Monophasic and biphasic defibrillation are two methods for delivering electric shocks. Medical professionals use them in emergencies like ventricular fibrillation or pulseless ventricular tachycardia. Both aim to restore a normal heartbeat. Yet, they differ in how they deliver the electrical current to the heart. Monophasic shocks send current in one direction. Biphasic shocks flow in two directions. This bidirectional flow is now more common in modern defibrillators. Users prefer it for its better efficiency and lower energy needs.
Monophasic and biphasic shocks differ in how the electrical current flows. In monophasic shocks, the current flows in a direction. Biphasic shocks reverse the current halfway through. This two-phase approach makes them more efficient.
Monophasic defibrillators were common in the beginning. Biphasic technology is now common in the U.S. This change is a step forward in defibrillation and took time. Understanding the two methods can boost AED users’ confidence in critical moments.
How defibrillation waveforms impact.
If you’ve ever seen a heart track, the moving line with its waves and peaks represents the heart’s rhythm. A normal, healthy pattern is known as a sinus rhythm in medical terms.
Alternating current (AC) was created in the late 1800s. It served as a different option to direct current. Its waveform looks a lot like the natural electrical signals of a human heartbeat. This makes the connection both practical and fascinating.
Even low-voltage shocks can mess with the heart’s rhythm. This might cause ventricular fibrillation. For utility workers, this disruption can result in sudden cardiac arrest and be fatal.
In 1956, Dr. Paul Zoll showed that you could treat ventricular fibrillation. He used alternating current applied to the chest. This was a big change from older methods that required direct heart shocks.
Researchers from the Soviet Union and Western countries show that both direct and alternating current can be used for external defibrillation. This finding is crucial for creating modern automated external defibrillators.
What is monophasic defibrillation?
The first external defibrillators used monophasic waveforms. They sent electrical current in one direction through the heart. This approach needed more energy, starting at 200 joules. For adults, it goes up to 360 joules. Children use lower doses.
Monophasic shocks work well to fix dangerous heart rhythms, such as ventricular fibrillation. They help bring the heart back to normal function. A 1999 study on anesthetized pigs found an 80% success rate. That means 8 out of 10 pigs revived after monophasic defibrillation.
What is biphasic defibrillation?
Research on biphasic waveforms started in the 1940s. Gurvich and Yuniev found that changing the electrical current in defibrillation made it work better. It also used less energy. Initial shocks typically need about 120 joules, increasing to around 200 if needed. Today, this approach is common in ICDs, hospital defibrillators, and external AEDs.
Advantages of Biphasic vs. Monophasic Defibrillation
Biphasic defibrillators work better than monophasic ones. That’s why they are the top choice in modern medical settings.
1. Biphasic defibrillation is less likely to burn the patient.
Biphasic defibrillation uses less energy. This lowers the risk of skin burns. This is important, especially when rescuers need many shocks during resuscitation.
2. Biphasic waveforms take a smaller toll on battery life.
Lower energy use per shock extends battery life, allowing more shocks on a single charge. This efficiency allows for smaller, portable AEDs. So, bystanders can respond faster in emergencies.
3. Biphasic waveform defibrillation may be more effective.
In the earlier pig study, biphasic shocks revived all subjects. They also had less effect on heart function than monophasic shocks. A study in Japan from 2005 to 2007 showed no big difference in one-month survival rates for the two methods.
Today, most defibrillators use biphasic technology. There are still talks about replacing older monophasic models. Check the latest advice from the American Heart Association for current guidance.
Examples of biphasic AEDs.
Since 1996, AEDs in the U.S. have used biphasic waveform technology. Now, it’s the standard in almost all new devices because it works well and is efficient.
ZOLL AED Plus
The ZOLL AED Plus features advanced biphasic waveform technology for effective defibrillation. It works well with different impedance levels. It provides preset energy levels for better performance.
Adults: Shock 1: 120 J; Shock 2: 150 J; Shock 3: 200 J
Children: Shock 1: 50 J; Shock 2: 75 J; Shock 3: 80 J
Philips HeartStart FRx
The Philips HeartStart FRx uses a biphasic waveform. It automatically adjusts shock strength for the patient’s impedance. Higher resistance means a person needs more energy to restore a normal heart rhythm.
At 25 ohms, the device gives 128 joules. Each phase lasts 2.8 milliseconds. When resistance rises to 175 ohms, it adjusts to 158 joules. This change extends the first phase to 12.0 milliseconds and the second phase to 8.0 milliseconds.
For children, biphasic shocks adjust to match impedance. They start at 43.4 joules over 2.8 milliseconds. Then, they can increase to 52.4 joules over 8.0 milliseconds if needed.
HeartSine Samaritan PAD
The HeartSine Samaritan PAD models 350P, 360P, and 450P use a unique shock delivery method. This feature makes them different from other defibrillators.
The HeartSine Samaritan PAD features SCOPE™ biphasic technology. This tech changes energy, slope, and duration depending on the patient’s impedance. It can range from 20 to 230 ohms. Its preset energy levels are designed to deliver effective defibrillation.
Adults: Shock 1: 150 J; Shock 2: 150 J; Shock 3: 200 J
Children: Shock 1: 50 J; Shock 2: 50 J; Shock 3: 50 J
A new battery or after six shocks, the device charges in about six seconds for a 150-joule shock. For a 200-joule shock, it takes about eight seconds.
The Takeaway About Shock Levels Across AED Brands
AED brands have different preset shock levels. Yet, they all adjust their energy without conscious effort. They do this by analyzing heart rhythm and patient impedance. Engineers designed these devices to stay within a largest output of 200 joules.
Getting the most out of your monophasic or biphasic AED.
Monophasic and biphasic shocks both help with ventricular fibrillation and pulseless ventricular tachycardia. Yet, most modern AEDs prefer biphasic defibrillation. This method is better because it uses less energy and is more effective.
If you manage an AED at a school, workplace, or worship site, follow U.S. maintenance guidelines. Replace the battery before it expires. A successful shock needs enough charge.
U.S. organizations with many locations must manage their AED programs well. This keeps them compliant with legal and technical standards. It also ensures devices are ready for emergencies. Timely shocks from monophasic or biphasic units, along with good CPR, can save lives.
FAQs
What’s the difference between monophasic vs biphasic defib shocks?
Monophasic defibrillators send a single-direction current through the heart. Biphasic AEDs provide current in two phases. They reverse direction during the shock. Biphasic devices are more efficient than monophasic ones. They use less energy but keep success rates high or even improve them.
Why are biphasic AEDs preferred over monophasic models today?
Biphasic AEDs are popular. They use less energy, lower the chance of skin burns, and save battery life. Biphasic defibrillators are often favored over monophasic ones in many medical settings. Their benefits make them a top choice.
How many joules does a biphasic defibrillator deliver?
The energy level of an iphasic defibrillator, measured in joules, depends on the patient’s impedance. Typically, the first shock is around 120–150 joules, increasing to about 200 joules if needed. Devices adjust automatically for optimal results.
Are monophasic defibrillators still in use?
Monophasic defibrillators are still in some older setups. Yet, they are being replaced by biphasic defibrillator models. The American Heart Association suggests you check for new guidance. Also, replace old units whenever you can.
Do biphasic shocks improve survival more than monophasic ones?
Studies show that both can restore normal rhythm. Yet, biphasic shocks are usually more effective than monophasic ones. They work better, especially at lower energy levels, and have less impact on the heart. Yet, some long-term studies found similar survival rates one month after cardiac arrest.
How does impedance affect biphasic defibrillation?
Biphasic defibrillators adjust shock delivery automatically in response to patient impedance. Lower resistance leads to shorter shocks with less energy. Higher impedance, thus, causes a longer phase. This results in more joules for a stronger response.
Why is AED program management important for organizations?
Businesses, schools, and places of worship need AEDs, like biphasic AEDs, for emergencies. Program management helps with compliance. It keeps batteries charged. This way, devices can deliver life-saving shocks when needed.
Conclusion
To sum up, recognizing the differences between monophasic and biphasic defibrillators is important. This knowledge is essential for anyone involved in cardiac emergency response. Biphasic defib technology can treat life-threatening rhythms like ventricular fibrillation. It has clear benefits in efficiency, safety, and portability. Biphasic AEDs now lead in modern care. They need less energy and make smarter impedance-based adjustments. Managing devices in workplaces, schools, or public spaces is crucial. Staying informed and keeping equipment up-to-date can save lives when every second counts.
