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How to use and operate the defibrillator

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Update time : 2023-11-07 16:01:00
Defibrillator, also known as cardioversion machine, is a medical electronic device that uses electric shock to rescue and treat arrhythmia. It has the advantages of high curative effect, fast action, easy operation and safety compared with drugs. It is widely used in medical units at all levels of the army.
How a defibrillator works
The method of using a strong pulse current to pass through the heart to eliminate arrhythmias and restore sinus rhythm is called electrical defibrillation or electrical cardioversion. Both pacing and defibrillation use exogenous current to treat arrhythmias, and both are modern methods of treating arrhythmias. The difference between cardiac pacing and defibrillation cardioversion is that in the latter, an instantaneous high-energy pulse is applied to the heart during electrical shock cardioversion. The general duration is 4 to 10 ms, and the electrical energy is within 40 to 400J (Joules). The device used to defibrillate the heart is called a defibrillator. It can complete the electrical cardioversion, that is, defibrillation. When patients develop severe tachyarrhythmias, such as atrial flutter, atrial fibrillation, supraventricular or ventricular tachycardia, etc., they often cause varying degrees of hemodynamic disorders.
The original defibrillator used industrial alternating current to directly defibrillate. This kind of defibrillator often caused casualties due to electric shock. Therefore, except for the use of alternating current for internal defibrillation (ventricular fibrillation) during cardiac surgery, it is generally used Direct current defibrillation.
The voltage converter converts DC low voltage into pulse high voltage, and then charges the energy storage capacitor C after high voltage rectification, so that the capacitor obtains a certain amount of energy storage. During defibrillation treatment, the high-voltage relay K is controlled to operate, so that the charging circuit is cut off, and the energy storage capacitor C, the inductor L and the human body (load) are connected in series to form an RLC (R is the resistance of the human body, the resistance of the wire itself, the human body and The sum of the three contact resistances of the electrodes) series resonance attenuated oscillation circuit.
In addition to the above-mentioned charging circuit and discharge circuit, the cardiac defibrillator should also have a monitoring device to promptly check the progress and effect of defibrillation.
There are two types of monitoring devices: one is an ECG oscilloscope, which monitors the output waveform of the defibrillator on the oscilloscope screen; the other is an automatic recorder like an electrocardiograph, which records the output waveform of the defibrillator and The electrocardiogram is automatically recorded on the recording paper for monitoring purposes. Of course, some have the above two devices at the same time, which can not only observe the waveform on the fluorescent screen, but also automatically trace the waveform.
Some cardiac first aid devices are composed of a pacemaker, a defibrillator, a monitor, and an automatic recorder. They are good instruments for cardiac first aid.
Defibrillator classification
(1) Divided according to whether it is synchronized with R wave
1. Asynchronous defibrillator. This kind of defibrillator is not synchronized with the patient's own R wave during defibrillation, and can be used in ventricular fibrillation and flutter (because there is no R wave with high enough amplitude and large enough slope).
2. Synchronous defibrillator. This type of defibrillator synchronizes with the patient's own R-wave during defibrillation. Generally, an electronic control circuit is used to control the delivery of current pulses with R wave, so that the electric shock pulse happens to fall on the descending branch of the R wave, so that the electric shock pulse does not fall in the irritable phase, thus avoiding ventricular fibrillation. It can be used for all tachyarrhythmias except ventricular fibrillation and flutter, such as supraventricular and ventricular tachycardia, atrial fibrillation and flutter, etc.
(2) According to the position of the electrode plate
1. Internal defibrillator. This type of defibrillator places electrodes inside the chest to directly contact the heart muscle to defibrillate. Early defibrillation is mainly used for direct myocardial shock during open heart surgery. This internal defibrillator has a simple structure. Modern internal defibrillators are embedded, which is different from early internal defibrillators. In addition to automatic defibrillation, they can also automatically monitor ECG, determine arrhythmias, and select therapies.
2. External defibrillator. This type of defibrillator places electrodes outside the chest and indirectly contacts the myocardium to defibrillate. Most of the defibrillators currently used clinically belong to this type.
Clinical application
1. Equipment
An electrical cardioversion machine, also called a defibrillator, is the main equipment for performing electrical cardioversion. Equipped with electrode plates, most of them have two pairs of large and small ones. The larger one is suitable for adults and the smaller one is suitable for children. Before use, check whether the functions of the defibrillator are intact, whether the power supply is faulty, whether the charging is sufficient, whether the various wires are broken and whether Poor contact. As a rescue equipment, the defibrillator should always maintain good performance and the battery should be fully charged so that it can implement emergency defibrillation at any time in an emergency.
2. Electrode
There are two positions for placing the electrode pads during extracorporeal cardioversion. One is called the anteroposterior position, that is, one electrode plate is placed in the subscapular area of the back; the other is placed at the level of the 3rd to 4th intercostal space on the left edge of the sternum. Some people believe that this method allows more current to pass through the heart, requiring less electrical energy and reducing potential complications. Selective electrical cardioversion should be done this way. The other is to place an electrode plate on the 2nd to 3rd intercostal space (bottom of the heart) on the right edge of the sternum. The other piece was placed in the 5th intercostal space (apex of the heart) in the left anterior axillary line. This method is quick and convenient and suitable for emergency defibrillation. The distance between the two electrode plates should not be <10cm. The electrode pads should be close to the patient's skin and slightly pressurized, with no gaps and no raised edges. The skin where the electrodes are placed should be coated with conductive paste, or saline gauze can be used. In an emergency, clean water can even be used, but alcohol is absolutely prohibited, otherwise it may cause skin burns. Those who are emaciated and have obvious sunken intercostal spaces and poor contact between the electrodes and the skin should use saline gauze, and several more layers can be used to improve the contact between the skin and the electrodes. The space between the two electrode plates should be kept dry to avoid short circuits caused by conductive paste or salt water. The electrode plate handles should also be kept dry. Cannot be contaminated by conductive paste or salt water,
To avoid injury to the operator. When cardiac surgery or open heart massage requires direct electric shock defibrillation of the heart, a proprietary small electrode plate is required. One is placed on the right ventricular surface; the other is placed on the apex of the heart. The surface of the heart is sprinkled with physiological saline, and the electrode plate Close to the ventricular wall.
3. Selection of electric energy
The electrical energy used in electrical cardioversion is represented by J. Charge according to the required amount, ventricular fibrillation is 250J~300J, asynchronous cardioversion. Ventricular tachycardia is 150J~200J, atrial fibrillation is 150J~200J, atrial flutter is 80J~100J, supraventricular tachycardia is 100J, all are synchronous cardioversion.
1. Get all the supplies next to the bed and turn on the power.
2. Expose the patient's chest and establish ECG monitoring if necessary.
3. Determine the patient's arrhythmia type.
4. Apply conductive glue evenly to the electrode plate.
5. Choose the appropriate energy: synchronous is generally 70-100J, non-synchronous is generally 200-360J (for adults, single-phase is 200J for the first time, 200-300J for the second time, 360J for the third time; 150J-150J-200J for biphasic).
6. Charging: Place the electrode plate at the appropriate location (the second intercostal space on the right edge of the sternum - the apex of the heart; the fifth intercostal space on the left front axillary line - the bottom of the heart). The distance between the two electrode plates is greater than 10cm; loudly ask other personnel to leave the patient and the hospital bed.
7. Press the discharge buttons under the two electrode plates with both hands at the same time. (Electrode plate adhesion strength 10-12kg)
8. Observe the patient's electrocardiogram changes.
9. If ventricular fibrillation/ventricular flutter (pulseless ventricular tachycardia) continues to occur, recharge immediately and repeat the steps.
10. After the operation is completed, return the energy switch to the zero position.
11. Clean the skin and position the patient.
12. Monitor heart rate and rhythm, and take medication as directed by your doctor.
13. Record.
14. Final processing.
1. Check the performance of the defibrillator in time and charge it in time.
2. The conductive glue should be applied evenly to prevent skin burns.
3. During discharge defibrillation, pay attention to the insulation between the patient and other people and objects.
4. Energy selection for children: 2J/kg for the first time, 2-4J/kg for the second time, and 4J/kg for the third time.
5. For ventricular tachycardia that can clearly distinguish between QRS and T waves, synchronized electrical cardioversion should be performed; if the distinction cannot be made, asynchronous electrical defibrillation should be used.
6. For cardioversion with the same indication, a slightly lower starting energy is usually selected according to the doctor's advice. The "synchronization" key should be pressed before selecting the energy.
Defibrillator maintenance
1. Clean the recorder print head
If the printed ECG strips are too light or have different shades, clean the print head with a cotton ball soaked in alcohol to remove any remaining paper debris.
2. Maintain the battery
The defibrillator can be powered by AC power or battery. After the battery is installed in the defibrillator, it should be charged for 24 hours to ensure that the battery reaches full capacity. The instrument should be connected to the AC power supply to ensure that it is fully charged after each use. Otherwise, Will reduce battery capacity and life. If the defibrillator is stored without AC power for more than 1 month, first charge the battery for 48 hours, then remove it from the instrument and place it in a cool, dry place, but it should not be stored below zero degrees Celsius. Charge stored batteries for at least 24 hours every 6 months to ensure that the batteries are not completely discharged during storage. When the battery is removed from the instrument, it should be immediately marked on the instrument that AC power is required to operate.
Leaving the battery uncharged for too long can cause permanent damage to the battery. Therefore, the battery capacity should be checked at least every 6 months. A new sealed lead-acid battery can provide a minimum of 2.5 hours of monitoring time. If it cannot provide a minimum of 2.5 hours of monitoring time, or the battery cannot provide 10 minutes of "battery voltage" When the "low" warning time is reached, the battery needs to be replaced.
3. Clean the outer surface
Keep the outside of the instrument free of dust and thoroughly remove the electrostatic glue on the defibrillation electrodes. Use soapy water, chlorine bleach and other non-corrosive detergents to clean the outside. Do not let any liquid enter the inside of the instrument during cleaning, and do not use strong force. Solvents such as acetone or acetone-based compounds can easily chip the display, so be very careful when cleaning. Do not steam or gas fumigate monitoring leads and defibrillation electrodes.
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