Manual defibrillation serves an important role in emergency medicine, providing a controlled electrical shock to the heart. Its purpose is to reset the heart’s electrical activity when it is experiencing life-threatening, chaotic rhythms. This intervention is life-saving in situations of sudden cardiac arrest, making it an essential part of advanced medical care.
The Mechanism of Manual Defibrillation
Manual defibrillation delivers a controlled electrical current through the heart muscle. This current momentarily halts all electrical activity, allowing its natural pacemaker to resume a normal, organized rhythm. The process begins with skilled medical personnel evaluating the patient’s heart rhythm using an electrocardiogram (ECG) on the defibrillator.
The device consists of a main unit, which generates the electrical charge, and either paddles or adhesive pads placed on the patient’s chest. Pads are now frequently used for safer operation and can remain in place for continuous monitoring. Once positioned, the operator manually selects the appropriate energy level, measured in joules.
Modern manual defibrillators use biphasic waveforms, which deliver current in two directions, requiring less energy than older monophasic devices. For adults, biphasic shocks range from 120 to 200 joules, while monophasic shocks use 360 joules. The operator charges the device and, after ensuring no one is touching the patient, delivers the shock. This control requires specialized training in advanced cardiac life support.
Conditions Requiring Manual Defibrillation
Manual defibrillation treats two cardiac rhythms: ventricular fibrillation (VF) and pulseless ventricular tachycardia (VT). These are severe electrical disturbances preventing the heart from effectively pumping blood. Both are medical emergencies leading to sudden cardiac arrest and death if not treated promptly.
Ventricular fibrillation occurs when the heart’s ventricles quiver chaotically and in an uncoordinated manner. This disorganized electrical activity means the heart cannot pump blood, leading to a loss of consciousness and no detectable pulse. Similarly, pulseless ventricular tachycardia involves the ventricles beating extremely rapidly, often over 100 beats per minute, but too fast to fill with blood, resulting in no pulse.
Defibrillation aims to stop this erratic electrical activity, allowing the heart’s natural pacemaker to re-establish a normal rhythm. Manual defibrillation is not effective for all types of cardiac arrest, such as asystole (a “flat-line” rhythm with no electrical activity) or pulseless electrical activity (PEA), where electrical activity is present but too weak to produce a pulse. In these cases, other resuscitative measures are necessary.
Distinguishing Manual from Automated Defibrillation
Manual defibrillators and Automated External Defibrillators (AEDs) deliver electrical shocks, but differ in operation and intended users. Manual defibrillators require a trained medical professional, such as a paramedic or physician, to interpret the patient’s heart rhythm, determine if a shock is needed, and manually select the appropriate energy level. This allows for greater control and adaptability, especially for complex cases or children, where energy levels need precise adjustment.
Automated External Defibrillators are designed for use by the general public with minimal training. AEDs automatically analyze the heart rhythm and provide voice and visual prompts, advising whether a shock is necessary. If a shock is indicated, many AEDs deliver it automatically, while semi-automatic models require a button press. This automation makes AEDs accessible and user-friendly, enabling rapid intervention in public settings.
Manual defibrillators include advanced features beyond shock delivery, such as monitoring oxygen levels, carbon dioxide concentration, and blood pressure, providing a comprehensive view of the patient’s condition. Unlike AEDs, which are typically found in public places, manual defibrillators are primarily used in healthcare settings like hospitals and ambulances, where trained professionals can use their advanced capabilities. The choice between a manual defibrillator and an AED depends on the situation and the training level of the rescuer.