David E. Snyder

Is Arrhythmia Detection by Automatic External Defibrillator Accurate for Children? Sensitivity and Specificity of an Automatic External Defibrillator Algorithm in 696 Pediatric Arrhythmias

Background—Use of automatic external defibrillators (AEDs) in children aged <8 years is not recommended. The purpose of this study was to develop an ECG database of shockable and nonshockable rhythms from a broad age range of pediatric patients and to test the accuracy of the Agilent Heartstream FR2 Patient Analysis System for sensitivity and specificity. Methods and Results—Children aged ≤12 years who either developed arrhythmias or were at risk for developing arrhythmias were studied. Two sources were used for the database: children whose rhythms were recorded prospectively via a modified AED and children who had arrhythmias captured on paper and digitized for subsequent analysis. The rhythms were divided into 5-second strips, classified by 3 reviewers, and then assessed by the AED analysis algorithm. A total of 696 five-second rhythm strips from 191 children (81 female and 110 male) aged 1 day to 12 years (median 3.0 years) were analyzed. There was 100% specificity for nonshockable rhythms. Sensitivity for ventricular fibrillation was 96%. Conclusions—There was excellent AED rhythm analysis sensitivity and specificity in all age groups for ventricular fibrillation and nonshockable rhythms. The high specificity and sensitivity indicate that there is a very low risk of an inappropriate shock and that the AED correctly identifies shockable rhythms, making the algorithm both safe and effective for children.

One-shock versus three-shock defibrillation protocol significantly improves outcome in a porcine model of prolonged ventricular fibrillation cardiac arrest

Background— The success of resuscitation with a 1-shock versus the conventional 3-shock defibrillation protocol was investigated subject to the range of treatment variation imposed by automated external defibrillators (AEDs). Methods and Results— Ventricular fibrillation was induced in 44 domestic pigs. After 7 minutes of untreated VF, animals were randomized among 4 groups representing all combinations of the 1- versus 3-shock protocol and 2 different AED regimens (AED1, AED2). Because few AEDs support a 1-shock protocol, manual defibrillators were used to replicate the AED treatment regimen: electrical waveform, dose sequence, and cardiopulmonary resuscitation (CPR) interruption intervals. Initial shock(s) were delivered, followed by 60 seconds of CPR, and the treatment was repeated until resuscitation was successful or for 15 minutes. The 1-shock protocol was associated with improved outcome, reducing CPR interruptions from 45% to 34% of total resuscitation time (P=0.019) and increasing survival from 64% to 100% (P=0.004). Survival was 91% for AED1 versus 36% for AED2 (P=0.024) with a 3-shock protocol but was increased to 100% for both by adoption of a 1-shock protocol. Improvements in postresuscitation left ventricular ejection fraction and stroke volume were observed with AED1 compared with AED2 (difference of means, 15% and 28% of baseline respectively, P<0.001) regardless of defibrillation protocol. Conclusions— Adoption of a 1-shock versus a 3-shock resuscitation protocol improved survival and minimized outcome differences imposed by variations in AED design and implementation. When a conventional 3-shock defibrillation protocol was used, however, the choice of AED had a significant impact on resuscitation outcome.

AED use in businesses, public facilities and homes by minimally trained first responders

BACKGROUND Automated external defibrillators (AEDs) have become increasingly available outside of the Emergency Medical Systems (EMS) community to treat sudden cardiac arrest (SCA). We sought to study the use of AEDs in the home, businesses and other public settings by minimally trained first responders. The frequency of AED use, type of training offered to first responders, and outcomes of AED use were investigated. In addition, minimally trained responders were asked if they had encountered any safety problems associated with the AED. METHODS We conducted a telephone survey of businesses and public facilities (2683) and homes (145) owning at least one AED for at least 12 months. Use was defined as an AED taken to a medical emergency thought to be a SCA, regardless of whether the AED was applied to the patient or identified a shockable rhythm. RESULTS Of owners that participated in the survey, 13% (209/1581) of businesses and 5% (4/73) of homes had responded with the AED to a suspected cardiac arrest. Ninety-five percent of the businesses/public facilities offered training that specifically covered AED use. The rate of use for the AEDs was highest in residential buildings, public places, malls and recreational facilities with an overall usage rate of 11.6% per year. In-depth interviews were conducted with lay responders who had used the AED in a suspected cardiac arrest. In the four cases where the AED was used solely by a lay responder, all four patients survived to hospital admission and two were known to be discharged from the hospital. There were no reports of injury or harm. CONCLUSIONS This survey demonstrates that AEDs purchased by businesses and homes were frequently taken to suspected cardiac arrests. Lay responders were able to successfully use the AEDs in emergency situations. Further, there were no reports of harm or injury to the operators, bystanders or patients from lay responder use of the AEDs.

Energy attenuator for pediatric application of an automated external defibrillator

Although automatic external defibrillators (AEDs) are extensively deployed to rapidly treat sudden cardiac arrest in adults, their applicability for children is presently limited. It is desirable to extend the indications for this lifesaving equipment to all ages, even though AED application to children will be rare compared with adults. It is imperative that the inherent simplicity of present adult AED operation not be compromised to extend its use to include children. We propose a method that does not affect the normal operation of an AED on adults. For adults, unmodified AEDs would be used normally with adult electrodes. However, special pediatric electrodes would be available as a disposable accessory. When used with the AED, the delivered energy would be reduced within the electrodes, and only a portion of the energy output by the AED would be delivered to the pediatric patient. These electrodes could be used in conjunction with currently deployed AEDs with electrocardiographic analysis algorithms appropriate for children. This eliminates the need for a separate AED specifically for children or the purchase of a new AED with pediatric capability to replace previously deployed models.

AUTOMATEDEXTERNALDEFIBRILLATORUSE BYUNTRAINEDBYSTANDERS: CAN THEPUBLIC-USEMODELWORK?

Objective. For automated external defibrillators (AEDs) to be practical for broad public use, responders must be able to use them safely and effectively. This studys objective was to determine whether untrained laypersons could accurately follow the visual and voice prompt instructions of an AED. Methods. Each of four different AED models (AED1, AED2, AED3, and AED4) was randomly assigned to a different group of 16 untrained volunteers in a simulated cardiac arrest. Four usability indicators were observed: 1) number of volunteers able to apply the pads to the manikin skin, 2) appropriate pad positioning, 3) time from room entry to shock delivery, and 4) safety in terms of touching the patient during shock delivery. Results. Some of the 64 volunteers who participated in the study failed to open the pad packaging or remove the lining, or placed the pads on top of clothing. Fifty-percent of AED2 pads and 44% of AED3 pads were not placed directly on the manikin skin compared with 100% of AED1 and AED4 pads. Adjacent pad displacements that potentially could affect defibrillation efficacy were observed in 6% of AED1, 11% of AED2, 0% of AED3, and 56% of AED4 usages. Time to deliver a shock was within 3.5 minutes for all AEDs, although the median times for AED1 and AED4 were the shortest at 1.6 and 1.7 minutes, respectively. No significant volunteer contact with the manikin occurred during shock delivery. Conclusions. This study demonstrated that the AED user interface significantly influences the ability of untrained caregivers to appropriately place pads and quickly deliver a shock. Avoiding grossly inappropriate pad placement and failure to place AED pads directly on skin may be correctable with improvements in the AED instruction user interface.

Immediate termination of fibrillation at 50% probability of overall success correlates with defibrillation dose-response curve width.

Introduction: Issues in transthoracic defibrillation, including waveform shape, fixed versus escalating dose protocol, and low‐ versus high‐energy shocks, can be addressed by examining the defibrillation dose‐response curve. We tested the hypothesis that, for commonly used defibrillation waveforms, the steepness of the overall defibrillation dose‐response curve, measured as normalized curve width, correlates with the probability of a successful defibrillation being immediate at the shock intensity producing 50% success.