CARDIAC MONITORING
&
RHYTHM RECOGNITION
How to monitor the ECG (1):
Monitoring leads
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3-lead system approximates to I, II, III
Colour coded
Remove hair
Apply over bone
Lead setting (II)
Gain
How to monitor the ECG (2):
Defibrillator paddles
• Suitable for “quick-look”
• Movement artefact
• Risk of spurious asystole
How to monitor the ECG (3):
Adhesive monitoring electrodes
• “Hands-free” monitoring and
defibrillation
Basic electrocardiography (1)
• Depolarisation initiated in SA node
• Slow conduction through AV node
• Rapid conduction through Purkinje fibres
Basic electrocardiography (2)
• P wave = atrial depolarisation
• QRS = ventricular depolarisation (< 0.12 s)
• T wave = ventricular repolarisation
Cardiac arrest rhythms
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Ventricular fibrillation
Pulseless ventricular tachycardia
Asystole
Pulseless Electrical Activity (PEA)
Ventricular fibrillation
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Bizarre irregular waveform
No recognisable QRS complexes
Random frequency and amplitude
Unco-ordinated electrical activity
Exclude artifact
– movement
– electrical interference
Pulseless ventricular tachycardia
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Broad regular complex rhythm
Rapid rate 100-300 per min
Constant QRS morphology
Atrial activity continues independently
Asystole
• Absent ventricular (QRS) activity
• Atrial activity (P waves) may persist
• Rarely a straight line trace
Pulseless Electrical Activity
• Clinical absence of cardiac output
despite electrical activity
• ECG is normal or near normal
DEFIBRILLATION
Mechanism of defibrillation
• Definition
“The termination of fibrillation or absence of
VF/VT at 5 seconds after shock delivery”
• Critical mass of myocardium depolarised
• Natural pacemaker tissue resumes control
Defibrillation
Success depends on delivery of
current to the myocardium
Current flow depends upon:
• Electrode position
• Transthoracic impedance
• Energy delivered
• Body size
Transthoracic Impedance
Dependent upon:
• Electrode size
• Electrode/skin interface
• Contact pressure
• Phase of respiration
• Sequential shocks
Defibrillators
• Design
– Power source
– Capacitor
– Electrodes
• Types
– Manual (monophasic or Biphasic waveform)
– Automated
Defibrillator waveforms
•Damped Monophasic
•Truncated Biphasic
Biphasic Defibrillators
• Require less energy for defibrillation
– smaller capacitors and batteries
– lighter and more transportable
• Repeated < 200 J biphasic shocks
have higher success rate for
terminating VF/VT than escalating
monophasic shocks
Automated external defibrillators
• Analyse cardiac rhythm
• Prepare for shock delivery
• Specificity for recognition of
shockable rhythm close to 100%
Automated external defibrillators
Advantages:
• Less training required
– no need for ECG interpretation
• Suitable for “first-responder” defibrillation
• Public access defibrillation (PAD) programs
SWITCH ON AED
• Some AEDs will automatically switch
themselves on when the lid is opened
ATTACH PADS TO CASUALTY’S
BARE CHEST
ATTACH PADS TO CASUALTY’S
BARE CHEST
ANALYSING RHYTHM
DO NOT TOUCH VICTIM
SHOCK INDICATED
• Stand clear
• Deliver shock
STOP !!!
DEFIBRILLATION
Approach safely
SHOCK DELIVERED
FOLLOW AED INSTRUCTIONS
or
NO SHOCK ADVISED
FOLLOW AED INSTRUCTIONS
Deliver CPR 30:2 !!
IF VICTIM STARTS TO BREATHE
NORMALLY PLACE IN RECOVERY
POSITION
CPR IN CHILDREN
• Adult CPR techniques can be used on children
• Compressions 1/3 of the depth of the chest
AED IN CHILDREN
• Age > 8 years
• use adult AED
• Age 1-8 years
• use paediatric pads / settings if available (otherwise use adult
mode)
• Age < 1 year
• use only if manufacturer instructions indicate it is safe
Manual Defibrillation
Relies upon:
• Operator recognition of ECG rhythm
• Operator charging machine and delivering
shock
• Can be used for synchronised
cardioversion
Defibrillator Safety
• Never hold both paddles in one hand
• Charge only with paddles on
casualty’s chest
• Avoid direct or indirect contact
• Wipe any water from the patient’s
chest
• Remove high-flow oxygen from zone
of defibrillation
Shock Energy
MONOPHASIC
• Initial and subsequent shocks energy 360
J*, repeat once if unsuccessful
• Deliver shocks singly
BIPHASIC
• Initial shock 150-200 J
• Subsequent shocks 200-360 J
• If defibrillation restores the patient’s
circulation and VF/VT recurs, start again at
150J*
Manual Defibrillation
• Diagnose VF/VT from ECG and signs of
cardiac arrest
• Select correct energy level
• Charge paddles on patient
• Shout “stand clear”
• Visual check of area
• Check monitor
• Deliver shock
Unresponsive ?
Open Airway
Look for signs of life
Call
Resuscitation
Team
CPR 30:2
Until defibrillator / monitor attached
Assess
Rhythm
Shockable
Non-shockable
(VF/ Pulsless VT)
(PEA / Asystole)
1 Shock
150-360 J biphasic
lub 360 J monophasic
Immediately resume:
CPR 30:2
For 2 min
Immediately resume:
CPR 30:2
For 2 min
Pulseless VT is treated with an
unsynchronised shock using
the VF protocol
Summary
• Defibrillation is the only effective
means of restoring cardiac output for
the patient in VF or pulseless VT
• Defibrillation must be performed
promptly, efficiently and safely
• New technology has improved
machine performance and simplified
use