Automatic External DefibrillationPast, Present & Future

Prof. John McC AndersonCTO HeartSine Technologies Ltd

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100THE DISTRIBUTION OF ACUTE CORONARY DEATHS

Mc NEILLY (BELFAST), 1965-66, 818 DEATHS

Modern Developments in Out-of-Hospital Defibrillation

Period Defibrillator Operator Comments

1960’s Physicians Physicians staff the first mobile coronary care unit (Belfast, New York City).

Early 1970’s Paramedics Extensively trained (400-1500 hours). Defibrillation added to many advanced life support skills.

Late 1970’s EMT’s trained in defibrillation

Rhythm recognition and skills of defibrillation taught to EMT’s in 10 hour course.

The Semi-Automatic Defibrillator

Flow Diagram for Ventricular Fibrillation Detection

Energy Ratio Characteristic

Energy Ratio i.e. Yellow/Red ratio constant in Sinus Rhythm

Energy Ratio i.e. Yellow/Red ratio continuously variable in Ventricular Fibrillation

Flow Diagram for Ventricular Fibrillation Detection

Flow Diagram for Ventricular Fibrillation Detection

Defibrillators in the Home (PDU)

The development of a CPR-ICG PAD

The evolution of ‘Smart Defibrillation’

The Future Management of Sudden Cardiac Death

The Personal Defibrillation Unit – PDU 400

More than 650,000 deaths per year from cardiovascular diseases

In the US around 800,000 patients suffer an AMI annually of whom 550,000 die

Over 80% of the deaths occur in the home

PEA accounts for over 65% of cardiac arrests

In 2005 the ERC and AHA guidelines were updated to emphasize the importance of effective chest compressions with minimal interruptions

In 2008 the AHA introduced the “hands-only” protocol

Statistics

Smaller Lighter Complete Resuscitation System High IP rating Advanced Algorithm Disposable User Friendly

Design Features

The Development of a CPR-ICG PAD

Transthoracic Impedance:

“Change in thoracic impedance may be due to any change in physical shape or content of the thorax, including ventilation, cardiopulmonary blood flow ….”

Miller JC, Horvath SM. Impedance Cardiography. Psychophysiology 1978; 15: 80-91

The History of Impedance Cardiography

ECG/ICG Timing

Impedance Cardiography (ICG)

The ICG measures the cardiac impedance during the cycle and gives a waveform relating to the change in blood volume within the heart during this time. (Cardiac Output)

Example Cases from RVH Database

Patient conscious ; HR=330BPM, QRS width varies between 133ms and 189ms.

Patient required terminating shock ; HR=189BPM, QRS width 201ms.

ECG

ICG

Blood Flow in the aortaBlood Flow through the

pulmonary vesselsContracting heartChanging resistivity of blood Improved contact with electrodes

Causes of change in Cardiac Output

PEA accounts for over 65% of cardiac arrests

In 2005 the ERC and AHA guidelines were updated to emphasize the importance of effective chest compressions with minimal interruptions.

In 2008 the AHA introduced the ‘hands-only’ protocol to further minimize interruptions.

Importance of Effective CPR

ICG can offer feedback on cardiac output during chest compressions

The morphology of the ICG waveform during CPR is distinctive

HeartSine has developed an algorithm based on the RVH database of CPR cases which uses a number of parameters to enable feedback on CPR efficacy for the user

CPR Feedback Indicator

ICG Waveform During CPR

ICG Waveform During Sinus Rhythm

ICG Waveform During PEA

ICG not present due to absence of CARDIAC OUTPUT during PEA

ICG During VF

ICG not present due to absence of CARDIAC OUTPUT during VF

Noise due to motion artifact

Noise due to incorrect pad or hand placement

Initial ICG algorithm classified some cases of noise as CPR

Challenges in Algorithm Development

It was found through a number of bench tests that excessive noise could be eliminated by measuring the rate and pulse width of the signal and by focusing efforts on good CPR training to ensure the correct hand positioning and applied force

Results from initial Bench Tests

Recording of Correctly Applied CPR During Initial Bench Testing

Recording of Poor CPR (No Compressive Force Applied)

Recording of CPR on Top of Pads

Proposed CPR-ICG Algorithm

“PUSH HARDER”

“PUSH FASTER/SLOWER”

“GOOD COMPRESSIONS”

Algorithm Results to Date

CPR CriteriaICG Test

Sample SizePerformance Specifications

PerformanceResults (%)

90% One-Sided Lower Confident Limit (%)

CPR Speed Good

82377Sensitivity: > 90%Specificity: > 90%

Sensitivity: 95.38Specificity: 93.11

Sensitivity: 83.40Specificity: 82.19

CPR Force Adequate

108728Sensitivity: > 90%Specificity: > 90%

Sensitivity: 99.96Specificity: 98.47

Sensitivity: 99.54Specificity: 96.29

Animal Study Results

2cm 4cm 5cm

ICG amplitude at varying compression depths:

The ICG amplitude (in ohms) is higher for higher CPR compression depths and values of ET CO2.

ICG

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Thrust/depth

2cm = 20kg

4cm = 30-40kg

6cm = 60-70kg

Summary

“In order to maintain high-quality CPR, feedback to rescuers is important. The use of prompt/feedback devices during CPR will enable immediate feedback to rescuers, and the data stored in rescue equipment can be

used to monitor the quality of CPR performance and provide feedback to

professional rescuers during debriefing sessions .”

ERC Guidelines 2010 - European Resuscitation Council Guidelines for Resuscitation 2010 Section 2. Adult basic life support and use of automated external defibrillators

HeartSine samaritan PAD 500P with CPR advisor was launched in August 2009 in Europe Preparations are under way for FDA 510(k) clearance in the US

The Development of a SMART Defibrillator

Optimal treatment for Sudden Cardiac Arrest (SCA)

Interactive CPR Accurate decision to defibrillate/CPRManagement of PEA

Features to be included in the SMART AED:

1. CPR-ICG Indicator

2. Pulse checker (Uses ICG to discriminate between PEA and SR)

3. Therapy Advisor (Uses DSP to extract information on frequency content of the ECG signal during cardiac arrest to determine whether CPR or defibrillation is the most appropriate therapy)

4. Using ICG to discriminate between CPR and shockable rhythms during the “hands-off” period

5. Continuous chest compressions until administration of shock

The FUTURE of Defibrillation

3-Phases of a Sudden Cardiac Arrest

Majority of customer queries result from non-adherence to the “hands-off” or analysis period of the PAD

Using ICG technology we plan to develop an algorithm to discriminate between CPR and a shockable rhythm to prevent the device from charging and then disarming following the discontinuation of CPR

The algorithm can output audio voice prompts which will advise the user to discontinue CPR

Failure to adhere to CPR prompts

CPR continued during analysis phase despite audio prompts

Shock advised due to inappropriate CPR

HeartSine Technologies currently has the basic science to build a SMART defibrillator.

A SMART defibrillator will provide the optimal treatment for Sudden Cardiac Death

SMART defibrillation will position HeartSine Technologies as a world leader in this field.

In 1775 Abilgard recorded that he

“shocked a single chicken into lifelessness and upon repeatingthe shock, the bird flew off and thus eluded further

experimentation”

Any Questions?