

 there is every possibility that the person may
form an earth circuit (provided that the floor
is not insulated) through whom the current is
earthed resulting in earth-shock.

B). Depending on the severity of shock: The
shock can be
(1) Mild-shock
(2) Severe-shock.

 When the intensity of the current that give
rise the shock, up to 20 mA, the patient may
only get a painful sensory stimulation, with
labored and upset breathing with a lot of fear
and distress.
 There is no loss of consciousness.
:

 If the current flow is more than 20 mA, it
results in difficulty in letting go, muscular
paralysis, fall in blood pressure, loss of
consciousness, cessation of respiration and
ventricular fibrillation and cardiac arrest in a
few cases resulting in death.
 Death usually occurs with a current that is
above 100 mA and is a must with a current of
200 mA and above, if immediate release is
not possible.

Causes of Electric Shock

 A person may obtain a shock without
touching the active wire of the power supply
by the following ways.

 If, while on the start of the treatment, the
low or medium frequency current is
switched on with the controls turned up or
if insufficient time is allowed for the
apparatus to warm up so that the current
comes on suddenly after the controls have
been turned up, it results in a sudden flow
of current giving shock.
 Shock may also occur if the intensity
controls is turned up unduly during the
intervals in the flow of an interrupted or
surged current. Dr. Rushikesh K. Joshi, PT

 Many electrical apparatus have metal casings.
 An active voltage can be actua1b shortened
to the casing because of the dropping of the
instrument, moisture, dust, deterioration of
the equipment due to misuse or age.
 A person (patient/therapist) touching the
casing could get a shock.

 In all electrical equipments, the intended
current carrying parts are separated from the
rest of the equipment by insulators.
 With high quality insulation materials and
good circuit designs, there will be no problem
with leakage currents but with poor designs
the leakage current from the wires carrying
the currents will be hazardous.

 It is important that all electrical equipment
should have a three pin connection with the
earth connection to avoid the leakage
currents and hazards from metal casings.
 The three-pin system offers the protection of
the fuse blowing, if there is a leakage oil
metal casing short circuit.

 The three-pin system has the protective
ground wire pin, always longer than the
others to ensure that the ground connection
is the first to b plugged in and the last to be
unplugged.
 The building itself must carry a good
grounding system for the power supply.
 If the above features are absent and a two pin
connection is used it may give the shock.

 The presence of faulty components such as a
faulty transformer or a leaky capacitor may be
hazardous giving electric shock.

 It is mandatory to have the floor of the
electrotherapy unit to be insulated through
vinyl or some other insulated floorings.
 If the floor is not insulated it enhances the
occurrence of the earth shock.

 It is essential that the switches and fuses
must break the live wire, if not it may
produce shock as described under the safety
devices.

Effect of Electric Shock

 Following a mild-shock the victim may
be frightened and get some pain.
 The respiratory and the heart rate may
be increased and the subject may have
breathing difficulty.
 Whereas following a severe-shock, the
victim may remain connected to the
circuit, there may be muscular paralysis,
fall in blood pressure, ventricular
fibrillation, loss of consciousness,
cessation of respiration and cardiac
arrest.

 The cessation of respiration is recognized by
lack of respiratory movements and cyanosis,
whereas the cardiac arrest can be recognized
by the absence or abnormality of respiratory
movements, absence of pulse in the carotid
artery and fully dilated pupils.

Treatment of Electric Shock

 In the event of a shock occurring, the first
step is to disconnect the victim from the
contact with the current source.
 The current should be switched off at once
but, if there is no switch in the circuit, the
victim must be removed from the contact
with the conductor but the rescuer must take
care not to get a shock by touching the
affected person

 The contact with the affected person should
only be made by a thick layer of insulated
material.
 After the person is removed a medical officer
is immediately consulted and the following
steps a taken.

 If the shock is a minor one, the victim is
reassured an given rest.
 The victim may be given water to drink but
hot drinks should be avoided, as they cause
vasodilatation an sweating and a further fall
in blood pressure.

 If the shock is more severe, the victim is
laid flat in supine a position that the
respiratory passages are clear.
 The tight clothing should be loosened and
plenty of air is circulate to avoid undue
warming, as it causes vasodilatation and
increases sweating.
 The external heat increases the metabolism
and so the demand for oxygen also
increases which is hazardous

 Do not give any thing in the mouth if the
patient is unconscious.
 If the respiration has ceased, clear the
airways and start artificial respiration by
mouth to mouth or mouth to nose method
and proceed for oxygen administration by a
bag and mask.

 In the event of cardiac arrest, start external
cardiac massage with mouth to mouth or
mouth to nose breathing in the following
manner.

 The patient is laid on the back, either on the
floor or on some hard surface with the neck
extended to open the airways.
 The operator places his/her hands one on top
of the other on the patients lower sternum
and commences forceful rhythmic
compressions at the rate of 60-100 per
minute.

 The operator after every 15 chest
compressions intersperses two chest
expansions, either through mouth to mouth
or mouth to nose ventilation (until the face
mask and bag are available).

 In this case the same procedure is followed
like the single operator handling except, one
operator giving chest compression, which is
interspersed by mouth to mouth or mouth to
nose breathing by the second operator after
every five chest compressions.

 In the events of respiratory failure or cardiac
arrest, it is essential to call for medical help
immediately, but no delay should be made in
starting the cardiopulmonary resuscitation.

1. CLINICAL ELECROPHYSIOLOGY – ANDREW J.
ROBINSON
2. CLAYTON’S ELECTROTHERAPY
3. ELECTRO SIMPLIFIED - NANDA

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