Safety and effectiveness of a portable external automatic defibrillator-pacemaker

Tripling survival from sudden cardiac arrest via early defibrillation without traditional education in cardiopulmonary resuscitation

BACKGROUND

Early defibrillation is the most important intervention affecting survival from sudden cardiac arrest (SCA). To improve public access to early defibrillation, we established Piacenza Progetto Vita (PPV), the first system of out-of-hospital early defibrillation by first-responder volunteers.

METHODS AND RESULTS

The system serves a population of 173 114 residents in the Piacenza region of Italy. Equipment for the system comprises 39 semiautomatic external biphasic defibrillators (AEDs): 12 placed in high-risk locations, 12 in lay-staffed ambulances, and 15 in police cars; 1285 lay volunteers trained in use of the AED, without traditional education in cardiac pulmonary resuscitation, responded to all cases of suspected SCA, in coordination with the Emergency Medical System (EMS). During the first 22 months, 354 SCA occurred (72+/-12 years, 73% witnessed). The PPV volunteers treated 143 SCA cases (40.4%), with an EMS call-to-arrival time of 4.8+/-1.2 minutes (versus 6.2+/-2.3 minutes for EMS, P=0.05). Overall survival rate to hospital discharge was tripled from 3.3% (7 of 211) for EMS intervention to 10.5% (15 of 143) for PPV intervention (P=0.006). The survival rate for witnessed SCA was tripled by PPV: 15.5% versus 4.3% in the EMS-treated group (P=0.002). A "shockable" rhythm was present in 23.8% (34 of 143) of the PPV patients versus 15.6% (33 of 211) of the EMS patients (P=0.055). The survival rate from shockable dysrhythmias was higher for PPV versus EMS: 44.1% (15 of 34) versus 21.2% (7 of 33), P=0.046. The neurologically intact survival rate was higher in PPV-treated versus EMS-treated patients: 8.4% (12 of 143) versus 2.4% (5 of 211), P=0.009.

CONCLUSIONS

Broad dissemination of AEDs for use by nonmedical volunteers enabled early defibrillation and tripled the survival rate for out-of-hospital SCA.

Effects of early defibrillation by ambulance personnel on short- and long-term outcome of cardiac arrest survival: the Munich experiment

OBJECTIVES

This study evaluates the feasibility of implementing early defibrillation of out-of-hospital cardiac arrest patients for basic life-support providers (EMT-D) in a two-tier emergency system in the city of Munich, Germany.

DESIGN

Retrospective consecutive analysis of all EMT-D attempts during a 5-year initiation phase (1990 to 1994) and prospective follow-up of all cardiac arrest survivors discharged from hospital.

SETTING

A strictly defined inner-city and suburban area of 978 km2 and a residential population of 1,530,000 inhabitants with 22 ICUs in urban hospitals. One dispatching center to alert a two-tier emergency system with 56 EMT-D-staffed ambulances and physician-staffed mobile ICUs stationed at the nearest of nine hospitals.

METHODS

AH EMT-D cases were identified and data on patients were documented in a standardized manner from patients' records, including the resuscitation protocol in the hospitals to which the patients were referred. For those patients discharged from the hospital, a standardized telephone interview was undertaken with the physician in charge of the patient and with the patient/relative leading to an assessment of the patient's status according to the Glasgow-Pittsburgh cerebral performance categories.

INTERVENTION

None.

RESULTS

During the 5-year initiation phase of the EMT-D program in the two-tier emergency system in Munich, there were 243 resuscitation attempts by EMTs, using the semiautomated defibrillator; 125 patients died immediately on the scene. In 118 patients, spontaneous circulation was reestablished and these patients were admitted to an ICU in 1 of the 22 urban hospitals. Median call-response interval for the EMT-D was 5 min (interquartile range, 3 to 6) and was 10 min (interquartile range, 7 to 13) for the second tier (p < or = 0.0001). In 34 cases (28.8%), EMT-D staff had reestablished spontaneous circulation (ROSC) before the second tier arrived on the scene. Patients with ROSC on the arrival of the second tier were more frequently discharged alive from hospital than were patients without ROSC at that time (p < or = 0.0001). The hospital discharge rate of initially successful resuscitated patients presenting with out-of-hospital ventricular fibrillation was 38.1% (45/118). Overall success rate of all EMT-D attempts was 18.5% (45/243). After a mean follow-up time of 39 (range, 22 to 64) months, 29 (66%) patients were still living. Twenty-five (56.8%) were neurologically not disabled or mildly disabled (CPC 1/2); disability was moderate in 3 (6.8%) patients and was severe in 1 (2.3%) patient. One case was lost to follow-up.

CONCLUSION

The present study demonstrates that the upgrading of basic life support providers with semiautomated defibrillators has a significant benefit for cardiac arrest victims outside the hospital in an urban environment.

Engineering excellence: options to enhance firefighter compliance with standing orders for first-responder defibrillation

STUDY OBJECTIVE

To assess the quality of care delivered during first-responder defibrillation and to determine the potential efficacy of modifying existing automated external defibrillator designs to improve first-responder performance.

DESIGN

Prospective case series.

SETTING

An urban emergency medical services system providing first-responder defibrillation and paramedic care.

TYPE OF PARTICIPANTS

Firefighters who completed a four-hour (two-session) course in automated external defibrillator operation.

METHODS

Heartstart 2000 defibrillators (Laerdal Medical Corp, Armonk, New York) were used in 241 consecutive resuscitation attempts. Written reports and memory module printouts were abstracted to assess firefighter performance of 11 critical actions. The firefighter's response to each opportunity to perform a critical action was scored using explicit pass/fail criteria.

RESULTS

Records of 235 automated external defibrillator uses (97.5%) were submitted for analysis. Firefighters shocked within 15 seconds of a "shock indicated" message in 95% of opportunities and reanalyzed the rhythm within 90 seconds of the third consecutive shock (ie, after one minute of CPR) in 80% of cases. However, firefighters reanalyzed the patient's rhythm too soon in 75% of cases, thereby interfering with recommended intervals of CPR. Firefighters failed to reanalyze the patient's rhythm after device-initiated "check patient" prompts 62% of the time. Memory modules were left in the automated external defibrillator during practice sessions in 64 cases, decreasing available memory to monitor automated external defibrillator use in the field. Three instances of failure to withhold CPR during rhythm analysis resulted in a single inappropriate patient shock. No firefighter was shocked inadvertently.

CONCLUSION

Current device algorithms result in effective delivery of the initial three shocks. However, firefighters often fail to interpose recommended intervals of CPR between further attempts at defibrillation. Modification of existing device algorithms to provide additional visual and auditory cues may be preferable to relying on the user to recall accurately all the steps in this infrequently performed procedure.

Influence of external defibrillator electrode polarity on cardiac resuscitation

Eight hundred forty-seven consecutive patients discovered in cardiac arrest by first responding firefighters received initial defibrillation attempts using automatic external defibrillators. The effect of electrode polarity on defibrillation and resuscitation was determined in the subset of 289 (34%) with ventricular fibrillation in a prospective, randomized trial. The ECG was recorded in 205 consecutive patients whose initial rhythm was ventricular fibrillation. Eighty-seven of 114 patients (76%) in whom the apex chest electrode was positive were defibrillated with the first 200-joule shock, compared to 70 of 91 patients (77%) in whom the apex electrode was negative. There was no difference in the type of rhythm established, e.g., organized versus brady-asystole following defibrillation with either electrode polarity. Resuscitation was possible in 56% of patients in whom the apex electrode was positive and 60% of those in whom the apex electrode was of negative polarity. Hospital survival rates (26% vs 27%) were also similar for both treatment groups. Unlike results during experimental external defibrillation of animals or those obtained using implantable defibrillators, this randomized trial of external defibrillation conducted during attempted out-of-hospital resuscitation showed no difference in outcomes related to electrode polarity.

From concept to standard-of-care? Review of the clinical experience with automated external defibrillators

There is now both national and international acceptance of the "principle of early defibrillation," which contends that whoever arrives first at the scene of a cardiac arrest should have a defibrillator. The almost revolutionary technological event that permits widespread implementation of this principle has been the development of automated external defibrillators (AEDs). The simplicity, accuracy, and safety of these devices markedly expands the range of people who can deliver early defibrillation, which includes minimally trained emergency personnel, lay and community responders, and family members of high-risk patients. Even though AEDs now approach the status of "standard of care," the AED, as an example of a new technology, has not followed the classic technology paradigm: conceptualization, experimentation, dissemination, and standard of care. Instead, like many other technical innovations in emergency medicine, the development of AEDs proceeded simultaneously on many fronts, and implementation often occurred before confirmation of important subissues. AEDs may experience the life cycle of many new ideas: initial enthusiasm and widespread adoption, followed by disillusionment and rejection, and finally a mature, proper perspective. Careful implementation and continued evaluation may help emergency personnel avoid periods of disillusionment with AEDs and move steadily and uneventfully to a proper perspective.

Use of the automatic external defibrillator in the management of out-of-hospital cardiac arrest

The automatic external defibrillator is a simple device that can be used by nonprofessional rescuers to treat cardiac arrest. In 1287 consecutive patients with out-of-hospital cardiac arrest, we assessed the results of initial treatment with this device by firefighters who arrived first at the scene, as compared with the results of standard defibrillation administered by paramedics who arrived slightly after the firefighters. Of 276 patients who were initially treated by firefighters using the automatic defibrillator, 84 (30 percent) survived to hospital discharge (expected rate according to a logistic model, 17 percent; P less than 0.001), as compared with 44 (19 percent) of 228 patients when fire-fighters delivered only basic cardiopulmonary resuscitation and the first defibrillation was performed after the arrival of the paramedic team. Few patients with conditions other than ventricular fibrillation survived. In a multivariate analysis of characteristics that influenced survival after ventricular fibrillation, a better survival rate was related to a witnessed collapse (odds ratio, 3.9; 95 percent confidence interval, 2.0 to 7.6), younger age (odds ratio, 1.2; 95 percent confidence interval, 1.0 to 1.4), the presence of "coarse" (higher-amplitude) fibrillation (odds ratio, 4.2; 95 percent confidence interval, 1.6 to 11.0), a shorter response time for paramedics (odds ratio, 1.4; 95 percent confidence interval, 1.0 to 2.1), and initial treatment by firefighters using an automatic external defibrillator (odds ratio, 1.8; 95 percent confidence interval, 1.1 to 2.9). These findings support the widespread use of the automatic external defibrillator as an important part of the treatment of out-of-hospital cardiac arrest, although the overall impact of the use of this device on community survival rates is still uncertain.

Cost-effectiveness of defibrillation by emergency medical technicians

Effective emergency systems using emergency medical technicians (EMTs) trained to defibrillate or paramedics can save more lives from out-of-hospital cardiac arrest due to ventricular fibrillation than can emergency systems staffed with basic EMTs who cannot defibrillate. This article focuses on the cost-effectiveness of systems staffed with each type of EMT. Data were collected from all 50 states and from the District of Columbia to determine the number of hours and estimated cost of initial training for the three types of EMTs in the United States in 1986. The median initial training hours for basic EMTs, EMTs trained in defibrillation, and paramedics were 110, 129, and 700, respectively. Median costs for initial training at each EMT level were +123, +150, and +1580/student. According to published survival data for emergency medical systems staffed with EMTs at each level, the total initial training personnel and equipment cost per life saved from ventricular fibrillation was +7687, +2126, and +2289 for systems staffed by the respective EMTs. The initial cost per life saved from ventricular fibrillation is more than three times greater in systems staffed by basic EMTs than in systems staffed by EMTs trained in defibrillation or paramedics. From a medical and a cost-effective standpoint, all communities served by basic EMTs should consider upgrading them to at least the defibrillation-trained EMT level.

Automatic external defibrillators: importance of field testing to evaluate performance

A new automatic external defibrillator was tested first against a tape-recorded data base of rhythms and then during use by first-responding fire fighters in a tiered emergency system. The sensitivity for correctly classifying ventricular fibrillation and ventricular tachycardia was substantially less during clinical testing in 298 patients than would have been predicted from preclinical results: 52% of ventricular fibrillation analyses in patients were correctly classified versus 88% of episodes in the data base, and 22 versus 86%, respectively, for ventricular tachycardia (p less than 0.001). The detection algorithm was modified and evaluated further in another 322 patients. The modified detector performed substantially better than did the one that had been designed from prerecorded rhythms: with its use, 118 (94%) of 125 patients in ventricular fibrillation were counter-shocked compared with 91 (77%) of 118 similar patients with use of the initial algorithm (p less than 0.001). No inappropriate shocks were delivered. This improvement resulted in a shorter time to first shock (p less than 0.01) and more shocks being delivered for persistent or recurrent episodes of ventricular fibrillation (p less than 0.05). Of 620 patients treated with the automatic defibrillator, 243 (39%) had ventricular fibrillation; 57 (23%) of the 243 regained pulse and blood pressure before paramedics arrived, 141 (58%) were admitted to hospital and 71 (29%) were discharged.(ABSTRACT TRUNCATED AT 250 WORDS)

What is a "save"?: Outcome measures in clinical evaluations of automatic external defibrillators

Automatic external defibrillators (AEDs) represent an important technologic innovation in the management of out-of-hospital cardiac arrest. We propose the following concept: AEDs are machines with the limited task of ventricular fibrillation (VF) identification, countershock delivery, and defibrillation. They cannot be expected to produce "saves" independently. This study tested this concept by using the same AED in two different emergency medical systems: outcomes dependent upon the device should be the same in both groups, whereas outcomes dependent upon patient and system factors should be different. Paramedics, with the AED as their initial monitor/defibrillator, treated 16 cardiac arrest patients in VF; EMTs (emergency medical technicians), with the same AED, treated 17 patients in VF. There were no significant differences in the outcomes proposed to be machine-dependent: sensitivity, defined as the percentage of VF rhythm segments shocked; specificity, defined as the percentage of non-VF rhythms not shocked; and defibrillation of segments of VF to non-VF rhythms. There were, however, differences in the outcomes dependent on patient and system factors (paramedic group presented first): percent converted to a perfusing rhythm (23% vs 69%; p less than 0.05); percent admitted to the hospital (19% vs 65%; p less than 0.025); and percent discharged from the hospital (6% vs 29%; p = N.S.). We conclude that AEDs should be compared and evaluated on device-dependent outcomes and not on the basis of producing "saves".

Automatic external defibrillation: evaluations of its role in the home and in emergency medical services

Many recent efforts to improve emergency medical services (EMS) and increase survival rates are simply efforts to get defibrillation to patients as rapidly as possible. In the 1960s physicians traveled in mobile coronary care units to bring the defibrillator to cardiac arrest patients. Later, paramedics, rather than physicians, were used. During the late 1970s the concept of early out-of-hospital defibrillation expanded as emergency medical technicians (EMTs) learned to defibrillate. Researchers in several settings confirmed the effectiveness of early defibrillation by EMTs. The automatic detection of ventricular fibrillation (VF) creates new opportunities for the early defibrillation concept. This includes both automatic implantable defibrillators and automatic external defibrillators (AED). The King County, Washington, EMS is conducting two projects to evaluate AEDs. One is a randomized, controlled crossover study in which EMTs use either an AED or a standard manual defibrillator. Outcome measurements include time to countershock, conversion rates, and survival rates. In the second project family members of patients who have survived out-of-hospital VF randomly receive an AED and cardiopulmonary resuscitation (CPR) instruction, or CPR instruction alone. This study was designed to determine whether family members can be trained adequately to use the device effectively. Psychological tests measure the effect of learning about, living with, and using such technology. These studies may help define the role of AEDs in the future management of out-of-hospital VF.

Sensitivity, accuracy, and safety of an automatic external defibrillator

An automatic external defibrillator (AED) was used by paramedics to detect ventricular fibrillation and deliver countershocks in 39 people with out-of-hospital cardiac arrests. The AED identified and delivered at least 1 countershock to 13 of the 16 people in ventricular fibrillation (81% sensitivity). The AED responded correctly to all 21 of the non-ventricular-fibrillation rhythms (8 other electrical rhythms, 13 asystole) with no countershocks (100% specificity). In 2 patients the rhythm could not be assessed. The device caused no injuries to patients or personnel. The performance of the AED was also analysed by considering each 15 s segment of ventricular fibrillation as a separate challenge; the device delivered a countershock in 19 of 29 such segments (66%).

Evaluation of a new defibrillation pathway: tongue-epigastric/tongue-apex route. II. Impedance characteristics in human subjects

An automated device for defibrillation using a vertical shock pathway (tongue-epigastric or tongue-apex) has been developed. The energy requirements for defibrillation using vertical pathways are uncertain and will be determined largely by the impedance of the pathway. The purpose of this study was to determine the impedance characteristics of vertical defibrillation pathways in human subjects. Twenty patients undergoing elective cardioversion of atrial fibrillation or atrial flutter, or both, were studied. Patients received shocks from electrodes placed in tongue-epigastric or tongue-cardiac apex positions. The tongue electrode was a 12 cm2 metal plate fixed to a standard plastic oropharyngeal airway. The epigastric or cardiac apex electrode was a 40 cm2 self-adhesive pad. The electrodes were connected to a standard damped-sinusoidal waveform defibrillator. It was found that the two vertical shock pathways had substantially higher impedance than the standard transthoracic pathway: tongue-epigastric pathway 130 +/- 11 omega (SD), tongue-apex pathway 115 +/- 12 omega, transthoracic pathway 68 +/- 11 omega (p less than 0.05). The higher impedance is probably due to the longer interelectrode distances of vertical pathways: tongue-epigastric 33 +/- 3 cm, tongue-apex 28 +/- 3 cm, transthoracic 23 +/- 3 cm (p less than 0.05). Vertical pathway shocks were successful in the cardioversion of 15 of 20 patients. Four of the five patients in whom vertical shocks were unsuccessful subsequently underwent successful cardioversion by transthoracic shocks; the transthoracic shocks achieved a higher current because of lower impedance of the transthoracic route.(ABSTRACT TRUNCATED AT 250 WORDS)