A defibrillator is a life saving device that issues a electrical shock to the heart in some cases of cardiac arrest. This process is called defibrillation and can help save lives. Cardiac arrest happens when the heart stops pumping bloody around the body. At this time it is critical that defibrillation happens as soon as possible.

This electrical shock depolarizes a critical mass of the heart muscle, terminates the arrhythmia, and allows the natural rhythm  of the heart to be re-established by the body’s organic pacemaker, in the sinoatrial node of the heart.

According to the British heart foundation for every minute that a patient is not giving defibrillation their chances of survival decrease by 14 per cent. In fact research also show that’s providing a shock within five minutes of the patient collapsing provide the best chance of survival.

Defibrillators can come in many forms and sizes. These can be external, transvenous, or implanted. This will all depend on the device used. The most common devices are called automated external defibrillators (AEDs) and because they automate the defibrillation process, by automation of the treatable rhythms, meaning that bystanders or people with very little or no training at all can use them.

Because of the importance of the defibrillators and the low numbers available, it is vital that these devices are strategically placed within an area. These are often placed where an ambulance would find it difficult to get to –  i.e.,  placed with traffic congestion, poor infrastructure, or where large crowds gather.

Defibrillation was first successfully performed in 1899 by two physiologists in Switzerland. It was found that small electrical shocks could induce ventricular fibrillation in dogs. However, it wasn’t until 1933 that a serious alternative to injecting powerful drugs straight to the heart. Dr Albert Hyman came up with the invention of a hollow needle, an insulated wire to the heart to deliver the electrical shocks.

These days Defibrillators have come a long way from the Hyman days. In order to use the AED, the machine is turned on and then a voice prompt will instruct the rescuer on what to do. The voice prompts the rescuer to place the pads into position on the chest and these then detect if a shock is needed by reading activity in the heart.

Defibrillation should never be seen as an alternative to to CPR, which can help by time before defibrillation is needed. The British Heart Foundation state that if more GP surgeries were equipped with defibrillators that survival could be increased by up to 60 per cent if the patient is treated immediately after entering cardiac arrest.

AED’s are often placed in highly visible areas and it is not recommended that these should be placed in locked or code restricted cabinets as this makes them inaccessible in time of emergency where the time taken is of essence. AED’s are often brightly coloured, and are often encased in protective cases. When these protective cases are opened nearby staff are alerted by a buzzer. 

Neil Maycock is a writer for Martek Medical. Focusing on topics such as health and safety and first aid at work.

Thanks, Neil, for this information about defibrillators.  After having seen an AED demonstrated in a CPR class, the verbal coaching that it gives makes it easy for most persons to use.  As stated in your article, CPR should be the first attempt of life-saving.  Hopefully, AED’s are becoming more prominent at many venues, from sports, to school activities, to churches.  A heart attack can happen any time, any where. pb