Reasons for the supreme position of biphasic machines are numerous, including the above-mentioned fact that the biphasic AEDs can achieve higher efficacy but with the equal or even lower amount of delivered energy. At the same time, they also produce less impairment of cardiac function, which is always important. Another benefit of biphasic defibrillators is that they normally do not produce other negative effects such as skin burns, which can happen with their monophasic counterparts.
Moreover, since they require a lower amount of energy to produce the same effects, biphasic AED machines are usually lighter, smaller, less demanding on batteries, and require lower maintenance than monophasic defibrillators. On the flip side, monophasic devices can be quite bulky and impractical to handle in hectic situations. As the technology keeps progressing alongside science, biphasic machines are becoming more versatile and practical in terms of features and options they provide to rescuers.
Although monophasic and biphasic machines are successful in performing defibrillation, the latter is considered a better option. They are more convenient, accurate, effective, and cost less and are able to prevent further damage to the heart. Biphasic machines require relatively lower peak current in order to lower the risk to heart damage, and are able to adjust impedance to work equally on different types of patients. Biphasic devices are going to completely take over the world as many companies stopped producing their older counterparts.
Confusion between monophasic and biphasic defibrillators. Resuscitation journal. March Volume 68, Issue 3, Pages — Comparison of monophasic and biphasic shocks for transthoracic cardioversion of atrial fibrillation.
Biphasic AED Biphasic waveform defibrillators are devices that utilize bidirectional current flow as opposed to monophasic AED, where the current flows are in one direction.
Biphasic AEDs: which is better? Monophasic vs. Conclusion Although monophasic and biphasic machines are successful in performing defibrillation, the latter is considered a better option. References [1] Richard J. Mindray and Cookies.
Mindray respects your privacy. Most defibrillator manufacturers offer manual defibrillators that use a biphasic waveform, and most automated external defibrillators AEDs are now biphasic. Studies of automated implantable cardioverters. Studies of automated implantable cardioverters have favored the biphasic over the monophasic waveform, but there are few data on the comparative effectiveness of the 2 waveforms for external defibrillation in the out-of-hospital setting.
These European investigators conducted the first prospective, randomized trial comparing monophasic and biphasic shocks in out-of-hospital cardiac arrest victims. Support was provided by the manufacturers of the AEDs used in the study. First responders and paramedics who may arrive first on-scene were randomized daily to use either monophasic shocks J, J, and J or biphasic shocks J, J, and J for patients with initial rhythms of ventricular fibrillation. Survival to discharge was 27 percent and 33 percent, respectively -- not a significant difference.
Biphasic waveforms could improve therapy and affect outcomes when compared to monophasic waveforms. Although the latest research shows biphasic defibrillation to be more effective than monophasic, international guidelines state that the care given using monophasic devices is neither unsafe nor ineffective.
Significant research into the safety, efficacy and success in terminating episodes of VF has been completed since the release of these guidelines. Biphasic waveforms are now becoming more popular for use in external defibrillators, due in part to these studies demonstrating improvements in patient care. Correlation of studies performed in-hospital may be difficult in out-of-hospital SCA. The out-of-hospital scenario is significantly different from the in-hospital time to delivery of the first shock.
Out-of-hospital VF is most often due to myocardial ischemia, frequently in the absence of CPR, within a rapidly developing hypoxia and acidosis. Resuscitations are dynamic events with multiple rescuers and interventions and intermediate outcomes.
Defibrillation has several outcomes: persistent VF or conversion to a perfusing rhythm, asystole or pulseless electrical activity. Furthermore, patients who have had defibrillation may later refibrillate and require more shocks. Shock delivery and outcome occur in combination with many other interventions, such as CPR and the arrival of ACLS personnel who provide endotracheal intubation and intravenous medications.
Clinical treatment data are difficult to correlate with data recorded by the event documentation components of the biphasic defibrillator. Biphasic defibrillation waveforms increase the rate of successful conversion of ventricular fibrillation, reduce the myocardium's exposure to high peak current and have the potential to improve outcomes. Emerging data show that postshock dysfunction, cellular injury, transmembrane effects, recovery time and skin effects are reduced and outcomes improved with clinically relevant defibrillation energies.
Several factors will optimize the application of biphasic defibrillators in EMS systems. Great training and patient preparation for defibrillation will improve outcomes in the use of this tool. The EMS system can minimize the time from accessing the patient to delivery of the first shock with training and review of the defibrillator, easy access to all needed equipment and supplies including a razor and electrodes , preconnection of the multifunction pads, if available, and rapid patient assessment.
Impedance may be increased in patients with a large chest, air in the lungs, chest hair and flaky dry skin. Reducing impedance can help improve the efficacy of biphasic defibrillation.
Sign in. EMS World Expo. Current Issue. Issue Archives. Start Print Subscription. Renew Print Subscription. Start Digital Subscription. Patient Care. Expo on Demand. CE Articles. Online Product Guide. Contact Us. Advisory Board. About Us. Copied to clipboard. Evolution of Defibrillation The common use of defibrillation technology to treat ventricular fibrillation or ventricular tachycardia VT is a relatively new phenomenon, having been developed only 50 years ago.
Monophasic Defibrillation Successful defibrillation depends on the defibrillator's ability to generate sufficient current flow through the heart. Biphasic Defibrillation Unlike conventional monophasic defibrillators, biphasic defibrillators deliver current in two directions. Reducing Myocardial Damage in Defibrillation The potential side effects of defibrillation include cell membrane damage, postshock dysrhythmias and postdefibrillation ST-segment depression on the electrocardiogram.
Increasing Efficacy and Reducing Post-Resuscitation Complications As demonstrated in the figures, a wave of electrical current has a shape that can be drawn as a "waveform," showing how the flow of current changes over time during the defibrillation shock.
More current may be delivered by increasing the energy selected on the defibrillator. Clinical Efficacy of Biphasic Defibrillation for EMS The objective in defibrillation is to achieve the highest efficacy with the lowest energy and current. Challenges for EMS Biphasic defibrillation waveforms increase the rate of successful conversion of ventricular fibrillation, reduce the myocardium's exposure to high peak current and have the potential to improve outcomes.
Multicenter, randomized, controlled trial of J biphasic shocks compared with to J monophasic shocks in the resuscitation of out-of-hospital cardiac arrest victims.
Circulation —87, Prospective, randomized comparison of rectilinear biphasic waveform shock versus truncated exponential biphasic waveform shock for transthoracic cardioversion of atrial fibrillation. JACC 41 6 : A, Comparison of six clinically used external defibrillators in swine. Resuscitation 57 1 —83, Apr Ischemically induced ventricular fibrillation VF : A comparison of fixed and escalating energy defibrillation. Acad Emerg Med , Biphasic and monophasic shocks for transthoracic defibrillation: A meta analysis of randomised controlled trials.
Resuscitation 58 1 :9—16, Jul Transthoracic biphasic waveform defibrillation at very high and very low energies: A comparison with monophasic waveforms in an animal model of ventricular fibrillation. Resuscitation 54 2 —, Aug Escalating energy is more effective than fixed energy defibrillation for ischemically induced ventricular fibrillation. Comparison of a novel rectilinear biphasic waveform with a damped sine wave monophasic waveform for transthoracic ventricular defibrillation.
ZOLL Investigators. J Am Coll Cardiol —, Comparison of the efficacy and safety of two biphasic defibrillator waveforms for the conversion of atrial fibrillation to sinus rhythm. Amer Joun Card 92 7 —14, Do clinically relevant transthoracic defibrillation energies cause myocardial damage and dysfunction? Resuscitation 59 1 —70, Oct Circulation —, Impedance and Defibrillation Impedance may be increased in patients with a large chest, air in the lungs, chest hair and flaky dry skin.
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