Defibrillation in Emergency Medical Services

Elderly man receives care from two rescuers

Defibrillation is one of the most important emergency medicine techniques in the case of life-threatening arrhythmias such as ventricular fibrillation. A cardiac arrest calls for immediate, appropriate intervention. Whether in emergency medical services and military medical corps, in hospital, or with civil protection – MEDUCORE Standard² from WEINMANN supports you in an emergency in a reliable yet user-friendly manner.

What is defibrillation?

Defibrillation is an emergency medicine technique that uses a DC current pulse to eliminate acute and life-threatening arrhythmias.

A defibrillator is used to deliver unsynchronized electrical shocks to the heart to restore the natural sinus rhythm. Early defibrillation is decisive in improving the patient’s survival chances.

How does a defibrillator work?

Two electrodes are attached to the chest area for defibrillation – one over the apex and one over the base of the heart. These electrodes monitor the cardiac activity and also deliver the electrical shock.

In the event of life-threatening arrhythmias, the heart muscle cells no longer work in a coordinated fashion. The heart may be active, but there is no orderly pump function from the activity, which ultimately leads to the cardiac arrest. A strong direct current shock is therefore delivered to the heart via the electrodes to depolarize as large a mass as possible of heart muscle cells.

This depolarization of the heart muscle cells interrupts the arrhythmia and generates a short-term asystole in the sense of a refractory period. If the defibrillation is successful, the sinus node can regain its normal function and restore the sinus rhythm.

After delivering the shock, the defibrillator can continue to monitor the heart activity to ensure restoration of the sinus rhythm. The process can be repeated if the defibrillation was not successful.

Why is defibrillation important?

A cardiac arrest as a result of a dangerous arrhythmia is one of the most common causes of death in Germany. If the heart’s pump function is impaired, organs are no longer supplied with sufficient oxygen. The brain function stops after just a few minutes so that an untreated cardiac arrest can be fatal within a short period of time.

Every second counts in such a medical emergency. If a cardiac arrest occurs outside a hospital, the probability of successful CPR is reduced by 3–5%1 with every minute of delay. Early defibrillation is therefore indispensable.

More than half of all cardiac arrests occur in a private setting. In most cases first-aiders are on hand that may be able to perform defibrillation before the EMS field providers arrive. For this purpose, an AED (automated external defibrillator) is used – a portable emergency medicine device that people with no medical training can also use in an emergency. The use of an AED by first-aiders within the first 5 minutes after a prehospital cardiac arrest results in survival rates of up to 70%2.



The American Heart Association and the European Resuscitation Council advise immediate use of defibrillation in the case of ventricular fibrillation3.

Not all arrhythmias that cause a cardiac arrest are shockable. A defibrillation is performed solely with shockable rhythms. These include:

  • Ventricular fibrillation
  • Ventricular flutter (frequency of the fibrillation waves from 280-350/min)
  • Pulseless ventricular tachycardia (pVT)


Non-shockable rhythms include:

  • Asystole
  • Pulseless electrical activity or electromechanical dissociation (PEA/EMD)


Defibrillation should not be performed either with:

  • Pulse present
  • Hypothermia below 27°C core body temperature
  • Myocardial infarction

Forms of defibrillation

A distinction is basically drawn between synchronous and asynchronous defibrillation as well as between automatic and manual defibrillation. The operating mode of a defibrillator is also either monophasic or biphasic.

Asynchronous defibrillation versus synchronous defibrillation 

Asynchronous and synchronous defibrillation differ by the timing of the shock delivery in relation to the ECG. A reference to just defibrillation will generally be referring to asynchronous defibrillation. Synchronous defibrillation by contrast is described as cardioversion.

Cardioversion or synchronous defibrillation is normally performed as part of an elective treatment of, say, atrial arrhythmia or as an emergency procedure with instable ventricular tachycardia. It is performed synchronized with the R wave in the ECG to avoid disrupting the vulnerable phase.

Asynchronous defibrillation, however, takes place with no synchronization with the ECG, as there is no coordinated excitation of the heart. Asynchronous defibrillation is an emergency technique.

Automatic versus manual defibrillation

An ECG analysis of the underlying heart rhythm must be performed before any defibrillation in order to determine whether there is a shockable rhythm or not. If the defibrillator detects a shockable rhythm the device is charged and prepares the shock. Automatic and manual defibrillation then differ in terms of who or what eventually delivers the shock.

Manual defibrillation involves the users deciding themselves whether and when a shock is delivered.

In the case of automatic defibrillation, the device decides when and whether a shock is delivered. However, with a semiautomatic defibrillator, the users trigger the shock by pressing a button.

Monophasic versus biphasic defibrillation

For a defibrillation there are various pulse configurations: monophasic and biphasic. They differ by virtue of the type of current pulse. Studies show that biphasic shocks with a defibrillation tend to be more effective and better suited than conventional monophasic shocks4.

Operating mode


Shock energy:
Up to 360 joules

Type of current pulse:

  • From one electrode to the other
  • Current flow in one direction
  • One phase

Shock energy:
150 - 200 joules (for adults)

Type of current pulse:

  • Current changes direction during the pulse
  • Two phases with reversed polarity of the electrodes

WEINMANN – Defibrillation devices

An arrhythmia can be life-threatening in certain circumstances and lead to a cardiac arrest. EMS field providers and medical personnel must act without delay in such emergencies. MEDUCORE Standard² from WEINMANN provides you with safe and reliable support.

MEDUCORE Standard² combines high-end functionality with user-friendly technology – for maximum safety for patient and user. The compact monitor/defibrillator has all the necessary functions for prehospital and in-hospital patient monitoring and enhanced diagnostics
MEDUCORE Standard² also supports you with intuitive operation with all steps of a manual defibrillation or cardioversion.

The application area of MEDUCORE Standard² includes prehospital emergences in emergency medical services as well as mobile care in the hospital. MEDUCORE Standard² is also used with the medical services in military medical corps and for civil protection.

Five advantages of MEDUCORE Standard²:

  • 1. Basic life support: basic monitoring with SpO₂, NIBP, 6-lead ECG, AED mode
  • 2. Advanced life support: 12-lead ECG, manual defibrillation, cardioversion
  • 3. Data transmission: e-mail, Wi-Fi, Bluetooth®
  • 4. Can be combined with a ventilator on a LIFE-BASE portable unit
  • 5. Light, space-saving, and rugged

Basic life support involves recording all vital signs at a glance by means of color coding. The AED mode guides users with acoustic and visual instruction simply and intuitively through the resuscitation.

The Advanced life support from MEDUCORE Standard² permits in manual mode both manual defibrillation and synchronized shock delivery as part of a cardioversion. 12-lead ECG mode allows further ECG diagnostics to be performed.

The Bluetooth® data transmission from MEDUCORE Standard² provides all data in a compatible system for digital patient data recording. The session data upload also allows device session data to be uploaded to the WEINMANN Connect web portal. Alternatively, various ECGs and reports can also be printed out directly.

WEINMANN has been developing reliable and user-friendly medical devices for emergency medicine for more than 45 years. The emergency medicine devices from WEINMANN Emergency are matched optimally in terms of their functionality and can be combined with virtually any of the respective portable units tailored to each application. They are also compact and rugged, and fast, easy, and intuitive to operate.

Contact person with headset

Are you interested in MEDUCORE Standard²?

If you would like more information or to arrange an individual consultation, do not hesitate to contact us directly.


You might also be interested in

MEDUMAT Standard² is operated by rescue personnel in BiLevel mode

Bluetooth® Data Transmission

Transfer ventilation data to your documentation system quickly and easily after every session – paperless documentation is made possible with Bluetooth® data transmission.

Learn more

Paramedic adjusts MEDUCORE Standard² during patient monitoring

MEDUCORE Standard2

Defibrillator with monitoring function and non-invasive blood pressure measurement

Learn more


We are your specialist for emergency and transport ventilation, defibrillation and suction for emergency medicine, transport and disaster medicine.

Learn more