cardiopulmonary resuscitation procedure.

2.  It is a device used for application of a preset
electrical current across the myocardium to cause
synchronous depolarization of the cardiac muscle
with the aim of converting a dysrhythmia into
normal sinus rhythm.
 “ Defibrillation” –is a common treatment of life
threatening cardiac arrhythmias –
 1. Ventricular fibrillation(VF)
 2. Pulseless ventricular tachycardia(pVT)
 VF/pVT- asynchronous rapid ineffective
contraction of muscle fibres the heart.

3.  The longer the duration of fibrillation, the
greater the deterioration of the myocardium,
because a fibrillating heart consumes a very
large amount of oxygen.
 Defibrillators deliver a brief electric shock to
the heart, which enables the heart's natural
pacemaker to regain control and establish a
normal sinus rhythm .
 One of the most crucial links in the “Chain of
survival”(AHA) – EARLY DEFIBRILLATION

4.  Physics behind Defibrillator
 3 major components of a defibrillator:
 a) Power supply
 b) Capacitor
 c) Inductor

5.  Power supply/ Voltage source
 Step-up transformers are transformers that
increase voltage
 Allow the doctor to choose among different
amounts of charge
 This output voltage is then fed to a capacitor,
which stores the high voltage charge.
 As an additional energy source, many
defibrillators also have internal rechargeable
batteries.

6.  Capacitors
 Capacitors store a large amount of energy in
the form of electric charge
 This stored energy is released over a short
period of time
 Inductors
 Coils of wire that produce a magnetic field when
current flows through them, prolong the
duration of current flow
 Inductors generate electricity that opposes the
motion of current passing through it

7. Types of defibrillators
 Internal defibrillator
 Implantable cardiac defibrillator (ICD)
 External defibrillator
 Manual external defibrillator
 Automated external defibrillator (AED)

8. Implantable cardiac defibrillator (ICD)
 An electronic device that constantly monitors heart
rate and rhythm.
 When it detects a very fast, abnormal rhythm, it
delivers energy to the heart muscle. This causes the
heart to beat in a normal rhythm again.
 Used for cardioversion, defibrillation, anti-
tachycardia pacing & bradycardia pacing.
 2 parts :
 a)The leads
 b)The pulse generator
 Electrodes/leads placed directly into the heart
 Have both defibrillation & pacing functions

9. Manual external defibrillator
 DC defibrillator
 Clinician decides what charge has to be set,
depending on prior knowledge and experience
 Shock will be delivered through paddles
applied to the patient’s chest.

10. Automated external defibrillator
 A unit based on computer technology and
designed to analyze the heart rhythm itself,
and then advise whether a shock is required or
not.
 Designed to be used by lay persons, who
require little training.
 Usually limited in the treatment of VF and VT
rhythms.
 Usually take time ( around 5-10 secs) in
diagnosing the rhythm

11.  Require self-adhesive electrodes(pads) instead
of handheld paddles
 The ECG signal acquired from self-adhesive
electrodes usually contains less noise and has
higher quality ⇒ allows faster and more
accurate analysis of the ECG ⇒better shock
decisions
 “Hands off” defibrillation – safer procedure for
the operator, especially if the operator has little
or no training.

12.  Defibrillator electrodes
 Defibrillator electrodes are of 3 types
 a) spoon shaped electrode – applied directly to
the heart
 b) paddle type electrode – applied against the
chest wall
 c) pad type electrode – applied directly on chest
wall.
 The electrodes for external defibrillation are metal
discs about 3-5 cm in diameter (or rectangular flat
paddles 5x10 cm ) and attached to highly insulated
handle.

13.  The size of electrodes plays an important part
in determining the chest wall impedance which
influence the efficiency of defibrillation.
 The capacitor is discharged only when the
electrodes make a good and firm contact with
the chest of the patient.
 For internal defibrillation when the chest is
open, large spoon-shaped electrodes are used.

14. Defibrillator with synchronizer
 Used for termination of unstable ventricular
tachycardia with pulse, atrial fibrillation and other
arrhythmias
 In this device the ECG of the patient is fed to the
defibrillator and the shock is given automatically
at the right moment
 There is a period in the heart cycle in which the
danger is least and defibrillation must take place
during this period (this is called “Synchronized
Cardio-version”)
 The function of the synchronizer circuit is to
permit placement of discharge at the right point on
the patient’s ECG ( avoided during the T wave and
it is approximately 20 –30 ms after the peak of the
R wave )

15.  Defibrillator Wave forms
 Monophasic wave form : Energy is delivered
through the patient’s chest in a “single
direction”
 Biphasic wave form : Energy is delivered
through the patient’s chest in two directions.
 Low-energy biphasic shocks may be as
effective as higher-energy monophasic shocks

16.  Energy levels for Defibrillation
 Defibrillation for Ventricular fibrillation and
Pulseless ventricular tachycardia :
 Monophasic : 360 J
 Biphasic : 120-200 J
 If unknown – Use maximum available dose (
manufacturer recommended)

17.  Synchronized Cardioversion
 Initial recommended doses:
 Narrow regular QRS complex tachycardia : 50-
100J
 Narrow Irregular complex tachycardia : 120-
200 J biphasic or 200 J monophasic
 Wide regular QRS complex tachycardia : 100 J
 Wide irregular QRS complex tachycardia :
Defibrillation dose(NOT synchronized)

18.  Energy levels for Defibrillation
 Pediatric defibrillation : 2J per Kg
 Defibrillation using INTERNAL
PADS/PADDLES :
 Monophasic : 50 J maximum
 Biphasic : 5J, 10J, 20J, 30J, 50J (max)

19.  Clinical indications
 Indications for Defibrillation :
 a) Ventricular fibrillation
 b) Pulseless Ventricular Tachycardia
 Indications for Cardioversion –
 a) Supraventricular Tachycardia (AVNRT/AVRT)
 b) Atrial fibrillation
 c) Atrial flutter
 d) Ventricular Tachycardia with pulse

20.  Contra-indications
 Any arrhythmia with enhanced automaticity like
Catecholamine induced tachycardia Digitalis toxicity
induced arrhythmias
 Multi focal atrial tachycardia
 PRECAUTIONS
 The paddles used in the procedure
 -should not be placed on a breast
 -over an internal defibrillator
 -over wet skin
 Before the paddle is used, a conducting jelly must be
applied and spread over the electrode surface

21.  Complications
 Most common- Harmless arhhythmias like
atrial/ventricular premature beats.
 Serious complications :
 a) ventricular fibrillation
 b) Thrombo-embolisation
 c) Myocardial necrosis
 d) Myocardial stunning
 e) Pulmonary edema
 f) Painful skin burns

22.  Defibrillator maintenance policy
 First, The daily test procedure - 30 J self-test : is
a low energy test to check the charging circuits
& the integrity of cables.
 Second, a weekly check - is carried out to test at
higher energy level using ECG simulator.
 Third, the detailed half-yearly test procedure-
should be performed by the biomedical
department in a hospital

23.  Daily low energy test
 Step 1 : Put the defibrillator on Battery mode and
ensure machine is disconnected from the AC
power supply .
 Turn the selector switch to ON and select Manual
mode
 Select leads to PADDLES/PADS
 Step 2 : Ensure the universal cable is connected to
the paddles
 Place paddles in paddle wells
 Step 3 : Select the ENERGY to 30 J
 Step 4 : Press the CHARGE button

24.  Step 5 : The unit charges to 30J, then the red LED
charge indicator illuminates and the charge tone
sounds
 Step 6 : Ensure DEFIB 30J READY displays on
screen
 Step 7 : Press and hold both paddles SHOCK
buttons
 Step 8 : The unit discharges. The TEST OK message
displays and the red LED turns off
 Step 9 : The above TEST OK message conforms
that low energy circuits are in proper working
condition

25.  Weekly test: Defibrillator internal discharge test
 Repeat the steps from 1 to 9
 Step 10 : Select ENERGY button to maximum
energy level 200J displays
 Step 11 : The unit charges to 200J, then the red LED
charge indicator illuminates and the charge tone
sounds
 Step 12 : Ensure DEFIB 200J READY displays on
screen
 Step 13 : Ensure the machine holds the charge for
50 seconds by giving a long continuous sound
 Step 14 : This confirms the unit is fully functional