Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Defibrillators”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,081 records · Page 60Linked to original sources
PubMedDate not supplied

Ten years of police defibrillation: program characteristics and personnel attitudes.

OBJECTIVE: In 1992,a study to evaluate the effectiveness of police defibrillation was initiated in seven suburban police departments. This paper describes the characteristics of those programs and the attitudes of chiefs and officers ten years after the commencement of that study. METHODS: A 32-item survey instrument including questions on department demographics, defibrillation program characteristics, and attitudes was mailed to the chiefs. A separate 25-item survey was developed to assess officers' attitudes; a non-management officer distributed and collected these surveys anonymously. Responses are reported descriptively. RESULTS: All seven chiefs and 78% of the officers completed surveys. Police arrive prior to emergency medical services on 80% or more of calls, with a mean +/- standard deviation response interval of 3.1 +/-1.7 minutes. All departments identify a program coordinator and six a medical director; three departments have a quality-improvement program. Five departments have liability coverage for the use of an automated external defibrillator (AED), and no department reported any liability-related problems. Five of the chiefs and 82% of the officers disagreed or strongly disagreed that liability issues are a concern or a source of hesitation in using the AED. Ninety-six percent of the officers agreed or strongly agreed that police AED use is beneficial to cardiac arrest victims. All seven police chiefs and 89% of the officers agreed or strongly agreed that AED use by police is appropriate. CONCLUSIONS: In these seven police departments with ten years of program experience, defibrillation has become integrated into the law-enforcement culture. Liability issues are not a prominent concern of chiefs or officers. Police chiefs and officers in these departments continue to support police-based defibrillation programs.

Adult↗
PubMed2006

Increase in rapid defibrillation programmes after publication of guidelines.

OBJECTIVE: . To monitor the implementation of in-hospital resuscitation strategies including (i) rapid defibrillation programmes, (ii) the use of amiodarone for prolonged ventricular fibrillation, and (iii) uniform data collection on resuscitation, all recommended by international guidelines published in 2000 and by Finnish national resuscitation guidelines published in 2002. DESIGN: In 2004, a questionnaire was sent to the chief anaesthesiologists. The results were compared with those of a previous study performed using similar methods in 2000. SETTING: All public hospitals that provide anaesthetic services in Finland. MAIN OUTCOME MEASURES: Number of hospitals allowing nurses to perform defibrillation without the presence of physician and number of hospitals using amiodarone as primary antiarrhythmic drug in resuscitation and performing uniform data collection. RESULTS: The response rate was 95% (52/55). The proportion of the hospitals with rapid defibrillation programmes on general wards had increased from 15% in 2000 to 67% in 2004, and most (79%) hospitals had obtained automated external defibrillators. Amiodarone was used in 88% of the hospitals. Data collection of resuscitation attempts using definitions provided in the Utstein guidelines was performed only in 22% of the hospitals. CONCLUSIONS: Rapid defibrillation programmes have markedly increased, and the use of amiodarone has been established in Finnish hospitals since the publication of the international and the national resuscitation guidelines.

Advance Directives↗
PubMed1980

Influence of time and therapy on ventricular defibrillation in dogs.

Factors that may influence energy requirements for ventricular defibrillation include the duration of fibrillation and the mode of resuscitation. The present study assesses the effect of these influences on the energy needed for defibrillation. Dogs were anesthetized, and arterial blood pressure and Lead II of the ECG were continuously recorded. Ventricular fibrillation was electrically induced in each dog for a period of 1, 3, 5, or 9 min. Three resuscitation techniques were evaluated: precountershock artificial ventilation (AV) and closed-chest cardiac massage (CCCM); precountershock AV/CCCM and epinephrine, 1 mg IV; and countershock without preliminary AV/CCCM or epinephrine. Each animal was shocked with successive doses of 1, 2, 4, and 8 J/kg, ceasing when either electrical conversion occurred or after the maximum dose had been delivered. If defibrillation was unaccompanied by resumption of spontaneous circulation (systolic pressure greater than 60 mm Hg greater than 2 min), AV/CCCM was administered for 1 min. In general, the incidence of defibrillation was inversely proportional to the duration of fibrillation. Epinephrine had no significant effect on the energy dose needed for conversion. After 2 min of fibrillation, however, epinephrine became increasingly important for restoration of circulation. The technique of immediate countershock was effective for episodes of fibrillation limited to approximately 3 min. Regardless of therapy, for intervals of fibrillation of up to 6 min, Gompertz data curves indicated that a delivered energy of 4--5 J/kg is the approximate energy dose associated with the maximum achievable incidence of defibrillation within the limits of this experimental protocol.

Animals↗
PubMed2002

Pharmacologic defibrillation.

Ventricular fibrillation (VF) is generally sustained. The mechanism is, at least in part, caused by progressive accumulation of intracellular sodium and calcium ions during untreated ventricular fibrillation, which subsequently increases defibrillation threshold. Cariporide, a potent and specific inhibitor of the sodium-hydrogen exchanger, has been shown to reduce intracellular sodium and calcium concentration in the setting of myocardial ischemia and reperfusion. We hypothesized that cariporide would facilitate defibrillation from prolonged ventricular fibrillation in a rodent model of cardiac arrest and resuscitation. Fifteen Sprague-Dawley rats were randomized to receive bolus injections of cariporide or placebo in a dose of 3 mg/kg into the right atrium either 5 mins before or at 8 mins after onset of ventricular fibrillation. Ventricular fibrillation was electrically induced and untreated for 8 mins. Precordial compression together with mechanical ventilation was then started and continued for an interval of 8 mins before attempted electrical defibrillation. All but one placebo-treated animal were successfully resuscitated. Spontaneous defibrillation with restoration of circulation was observed in both cariporide pretreatment and treatment groups but in none of the placebo-treated animals. The duration of postresuscitation survival was significantly increased in animals pretreated with cariporide. Therefore, sodium-hydrogen exchanger inhibitors may provide new options in settings of cardiopulmonary resuscitation to facilitate defibrillation.

Animals↗
PubMed1993

Effects of flecainide on defibrillation threshold in pigs.

Flecainide has been reported to decrease defibrillation efficacy in pentobarbital-anesthetized dogs. Conversely, flecainide did not alter defibrillation energy requirements in halothane-anesthetized pigs. We wished to determine whether these discrepancies were related to defibrillation technique, interaction with the anesthetic regimen, or animal species. The effects of three doses of flecainide on defibrillation threshold (DFT) were determined using single- and sequential-pulse shocks in halothane-anesthetized open-chest pigs. Triplicate DFTs were obtained before and after three doses of flecainide (n = 34) or saline (n = 13) infusion. Similarly, the effects of the highest dose of flecainide were determined using barbiturate-anesthetized animals (n = 10). Flecainide did not alter DFT at any dose with either the single-pulse shock (control 17.7 +/- 2.1 J, highest dose of flecainide 19.1 +/- 3.2 J, p = NS) or sequential-pulse shock (control 9.2 +/- 1.0 J, highest dose of flecainide 8.4 +/- 1.4 J, p = NS) when halothane anesthesia was used. Similar results were obtained using barbiturate anesthesia either with sequential (control 8.7 +/- 0.9 vs. 8.2 +/- 0.6 J, p = NS) or single shocks (control 13.2 +/- 0.8 vs. 13.7 +/- 1.0 J, p = NS). Flecainide did not alter DFT in our model, regardless of defibrillation technique or anesthetic regimen.

Animals↗
PubMed1994

Shock-induced refractory period extension and pharmacologic modulation of defibrillation threshold.

Shock-induced refractory period extension (RPE) has been suggested as a mechanism of electrical defibrillation. We measured RPE caused by localized field stimulation measured before and during infusion of disopyramide (n = 5), flecainide (n = 5), or E-4031 (n = 5) in anesthetized dogs and determined the effect of the drugs on the internal defibrillation threshold (DFT). In the baseline state (n = 15), 16 V/cm S2 field stimulation prolonged the effective RP by 36 +/- 15 ms (22 +/- 12% of RP without S2), whereas 4 and 8 V/cm S2 stimuli did not cause marked RPE. The RPE normalized by the RP without S2 was not significantly influenced by any drug (16 V/cm: disopyramide 30 +/- 11 vs. 27 +/- 11, flecainide 25 +/- 5 vs. 19 +/- 12, and E-4031 18 +/- 13 vs. 22 +/- 14%). Disopyramide did not alter the defibrillation threshold (4.2 +/- 0.6-4.4 +/- 0.6 J). In 2 dogs given flecainide, ventricular fibrillation became refractory to defibrillation. In contrast, E-4031 lowered the threshold from 4.5 +/- 2.4 to 2.2 +/- 1.2 J (p < 0.01). The results suggest that flecainide and E-4031 do not modulate defibrillation efficiency through their effects on RPE.

Animals↗
PubMed2002

Investigation of capacitor failures in an automated external defibrillator.

Over the past 2 years, the Canadian Medical Devices Bureau has received a number of reports of capacitor failures on the high voltage board of an automated external defibrillator. Twenty-five cases of broken capacitor leads were found during routine preventive maintenance by the biomedical engineering staff of the institutions reporting the incidents. The Bureau has carried out a laboratory investigation to determine the effect of missing capacitors on the energy delivered by the defibrillator and to assess whether these capacitor failures represent a significant risk to patients. Our findings indicate that the automated external defibrillator will not perform acceptably with two broken capacitors. They further suggest that, during preventive maintenance, operators should use a defibrillator analyser to measure the delivered energy output rather than using the internal energy measurement circuit within the automated external defibrillator.

Canada↗
PubMed2002

Feasibility of public access to defibrillation.

Immediate defibrillation is the single most effective therapy to reverse ventricular fibrillation cardiac arrest today. The once physician-only skill of defibrillation has entered mainstream society and is saving the lives of many sudden cardiac arrest (SCA) victims in a variety of settings. The automated external defibrillator (AED) and the concept of public access defibrillation (PAD) are a result of collaborative efforts between the American Heart Association (AHA) and medical manufacturers. Today, airports, airlines, casinos, cruise ships, and other public venues have modernized their first aid kits to include an AED. The success of these programs has ignited a trend in public safety and subsequently marketed the worth of AEDs in the home. Although optimal placement of AEDs remains uncertain, PAD is showing great promise in reducing the death rate from SCA. The lay public, both trained and untrained, is emerging as the next level of emergency care responders able to use a defibrillator.

Cardiopulmonary Resuscitation↗
PubMed1997

Electrical defibrillation optimization: an automated, iterative parallel finite-element approach.

To date, optimization of electrode systems for electrical defibrillation has been limited to hand-selected electrode configurations. In this paper we present an automated approach which combines detailed, three-dimensional (3-D) finite-element torso models with optimization techniques to provide a flexible analysis and design tool for electrical defibrillation optimization. Specifically, a parallel direct search (PDS) optimization technique is used with a representative objective function to find an electrode configuration which corresponds to the satisfaction of a postulated defibrillation criterion with a minimum amount of power and a low possibility of myocardium damage. For adequate representation of the thoracic inhomogeneities, 3-D finite-element torso models are used in the objective function computations. The CPU-intensive finite-element calculations required for the objective function evaluation have been implemented on a message-passing parallel computer in order to complete the optimization calculations in a timely manner. To illustrate the optimization procedure, it has been applied to a representative electrode configuration for transmyocardial defibrillation, namely the subcutaneous patch-right ventricular catheter (SP-RVC) system. Sensitivity of the optimal solutions to various tissue conductivities has been studied. Results for the optimization of defibrillation systems are presented which demonstrate the feasibility of the approach.

Algorithms↗
PubMed2006

Experimental verification of theoretical predictions concerning the optimum defibrillation waveform.

The efficacy of electrical therapy at terminating ventricular fibrillation is highly dependent on the waveform used. We present experimental results which test one theory for defibrillation waveform dependence. Forty-four defibrillation waveforms (22 monophasic, 22 biphasic) were designed according to the theoretical construct of Fishier (2000). The waveforms were then tested on 67 male guinea pigs (46 for monophasic, 21 for biphasic waveforms) using a custom designed defibrillator and 12-mm subcutaneous disc electrodes. There was considerable agreement between the theoretical and experimental results. For example, as predicted, the ascending exponential waveform of 1 ms proved to be the most effective (86.4%) monophasic waveform, where efficacy is the number of successful shocks divided by the total number delivered. In addition, the efficacy decrease with duration increase was accurately predicted by the model for monophasic waveforms. For biphasic waveforms, as predicted by the model, when the first phase was optimized, an increase in second phase duration caused an increase in defibrillation efficacy (10 of 11 tested duration pairs). We conclude that the theoretical framework adequately explains the mechanism by which the defibrillation waveform affects efficacy for monophasic waveforms and, in at least one aspect, biphasic waveforms.

Animals↗
PubMed2001

Teaching colleagues and the general public about automatic external defibrillators.

Every year 250,000 or more people with cardiovascular disease die within an hour of symptom onset and before they arrive at a hospital. With appropriate early defibrillation and follow-up treatment many people who might have died can now live. Nurses are key health care professionals for using automatic external defibrillators in hospitals and for teaching other first responders--inside and outside hospitals--how to use automatic external defibrillators. Features of automatic and semiautomatic external defibrillators are reviewed as well as ethical considerations for the use of automatic external defibrillators.

Automation↗
PubMed1987

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.

Aged↗
PubMed1985

Emergency defibrillation using a temporary pacing electrode catheter.

Direct application of electrical current to the heart utilizing special equipment such as implantable defibrillators or specially designed catheters has been useful in patients with recurrent ventricular tachyarrhythmias. We describe a patient who developed intractable ventricular fibrillation (VF) during the course of electrophysiologic testing. VF continued for 50 minutes, during which time multiple transthoracic shocks of 360 joules failed to convert the arrhythmia. Intracardiac shocks were then delivered via a transvenous 6 French standard quadripolar pacing catheter positioned in the right ventricular apex by direct application of the defibrillator paddle to the catheter, with the patient lying on the posterior paddle. Energy of up to 300 joules failed to defibrillate the patient, but use of 360 joules delivered in this fashion defibrillated the patient twice. Despite the protracted time of cardiac arrest, the patient recovered without sequelae. We report this case to demonstrate that VF refractory to transthoracic defibrillation may be converted by intracardiac shocks using a temporary pacing catheter without special equipment.

Cardiac Catheterization↗
PubMed1989

Anxiety and anger in patients with ventricular tachyarrhythmias. Responses after automatic internal cardioverter defibrillator implantation.

In order to assess the psychological profile of patients with malignant ventricular tachyarrhythmias, eight patients who underwent implantation of the automatic internal cardioverter defibrillator for refractory arrhythmias were evaluated. Six men and two women with a mean age of 53 years were examined with the Symptom Checklist-90, the State Trait Personality Inventory and a specifically designed questionnaire about the automatic internal cardioverter defibrillator. The group studied manifested high degrees of both anger and anxiety compared to normal controls or to other medically ill populations. The trait scores remained essentially unchanged before and after the AICD implantation. The state of anxiety was markedly reduced by 26 percentage points after implantation (P less than 0.01), while the state of anger remained unchanged. In evaluating the number of AICD discharges, it was observed that the number of discharges in the first 6 months was higher than that observed in the subsequent follow-up period (mean 30 months). The reduction in AICD discharges demonstrated a trend (P = 0.094). Patient acceptance of the automatic internal cardioverter defibrillator was high. They became accustomed to the pulse generator after a mean of 3.6 months. The defibrillator permitted resumption of normal activities. If the device became battery depleted, all patients would insist on replacement. The evaluation of this group of patients with malignant ventricular arrhythmias indicates a high degree of anxiety and anger, which potentially may influence outcome. The reduction in defibrillator discharges after the first 6 months in addition to a reduced state of anxiety is a relationship that merits further investigation.

Anger↗
PubMed1990

The fundamental law of electrostimulation and its application to defibrillation.

Around the turn of the last century, there was an intensive discussion among physiologists as to whether there is a law describing the phenomena of electrostimulation and which formula may best approximate it mathematically. J.L. Hoorweg found in 1892 that the voltage at which a capacitor must be charged to elicit an excitation, was a function of the capacitance in an inverse correlation. G. Weiss reported in 1901 that according to his investigations a linear relationship existed between the duration of a pulse and the corresponding quantity of electricity applied and called it "formule fondamentale." We are now able to give the "fundamental formula" a physical interpretation that yields, as result, the electric field produced by the electrode acting on the excitable membrane. The electric field in the extracellular space is transformed by the cell geometry ratio: cell length to membrane thickness yielding a high transmembrane field capable of reducing the inherent electric field to its threshold level. The consequences drawn from this hypothesis are remarkable and (should) have an influence on all applications of electrostimulation including the discussions on defibrillation. The application of the stimulation theory to defibrillation yields as results: (1) The basic engineering principle of defibrillation is to produce an electric field within the ventricles of 400 V/m or more. An orthogonal pulse application may reduce the energy requirements, as more fibers are longitudinally reached by the electric field; (2) The shape of the defibrillation pulse and its polarity plays no role. Consequently it follows that biphasic pulses must be less efficient than monophasic pulses, if they are close to the chronaxie; and (3) The most serious disadvantage in today's defibrillation practice is its dose characterization in "energy"; but this physical quantity cannot be justified in the light of the fundamental law of electrostimulation.

Animals↗
PubMed1991

Comparison of titanium-mesh and porous disc electrodes for epicardial defibrillation.

The object of this study was to compare the effectiveness of chronically implanted porous electrodes with that of smooth mesh titanium electrodes of the same diameter but smaller effective surface area. The criteria used in evaluating the electrodes were (1) acute, subacute, and chronic resistance and (2) acute, subacute, and chronic defibrillation thresholds. Electrode pairs 2.5 cm in diameter were implanted in each of 17 dogs (ten mesh and seven porous). One electrode of each pair was sutured to the right ventricle and one to the left ventricle near the cardiac apex. Defibrillation threshold energy and total resistance were measured at the time of implantation and again 6 and 12 weeks after implantation. The mean initial resistance of the titanium electrodes was 131.7 omega; the mean defibrillation values for the porous electrode implant were 96.9 omega and 7.5 joules, respectively. Three to 6 weeks after implantation, the values for the titanium mesh electrode were 88.9 omega and 12.0 joules, while those for the porous electrode were 59.9 omega and 8.0 joules. In the chronic state, the figures for the titanium mesh electrode were 78.1 omega and 13.0 joules, while those for the porous electrode were 64.3 omega and 8.3 joules. We conclude that defibrillation can be achieved successfully with small epicardial electrodes. The findings suggest that a porous electrode, with its larger effective surface area, has lower electrode/tissue interface resistance in the acute and chronic phases, and, therefore, provides lower defibrillation threshold energy.

Animals↗
PubMed1991

Renal extracorporeal shock wave lithotripsy performed in patient with implantable cardioverter defibrillator.

The effect of extracorporeal shock wave lithotripsy on the automatic implantable cardioverter defibrillator is unknown. To evaluate what effect might occur, a non-implanted automatic implantable cardioverter defibrillator was subjected to a full course of extracorporeal shock wave lithotripsy while inactive. Bench testing by the manufacturer after lithotripsy demonstrated normal function of the device. A patient with an automatic implanted cardioverter defibrillator who required contralateral extracorporeal shock wave lithotripsy then underwent this procedure. The right renal calculus was destroyed successfully with no apparent damage to the automatic implantable cardioverter defibrillator. A test of the automatic implantable cardioverter defibrillator after lithotripsy demonstrated normal sensing and conversion of induced ventricular tachycardia.

Aged↗
PubMed1993

The effect of phase separation on biphasic waveform defibrillation.

It has been hypothesized that the defibrillation efficacy of a biphasic shock is caused by the large change in voltage between the two phases. This study examined the effects of separating the two phases in time thus splitting in half the rapid voltage change at phase reversal. The study was performed in three parts each using six dogs. Part I determined defibrillation thresholds (DFTs) for two exponentially truncated biphasic waveforms (3.5/2 msec and 6/6 msec) with interphase time delays of 0, 1, 2, 3, 4, 6, 8, and 10 msec. In Part II, probability of success curves were generated using an up down method with 15 shocks for each delay for the 3.5/2 msec biphasic waveform with interphase delays of 0, 2, 3, 4, and 5 msec. In Part III, DFTs were determined using a 3.5/2 msec and 6/6 msec biphasic as well as a third waveform that consisted of two sequential 6-msec pulses of the same polarity with interphase delays of 0, 5, 10, 15, 20, 25, 50, and 100 msec. In all three parts the defibrillating cathode was a 6.17 cm2 transvenous spring electrode positioned in the RV apex and the anode was a 113 cm2 cutaneous left chest wall electrode patch. With all waveforms, the trailing edge voltage of the first phase was equal to the negative of the leading edge voltage of the second phase. There was no statistical difference in DFTs or in 50% successful defibrillation points for phase separations from 0 to 6 msec and 0 to 5 msec for Parts I and II, respectively. In Part I there was a significant increase in DFTs for phase separations of 8 and 10 msec compared to a phase separation of 0 msec. In Part III there was no significant difference for separations of 0 and 5 msec; however, there was a significant increase in DFT requirements for separations from 5 to 50 msec, which then decreased with a separation of 100 msec for all three waveforms tested. In conclusion, defibrillation efficacy was unchanged with phase separations up to 6 msec. With phase separation, the rapid voltage change during phase reversal is split in half and, thus, cannot explain the improved efficacy of biphasic waveforms.

Animals↗