Interactions between advanced life support (ALS) providers and automated external defibrillators (AEDs) Prof. dr. P. Calle Emergency physician Ghent University Hospital, Belgium No conflict of interests
Introduction AEDs are programmed to combine defibrillation and basic life support (BLS) Voice prompts give guidance to caregivers ALS providers continuing a resuscitation attempt started with an AED may for various reasons decide not to follow an AED voice prompt (Wrongful) interactions between AEDs and caregivers are poorly studied
Aims of lecture 1. To clarify the AED algorithms 2. To present data on wrongful interactions between caregivers and AED 3. To draw up guidelines for ALS providers using an AED
AED algorithms 1. Shock / no shock-decision (1) sensitivity : 90 to 95% caveat : VF with low amplitude and pulseless VT < 180/min specificity : 99%
AED algorithms 1. Shock / no shock-decision (2) AED algorithm does not include vital signs caveat : conscious patients with VT > 180/min external artifacts give rise to reduced sensitivity and specificity (leading to delayed defibrillation and/or spurious shocks)
Ventricular fibrillation (of low amplitude) with numerous external artifacts
Asystole with chest compressions
AED algorithms 1. ECG analysis-algorithm 2. Shock / BLS-algorithm ECG analysis for shock delivery, e.g. at start and every 2 minutes BLS as soon as indicated (but not during ECG analyses), guided by voice prompts
Data on wrongful interactions between caregivers and AED Prospective observational study in the Ghent area Ambulance crew uses Laerdal FR 2 -AEDs (with ECG display and ability to switch to manual mode) ALS providers are free to continue or finish AED use All 135 cases after re-training according International Guidelines 2005 included Standardized review of all 510 ECG analyses
Results (1) ALS data : 286 ECG rhythm analyses 96 shockable rhythms ext. artifacts in 35 (36%) * wrongful no shock in 19 (20%) + no delivery of appropriate shock in 7 (7%) 190 non-shockable rhythms ext. artifacts in 120 (63%) spurious shock in 1 (0.5%) * delay to defibrillation : 78 + 62 sec
Results (1 + 2) ALS/EMTs data : 286/224 ECG rhythm analyses 96/67 shockable rhythms ext. artifacts in 35 (36%)/18 (27%) * wrongful no shock in 19 (20%) /3 (4%) + no delivery of appropriate shock in 7 (7%)/0 190/157 non-shockable rhythms ext. artifacts in 120 (63%)/87 (55%) spurious shock in 1 (0.5%) / 0 * delay to defibrillation : 78 + 62 sec in ALS cases and 22, 40 and 60 sec in EMTs cases
Guidelines for ALS providers? (1) 1. ALS procedures (endotracheal intubation + i.v. line) + chest compressions for 2 to 3 minutes (if appropriate) inactivate AED to avoid chaos (voice prompts, appropriate/inappropriate charging process, unsafe shocks, )
Guidelines for ALS providers? (2) 2. Choose between AED and manual defibrillator always manual defibrillator if - AED without ECG display - ALS providers not familiar with AED concept and/or particular AED in use - AED not adapted to International Guidelines 2005 advantages of continued AED use - fast, easy and safe - shock/no shock-algorithm and shock/bls-algorithm
Guidelines for ALS providers? (3) 3. Look after AED dysfunctions / limitations - false positive and false negative ECG analysis - disturbing voice prompts - synchronized shock not possible - shocks never terminating VF manual defibrillator or (if possible and/or indicated) manual mode of AED
Particular AED features (1) Heartstart FR 2 (Laerdal) only150 J manual mode to be selected via 2 push buttons Heartstart FR X (Philips) only 150 J
Particular AED features (2) upper button to be pushed 2 times to deliver manual shock display of Heartstart FR 2 after reset to manual mode lower button to be pushed by caregiver for ECG analysis by AED at any time
Particular AED features (3) display of Heartstart FR 2 for 2 minutes after a shock (only in automated mode) lower button to be pushed to override programmed post shock pause : USELESS
Particular AED features (4) SMART analysis-concept (optional) Continuous monitoring of ECG tracings aimed to detect shockable rhythms early (also during BLS!! Caveat: low specificity) Shock / no shock-decision only after usual ECG analysis preceded by stand clear voice prompt
Wrongful BLS interruptions by smart analysis-concept related to chest compressions at > 140/minute
Wrongful BLS interruptions by smart analysis-concept : data from study in Ghent area 203 smart analyses 47 true positives (23%) 156 false positives (77%) in 79 cases (51%) chest compressions > 140/min no BLS : 0 to 56 seconds (mean: 14 seconds)
Conclusions External artifacts during ECG analysis frequently lead to BLS interruptions, delayed defibrillation, and even spurious shocks ALS providers should be familiar with the device(s) most frequently used in order to select the best approach for a resuscitation attempt started with AED
Thank you for your attention