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Defibrillation- Definition, Types, and Purpose

Defibrillation is a procedure that makes use of the defibrillation machine for treating life-threatening conditions. The conditions are mainly related to the abnormal functioning of the heart such as cardiac arrhythmia. The process of defibrillation is carried out side by side with the process of cardiopulmonary resuscitation (CPR). Based on the necessity, there can be some variations in the defibrillation process and the devices. So, here we will be discussing the relation of defibrillation with CPR. Besides that, we will also discuss the types of defibrillation machines and their applications in different departments of the hospital, and outside of the hospital.

What is defibrillation in CPR?

Cardiopulmonary Resuscitation (CPR) is a life-saving, chest compression technique that is applied to the patient who has been the victim of cardiac arrest or any other abnormal cardiac rhythm of the heart. It is a sudden step that is applied before any other help arrives. In other words, it is a kind of first aid applied to cardiac patients.

When the patient becomes a victim of cardiac arrest, your first priority should be to defibrillate the patient. But for the purpose of defibrillation, you need to turn on the machine, connect the electrodes and ECG cables. In other words, it will take time to prepare for defibrillation. So, in such a case you can use the CPR procedure. Once the machine is ready, you may carry on the process of defibrillation.

Finally, the purpose of both CPR and defibrillation are the same. They both are used to restore the normal heart function of the patient.

Types of defibrillation devices

Defibrillation devices can be classified into two types. They are as follows.

1. Manual Defibrillator

The manual defibrillator is a type of defibrillator that is used in conjunction with the ECG. The manual defibrillator can further be classified into internal and external defibrillators. The external defibrillator is more popular between these two types. In this case, the paddles of the defibrillator are placed on the skin of the chest region. In the case of the internal defibrillator, the paddles are placed directly on the heart of the patient. It is used mostly in cardiac surgery such as bypass surgery.

2. Automated External Defibrillator (AED)

The AED can be either fully automatic and semi-automatic types. In the case of the fully automatic type of AED, the machine analyzes the ECG signal and then delivers sock whenever needed. In the case of the semi-automatic type of AED, the machine analyzes the ECG signal and informs the operator to deliver the shock when needed.

Monophasic Vs Biphasic Defibrillator

Based on the direction of the flow of waveform (energy) the defibrillators can be either monophasic or biphasic in nature.

Monophasic Biphasic
In this case, a one-directional waveform is supplied from one electrode to another. A bidirectional waveform is supplied during a single shock. In this case, the polarity of the electrode is reversed.  Also, the second waveform has a lower energy level than the initial one.
The energy supplied will be greater towards the electrodes.  But away from the electrodes, the energy decreases. Thus, the energy dissipation will not be uniform. Since the flow of energy (waveform) is bidirectional, the dissipation of the energy will be uniform.
Since the energy dissipation is not uniform, more energy will be necessary to trigger all the heart cells. Since the energy dissipation will almost be uniform, less energy will be necessary to trigger the heart cells.

How to identify if a machine is monophasic or biphasic?

Nowadays the monophasic machines are being replaced by biphasic ones. However, sometimes you may be confused about whether the machine is biphasic or monophasic. In such a case you can use a number of techniques to identify it.

The simplest method is to go through the user manual or the brochure. The other method can be by setting the discharge current. We know that the biphasic defibrillator needs to deliver a lower current in comparison to that of the monophasic machine for the same efficiency. So, by looking at the maximum value of the discharge current you can guess the machine. For example, a machine that can deliver more than 360 joules of energy is likely to be a monophasic defibrillator. Similarly, the machine that does not deliver more than 300 joules of energy is likely to be a biphasic defibrillator. However, this may not be valid for every kind of defibrillator.

The other method is by looking at the resistance value while discharging. For example, when the machine is discharged, the resistance value may or may not be displayed at the end of the screen. If the machine shows the resistance value, then it is a biphasic defibrillator. Else, it is a monophasic machine.

What is the purpose of defibrillation?

The defibrillation machine is useful primarily for patients experiencing symptoms of cardiac arrest in the post-trauma situation. In other words, it is useful for the correction of heartbeat or correct the arrhythmia. The machine can be applied to adults and children. The machine may even have additional features for the monitoring of the pulse rate, ECG waveform, etc.

A manual type of defibrillator is useful for the emergency responders who are trained in advanced life support, cardiac care techniques, and the interpretation of the ECG waveforms. Similarly, the defibrillator with the AED function or a separate AED machine is useful for the emergency responders or the physicians in an ambulance or at the scene of an emergency. The AED is also useful during the transport of the patients between any of the locations mentioned above.

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