A defibrillator is a device that briefly delivers a powerful electrical pulse to the heart. The device is used in case of violation of the conduction of the heart muscle (fibrillation, arrhythmias) ─ scattered and unproductive work of muscle fibers, which cannot pump blood.
In medicine, the concepts of ventricular and atrial fibrillation are shared. However, in both situations, the heart begins to beat at an accelerated rate, up to 700 beats per minute, losing synchronization. It loses its pumping function, depriving the internal organs of blood flow. In this case, the defibrillator helps bring the heart back to normal by restoring its rhythm.
This effect is simply explained: at rest, the cells of the atria and ventricles are polarized. The outer surface of the cell is positively charged, while the inner surface is negatively charged. The supply of a powerful electrical impulse, reaching 360 J (7000 Volts), depolarizes the critical mass of the heart muscle cells, changing the polarity of the surface and inner part of the cell. As a result, an attack of arrhythmia is eliminated since most cells begin to work harmoniously.
Why do I need a defibrillator?
Fibrillation is dangerous because it excludes the normal blood supply to the brain and vital organs. The ventricles are the parts of the heart that pump blood from the heart through the blood vessel system. Blood provides oxygen and nutrients to organs and cellular structures. If these structures don’t get enough blood, they stop functioning. In the absence of the ability to quickly restore blood flow, death occurs.
Fibrillation can be successfully corrected by the timely use of a defibrillator. In intensive care units, the immediate use of specialized equipment allows the majority of patients with a difficult condition to be brought back to life. If ventricular fibrillation occurs outside the hospital and defibrillation cannot be performed within the first minutes, the chances of resuscitation of the person are reduced. They fall by 10% every minute.
How does a defibrillator work?
When using a defibrillator, an electric current is applied to the heart muscle. Its frequency corresponds to the normal sinus rhythm, and therefore, within a matter of minutes, the resuscitation team manages to start a person’s life “motor” into work.
ZOLL automatic external and manual professional defibrillators operate on the basis of the Rectilinear Biphasic ™ (RBW) rectilinear biphasic heart pulse.
The technology shows several times greater effect compared to monophasic pulses. With a discharge dose of only 200 J of PBI during electrical defibrillation, a more intense exposure to current is provided than with 360 J.
Thanks to such indicators, it is possible to carry out resuscitation measures on the atria and ventricles with high transthoracic impedance and during out-of-hospital cardiac arrest.
Types of equipment
Determination of the specific type of defibrillator for purchase is based on the qualifications of the intended users and the conditions for the subsequent use of the equipment. Medical workers use several types of defibrillators:
- Manual control is optimal for professional use. The defibrillator has many functions and a wide range of settings. It is suitable for use in intensive care, ambulance crews. Specialists manually set the necessary parameters before working with the patient. The advantages of buying the device are obvious: it is cheaper than automatic analogs, it is equipped with reusable electrodes, which makes it economical to use. However, there are drawbacks. Such devices are oversized, which reduces their mobility;
- An automatic defibrillator is self-operating equipment that is ideal for the work of rescuers, specially trained volunteers, sports trainers. It detects arrhythmia of the heart and then signals the need for a discharge. The device is supplemented with disposable electrodes held on the chest with a sticky base. The advantages are compact size, good mobility, a wide range of applications. The main disadvantage is the high price of a defibrillator, but the advantages of the technology justify it;
- Combined control ─ combines the capabilities of an automatic and manual defibrillator.
In addition to the options presented, there is an implantable defibrillator that is implanted in a patient by an operative method. The difference in mono- and biphasic equipment also exists on the market. However, bipolar models are actively replacing outdated monopolar defibrillators.
Where is it recommended to install a defibrillator?
In addition to intensive care units and resuscitation units, automatic defibrillators are recommended to be installed in crowded places, such as airports. In the hot season, with intensive passenger traffic in the halls of the air harbor, there is a high probability of dangerous situations. The presence of an automatic external defibrillator in these conditions is becoming a mandatory requirement for the safety of passengers with heart rhythm problems.
It is recommended to equip shopping centers, concert and leisure complexes, pharmacies and other places with specialized equipment.
Modern defibrillators are easy to operate, have an intuitive interface, are compact in size and shockproof. The devices automatically analyze the patient’s heart rate and give a command for automatic defibrillation. To execute this command, just press the start button. The device sets the heart to a normal rhythm with a current discharge.
Defibrillator safety precautions
- Contact of the electrodes with each other (direct or through an electrically conductive medium) is prohibited;
- Only the specialist providing assistance remains near the patient, the rest of the staff must move away;
- During defibrillation, the ventilator and ECG are disconnected from the patient;
- Metallic objects should not touch the patient.
The defibrillation procedure is performed as follows: an electric discharge is passed through the chest for 0.01 seconds: its voltage is 4-7 kV, and the source is a capacitor connected to the network or working autonomously. Only 4% of the discharge passes through the heart muscle, the rest passes through the chest.
Due to the passage of the discharge, the muscle fibers of the myocardium are synchronously excited, while their chaotic contractions are blocked, and the correct rhythmic contractions, on the contrary, are restored.
To avoid post-resuscitation cardiopathy due to excess power, a smaller starting capacitor discharge is used at the beginning of defibrillation. If the effect is not achieved, then the discharge voltage is increased.
In most modern modifications of defibrillators, the bipolar pulse at the output corresponds to the second negative half-wave. This provides a pronounced antiarrhythmic effect while minimizing the damaging effect on the heart muscle.
Common mistakes during defibrillation
The survival rate of circulatory arrest increases with defibrillation. Since a defibrillator is a hazardous device, there are rules that must be followed when working with it. The common mistakes that users make when conducting defibrillation are as follows:
- Contact with patients while they are being shocked;
- Failure to comply with the two-minute interval in rhythm assessment and when delivering shocks;
- Close contact with an oxygen source at the time of discharge;
- Increased chest impedance through ventilation prior to shock;
- Carrying out additional cycles before the first discharge;
- Delayed discharge after stopping chest compression;
- Checking vital functions after discharge.