Semi-automatic Defibrillator Research Articles

Early defibrillation by emergency physicians or emergency medical technicians? A controlled, prospective multi-centre study

In a controlled, prospective multi-centre study, defibrillation by emergency medical technicians (EMTs) was compared with the current standard of care in Germany — defibrillation by emergency physicians (EPs) — in order to answer the following questions: can EMTs in a two-tiered emergency medical services (EMS) system with physicians in the field defibrillate earlier than, and as safely as EPs? Does defibrillation by EMTs (study group) affect survival rate and long-term prognosis of patients in ventricular fibrillation (VF), as compared with the current national standards in resuscitation (basic cardiopulmonary resuscitation (CPR) by EMTs, and defibrillation by physicians; control group)? Methods: Prior to the onset of the study, all EMTs completed retraining in basic life support (BLS). Randomly assessed EMTs were then trained to use semi-automatic defibrillators. With the help of on-line tape recording, the complete resuscitation sequence was evaluated. Follow-up of the patients was carried out with the help of the Glasgow Coma Scale as well as Pittsburgh Cerebral and Overall Performance Categories. Results: A total of 159 patients with VF were included in the study. In 121 cases, collapse was witnessed. Of the patients receiving defibrillation by EMTs 25% were discharged from hospital alive, compared to 24% of the patients defibrillated by EPs. Of the study patients 67% were defibrillated within 12 min, while the percentage of control patients was 46%. Study patients were defibrillated earlier ( P < 0.01), the return of spontaneous circulation (ROSC) was achieved earlier ( P < 0.05), and the rate of patients requiring no adrenalin during resuscitation was higher in the study group ( P < 0.05). The total amount of adrenalin administered in the study group was lower ( P < 0.05). No statistically significant differences were found concerning the neurologic long-term prognosis. Conclusions: In our study, EMT defibrillation was equally effective as defibrillation by EP's, but failed to improve survival or long-term outcome of patients in VF significantly, compared to EP defibrillation. Due to reduction in the time intervals from collapse to defibrillation and to ROSC, as well as in adrenalin doses, by EMT-defibrillation, EMTs in Germany should defibrillate if they reach a patient prior to an EP, provided they have received continuous medical training and supervision.

Survival after cardiac arrest outside hospital over a 12-year period in Gothenburg

Background: A two-tiered ambulance system with a mobile coronary care unit and standard ambulance has operated in Gothenburg (population 434 000) since 1980. Mass education in cardiopulmonary resuscitation (CPR) commenced in 1985 and in 1988 semiautomatic defibrillators were introduced. Aim: To describe early and late survival after cardiac arrest outside hospital over a 12-year period. Target population: All patients with prehospital cardiac arrest in Gothenburg reached by mobile coronary care unit or standard ambulance between 1980 and 1992. Results: The number of patients with cardiac arrest remained fairly steady over time. Among patients with witnessed ventricular fibrillation, the time to defibrillation decreased over time. The proportion of patients in whom bystander initiated CPR was increased only moderately over time. The proportion of patients given medication such as lignocaine and adrenaline successively increased. The number of patients with cardiac arrest who were discharged from hospital per year remained steady between 1981 and 1990 (20 per year), but increased during 1991 and 1992 to 41 and 31 respectively. Conclusions: Improvements in the emergency medical service in Gothenburg over a 12-year period have lead to: (1) a shortened delay time between cardiac arrest and first defibrillation and (2) an improved survival of patients with cardiac arrest outside hospital probably explained by this shortened delay time.

Comparative assessment of the ventricular fibrillation detection algorithms in five semi-automatic or advisory defibrillators

The sensitivity and specificity of ventricular fibrillation (VF) detection in three semi-automatic defibrillators (Laerdal Heartstart 3000, Spacelabs First Medic 610, Physio-Control Lifepak 300) and two advisory defibrillators (S&W DMS940, Marquette Responder 1500) were assessed with 25 ECG recordings, each of length 40 s. Of the 25 ECG recordings, 12 contained VF requiring defibrillation, three contained a tachyarrhythmia with a waveform similar to VF but which self-terminated, and 10 were selected from abnormal rhythms and artefacts which contained some features similar to VF. Sensitivity was assessed from the VF data. Specificity was assessed from both the rhythm preceding VF or the tachyarrhythmias, and from the VF-like data. The response to a changing rhythm was assessed from the self-terminating tachyarrhythmias. Each recording was replayed to the defibrillators at three signal amplitudes (normal, half and double). For each defibrillator, requests to check the patient and advice to shock were noted separately. The sensitivity for recommending a shock when a shock was required varied from 81 to 97%. The sensitivity for drawing attention to VF, either through requesting the patient to be checked or advising a shock, varied from 92% to 100%. There were no false detections in the rhythms preceding VF or the tachyarrhythmias (specificity with good quality signals 100%). The specificity with the VF-like data ranged from 63 to 90% for recommending a shock, and from 63% to 70% for requesting the patient be checked or shocked. There was no difference between the defibrillators for VF detection, but there was a significant difference between the semi-automatic and advisory defibrillators (P < 0.05) for the specificity of the final recommendation.

Early defibrillation program: Problems encountered in a rural/suburban EMS system

Many studies have shown improved survival of cardiac arrest patients by the use of early defibrillation (EMT-D) in the field. This prospective study was the first in Pennsylvania and was undertaken to determine if an EMT-D program would be successful in our suburban/rural setting. One hundred two EMTs were trained to use a semi-automatic defibrillator and data were collected over 16 months. There were 96 cardiac arrests, with only 33 patients (34%) presenting with initially treatable dysrhythmias—ventricular fibrillation (VF) or tachycardia (VT). Twenty-three patients (24%) were admitted to the hospital; survival to hospital discharge occurred in only 5 patients (5.2%). Survival to hospital admission was higher among VF/VT presenting rhythms (36%) than for those with other rhythms (17%, P = 0.07), but survival to discharge among VF/VT rhythms (9%) was not statistically different from other rhythms (3%, P = 0.45). Among VF/VT patients, survival to discharge was correlated with shorter call to first defibrillation intervals. Mean call to response interval was longer than in other reported studies (7.2 ± 4.3 minutes). In addition, there was a high drop-out rate of EMT participants, no central/uniform early access system (that is, 911), and a lower rate of CPR than reported in other studies. It is concluded that introduction of an EMT-D program without careful analysis of systems response factors will not lead to the improved cardiac arrest survival percentages that have previously been reported.

Semi-automatic external defibrillator (AED): the italian experience

Semi-automatic external defibrillator (AED): the italian experience

In-field comparison between fully automatic and semi-automatic defibrillators: Bocka JJ, Swor R. Prehosp Disaster Med. 1991;6: 415–419

In-field comparison between fully automatic and semi-automatic defibrillators: Bocka JJ, Swor R. Prehosp Disaster Med. 1991;6: 415–419

The accuracy of decision-making of a semi-automatic defibrillator during cardiac arrest

The accuracy of decision-making of a semi-automatic defibrillator was assessed at 57 cardiac arrests in 55 patients. The initial rhythm was ventricular fibrillation at 40 arrests and was correctly identified in 37 (sensitivity 92.5%). In the other 17 arrests initial rhythms were not ventricular fibrillation and 16 were correctly identified (specificity 94%). Continuous electrocardiographic recordings of the arrests were analysed in 8-12 s segments: of 432 segments showing ventricular fibrillation, 352 were correctly identified (sensitivity 81%); 3895 of 4139 segments showing rhythms other than ventricular fibrillation were correctly identified (specificity 94%). The percentage accuracy of detection of ventricular fibrillation varied from 0-100% (mean 91%) and for non-ventricular fibrillation from 51-100% (mean 92%). When 104 segments of ventricular fibrillation and 470 segments of non-ventricular fibrillation with cardiopulmonary resuscitation artefact were excluded from the analysis, a sensitivity of 91% and specificity of 96% were obtained. Thus the detection of cardiac arrest rhythms using a microprocessor based detection system for patients with cardiac arrest has a high sensitivity for ventricular fibrillation and specificity for non-ventricular fibrillation.

The scientific basis of cardiopulmonary and cerebral resuscitation

A survey is given on the scientific background of cardiopulmonary-cerebral resuscitation, which supposedly will be the basis of all clinical practice in this field. Haemodynamic, respiratory, acid-base, and cerebral problems are discussed in detail. As for haemodynamics, the pathomechanisms of the conventional "heart pump" and the "thoracic pump" as background of the "New CPR" are compared, the flow being generated by a direct compression of the heart in the former and by a phasic increase of the intrathoracic pressure in the latter case. Combined effects of both modalities mainly depending on the geometry of the thoracic cage, are usually seen. Improvement of flow by modifying the criteria of thorax compression (duration, frequency, strength) is then discussed, and new methods or CPR as e.g. simultaneous/synchronous compression/respiration, Vest-CPR, MAST-CPR, abdominal compression and Cough-CPR are mentioned and their mechanisms explained. Finally, open cardiac massage is no doubt superior to all the other indirect and closed methods of cardiac resuscitation. Defibrillators and heart-lung "thumpers" are then described, mentioning the improvements in respect of automatic and semi-automatic defibrillation and the progress made by developing flexible and individually adaptable types of "thumpers". On assessing the sympathicomimetic drugs, it is evident that epinephrine is the method of choice in the acute phase of resuscitation; the pure beta-adrenergics isoprenaline and orciprenaline are not used any more, whereas the alpha-mimetics, although acutely effective similar to epinephrine, cannot produce positive long-term effects; the combination of dobutamine and dopamine seems to be ideal for establishing stable haemodynamic situations following a successful acute reanimation procedure.(ABSTRACT TRUNCATED AT 250 WORDS)

Should semi-automatic defibrillators be used by emergency medical technicians in Belgium? The Belgian Cerebral Resuscitation Study Group.

Early external defibrillation is the single most effective intervention in patients with out-of-hospital cardiac arrest. Literature data indicate that instructing emergency medical technicians (EMTs) to use defibrillators is beneficial, provided the local emergency medical system is well organized. We tried to estimate the potential benefit of early defibrillation in some centres in Belgium by retrospectively analyzing the data from the Belgian Cardio-Pulmonary-Cerebral Resuscitation Registry collected between 1983 and 1987 in Belgian centres with a Mobile Intensive Care Unit (MICU). The data show that 2310 out of 3371 patients (69%) were first attended by the EMTs; on subsequent arrival of the MICU-teams, 584 of these 2310 patients i.e. 17% of the whole study population, presented with ventricular fibrillation. Analysis of estimated time factors in these 2310 patients revealed that the median time interval between collapse and start of resuscitation by EMTs was 8 min; the median time interval between collapse and start of MICU-resuscitation attempts was 16 min. The duration of EMT-resuscitation before MICU-arrival was probably more than 5 min and 10 min in 58% and 23% of the cases respectively. It is concluded that EMTs can be expected to reach a substantial number of ventricular fibrillation victims within a few minutes after the collapse and many minutes before arrival of the MICU. Therefore, training of EMTs in the use of semi-automatic defibrillators seems worthwhile in MICU-served regions in Belgium.

In-Field Comparison between Fully Automatic and Semi-Automatic Defibrillators

AbstractThe purpose of this clinical study was to compare the prehospital use of fully automatic defibrillators versus semi-automatic defibrillators.Methods:Fully and semi-automatic defibrillator use by EMTs in neighboring communities was compared.Results:Both programs had similar response times, age and gender distribution, proportion of witnessed arrests, and proportion of patients found initially with ventricular fibrillation (VF). The time-to-shock from proper lead placement was shorter when the fully automatic defibrillator was used (16.6 vs. 44.3 seconds; p&lt;.001) and the survival to hospital discharge rate was greater (26% vs. 0%; p=.O4). The semi-automatic defibrillators were more sensitive in detecting VF than were the fully automatic devices.Conclusions:These data support the need for further comparison of the efficacy and effectiveness of semi- and fully automatic, external defibrillators.

Clinical experience with three different defibrillators for resuscitation of out of hospital cardiac arrest

Three defibrillators, one manual and two different semiautomatic, were prospectively compared during a one year period for out-of-hospital use by ordinary ambulance personnel with short additional training. Eighty-three cardiac arrest patients were treated with one of two different semiautomatic defibrillators and 26 by an ordinary manual defibrillator. Twenty-nine were found in ventricular fibrillation. Five of these patients were successfully resuscitated and admitted for further hospital care, two survived to be discharged home. The semiautomatic defibrillators were found to be accurate in ECG interpretation, sensitivity and specificity was 100%, respectively, and both were equally effective in defibrillation. There were no differences in conversion rate or in the clinical outcome between the three defibrillators tested. Both semiautomatic defibrillators tested seemed to be safe, reliable and cost-effective. The low survival rate found is most certainly due to a long ambulance delay.

Development of a decision algorithm for a semiautomatic defibrillator

A decision algorithm was developed for a semiautomatic defibrillator. The function of the algorithm is to evaluate the ECG of a patient and determine whether a defibrillation shock should be delivered. The development process included establishment of defibrillation criteria, creation of ECG databases, algorithm design, development of test protocols, and clinical testing. The result was an algorithm with sensitivity and specificity sufficiently accurate to allow a defibrillation shock to be delivered safely outside the hospital.

Energy requirement for early defibrillation.

The appropriate energy requirement for defibrillation of out-of-hospital ventricular fibrillation has been a matter of discussion. We analysed the effects of 360 J, 200 J or a combination of 200 and 360 J DC shocks given by ordinary manual defibrillators or semiautomatic defibrillators. 120 of 127 ventricular fibrillation episodes were converted by three or less 360 J DC shocks delivered by a manual defibrillator. All 28 ventricular fibrillation episodes were converted by an average of 1.9 DC shocks when 360 J were delivered by a semiautomatic defibrillator. 139 of 152 ventricular fibrillation episodes were converted by three or fewer 200 J DC shocks and 52 of 53 by 2 x 200 J followed, if needed, by 1 x 360 J DC shock delivered by the same semiautomatic defibrillator. Three or fewer 360 J DC shocks seems completely adequate for conversion of most episodes of out-of-hospital ventricular fibrillation. There is no difference in the result of defibrillation by manual and semiautomatic defibrillators.

One year's experience of early defibrillation in Stockholm.

The effects of resuscitation on patients who died suddenly out of hospital were evaluated after the introduction of early defibrillation performed by ambulance personnel using semi-automatic defibrillators. Resuscitation attempts were initiated in 548 patients during the 1-year study period. Mean ambulance delay was 7.5 min, 22% of the cardiac arrest patients had received bystander cardiopulmonary resuscitation (CPR). Sensitivity and specificity for the semi-automatic defibrillator in the interpretation of ventricular fibrillation was found to be 97 and 100% respectively. Only 28 (14%) of the 206 defibrillated patients regained circulation and were admitted for further hospital care. Only three survived to be discharged. Among the 342 patients in whom defibrillation was not indicated, 16 (5%) regained circulation and were admitted for further hospital care and one (0.3%) survived to be discharged. Semi-automatic defibrillators seem reliable, safe and inexpensive; however, the isolated addition of defibrillation to basal ambulance service seems to be inadequate in Stockholm. We need to evaluate what further resources are of importance to guarantee a successful outcome.

Experience with an automatic external defibrillator.

One emergency ambulance serving an urban part of the greater Stockholm area was equipped with a semi-automatic defibrillator Life Pack 200 Physio Control during an 8-month study period. The equipment advises the user whether defibrillation is required or not, and in cases of detected ventricular fibrillation, defibrillation is advised. The user then has to press a button to defibrillate through the same electrodes that record the electrocardiogram. A built-in tape recorder was used for documentation of the underlying rhythm disturbance. In all, advice was requested 332 times. Accuracy in interpretation of ventricular fibrillation was found to be high. The sensitivity and specificity in interpretation of ventricular fibrillation were 93% and 100%, respectively. No defibrillations were performed in patients without ventricular fibrillation. All instances of ventricular fibrillation were converted to another rhythm or asystole. Seven percent of the patients with cardiac arrest caused by ventricular fibrillation survived.