Generality
The defibrillator is the electronic device used to perform electrical defibrillation, a medical procedure for restoring normal heart rhythm in subjects with an arrhythmia.
There are different types of defibrillators: the manual defibrillator, the semi-automatic defibrillator, the automatic defibrillator and the implantable cardiac defibrillator.
The use of the defibrillator associated with cardiopulmonary resuscitation is a medical intervention that, if performed promptly and correctly, can save people who are victims of cardiac arrest.
Brief anatomical and functional recall of the heart
The heart is an unequal organ, which can be divided into four cavities (the right atrium, the left atrium, the right ventricle and the left ventricle) and composed of a very particular muscle tissue: the myocardium .
The peculiarity of the myocardium is its ability to generate and conduct nerve impulses by contraction of the atria and the ventricles .
The source of these nerve impulses, which are comparable to electrical signals, resides at the level of the right atrium of the heart and is called the atrial sinus node .
The atrial sinus node has the task of scanning the right frequency of contraction of the heart ( heart rate ), in such a way as to guarantee a normal heart rhythm.
When the heart contracts under the action of the atrial sinus, doctors and cardiologists speak of normal heart rhythm or sinus rhythm .
Figure: the normal heart rhythm (or sinus rhythm) of an adult human being has a contraction frequency at rest of between 60 and 100 beats per minute. Alterations of sinus rhythm are called arrhythmias .
In the presence of an arrhythmia, the normal heart rhythm can become faster or slower, or assume an irregular frequency.
What is the defibrillator?
The defibrillator is the electronic device that, thanks to its ability to generate specific electrical discharges, allows performing the so-called electrical defibrillation .
Electrical defibrillation is the medical procedure, sometimes with a life-saving value, which allows the restoration of the normal heart rhythm in individuals with a heart affected by arrhythmia, ie an alteration of the sinus rhythm.
Principle of operation
The defibrillator is an instrument, battery-powered or connectable to a power outlet, designed to generate precise electrical discharges and transmit them to an individual through two metal plates (or electrodes or paddles, in English).
The application of the two electric plates can take place in different points of the bust:
- One just below the shoulder (right under the claw) and one just below the left armpit (left middle axillary). These two positions are the most frequent.
- One in the middle of the chest, between the two breasts, and one on the back, exactly the opposite of the plate on the chest.
- One just below the right armpit and one just below the left armpit (right and left side buckle).
According to a rather specialized definition, the defibrillator is "the instrument capable of depolarizing the muscular walls of the heart (ie the myocardium), restoring the normal heart rhythm imposed by the atrial sinus node".
Types and methods of use
There are different types of defibrillators.
The main types are:
- The external manual defibrillator
- The external semi-automatic defibrillator
- The automatic external defibrillator
- The implantable cardiac defibrillator
It is important to point out, immediately, that the implantable cardiac defibrillator is a particular instrument, which, in terms of size and use, is more reminiscent of a pacemaker than a generic defibrillator.
EXTERNAL MANUAL DEFIBRILLATOR
The external manual defibrillator, or simply a manual defibrillator, is a defibrillator conjugated to an electrocardiogram ( electrocardiograph ) instrument, which works exclusively under the guidance of a medical operator .
From the functional point of view, the conjugation of the manual defibrillator to an electrocardiogram instrument is fundamental. In fact, it is based on the resulting electrocardiographic trace, that the medical operator decides which electrical discharge to transmit to the patient.
Figure: manual defibrillator.
Correct use of the manual defibrillator requires specific preparation both on how the defibrillation instrument works and on how an electrocardiograph works (reading the tracks, knowing how to recognize an arrhythmia, etc.).
For the specific preparation required, and for other reasons, the manual defibrillator is a device that is generally used only in hospitals or in some ambulances.
EXTERNAL SEMIAUTOMATIC DEFIBRILLATOR
The semi-automatic external defibrillator, also known as a semi-automatic defibrillator or AED, is a defibrillator built with a technology that allows it to analyze an individual's heart rate and independently determine which electrical discharge to impart.
The analysis of the cardiac rhythm takes 10 to 20 seconds and takes place by means of the same metal plates used for the transmission of the electric discharge.
The release of the electric discharge depends on the typing of a specific button, usually present in the center of the instrument and marked by a flash.
Today's semi-automatic defibrillators are practical, simple to use and require minimal preparation to be able to use them correctly. Once activated, in fact, they emit a guiding voice, which serves to support the rescuer user in the delicate defibrillation procedure and to tell him when to press the button for the electric discharge.
In recent years, following some tragic deaths due to cardiac arrest, more and more public access premises - including airports, restaurants, sports centers, hotels, schools, university shops, government offices, etc. - have begun to acquire one or more semiautomatic defibrillators and to instruct some staff members to use this equipment.
Preparation for use of the semi-automatic defibrillator
Currently, with a course of 6-8 hours total, including a theoretical part and a practical part, anyone can learn to correctly use a semi-automatic defibrillator.
Usually, those who participate in these courses using a semi-automatic defibrillator also receive instructions on how to provide cardiopulmonary resuscitation, a complementary procedure to defibrillation.
EXTERNAL AUTOMATIC DEFIBRILLATOR
The automatic external defibrillator, also known as an automatic defibrillator, is a defibrillator capable of analyzing the cardiac rhythm, independently establishing the electrical discharge to be transmitted to the patient and emitting it without any button input by the rescuer user.
Figure: semi-automatic defibrillator
In other words, those who use an automatic defibrillator need only operate the instrument, place the metal plates on the individual who needs defibrillation and let the device do its operations.
In public places, automatic defibrillators are less common than semi-automatic models.
IMPLANTABLE CARDIAC DEFIBRILLATOR
The implantable cardiac defibrillator, or implantable cardioverter defibrillator or ICD, is a small, portable defibrillator capable of monitoring an individual's heart rhythm and delivering an electric shock to the heart when needed.
As mentioned, the implantable cardiac defibrillator looks a lot like a pacemaker. In fact, in the same way as the latter:
- Requires surgery for its subcutaneous insertion, just below the left clavicle;
- It is joined to the heart by means of leads, which perform the function of monitoring the cardiac rhythm and the function of transmission of the electric discharge;
- Once installed, a cardiologist must program it through a computerized device specifically designed for this purpose. For obvious reasons, programming depends on the heart condition that afflicts the patient.
To learn more, read the article on cardioversion
Indications
The external manual defibrillator has slightly different indications than the semi-automatic defibrillator and automatic defibrillator.
The implantable cardiac defibrillator is a special case, to be treated separately.
INDICATIONS OF THE MANUAL DEFIBRILLATOR
The manual defibrillator is suitable for restoring the heart rhythm of people with:
- Ventricular fibrillation
- Ventricular tachycardia
- Cardiac arrest
- Atrial fibrillation
- Atrial flutter
INDICATIONS OF THE SEMIAUTOMATIC AND AUTOMATIC DEFIBRILLATOR
The semi-automatic defibrillator and automatic defibrillator are suitable for restoring the heart rhythm of people with:
- Ventricular fibrillation
- Ventricular tachycardia
- Cardiac arrest
INDICATIONS OF IMPLANTABLE CARDIAC DEFIBRILLATOR
The implantable cardiac defibrillator is suitable for people who, due to their general health conditions, may suffer from:
- Ventricular fibrillation (main indication)
- Ventricular tachycardia (main indication)
- Supraventricular tachycardia (more rarely)
- Atrial fibrillation (more rarely)
From the point of view of functioning, when the heart rhythm undergoes an alteration such as to activate the ICD, the latter is activated and imparts an adequate electrical discharge.
Warnings
The most important warning concerning the use of the manual defibrillator, the semi-automatic defibrillator and the automatic defibrillator is to keep a distance from the patient, when the medical operator or a generic rescuer presses the button for the electric discharge.
In fact, if a person touches the patient, when the patient receives the electric shock, he also absorbs part of the imparted discharge and could develop a more or less severe arrhythmia.
RISKS OF IMPLANTABLE CARDIAC DEFIBRILLATOR
Dangers of the separate implant operation, the implantable cardiac defibrillator has the possible drawback of emitting electric shocks without any reason due to a malfunction.
Defibrillation and cardiopulmonary resuscitation
Defibrillation and cardiopulmonary resuscitation ( CPR ) are two medical procedures that can save the lives of those who are victims of cardiac arrest .
To be more precise, during a cardiac arrest it is essential:
- First of all, call 118 ;
- Secondly, practice defibrillation ;
- Thirdly, proceed with cardiopulmonary resuscitation .
If the defibrillator is not immediately available (but on arrival), it is good to start immediately with pulmonary resuscitation; as soon as the tool is available, however, it must be used.
CARDIOPULMONARY RESUSCITATION (CPR)
Cardiopulmonary resuscitation can save a person's life, because, with its correct execution, it allows the oxygenated blood to reach the different organs of the body, primarily the brain, and to keep them alive.
The SPC consists of alternating the so-called cardiac massage with artificial respiration. The cardiac massage, performed with strong manual compressions at chest level, simulates the pumping action of the heart; while artificial respiration, carried out mouth to mouth and with the patient's nostrils closed, allows new oxygen to be introduced into the airways.
SPC can be a life-saving procedure even in the event of drowning, suffocation and myocardial infarction.
| CPR for those who are inexperienced | Frequently asked questions about cardiopulmonary resuscitation |
RCP inexperienced rescuers will receive all the necessary information when they call 118. Except in cases of drowning and suffocation (for which the supply of new oxygen is essential), with the call to the 118 will receive the indication to practice a continuous cardiac massage, to 100 compressions per minute, until the arrival of the rescue hospital. | In the event of cardiac arrest, is cardiac massage or artificial respiration more important? Cardiac massage is of primary importance, as oxygen remains in the blood for several minutes. When should the SPC be stopped? A rescuer should perform the CPR until hospital assistance arrives or until the rescuer does not exhaust his strength (NB: cardiac massage is very tiring). If the rescuers are more than one, they can alternate in the practice of cardiac massage and in this way to rest. What should be done before artificial respiration? First of all, the patient's head must be gently tilted backwards so as to open the airways and then close the nasal passages to prevent the air entering through breathing from coming out of the nostrils. |
WHAT TO DO IF YOU DON'T HAVE A DEFIBRILLATOR
If a defibrillator is not available, the rescuer should not be alarmed, but quickly call 118 and immediately engage in cardiopulmonary resuscitation. The defibrillator is important, but an individual's life can be saved even with the SPC.
