The most common approach to shorten the interval between collapse and arrival of emergency personnel has been to acquire more ambulances,^2,3 which is both expensive and inefficient, especially if the EMS system is established. Studies have shown that after a certain point an increase in the number of ambulances fails to lower response time significantly.⁴ In one model, response time varied inversely as the square root of the number of vehicles per square mile; an 80% increase in the number of vehicles reduced average response time by only 1 minute.⁴ This same 1-minute reduction in average response time could be achieved by greater public awareness and more efficient dispatching systems, and at far less cost.

The early access link can be strengthened through public education, especially persons most likely to witness a cardiac arrest, and by installation of an efficient emergency communication system. Educational and public service programs such as those of the American Heart Association¹ and the American Red Cross⁵ are designed to make the public aware of what to do when cardiac arrest occurs. Participants in classes on cardiopulmonary resuscitation (CPR) and AHA-sponsored schoolsite and worksite training learn the warning signs of heart attack, how to recognize a person in cardiac arrest, and to quickly call the EMS system when a person collapses. Persons who are uninformed about chest pain and respiratory distress may not comprehend signs of an impending cardiac arrest. When a person collapses, such a witness may wait a long time before calling the emergency dispatch center. A witness may telephone neighbors, relatives, or even his or her personal physician before calling the emergency number, as observed in both central London⁶ and rural Iowa.⁷ In Belgium and Holland it is almost the rule to first call the local physician. This poses a problem in terms of early defibrillation because physicians are less likely to carry defibrillators than emergency responders. In Iowa a "phone first" program has been started to achieve immediate notification of the EMS system when a person collapses.⁷ Such educational campaigns may become more widespread. Early access ensures that precious minutes are not wasted at the start of cardiac arrest.

Lack of a three-digit 999 emergency dispatch system (or its equivalent) can produce confusion and delays because witnesses may call the wrong number, call multiple numbers, or spend time searching for the number. In one community in North Carolina, 85 different emergency numbers are listed in the local telephone book.^8,9 In contrast, in Seattle, Washington, which has an enhanced 911 system, 90% of 1,271 people interviewed identified 999 as their EMS notification number.¹⁰ Investigators from Minneapolis who performed a before-and-after evaluation of a 911 system¹¹ noted that the percentage of emergency callers who could activate the EMS system in less than a minute rose from 63% before implementation of the system to 82% afterward. The percentage of callers who made only one telephone call to activate the system went from 40% before the 911 system was started to 74% after the system began.

Another study showed that imprecise knowledge of how to notify the emergency system can cause confusion and delays.¹² In this telephone survey, people living in 999 system communities knew the correct number to call 85% of the time; in regional systems with several fire department operating from one dispatching center, people knew the correct number to call only 47% of the time; in systems with a local seven-digit number for a particular fire district, people gave the correct number only 36% of the time. Many people who lived near a 999 area thought 999 was their emergency number; when they mistakenly called 999, delays of 30 seconds to 2 minutes resulted. Establishment of a 999 emergency system is a key step. Given the transient and mobile nature of today's population, a universal access number must be adopted by EMS systems. By 1992 a common emergency telephone number will be introduced in the European community and will cover a population of more than 350 million.

The Early CPR Link

The next link in the chain of survival is early initiation of basic CPR.^1,13 Basic CPR should be started immediately after cardiac arrest is recognized and should coincide with efforts to gain access to and activate the EMS system. EMS systems should rely on trained citizens rather than emergency responders to initiate CPR. With rare exceptions, initiation of CPR by emergency personnel is too late. Only systems with rapid response times, such as that in Milwaukee, Wisconsin,^14,15 can employ EMS providers as the primary initiators of CPR.

For almost 3 decades the chest compressions and positive pressure ventilations of standard CPR have helped return pulseless, nonbreathing patients to spontaneous respiration and cardiac perfusion.^16,17 The value of early CPR is that it can buy time for the primary cardiac arrest patient^1,13,18-22 by producing enough blood flow to the central nervous system and the myocardium to maintain temporary viability. To do so, however, basic CPR must be started early, and the earlier the better. Initial CPR must be followed by rapid defibrillation, intubation, and administration of cardiovascular medications by EMS personnel.²³ Early bystander CPR is less helpful in resuscitation if EMS personnel equipped with the defibrillator arrive late, or about 8-12 minutes after collapse.²⁴ Recent data from the Belgium Cardio-Pulmonary-Cerebral Resuscitation Registry¹⁸ and Scotland,²⁵ however, suggest some prolonged benefit from bystander CPR even with late arrival of advanced live support personnel. The combination of late CPR (more than 4 minutes) and late advanced life support (more than 12 minutes) is particularly lethal.^22,24,26 Several researchers have called these time dimensions the resuscitation "failure zone."²⁷

Many reports contain data to compare the survival rates of cardiac arrest victims who receive early CPR (defined as citizen-initiated CPR) with the survival rates of those who receive late CPR (defined as emergency responder-initiated CPR).^{22,24,28,29-42} Table 1 presents summary data from these studies, including estimated odds ratios for survival. Early CPR usually differs from late CPR by about 4 minutes. In all but one system, researchers observed a positive benefit of early CPR when they compared survival rates between persons who received early CPR and those who received late CPR. The magnitude of this contribution may be considerable since the odds ratios for improved survival with early CPR can range as high as 11.5 (Table 1). In Milwaukee,^14,36 the only system in which this benefit was not observed, emergency personnel performed late CPR an average interval of only 2 minutes after early bystander-initiated CPR. Thus the data from Milwaukee simply compare early CPR with even earlier CPR. The similar survival rates for people who received bystander CPR compared with those deprived of bystander CPR are not surprising and provide additional support for the concept of a narrow window of CPR effectiveness.³⁸ The association between early CPR and improved survival appears related to the effect of basic CPR on ventricular fibrillation.^18,38,43,44 Researchers have observed that when rescuers start CPR early, the patient is more likely to be in ventricular fibrillation when a monitoring unit arrives.⁴⁴

Investigators in King County, Washington, observed that 80% of cardiac arrest victims were in ventricular fibrillation/ventricular tachycardia if they had received early bystander CPR, compared with 68% if they had received delayed CPR.³⁸ In Stockholm, 67% of people in cardiac arrest in whom CPR was started by bystanders were in ventricular fibrillation/ventricular tachycardia, whereas only 45% of persons not given bystander CPR were in ventricular fibrillation/ventricular tachycardia.43 The Belgian Cardio-Pulmonary-Cerebral Resuscitation Registry has reported a 42% prevalence of ventricular fibrillation in cardiac arrest patients who received bystander CPR, compared with 29% in arrest patients who received delayed CPR.¹⁸

These three studies suggest that CPR prolongs the duration of ventricular fibrillation. In addition, they suggest that the presence of ventricular fibrillation operates as a dependent variable rather than an independent variable in analyses of survival data.^18,22 Victims who receive early CPR are also more likely after electrical shock to convert to a cardiac rhythm associated with restoration of spontaneous circulation.^22,26,38 In King County, Washington, persons in ventricular fibrillation when EMS personnel arrived has a 37% rate of long-term survival if they were given bystander CPR, compared with 29% if they were not.³⁸ In Houston, 40% of patients with ventricular fibrillation/ventricular tachycardia were discharged from the hospital if they had received bystander CPR, versus 19% for such patients not given bystander CPR.²²

Several approaches ensure the performance of basic CPR by bystanders before emergency responders arrive. The most widely advocated is citizen CPR training. Community-based CPR training programs, endorsed and conducted by the American Heart Association and the American Red Cross, have trained millions of laypersons in CPR.¹ The American Heart Association has suggested that if 20% of adults were trained in CPR, morbidity and mortality from out-of-hospital cardiac arrest might be significantly reduced.⁴⁵ Some communities have actually achieved this level of adult training, despite physician reluctance to "prescribe" CPR training for family members and friends of high-risk patients.^10,46,47 In the Seattle area, for example, Leonard Cobb and coworkers48 have trained over 2 million people. In Minneapolis a survey of 2,310 adults noted that 23% were trained in CPR.⁴⁹

However, there are problems with the concept that a threshold level of citizen training can be "protective." Most people trained in CPR never see an arrest; most people who see an arrest have not been trained in CPR.49,50 The Minneapolis survey found that only 10% of the population trained in CPR had witnessed a cardiac arrest49 and only 30% of witnesses to a cardiac arrest had been trained in CPR. Only 19% of persons trained in Minneapolis continued retraining every year.49 This figure nearly duplicates that in a report by Gombeski,⁵⁰ who noted that only 21% of their trainees returned for 1-year retraining.

Other data, however, suggest a more positive picture.^51-54 Eisenberg et al⁵¹ observed that some knowledge of CPR techniques is so prevalent that many citizens attempt CPR without formal training. In addition, they perform CPR despite a high prevalence of disagreeable physical characteristics (the presence of saliva, blood, or emesis) encountered during performance of bystander CPR.⁵² Cobb et al^53,54 observed that outcomes for CPR by untrained citizens is similar to outcomes for trained laypersons. The Belgian Cardio-Pulmonary-Cerebral Resuscitation Registry has noted that the quality of bystander CPR is difficult to evaluate.⁵⁵ In Belgium the most common bystander CPR errors were omission of mouth-to-mouth ventilations, which occurred 46% of the time, and omission of chest compressions, which occurred 17% of the time.⁵⁵ Outcomes were significantly better when rescuers performed both ventilations and chest compressions, compared with ventilations alone or compressions alone.⁵⁵

Another approach to early CPR is the concept of targeted CPR training.^{10,53,54,56-59} Such programs are for persons who have an increased likelihood of having to perform CPR, including middle-aged persons, residents and staff of senior centers, survivors of myocardial infarction, and family members of persons identified as having cardiac arrest risk factors. These programs are slowly becoming more widespread and represent an important change in the focus of CPR training. Much CPR training in the United States focuses on the young, especially school-age children and young adults,⁵⁷ who are easy to train and show energetic interest. However, they are not likely to witness a cardiac arrest or to take a CPR course. They do, of course, become the "future" performers of CPR as they enter the age group where risk increases. Cardiac arrest victims are typically aging men, who live at home^6,18,60 and are usually poorly educated and nonprofessional.⁶¹ In King County, Washington, the average age of cardiac arrest patients is 65 years; 77% of cardiac arrests happen at home, and 75% of the victims are men.^60,62 Therefore, persons with the highest likelihood of witnessing a cardiac arrest and being called upon to perform CPR are those living with or closely associated with middle-aged men. Regardless of age, the prognosis for persons resuscitated from cardiac arrest, even the elderly (those over 70 years old), is excellent.^63,64 Unfortunately, few middle-aged women in the United States have received formal CPR training, and those who have received training seldom live with high-risk patients.^10,11 In one survey of people trained to perform CPR, only 7% lived with family members known to have heart disease.¹⁰

A final method to achieve early CPR is dispatcher-assisted CPR instruction, programs in which emergency telephone dispatchers offer CPR instructions to persons who call to report a cardiac arrest.^51,54-67 Delivery of instructions and performance of a complete CPR cycle of 15 chest compressions and 2 ventilations can be accomplished in 3-4 minutes,^51,65,67 even by persons who have never received CPR training. Telephone instruction also improves the quality of CPR performed by persons with prior CPR training in manikin simulations.^22,67 Panicked bystanders can be calmed and directed by dispatchers and encouraged to perform CPR, despite their alarm at the sudden sight of a loved one who is cyanotic and breathless. With this program, plus other educational efforts, the percent of cardiac arrests in which CPR was initiated by bystanders in King County, Washington, has increased from 30% in 1980 to 60% in 1988 (unpublished data).

The Early Defibrillation Link

The purpose of early defibrillation is to reestablish a normal spontaneous rhythm in the heart. Several new approaches can help achieve early defibrillation:

• Automated defibrillators used by the first responding emergency personnel
• Automated defibrillators used by community responders, that is, persons whose usual occupation or training does not require responding to emergencies.
• Home defibrillation programs for high-risk patients
• Transtelephonic defibrillation
  

The rationale for early defibrillation emerges from data that demonstrate that almost 85% of persons with ambulatory, out-of-hospital, primary cardiac arrest experience ventricular tachyarrhythmias during the early minutes after collapse.

⁶⁸ In one report 157 ambulatory (not hospitalized) patients experienced fatal arrhythmias during continuous cardiac monitoring.⁶⁸ The initial dysrhythmia in 62% of patients was ventricular tachycardia that quickly evolved to ventricular fibrillation, in 8% the dysrhythmia was primary ventricular fibrillation, and in 13% it was torsades de pointes. The duration of the ventricular tachycardia that preceded the ventricular fibrillation ranged from a few seconds to several minutes. This study involved a select population of patients who had some indication for ambulatory cardiac monitoring. Nevertheless, the rhythms they experienced are probably representative of the usual initial rhythms of the sudden cardiac arrest victim.

In prehospital studies, the rhythm of arrest cannot be identified until emergency personnel arrive with a defibrillator/monitor, 4-8 minutes later. In these studies the percent of people in ventricular tachyarrhythmias was lower, at 60% of less.^22,62 Most eventual survivors emerge from the group of people who remain in ventricular fibrillation when emergency personnel arrive. For example, in King County, Washington, over 92% of cardiac arrest survivors were from this group,⁶² and over 80% in Houston.²²

Additional evidence about the importance of early defibrillation comes from cardiac arrest experiences in supervised cardiac rehabilitation programs. On the rare occasion when a person in such a program experiences cardiac arrest, it is witnessed, CPR is started immediately, and defibrillation is performed within minutes. Fletcher and Cantwell⁶⁹ reported five cardiac arrests in a medically supervised exercise program; all were resuscitated. Haskell⁷⁰ reported that among 13,570 patients in 30 exercise centers, 50 cardiac arrests occurred and 42 (84%) were resuscitated. Hossack and Hartwig⁷¹ observed 2,464 people in a supervised cardiac rehabilitation program over a 13-year period. In this group 25 men suffered a cardiac arrest, and all 25 (100%) were successfully resuscitated. Van Camp and Peterson⁷² summarized the experience in 167 cardiac rehabilitation programs; 21 cardiac arrests occurred, and personnel resuscitated 18 (86%) without neurologic sequelae. The type of rhythm at arrest in these series was not reported, but sudden arrest during exercise suggests that the large majority of these patients were in ventricular fibrillation. Overall, of 101 cardiac arrests in these reports, staff members resuscitated 90 (89%) of the victims. This is the highest survival rate reported among defined population groups, and it confirms the value of immediate efforts in early CPR and defibrillation.

In England, general practitioners, the most frequent responders to patients with chest pain and cardiac arrest, have observed that early defibrillation alone produces successful resuscitations.⁷³ Many patients in Britain call their general practitioner during the early stages of a myocardial infarction. About 5% of these patients experience a cardiac arrest after the physician arrives.^74,75 The British Heart Foundation donated 78 defibrillators to 25 general practices and reported on the experiences after 1 year.⁷³ A total of 19 patients suffered cardiac arrest in the presence of a general practitioner who had a defibrillator: 13 (68%) were in ventricular fibrillation, nine were successfully resuscitated outside the hospital, and six were discharged from the hospital.⁷³

In the earliest prehospital programs,^{33-35,42,76-86} only paramedics provided defibrillation. In most studies of paramedic-only systems, the time between collapse and arrival of paramedics averaged more than 12 minutes. These programs therefore generally provide what is more correctly termed late defibrillation.

Consequently, the reported survival rates for these systems have been modest, ranging from 7% to 18% for all rhythms.⁸⁷ Researchers in the early 1980s demonstrated the ability of personnel less well trained than paramedics, namely, emergency medical technicians (EMTs), to successfully use defibrillators.^88-91 Early defibrillation programs implemented for firefighters and minimally trained EMS first responders spread slowly, more often because of implementation barriers and administrative inertia than from doubt of clinical efficacy.^92,93

The proposals to allow less well trained emergency personnel to operate defibrillators initially provoked controversy, but most concerns have since disappeared. Conceptually, early defibrillation programs represented the transfer of what was a medical act – diagnosis of the rhythm and operation of a defibrillator – into the hands of nonphysicians. Some authorities accepted the transfer of skills to paramedics. However, many authorities hesitated to permit defibrillation by less well trained emergency personnel. Rational reasons for this hesitancy vanished by the late 1980s with widespread acceptance of the principle of early defibrillation^1,20,23 and the success of automated external defibrillators.^94,95 Regrettably, in Germany, France, Japan, and other countries, medicolegal factors still prevent implementation of early defibrillation programs by nonphysicians.

The principle of early defibrillation holds that the professional rescuer who arrives first at the scene of a cardiac arrest should carry a defibrillator and be trained to operate it.^1,20,23 With few exceptions, the defibrillator should be automated and external.^93,94,96-102 Automated external defibrillators are highly accurate^{98,99,101-103} and eliminate the need for training in the complex skills of rhythm recognition. The operator simply attaches the defibrillator's adhesive electrodes to the chest of the person thought to be in cardiac arrest. When activated by a single control, the device analyzes the rhythm, and if ventricular fibrillation or tachycardia is present, the device either charges and delivers a shock (automatic devices) or indicates to the operator that a shock is needed (semiautomatic, or shock-advisory, devices).^104,105 With shock-advisory devices, the operator delivers the shock by pushing a second control.^104,106 This simplicity of operation decreases the time and expense of initial training and continuing education and markedly increases the number of persons who can operate the devices. Clinical studies also show that systems using automated defibrillators can deliver the first shock up to 1 minute faster than conventional defibrillators because of the speed with which these devices can be attached and with which they operate.^98,99

Each year more communities in the United States allow the use of both automated and conventional defibrillators by EMTs and by less trained personnel call first responders, a term that refers specifically to persons who have completed a 40-hour course. The term can refer to a much larger group of public safety employees, including firefighters, ambulance personnel, part-time emergency volunteers, police officers, highway patrol personnel, security guards, merchant marine sailors, and airline, railroad, and other public transportation vehicle crews.

Automated defibrillators are used by first responders around the world,^107,108 with early defibrillation programs in Scotland,²⁵ Denmark,¹⁰⁹ England,⁶ West Berlin,^107,108 Norway,¹¹⁰ Sweden,⁴³ Australia,¹¹¹ Singapore,¹¹² Finland, Belgium, and many other countries. By 1988, 37 states in the United States had passed legislation permitting early defibrillation by EMTs and, in some states, basic first reponders.¹¹³ An additional 10 states planned to initiate similar programs in 1989.¹¹³ Many communities permit first-responder (usually firefighter) defibrillation, including Houston; Dallas; Memphis; San Francisco; Salt Lake City; Seattle; King County, Washington; and Eugene-Springfield, Oregon.^102,114-116 The International Association of Fire Chiefs has endorsed this concept and has started an initiative called RapidZap,^114-116 which has the goal of equipping all fire department emergency response vehicles with automated defibrillators by the year 2000. The fire chiefs adopted this concept not only out of concern to provide effective care for all citizens but also concern for the well-being of their personnel. Surveys of firefighter deaths have noted that the majority of on-duty deaths are due to sudden cardiac arrest.^117,118

How effective are programs in which defibrillators are given to EMTs and first responders? Variable degrees of success have been observed in clinical studies thus far. The published survival rates for systems whose prehospital response teams consist only of EMTs trained in defibrillation range from 6% to 26% for patients found to be in ventricular fibrillation.^{43,88,89,119-121} The most important comparison, however, is between the survival rate in communities before and after institution of an early defibrillation program. In suburban communities in King County, Washington, for example, the survival rate for patients in ventricular fibrillation increased from 7% to 26%.⁸⁸ Similarly, in communities in Iowa it increased from 3% to 19%.⁹⁰ In southeastern Minnesota the survival rate was 4% without EMT defibrillation and 17% with such a program,¹¹⁹ whereas in northeastern Minnesota the survival rate was 2.5% without and 9.9% with EMT defrillation.⁷⁷ When an early defibrillation program was started in certain Wisconsin communities, the survival rate rose from 3.6% to 6.4% for all cardiac arrests and was 11% for patients initially noted to be in ventricular fibrillation (Table 2),¹²² It is important to note that these programs should maintain and increase initial improvements in survival rates as experience and competency improve over time.

Home and community responder defibrillation programs. Two other techniques advocated to help achieve early defibrillation are home defibrillation programs for high-risk patients and early defibrillation by community responders. Community responders include public safety workers or laypersons who may have a perceived duty to respond to an emergency.^96,123-125 Although these approaches have been under evaluation for several years, their specific effects on community-wide survival rates from cardiac arrest have not been determined.¹²³ Moore et al¹²⁶ observed that of 95 survivors of ventricular fibrillation, only 63 (66%) were eligible for a home defibrillator, and only 38 of 47 (81%) persons approached agreed to participate. This suggests that approximately half (0.66x0.81) of ventricular fibrillation survivors would receive the device and appropriate training. McDaniel et al¹²⁷ also experienced recruitment problems in a similar home-defibrillation study. Only 8% of survivors of acute myocardial infarction participated in their study. The reasons for low participation included patients living alone, patients discharged to nursing homes, patients having no telephone, resuscitation considered medically inappropriate, implantation of automatic internal defibrillators, residence outside the study areas, no perceived chance of repeat cardiac arrest, religious objections, and elimination from the study at the demand of personal physicians.^126,127

Nevertheless, enough experience has accumulated to establish the feasibility of training family members of high-risk patients and community responders to use automated defibrillators.^126-129 Despite some decline in skill retention and performance, family members and lay responders can remember most training and retain the skill for up to 1 year and can use the device at the moment of cardiac arrest of a family member or coworker.¹²⁸

So far, only limited clinical experience demonstrates the practicality and effectiveness of home and community responder defibrillation programs. Chadda et al¹³⁰ reported a case series of 30 patients with witnessed cardiac arrest. Lay persons used automated defibrillators before the arrival of trained emergency personnel. Rescuers resuscitated eight of these patients to an organized rhythm associated with spontaneous circulation. Five were discharged from the hospital. Swenson et al¹³¹ reported a series of 48 high-risk patients where the research team trained family members to operate automated defibrillators. Five cardiac arrests occurred in this series. The trained home responders used the automated defibrillator four times, and three patients had successful restoration of circulation.

Researchers from King County, Washington, however, have experienced less positive results with home¹³² and community responder defibrillation.¹²⁸ Eisenberg et al¹³² placed automated defibrillators in the homes of 59 persons who had survived prehospital cardiac arrest. Ten cardiac arrests occurred; home responders used the device in six patients. Only two patients were in ventricular fibrillation. One of the two patients was resuscitated but survived only a few months with residual neurological deficits. In another King County study, researchers placed 14 automated defibrillators in a variety of community settings and trained 146 lay people working in those settings to operate the device.¹²⁸ Only three cardiac arrests occurred. Recognition and operation errors prevented proper attachment and use of the defibrillator for all three patients. However, manufacturers have since developed simpler, lighter, and more sophisticated automated defibrillators with more user-friendly protocols and simpler placement of electrode pads. Researchers may achieve better results if they conduct future studies with the currently available devices.

In contrast, several other studies have achieved better results when automated defibrillators were placed with community responders. Weaver et at¹³³ trained 160 security personnel at the 1986 World's Exposition in Vancouver, British Columbia, to operate an automated defibrillator in the event of a cardiac arrest. There were five cardiac arrests among 22.1 million visitors. Rescuers used automated external defibrillation on each victim, two of whom were in ventricular fibrillation. Automated external defibrillation was successful in both patients, and sustained circulation returned. Both patients were moving and semiconscious by the time emergency personnel arrived. In England researchers placed automated external defibrillators on long-distance aircraft of an international air carrier.¹³⁴ This preliminary study ceased when another company purchased the air carrier, but senior cabin attendants trained with great enthusiasm. Several other airlines are likely to implement similar programs in the near future. In London researchers trained conductors at several British Rail stations to operate automated defibrillators. There are early anecdotal reports of successful resuscitation.¹³⁴ High-risk or isolated industrial settings represent another interesting target group for implementation of early defibrillation programs. Safety personnel have, for example, placed and successfully used automated external defibrillators on oil platforms in the North Sea, at electricity plants, and on passenger cruise ships and merchant marine vessels.^{95,100,110,130}

Future research will help establish the exact role of these innovative approaches. However, clinical evidence is insufficient to support widespread home placement of automated external defibrillators with high-risk patients. The evidence is more encouraging for busy public places such as airports, railway stations, convention centers, major hotels, and large public assemblies, and high-risk or remotely located industries with trained safety personnel.

Transtelephonic defibrillation. Transtelephonic defibrillation is a recently introduced method to provide early defibrillation.^135-137 However, it should not be classified with automated external defibrillation. In transtelephonic defibrillation a trained family member or other companion attaches adhesive monitor/defibrillator pads to a person with cardiac complaints or in cardiac arrest. The defibrillator pads are attached through cables to a home unit that then transmits the rhythm by telephone circuitry (either hard-wired or cellular) to a remote base station. Emergency personnel at the base station interpret the rhythm and make the decision to deliver a shock. Base station controls can be used to charge the home defibrillator unit and deliver the shock. A two-way speaker phone provides simultaneous voice communication between the home and the base station.
Researchers have confirmed this concept of remote defibrillation in hospital settings.^136,137 Physicians have attached the device to patients in one hospital location (usually a coronary care unit for elective cardioversions) and operated it from another. This approach offers potential advantages over automated external defibrillators when used in the home setting, including two-way voice communication, automatic dialing of 911, and transfer of decision making to emergency personnel.¹³⁸ Although approved for clinical use, clinical experience confirming the effectiveness of prehospital transtelephonic defibrillation is limited to a single patient, widely reported in the lay press.¹³⁹ It remains to be seen whether transtelephonic defibrillation will be considered cost-effective and put to major practical use. This doubt is especially valid since clinicians have already confirmed the ability of automated external defibrillators to interpret rhythms and deliver shocks satisfactorily.

The Early Advanced Cardiac Life Support Link
In many instances CPR and defibrillation alone do not achieve or sustain resuscitation. The unique interventions of the early advanced cardiac life support link – endotracheal intubation and intravenous medication – are necessary to further improve the chances of survival. In the United States, paramedics provide advanced cardiac life support for prehospital cardiac arrest patients.¹⁴⁰ Paramedics receive 1,000-3,000 hours of classroom training and field instruction and can provide intubation, defibrillation, and intravenous medications.

EMS systems in other countries provide many models of care. Some are more innovative than those used in the United States. There are no paramedics as such in Europe. Ambulance personnel in the first responding units are sometimes provided with extensive training, which may be from 400 to 500 hours. In Oslo, for example, ambulance personnel (equivalent to US basic EMTs) are taught to perform endotracheal intubation. In Holland a registered nurse who can operate a manual defibrillator arrives on more than 80% of the first-responding ambulances. Other systems, such as that in Göteborg, Sweden, use a second responding unit manned by specially trained nurses on 24-hour duty, similar to a US paramedic unit. Physician-manned mobile coronary care units are also common.

In other locations, especially in France, Israel, and Germany, and to a much lesser extent in England, Australia,⁴² and Finland, emergency physicians (called ambulance doctors) provide advanced cardiac life support.¹⁰⁷ They respond in specially equipped vehicles, known as doctor-manned ambulances. Systems in the United States, however, abandoned programs with physicians or nurses on ambulances years ago because physician-staffed ambulances in the United States were considered an inefficient use of physician resources. In addition, paramedics can perform the same functions with comparable effectiveness.¹⁴⁰

Physician-staffed ambulances in Europe, however, may well be more cost-effective than they are in the United States, depending on relative operating costs, professional salaries, population density, and combined services such as air rescue. In Norway, for example, nine doctor-ambulance units combined with helicopter services respond effectively to about 4,500 patients a year in a population service area of 4 million people. These units depend on public subscriptions and have been quite popular. In Australia several states and localities use a single-layer ambulance response. The ambulance training, however, includes both early defibrillation and administration of up to 20 drugs (but not intubation). The guiding principle in all systems, no matter how organized, is to provide the necessary treatment to the patient in the most timely and cost-effective manner.

Defibrillation and advanced cardiac life support. Observers classically have considered defibrillation a part of advanced cardiac life support care. Now, however, early defibrillation is a separate link in the chain of survival. EMTs and other early responders¹¹³ share this skill with paramedics, physicians, and nurses. Still, in view of the simultaneous therapies employed during a resuscitation attempt, it is difficult to separate the value of defibrillation from the value of intubation and intravenous medications.

What incremental benefit can be derived from these advanced procedures compared with defibrillation alone? Evidence from different locations, with different emergency response systems, sheds some light on this question. Differences in survival rates exist between a system that provides only early defibrillation and early advanced cardiac care. These differences may indicate the additional benefit of advanced cardiac life support. In Iowa, for example, small communities that have provided early defibrillation without prehospital advanced cardiac life support care have achieved a ventricular fibrillation survival rate of 19%.⁹⁰ Meanwhile, suburban King County, Washington, which uses a tiered system (early defibrillation crews followed by advanced cardiac life support crews), has achieved an even greater survival rate. This system reports a 29% survival rate for patients with witnessed ventricular fibrillation arrest.⁸⁹ Emergency personnel resuscitated about 30% of persons who survived with defibrillatory shocks alone, either from emergency medical technicians trained to defibrillate (EMT-Ds) or from paramedics. These people did not require subsequent intubation or intravenous medications.¹⁴¹

The average survival rate for EMT-D-only systems has been 16%^{43,90,119,120,142} (see Table 3). This rate refers to patients in witnessed cardiac arrest and in ventricular fibrillation. This is significantly lower than the average ventricular fibrillation survival rate of 29% in combined EMT-D and paramedic systems.^89,143 Paramedic-only systems have an average survival rate of 17%, almost exactly the same survival rate as EMT-D-only systems.^33-35,76-86 Paramedic-only and EMT-D-only systems average the same survival rate for a specific reason. In paramedic-only systems all advanced cardiac life support interventions (defibrillation, intubation, and administration of medications) are performed, but performed late. Only basic CPR and defibrillation are performed in EMT-D-only systems, but these interventions are performed much earlier.

These observations confirm that a considerable portion of all survivors are alive because of early defibrillation alone. These data also imply the important additional value of intubation and intravenous medications. Researchers think that these interventions not only promote return of spontaneous rhythm and circulation but also stabilize and maintain patients during the immediate postresuscitation period. Ventricular fibrillation survival rates in EMT-D-only systems (Table 3) can be compared with survival rates of tiered EMT-D/paramedics systems. Such a system comparison hints at the relative value of these two system types. The table shows that EMT-D systems alone resuscitate about half of all potential ventricular fibrillation survivors.

Systems already staffed with paramedics or, as in Europe, with doctor-manned ambulances should consider the addition of a basic EMT- or ambulance-defibrillation program, which may significantly increase the ventricular fibrillation survival rate. However, no system should delay the start of an early defibrillation program because of the absence of paramedics or doctor-manned ambulances. In fact, some paramedic-only⁴² or doctor-manned systems^73,111 have such long response times and such poor outcomes that they may be abandoned in favor of or supplemented by early automated defibrillation.

Resources may prevent establishment of a tiered response system that includes first-responder defibrillation as well as paramedics. In these circumstances, first-responder defibrillation, rather than paramedics alone, is probably the most efficient method to improve survival from cardiac arrest. For locations without an effective method of rapid delivery of prehospital defibrillation, the rational approach is to start with first-responder automated defibrillation. Innovative leaders in such locations as Japan,¹⁴⁴ Scotland,²⁵ Singapore,¹¹² England,⁶ Norway,¹¹⁰ Australia,^111,145 Sweden,⁴³ and Hong Kong¹⁴⁶ have all abandoned inappropriate plans to institute or continue paramedic systems. Instead, these programs are going directly to the more efficient and more effective approach of automated defibrillation.

Commentary

What is the maximum practical survival rate? The number of people resuscitated from sudden cardiac death by emergency personnel is not known. Nor is it known how many people can be resuscitated with a reasonable chance of surviving and remaining neurologically intact. Cardiac disease, in general, is the single greatest cause of death in the United States.^22,147 For the adult American population, epidemiologists have estimated the annual incidence of out-of-hospital sudden cardiac arrest at about 1 in 1,000 per year.¹⁴⁷ Other statistics from the American Heart Association are often quoted: 1.5 million "generic" heart attacks per year in the United States, of which 25%, or 350,000-400,000, die out of the hospital.¹⁴⁷ Though no national averages are available on the proportion of people who survive out-of-hospital cardiac arrests, current estimates suggest that no more than 1-3% of victims live to be discharged from the hospital. The true percentage is probably even less.¹⁴⁸

It could be argued that the highest survival rates currently reported for out-of-hospital cardiac arrests are a reasonable target for all locations. While achievements of such survival rates are not practical in every community, this approach does expose the gap between what a community does achieve and what is possible. The highest published rates come from sophisticated urban/suburban systems like King County, Wisconsin,⁶² and Seattle.¹⁴³ Both can be described as mature EMS systems. Over the past 10-15 years these locations established strong links in the chain of survival. The annual survival rates for King County, Washington, from 1976 through 1987, fluctuate between 15% and 20% for all cardiac arrests and 25-30% for all patients in ventricular fibrillation (Figure 2). These overall survival rates, however, have remained moderately stable despite a number of system interventions, such as EMT defibrillation with manual defibrillators,⁸⁸ EMT defibrillation with automated defibrillators,⁹⁸ dispatcher-assisted CPR,⁵¹ and transcutaneous pacing.¹⁴⁹ Therefore, this level of ventricular fibrillation survival may represent the practical limits for prehospital emergency care.

How many people would survive if all emergency medical systems in the United States approached the hypothesized maximum survival rate of 20% that occurs in these mature EMS systems? If an estimated 3% survival rate¹⁴⁸ is applied to the presumed annual 400,000 cardiac arrests, approximately 12,000 people per year now survive out-of-hospital cardiac arrest.¹⁴⁷ A 20% survival rate for this population of nontraumatic cardiac arrest patients would yield 80,000 survivors, or an additional 68,000 people. The American Heart Association estimates that nationwide implementation of all life-saving emergency cardiac care mechanisms in each community may save between 100,000 and 200,000 lives annually in the United States.¹ Without proper implementation of a full prehospital care system, however, emergency services cannot achieve such rates. People not resuscitated before hospital arrival rarely survive.^150,151

Figure 2. Ventricular fibrillation survival rates over time. Percentage of people in nontraumatic cardiac arrest with initial rhythm ventricular fibrillation who survive to hospital discharge. Data from King County, Washington, Division of Emergency Medical Services, Seattle-King County Department of Public Health, Seattle.

Design Imitation?
Is it possible for EMS systems to imitate the design of more successful locations and thus achieve the same survival rates? Table 3 summarizes data published on cardiac arrest survival from many cities worldwide.^{31, 33-35, 38, 39, 43, 76-90, 101, 119, 120, 142, 143, 152-158.} These data show marked variation in survival rates among the different types of EMS systems, ranging from 5% to 17% survival for patients in all cardiac arrest rhythms and from 12% to 29% for patients specifically in ventricular fibrillation.

Simple structural imitation of successful EMS organizations, however, does not always succeed. Even in locations with similarly structured EMS systems, marked differences in the observed survival rates persist. For example, studies from 15 different paramedic-only or doctor-manned ambulance systems (Table 3, row C) reported survival rates from 7% to 18% for all rhythms and from 13% to 30% for ventricular fibrillation.^{6,33-35,76-86} Table 3 summarizes results from nine EMT-paramedic systems (row D). These systems display the same wide variations.^{33,38,39,101,154-158}

It is unclear exactly why these differences occur within the same types of systems. Part of the explanation is that definition of terms and reporting of data are not standardized.¹⁵⁹ While some researchers have proposed uniform reporting systems, many others have pointed to the need for an international standardized nomenclature.^{18,27,35,39,87,159,160} Regardless, part of these differences may very well be due to variable effectiveness or lack of EMS medical leadership and direction.^161-165

It can also be argued that similarly constructed systems have different survival rates because they differ in how well they develop and implement each link in the chain of survival.^87,163,166 This appears particularly true for early initiation of CPR and early arrival of personnel trained to operate a defibrillator. Many cities in the United States, for example, established a strong link for early advanced life support by starting paramedic services at great expense and effort.^33-35,76-86 Most of these paramedic-only systems have achieved disappointingly low survival rates. In part this is because citizens in these locations seldom attempted to perform CPR. In addition, long paramedic response times, in the absence of an early defibrillation program, precluded early defibrillation and early advanced care. In paramedic-only systems, paramedics are generally preoccupied with many other minor emergencies and consequently are less available (and less skilled) to deal with cardiac arrest patients.¹⁶³

To strengthen the early CPR link in the chain of survival, several EMS systems have mounted extensive CPR campaigns. They have trained a large percentage of the population in basic CPR skills. Unfortunately, these systems also have observed diminished survival rates because they failed to provide an emergency medical service with rapid defibrillation and rapid advanced life support.^{18,39,43,78,153,155} Enhancements of early CPR programs, such as targeted CPR training^10,53-59 and dispatcher-assisted CPR programs,^51,65,67 will also fail if defibrillation does not occur soon after collapse.

Conversely, systems that have established early defibrillation programs by training their less advanced ambulance personnel to use defibrillators^{43,90,119,120,142} may experience low success rates if they do not also train citizens to recognize cardiac arrest early or to call the emergency service immediately. The defibrillator will not arrive quickly enough if the EMS system is not called immediately, if local ambulances or first-responder units are not equipped with defibrillators, or if managers do not strategically deploy emergency response vehicles with defibrillators.

Responsible people must apply continuous quality improvement concepts to each link in the chain of survival. In early CPR, for example, it is not only a matter of the number of people who are trained. Systems can achieve better results by targeting the right groups and evaluating training programs, short-term results, and long-term trends. Automated defibrillators must be placed, then complemented with carefully planned training and follow-up programs and close medical control of the system, including individual case reviews and overall data management programs. Without these quality improvement methods, a system will not realize the full benefit of any new organization.

Summary

The chain of survival concept embodies standard principles of system management. The phrase restates¹⁶⁷ the familiar emergency medical services continuum pioneered by Peter Safar, who coined the term life support chain.¹⁶⁸ Other authors have referred to the concept with various phrases.^{1,3,20,23,140} As a pedagogic construct, it emphasizes that there are no easy, single-step approaches to improving survival from cardiac arrest.^166,167

Early access to the EMS system ensures early CPR, defibrillation, and advanced care. Early access is easiest to achieve with 911 systems and widespread community education and publicity. Instructors may also teach early access during citizen CPR classes. Early CPR helps patients by slowing the process of dying, but its effectiveness disappears within minutes, and defibrillation must soon follow. Early recognition and early CPR are best achieved when citizens are well informed about cardiac emergencies and well trained in CPR. The earliest possible delivery of defibrillation is critical and almost by itself is sufficient for many victims of sudden cardiac death.
Defibrillation has therefore emerged as the single most effective intervention for patients in nontraumatic cardiac arrest. Automated external defibrillators help to accomplish this goal and permit widespread implementation of a variety of early defibrillation programs. Early advanced care helps those who do not immediately convert to an organized cardiac activity or who do not achieve a spontaneous circulation following early defibrillation. Advanced care allows the highest possible survival rate through respiratory and antiarrhythmic stabilization and monitoring of patients in the post-resuscitation period.

At present, early CPR and rapid defibrillation, combined with early advanced care, can result in long-term survival rates for witnessed ventricular fibrillation as high as 30%. Researchers have observed that neurological and psychological recovery from cardiac arrest depends on the time within which these critical interdependent treatment modalities are delivered.^22,169 Therefore, high resuscitation rates will also lead to a high percentage of patients who recover to the neurological level they had before their arrest.

The future of the chain of survival will be highly dependent on multicenter cooperative studies of cardiac arrest in both in-hospital and out-of-hospital settings.^150,162,170 In addition to scientific research, the training of those responsible for implementing and maintaining the chain of survival must become a priority.^150,162,164 For emergency medical services the challenge is to develop programs that will allow recognition, access, bystander CPR, defibrillation, and advanced care to occur as quickly as possible. Ideally systems should deliver these interventions within moments after sudden death victims collapse. Achievement of such a goal requires the deployment of multiple, properly directed programs, within an EMS system. Each program should lend strength to the chain of survival, thereby enhancing successful recovery and long-term survival.

Recommendations

The Advanced Cardiac Life Support Subcommittee and the Emergency Cardiac Care Committee of the American Heart Association recommend that all communities take the following actions to strengthen their Chain of Survival:

1. Early Access

• All communities should implement an enhanced 999 system.
• All communities should develop education and publicity programs that focus on cardiac emergencies and a proper response by citizens.

2. Early CPR

• Communities should continue to vigorously implement and support community-wide CPR training programs.
• Community CPR programs should emphasize early recognition, early telephone contact with the EMS system, and early defibrillation.
• Community CPR programs should develop and use training methods that will increase the likelihood that citizens will actually initiate CPR.
• Communities should adopt more widespread and effective targeted CPR programs.
• Communities should implement programs to establish dispatcher-assisted CPR.

3. Early Defibrillation

• All communities should adopt the principle of early defibrillation. This principle applies to all personnel who are expected, as part of their professional duties, to perform basic CPR: they must carry an automated external defibrillator and be trained to operate it.
• Health professionals who have a duty to respond to a person in cardiac arrest should have a defibrillator available either immediately or within 1-2 minutes.
• Responsible personnel should authorize and implement more widespread use of automated external defibrillation by community responders and allied health responders.
  

4. Early Advanced Life Support

• Advanced life support units should be combined with first-responding units that provide early defibrillation.
• Advanced life support units should develop well-coordinated protocols that combine rapid defibrillation by first-responding units with rapid intubation and intravenous medications by the advanced cardiac life support units.

Acknowledgments

Over the years many people have contributed to the chain of survival concept. In particular, we want to mention Professor F. W. Ahnefeld of Ulm, Germany, who pioneered the "rescue chain" concept in emergency medical care in the early 1960s.

The Advanced Cardiac Life Support Subcommittee and the Emergency Cardiac Care Committee thank the following persons for their contributions to this statement: Mickey Eisenberg, Tore Laerdal, Leo Bossaert, Stig Holmberg, Thomas R. Hearne, Judith Reid Graves, Allan Jaffe, Mary Newman, Mary Pat Larsen, and Douglas Austin Jr.

References

1. Standards and guidelines for cardiopulmonary resuscitation (CPR) and emergency cardiac care (ECC). JAMA 1986;255:2905-2914

2. Graf WS, Polin SS, Paegel BL: A community program for emergency cardiac care: A three-year coronary ambulance-paramedic evaluation. JAMA 1973;226:156-160

3. Schwartz L: Pre-hospital care: Field intervention medicine, in Schwartz GR, Safar P, Stone J, Storey P, Wagner D (eds): Principles and Practice of Emergency Medicine. Philadelphia, WB Saunders Co, 1986, pp 593-619

4. Hallstrom AP; Improving the EMS system, in Eisenberg MS, Bergner L, Hallstrom AP (eds): Sudden Cardiac Death in the Community, Philadelphia, Praeger Pubs, 1984, pp 126-139

5. American Red Cross: Adult CPR. Boston, Mass, American National Red Cross, 1987

6. Walters G. Glucksman E: Planning a pre-hospital cardiac resuscitation programme: An analysis of community and system factors in London. J R Coll Physicians Lond 1989;23:107-110

7. Stults KR: Phone first. J Emerg Med Services 1987;12:28

8. Hunt RC, Allison EJ Jr, Yates JG III: The need for improved emergency medical services in Pitt county. N C Med J 1986;47:39-42

9. Hunt RC, McCabe JB, Hamilton GC, Krohmer JR: Influence of Emergency Medical Services systems and prehospital defibrillation on survival of sudden cardiac death victims. Am J Emerg Med 1989;7:68-82

10. Mandel LP, Cobb LA: CPR training in the community. Ann Emerg Med 1985;14:669-671

11. Mayron R, Long RS, Ruiz E: The 911 emergency telephone number: Impact on emergency medical systems access in a metropolitan area. AM J Emerg Med 1984;2:491-493

12. Eisenberg M, Hallstrom A, Becker L: Community awareness of emergency phone numbers. Am J Public Health 1981;71:1058-1060

13. Cummins RO, Eisenberg MS: Prehospital cardiopulmonary resuscitation: Is it effective? JAMA 1985;253:2408-2412

14. Thompson BM, Stueven HA, Mateer JR, Aprahamian CC, Tucker JF, Darin JC: Comparison of clinical CPR studies in Milwaukee and elsewhere in the United States. Ann Emerg med 1985;14:750-754

15. Kowalski R, Thompson BM, Horwitz L, Stueven H, Aprahamian C, Darin JC: Bystander CPR in prehospital coarse ventricular fibrillation. Ann Emerg Med 1984;13:1016-1020

16. Kouwenhoven WB, Jude JR, Knickerbocker GG: Closed-chest cardiac massage. JAMA 1960;173:1064-1067

17. Safar P, Brown TC, Holtey WJ, Wilder RJ: Ventilation and circulation with closed-chest cardiac massage in man. JAMA 1961;176:574-576

18. Bossaert L, Van Hoeyweghen R, Cerebral Resuscitation Study Group: Bystander cardiopulmonary resuscitation (CPR) in out-of-hospital cardiac arrest. Resuscitation 1989;17(suppl):S55-S69

19. Cummins R, Graves J: Clinical results of standard CPR: Prehospital and inhospital, in Kaye W, Bircher N (eds): Cardiopulmonary Resuscitation. New York, Churchill Livingstone, Inc., 1989, pp 87-102

20. Advanced cardiac life support in perspective, in Textbook of Advanced Cardiac Life Support. Dallas, American Heart Association, 1987, pp 1-10

21. Safar P: History of cardiopulmonary-cerebral resuscitation, in Kaye W, Bircher N (eds): Cardiopulmonary Resuscitation. New York, Churchill Livingstone, Inc, 1989, pp 1-54

22. Pepe P: Advanced cardiac life support: State of the art, in Vincent JL (ed): Emergency and Intensive Care. Berlin, Springer-Verlag, 1990, pp 565-585

23. Putting it all together: Resuscitation of the patient, in Textbook of Advanced Cardiac Life Support. Dallas, American Heart Association, 1987, pp 235-248

24. Eisenberg M, Bergner L, Hallstrom A: Paramedic programs and out-of-hospital cardiac arrest: I. Factors associated with successful resuscitation. Am J Public Health 1979;69:30-38

25. Carrington D: Heartstart Scotland: Early defibrillation for the whole of Scotland, in Proceedings of the 6th World Congress on Disaster and Emergency Medicine. Hong Kong, Excerpta Medica, 1989, p 66

26. Pepe P: Presumptive diagnosis of death versus whom to resuscitate, in Kuehl A (ed): EMS Medical Director’s Handbook for the National Association of EMS Physicians. St. Louis, CV Mosby Co, 1989, pp 275-289

27. Mullie A, Van Hoeyweghen R, Quets A, Cerebral Resuscitation Study Group: Influence of time intervals on outcome of CPR. Resuscitation 1989;17(suppl):S23-S33

28. Lund I, Skulberg A: Cardiopulmonary resuscitation by lay people. Lancet 1976;2:702-704

29. Copley DP, Mantle JA, Rogers WJ, Russell RO Jr: Improved outcome for prehospital cardiopulmonary collapse with resuscitation by bystanders. Circulation 1977;56:901-905

30. Thompson RG, Hallstrom AP, Cobb LA: Bystander-initiated cardiopulmonary resuscitation in the management of ventricular fibrillation. Ann Intern Med 1979;90:737-740

31. Tweed WA, Bristow G, Donen N: Resuscitation from cardiac arrest: Assessment of a system providing only basic life support outside of hospital. Can Med Assoc J 1980;122:297-300

32. Gudjonsson H, Baldvinsson E, Oddsson G, Asgeirsson E, Kristjansson H, Hardarson T: Results of attempted cardiopulmonary resuscitation of patients dying suddenly outside the hospital in Reykjavik and the surrounding area, 1976-1979. Acta Med Scand 1982;212:247-251

33. Vertesi L, Wilson L, Glick N: Cardiac arrest: Comparison of paramedic and conventional ambulance services. Can Med Assoc J 1983;128:809-812

34. Guzy PM, Pearce ML, Greenfield S: The survival benefit of bystander cardiopulmonary resuscitation in a paramedic-served metropolitan area. Am J Public Health 1983;73:766-769

35. Roth R, Stewart RD, Rogers K, Cannon GM: Out-of-hospital cardiac arrest: Factors associated with survival. Ann Emerg Med 1984;13:237-243

36. Stueven H, Troiano P, Thompson B, Mateer JR, Kastenson EH: Bystander/first responder CPR: Ten years experience in a paramedic system. Ann Emerg Med 1986;15:707-710

37. Ritter G, Wolfe RA, Goldstein S, Landis JR, Vasu CM, Acheson A, Leighton R, Medendrop SV: The effect of bystander CPR on survival of out-of-hospital cardiac arrest victims. Am Heart J 1985;110:932-937

38. Cummins RO, Eisenberg MS, Hallstrom AP, Litwin PE: Survival of out-of-hospital cardiac arrest with early initiation of cardiopulmonary resuscitation. Am J Emerg Med 1985;3:114-119

39. Eitel DR, Walton SL, Guerci AD, Hess DR, Sabulsky NK: Out-of-hospital cardiac arrest: A six-year experience in a suburban-rural system. Ann Emerg Med 1988;17:808-812

40. Spaite DW, Hanlon T, Criss EA, Valenzuela TD, Wright AL, Keeley KT, Meislin HW: Prehospital cardiac arrest: The impact of witnessed collapse and bystander CPR in a metropolitan EMS system with short response times. Ann Emerg Med 1990;19:1264-1269

41. Lewi PJ, Mullie A, Quets A: Relevance and significance of pre-CPR conditions in cardiopulmonary-cerebral resuscitation: A graphic analysis by means of Spectramap. Resuscitation 1989;17(suppl):S35-S44

42. Wright D, James C, Marsden AK, Mackintosh AF: Defibrillation by ambulance staff who have had extended training. BMJ 1989;299:96-97

43. Jakobsson J, Nyquist O, Rehnqvist N: Cardiac arrest in Stockholm with special reference to the ambulance organization. Acta Med Scand 1987;222:117-122

44. Weaver WD, Cobb LA, Dennis D, Ray R, Hallstrom AP, Copass MK: Amplitude of ventricular fibrillation waveform and outcome after cardiac arrest. Ann Intern Med 1985;102:53-55

45. Selby ML, Kautz JA, Moore TJ, Gombeski WR Jr, Ramirez AG, Farge EJ, Forthofer RN: Indicators of response to a mass media CPR recruitment campaign. Am J Public Health 1982;72:1039-1042

46. St. Louis P, Carter WB, Eisenberg MS: Prescribing CPR: A survey of physicians. Am J Public Health 1982;72:1158-1160

47. Goldberg RJ: Physicians and CPR training in high-risk family members. Am J Public Health 1987;77:671-672

48. Cobb LA, Werner JA, Trobaugh GB: Sudden cardiac death: I. A decade’s experience with out-of-hospital resuscitation. Mod Concepts Cardiovasc Dis 1980;49:31-36

49. Murphy RJ, Luepker RV, Jacobs DR Jr, Gillum RF, Folsom AR, Blackburn H: Citizen cardiopulmonary resuscitation training and use in a metropolitan area; The Minnesota Heart Survey. Am J Public Health 1984;74:513-515

50. Gombeski WR Jr, Effron DM, Ramirez AG, Moore TJ: Impact on retention: Comparison of two CPR training programs. Am J Public Health 1985;72:849-852

51. Eisenberg MS, Hallstrom AP, Carter WB, Cummins RO, Bergner L, Pierce J: Emergency CPR instruction via telephone. Am J Public Health 1985;75:47-50

52. McCormack AP, Damon SK, Eisenberg MS: Disagreeable physical characteristics affecting bystander CPR. Ann Emerg Med 1989;18:283-285

53. Cobb LA, Hallstrom AP, Thompson RG, Mandel LP, Copass MK: Community cardiopulmonary resuscitation. Annu Rev Med 1980;31:453-462

54. Cobb LA, Hallstrom AP: Community-based cardiopulmonary resuscitation: What have we learned? Ann N Y Acad Sci 1982;382:330-342

55. Bossaert L, Van Hoeyweghen R, Cerebral Resuscitation Study Group: Evaluation of cardiopulmonary resuscitation (CPR) techniques. Resuscitation 1989;17(suppl):S99-S109

56. Murphy RJ, Luepker RV, Jacobs DR Jr, Gillum RF, Folsom AR, Blackburn H: Citizen cardiopulmonary resuscitation training and use in a metropolitan area: The Minnesota Heart Survey. Am J Public Health 1984;74:513-515

57. Goldberg RJ, Gore JM, Love DG, Ockene JK, Dalen JE: Layperson CPR – Are we training the right people? Ann Emerg Med 1984;13:701-704

58. Pane G, Salness K: Targeted recruitment of senior citizens and cardiac patients to a mass CPR training course. Ann Emerg Med 1989;18:152-154

59. Pane GA, Salness KA: A survey of participants in a mass CPR training course. Ann Emerg Med 1987;16:1112-1116

60. Litwin PE, Eisenberg MS, Hallstrom AP, Cummins RO: The location of collapse and its effect on survival from cardiac arrest. Ann Emerg Med 1987;16:787-791

61. Kraus JF, Borhani NO, Franti CE: Socioeconomic status, ethnicity and risk of coronary heart disease. Am J Epidemiol 1980;111:407-414

62. Eisenberg MS: Who shall live? Who shall die? in Eisenberg MS, Bergner L, Hallstrom AP (eds): Sudden Cardiac Death in the Community. Philadelphia, Praeger Pubs, 1984, pp 44-58

63. Bonnin M, Pepe P, Clack P: Survival prognosis for the elderly after out-of-hospital cardiac arrest (abstract). Ann Emerg Med 1989;18:469

64. Safar P, Abramson N, Detre K: Old age does not negate good outcome after cardiac arrest and CPR (abstract). Crit Care Med 1989;17:575

65. Carter WB, Eisenberg MS, Hallstrom AP, Schaeffer S: Development and implementation of emergency CPR instructions via telephone. Ann Emerg Med 1984;13:695-700

66. Clawson JJ: Emergency medical dispatching, in Roush WR, Aranosian RD, Blair TMH, Handal KA, Kellow RD, Stewart RD (eds): Principles of EMS Systems: A Comprehensive Text for Physicians. Dallas, American College of Emergency Physicians, 1989, pp 119-133

67. Kellerman AL, Hackman BB, Somes G: Dispatcher-assisted cardiopulmonary resuscitation: Validation of efficacy. Circulation 1989;80:1231-1239

68. Bayés de Luna A, Coumel P, Leclercq JF: Ambulatory sudden cardiac death: Mechanisms of production of fatal arrhythmia on the basis of data from 157 cases. Am Heart J 1989;117:151-159

69. Fletcher GF, Cantwell JD: Ventricular fibrillation in a medically supervised cardiac exercise program: Clinical, angiographic, and surgical correlations. JAMA 1977;238:2627-2629

70. Haskell WL: Cardiovascular complications during exercise training of cardiac patients. Circulation 1978;57:920-924

71. Hossack KF, Hartwig R: Cardiac arrest associated with supervised cardiac rehabilitation. J Cardiac Rehab 1982;2:402-408

72. Van Camp SP, Peterson RA: Cardiovascular complications of outpatient cardiac rehabilitation programs. JAMA 1986;256:1160-1163

73. Colquhoun MC: Use of defibrillators by general practitioners. BMJ 1988;297:336-337

74. Rawlins DC: Study of the management of suspected cardiac infarction by British immediate care doctors. Br Med J [Clin Res] 1981;282:1677-1697

75. Pai GR, Haites NE, Rawles JM: One thousand heart attacks in Grampian: The place of cardiopulmonary resuscitation in general practice. Br Med J [Clin Res] 1987;294:352-354

76. Amey BD, Harrison EE, Straub EJ: Sudden cardiac death: A retrospective and prospective study. JACEP 1976;5:429-433

77. Bachman JW, McDonald GS, O’Brien PC; A study of out-of-hospital cardiac arrests in northeastern Minnesota. JAMA 1986;256:477-483

78. Crawford GC, Denton M, Fisher CA, Giaonz IL, Sharpe N, Scragg R: Resuscitation outside hospital in Auckland, N Z Med J 1986;99:452-455

79. Diamond NJ, Schofferman J, Elliott JW: Factors in successful resuscitation by paramedics. JACEP 1977;6:42-46

80. Eisenberg MS, Hadas E, Nuri I, Applebaum D, Roth A, Litwin PE, Hallstrom A, Nagel E: Sudden cardiac arrest in Israel: Factors associated with successful resuscitation. Am J Emerg Med 1988;6:319-323

81. Goldstein S, Landis JR, Leighton R, Ritter G, Vasu CM, Lantis A, Serokman R: Characteristics of the resuscitated out-of-hospital cardiac arrest victim with coronary heart disease. Circulation 1981;64:977-984

82. Lauterbach SA, Spadafora M, Levy R: Evaluation of cardiac arrest managed by paramedics. J Am Coll Emerg Med 1978;7:355-357

83. Liberthson RR, Nagel EL, Hirschman JC, Nussenfeld JD: Prehospital ventricular defibrillation: Prognosis and follow-up course. N Engl J Med 1974;291:317-321

84. Mackintosh AF, Crabb ME, Grainger R, Williams JH, Chamberlain DA: The Brighton resuscitation ambulances: Review of 40 consecutive survivors of out-of-hospital cardiac arrest. Br Med J [Clin Res] 1978;1:1115-1118

85. McSwain GR, Garrison WB, Artz CP: Evaluation of resuscitation from cardiopulmonary arrest by paramedics. Ann Emerg Med 1980;9:341-345

86. Rose LB: The Oregon Coronary Ambulance Project: An experiment. Heart Lung 1974;3:753-755

87. Eisenberg MS, Horwood BT, Cummins RO, Reynolds-Haertle R. Hearne TR: Cardiac arrest and resuscitation: A tale of 29 cities. Ann Emerg Med 1990;19:179-186

88. Eisenberg MS, Copass MK, Hallstrom AP, et al: Treatment of out-of-hospital cardiac arrest with rapid defibrillation by emergency medical technicians N Engl J Med 1980;302:1379-1383

89. Eisenberg MS, Hallstrom AP, Copass MK, Bergner L, Short F, Pierce J: Treatment of ventricular fibrillation: Emergency medical technician defibrillation and paramedic services. JAMA 1984;251:1723-1726

90. Stults KR, Brown DD, Schug VL, Bean JA: Prehospital defibrillation performed by emergency medical technicians in rural communities. N Engl J Med 1984;310:219-223

91. Weaver WD, Copass MK, Bufi D, Ray R, Hallstrom AP, Cobb LA: Improved neurologic recovery and survival after early defibrillation. Circulation 1984;69:943-948

92. White RD: EMT-defibrillation: Time for controlled implementation of effective treatment. Emerg Cardiac Care Newsletter 1986;8:1-3

93. Cummins RO: EMT-defibrillation: National guidelines for implementation. Am J Emerg Med 1987;5:254-257

94. Cummins RO, Eisenberg MS, Moore JE, Hearne TR, Andresen E, Wendt R, Litwin PE, Graves JR, Hallstrom AP, Pierce J: Automatic external defibrillators: Clinical, training, psychological, and public health issues. Ann Emerg Med 1985;14:755-760

95. Cummins RO: From concept to standard-of-care? Review of the clinical experience with automated external defibrillators. Ann Emerg Med 1989;18:1269-1275

96. Cummins RO, Eisenberg MS, Bergner L, Hallstrom AP, Hearne T, Murray JA: Automatic external defibrillation: Evaluations of its role in the home and in emergency medical services. Ann Emerg Med 1984;13(9, pt 2):789-801

97. Cummins RO, Eisenberg MS, Stults KR, Automatic external defibrillators: Clinical issues for cardiology. Circulation 1986;73:381-385

98. Cummins RO, Eisenberg MS, Litwin PE, Graves JR, Hearne TR, Hallstrom AP: Automatic external defibrillators used by emergency medical technicians: A controlled clinical trail. JAMA 1987;257:1605-1610

99. Stults KR, Brown DD, Kerber RE: Efficacy of an automated external defibrillator in the management of out-of-hospital cardiac arrest; Validation of the diagnostic algorithm and initial experience in a rural environment. Circulation 1986;73:701-709

100. Paris PM: EMT-defibrillation: A recipe for saving lives. Am J Emerg Med 1988;6:282-287

101. Weaver WD, Cobb LA, Hallstrom AP, Copass MK, Ray R, Emery M, Fahrenbruch C: Considerations for improving survival from out-of-hospital cardiac arrest. Ann Emerg Med 1986;15:1181-1186

102. Atkins J, Streigler H, Burstain T, Foster G: Improved survival rates with automatic defibrillators (abstract). Prehospital Disaster Med 1989;1:69

103. Cummins RO, Stults KR, Haggar B, Kerber RE, Schaeffer S, Brown DD: A new rhythm library for testing automatic external defibrillators: Performance of three devices. J Am Coll Cardiol 1988;11:597-602

104. Bocka JJ: Automatic external defibrillators. Ann Emerg Med 1989;18:1264-1268

105. Edwards DG: Development of a decision algorithm for a semiautomatic defibrillator. Ann Emerg Med 1989;18:1276-1279

106. Stults KR, Cummins RO: Fully automatic vs. shock advisory defibrillators: What are the issues? J Emerg Med Services 1987;71-73

107. Newman MM: Advancing resuscitation abroad. J Emerg Med Services 1987;12:22-26

108. Newman MM: An international movement for earlier defibrillation. J Emerg Med Services 1988;13:19-21

109. Fonsmark L, Sandře E, Kastrup J, Svendsen JH: Treatment of cardiac arrest outside of the hospital with a semiautomatic defibrillator – Heartstart 2000. Ugeskr Laeger 1989;151:1048-1051

110. Hapnes S: The chain of survival: The Scandinavian experience, in Proceedings of the 6th World Congress on Disaster and Emergency Medicine. Hong Kong, Excerpta Medica, 1989, p 43

111. Bett JH: Experience with a mobile coronary care unit in Brisbane. Ann Emerg Med 1989;18:969-974

112. Anatharaman V, Koo C, Tan T: Pre-hospital cardiac defibrillation programme in Singapore, in Proceedings of the 6th World Congress on Disaster and Emergency Medicine. Hong Kong, Excerpta Medica, 1989, p 44

113. Newman MM: Defibrillation shakes the nation: Results of the Journal of Emergency Medical Services 1988 National Early Defibrillation Study. J Emerg Med Services 1989;14:50-59

114. Newman MM: The survival advantage: Early defibrillation programs in the fire service. J Emerg Med Services 1987;12:40-46

115. Murphy DM: Rapid defibrillation: Fire service to lead the way. J Emerg Med Services 1987;12:67-71

116. Murphy DM: RapidZap, in Graves JR, Austin DJ, Cummins RO (eds): RapidZap: Automatic Defibrillation. Englewood Cliffs, NJ, Brady Communications Co, Inc, 1989, pp 1-3

117. IAFC on Scene, Newsletter, International Association of Fire Chiefs. Washington, DC, 1987, p 1

118. Dibbs E, Thomas HE Jr, Weiss ST, Sparrow D: Fire fighting and coronary heart disease. Circulation 1982;65:943-946

119. Vukov LF, White RD, Bachman JW, O’Brien PC: New perspective on rural EMT defibrillation. Ann Emerg Med 1988;17:318-321

120. Gray AJ, Redmond AD, Martin MA: Use of the automatic external defibrillator-pacemaker by ambulance personnel: The Stockport experience. Br Med J [Clin Res] 1987;294:1133-1135

121. Gentile D, Auerbach P, Gaffron J, Foon G, Phillips J Jr: Prehospital defibrillation by emergency medical technicians: Results of a pilot study in Tennessee. J Tenn Med Assoc 1988;81:144-148

122. Olson DW, LaRochelle J, Fark D, Aprahamian C, Aufderheide TP, Mateer JR, Hargarten KM, Stueven HA: EMT-defibrillation: The Wisconsin experience. Ann Emerg Med 1989;18:806-811

123. Jacobs L: Medical, legal, and social implications of automatic external defibrillators. Ann Emerg Med 1986;15:863-864

124. Hallstrom AP, Eisenberg MS, Bergner L: The potential use of automatic defibrillators in the home for management of cardiac arrest. Med Care 1984;22:1083-1087

125. Eisenberg MS, Cummins RO: Automatic external defibrillation: Bringing it home. Am J Emerg Med 1984;3:568-569

126. Moore JE, Eisenberg MS, Cummins RO, Hallstrom A, Litwin P, Carter W: Lay person use of automatic external defibrillation. Ann Emerg Med 1987;16:669-672

127. McDaniel CM, Berry VA, Haines DE, DiMarco JP: Automatic external defibrillation of patients after myocardial infarction by family members: Practical aspects and psychological impact of training. PACE 1988;11:2029-2034

128. Cummins RO, Schubach JA, Litwin PE, Hearne TR: Training lay persons to use automatic external defibrillators: Success of initial training and one-year retention of skills. Am J Emerg Med 1989;7:143-149

129. Chadda KD, Kammerer R: Early experiences with the portable automatic external defibrillator in the home and public places. Am J Cardiol 1987;60:732-733

130. Chadda KD, Kammerer RJ, Kuphal J, Miller K: Successful defibrillation in the industrial, recreational and corporate settings by laypersons (abstract). Circulation 1987;76(suppl IV):IV-12

131. Swenson RD, Hill DL, Martin JS, Wirkus M, Weaver WD: Automatic external defibrillators used by family members to treat cardiac arrest (abstract). Circulation 1987;76(suppl IV):IV-463

132. Eisenberg MS, Moore J, Cummins RO, Andresen E, Litwin PE, Hallstrom AP, Hearne T: Use of the automatic external defibrillator in home or survivors of out-of-hospital ventricular fibrillation. Am J Cardiol 1989;63:443-446

133. Weaver WD, Sutherland K, Wirkus MJ, Bachman R: Emergency medical care requirements for large public assemblies and a new strategy for managing cardiac arrest in this setting. Ann Emerg Med 1989;18:155-160

134. Chapman PJC, Chamberlain DA: Death in the clouds. Br Med J [Clin Res] 1987;294:181

135. Gessman LJ, Li JK-J, Lewandowski J, Yamazaki H, Helfant RH: Transtelephonic resuscitation: A new approach to sudden death (abstract). Am J Cardiol 1979;43:422

136. Ruffy R, Gessman LJ, Barbey JT, Allen ET, Smith M, Steinberg S: Pilot study of transtelephonic cardioversion/defibrillation in man. Circulation 1987;76(suppl IV):IV-463

137. Dalzell GW, Cunningham SR, Prouzina S, Anderson J, Magee H, Adgey AA: Assessment of a device for transtelephonic control of defibrillation. Lancet 1988;1:695-697

138. Herlitz B, Lebow F: Telephonic defibrillator helps close "critical window." Emergency Medical News 1989;26:29

139. Associated Press: Portable defibrillator saves woman stricken at home. Seattle Times, July 7, 1989, B-3

140. Atkins JM: Emergency medical service systems in acute cardiac care: State of the art. Circulation 1986;74(suppl IV)IV-4-IV-8

141. Cummins RO, Graves JR, Horan S, Larsen MP, Crump K: The relative contributions of early defibrillation and ACLS interventions to resuscitation and survival from prehospital cardiac arrest (abstract). Ann Emerg Med 1989;18:468-469

142. Eisenberg MS, Bergner L, Hallstrom A: Out-of-hospital cardiac arrest: Improved survival with paramedic services. Lancet 1980;1:812-815

143. Weaver WD, Hill D, Fahrenbruch CE, Copass MK, Martin JS, Cobb LA, Hallstrom AP: Use of the automatic external defibrillator in the management of out-of-hospital cardiac arrest. N Engl J Med 1988;319:661-666

144. Ishida T: Prognosis of cardiac arrest patients and proposals for improved outcomes, in Proceedings of the 6^th World Congress on Disaster and Emergency Medicine. Hong Kong, Excerpta Medica, 1989, p 43

145. Oxer H: Strengthening the chain of survival: Australia, in Proceedings of the 6th World Congress on Disaster and Emergency Medicine. Hong Kong, Excerpta Medica, 1989, p 44

146. Moles M: Travel light, travel fast: Motorcycle paramedics in Hong King. Prehospital Disaster Med 1989;4:179

147. 1987 Heart Facts. Dallas, American Heart Association, 1986, p 31

148. Eisenberg MS, Bergner L, Halltsrom AP, Cummins RO: Sudden cardiac death. Sci Am 1986;254:37-43

149. Cummins RO, Graves JR: Prehospital transcutaneous pacing by paramedics and emergency medical technicians: Clinical and system effectiveness. Prehospital Disaster Med 1989;4:196

150. Bonnin M, Pepe P: Key role of prehospital resuscitation in survival from out-of-hospital cardiac arrest (abstract). Ann Emerg Med 1990;19:466

151. Kellermann AL, Staves DR, Hackman BB: In-hospital resuscitation following unsuccessful prehospital advanced cardiac life support: "Heroic efforts" or an exercise in futility? Ann Emerg Med 1988;17:589-594

152. Wilson BH, Severance HW Jr, Raney MP, Pressley JC, McKinnis RA, Hindman MC, Smith M, Wagner GS: Out-of hospital management of cardiac arrest by basic emergency medical technicians. Am J Cardiol 1984;53:68-70

153. Holmberg S, Wennerblom B: Out-of-hospital cardiac arrest: Effect of special ambulances I Göteborg on mortality. Am J Emerg Med 1984;2:222-224

154. Lewis RP, Stang JM, Warren JV: The role of paramedics in resuscitation of patients with prehospital cardiac arrest from coronary artery disease. Am J Emerg Med 1984;2:200-203

155. Pressley JC, Raney MP, Wilson BH, Severance HW, Wagner GS: Assessment of out-of-hospital resuscitation. Am J Emerg Med 1984;2:215-216

156. Stueven H, Troianop P, Thompson B, Mateer JR, Kastenson EH, Tonsfeldt D, Hargarten K, Kowalski R, Aprahamian C, Darin J: Bystander/first responder CPR: Ten years experience in a paramedic system. Ann Emerg Med 1986;15:707-710

157. Rockswold G, Sharma B, Ruiz E, Asinger R, Hodges M, Brieter M: Follow-up of 514 consecutive patients with cardiopulmonary arrest outside the hospital. JACEP 1979;8:216-220

158. Sammel NL, Taylor K, Selig M, O’Rourke MF: New South Wales intensive care ambulance system: Outcome of patients with ventricular fibrillation. Med J Aust 1981;2:546-550

159. Eisenberg MS, Cummins RO, Damon S, Larsen MP, Hearne TR: Survival rates from out-of-hospital cardiac arrest: Recommendations for uniform definitions and data to report. Ann Emerg Med 1990;19:1249-1259

160. Eisenberg MS, Bergner L, Hearne T: Out-of-hospital cardiac arrest: A review of major studies and a proposed uniform reporting system. Am J Public Health 1980;70:236-240

161. Pepe P: The past, present and future of emergency medical services. Prehospital Disaster Med 1989;4:47-49

162. Pepe P, Bonnin M, Mattox K: Regulating the scope of EMS. Prehospital Disaster Med 1990;5:59-63

163. Pepe P, Bonnin M, Almaquer D, Prentice F, Mattox K: The effect of tiered system implementation on sudden death survival rates. Prehospital Disaster Med 1989;4:71

164. Pepe P, Mattox K, Prentice F: Impact of full-time physician supervision on an urban emergency medical services system (abstract). Prehospital Disaster Med 1989;5:70

165. Pepe P, Copass M, Joyce T: Prehospital endotracheal intubation – The rationale for training emergency medical personnel. Ann Emerg Med 1985;14:1085-1092

166. Newman MM: Early access, early CPR and early defibrillation: Cry of the 1988 Conference on Citizen CPR. J Emerg Med Services 1988;13:30-35

167. Newman MM: Chain of Survival concept takes hold. J Emerg Med Services 1989;14;11-13

168. Safar P, Bircher N: History and phases and stages of cardiopulmonary cerebral resuscitation, in Safar P, Bircher N (eds): Cardiopulmonary Cerebral Resuscitation, ed 3. Philadelphia, WB Saunders Co, 1988

169. Abramson N, Safar P, Detre K, Group BIS: Factors influencing neurologic recovery after cardiac arrest (abstract). Ann Emerg Med 1989;18:477-478