When using medical equipment, ensuring the safety of patients and operations is the primary mission of the operator. It is necessary to go through the process of skill evaluation, acceptance, regular maintenance, scheduled maintenance, and defect repair when purchasing the equipment, and implement safety procedures. To achieve this, it is necessary to grasp the following matters: (1) human characteristics; (2) The energy characteristics selected in the equipment; (3) The effect of energy on the human body and safety boundaries; (4) Safety regulations and their viewing methods; (5) Safe handling methods.
The effects and safety boundaries of various energies on the human body
1.1 Safety boundary of energy. To consider safety concerns, it is necessary to understand the energy sources used in the equipment, their safety boundaries, and the characteristics of the human body. In practice, there are some differences due to environmental conditions, peak values of pulses, and duration of effects.
1.2 Response of the human body to electrical shock. Cells inside the human body are good conductors containing 0.9% saline solution. Once an electric current flows through the muscle tissue, it causes it to shorten. Most medical equipment is powered by mains electricity, so when considering the safety of the equipment, the first thing to consider is the electrical shock incident. The response of the human body to electrical shock varies depending on the location where the current flows in and out, the frequency of the current, and the value of the current. Unlike the impact current on the body surface, the current flowing directly through the heart, even if small, can cause ventricular tremors. Secondly, the impact of different frequencies of impulse currents on the human body varies, meaning that the human body is more sensitive to currents ranging from 50Hz to 100Hz.
2 Electrical safety measurement
2.1 For safety concerns, it is important to consider the leakage current, which is the main cause of electric shock incidents. As mentioned earlier, the impact of surge current on different parts of the human body varies in degree. The leakage current flowing through the patient through some electrodes that are directly touched by the patient (such as the electrodes of an electrocardiograph) should be one tenth of the minimum perceived current of 1mA on the body surface, which is less than 0.1mA, while the current directly affecting the patient's heart should be less than one tenth of the threshold current of 0.1mA for ventricular fibrillation, which is 0.01mA. Based on the above situation, medical equipment can be divided into two types: Type A and Type B. Type A only applies current to the body surface, while Type B applies current directly to the heart. Leakage current can also be divided into several types. Leakage current flowing through the ground terminal of the 3P medical plug, leakage current of the casing, and leakage current passing through the patient.
2.2 Measurement of Leakage Current: A measuring device used for measuring leakage current. The threshold of the impact of current with a frequency of 1kHz or higher on the human body increases proportionally to the frequency. The measured leakage current is the millivolt meter reading divided by the resistance of 1k Ω.
2.2.1 Measurement of Ground Terminal Leakage Current: Use a 3P-2P converter to convert a medical 3P plug into a 2P plug, insert it into a wall socket, connect the leakage current tester between the ground terminal on the wall and the ground terminal of the medical 3P plug, change the polarity of the power supply, and the maximum reading at this moment is the ground terminal leakage current.
2.2.2 Measurement of leakage current of the casing: Connect the leakage current measuring device to the ground terminal on the wall and measure it between the casing.
2.2.3 Measurement of leakage current flowing through the patient: Connect the leakage current measuring device to the wall and ground, and directly measure it between the device and the patient's touch points (such as the electrodes of an electrocardiograph).
3 Security Handling Skills
3.1 Pre purchase feasibility study: Prior to purchase, clinical physicians and engineering skilled personnel should exchange opinions extensively. After conducting rigorous research on the functions, safety, social benefits, and economic benefits of various devices sold in the market, abundant skills will be provided to the decision-making plan section.
3.2 Acceptance and safety measures: Upon arrival, open the box and install the device, and inspect each skill indicator and safety function item by item. If you have any questions, please contact the manufacturer in a timely manner. The vast majority of medical equipment is equipped with a 3P medical power plug, with one end serving as the grounding terminal. But to ensure the safety of patients and operators, the following methods can be adopted:
(1) Protect grounding. In order to avoid electric shock caused by poor touch or falling of the grounding terminal of the 3P medical plug, an additional protective grounding wire is added. Connect the casing to the grounding terminal with an impedance below 10 Ω, which is easily achieved using metal equipment in buildings.
(2) Equipotential grounding. Use wires with an impedance of 0.1 Ω or less to connect all instruments, equipment, and exposed metals that indoor patients can touch to the ground, so that the potential difference between all metal surfaces is minimized; lt;10mV。 Assuming the minimum equivalent impedance of the patient is 1k Ω, regardless of the current flowing through the patient; Lt; 10mV/1k Ω=below 10 μ A. The equipotential bonding method is used for equipment in ICU wards, operating rooms, and other departments to avoid shock incidents caused by excessive current flowing directly through the patient's heart.
(3) Non grounded wiring method. An insulation transformer is installed on one side of the equipment, and the secondary circuit is not grounded. This wiring method, when many devices are gathered together, does not require power outage repair due to the malfunction of one device or poor insulation to ground. Suitable for places where life sustaining devices are gathered, such as artificial kidneys.
(4) Very powerful. In operating rooms and ICU wards, sometimes patients' lives are protected by certain devices. These devices cannot stop working for a moment. Therefore, it is necessary to have a sufficient power supply. According to the requirements of the equipment, it is necessary to consider factors such as the establishment time of normal voltage and the maintenance time of the power supply.
During the practice process, it is necessary to practice with the operator to ensure the safety of both the patient and the operator. The manufacturer serves as a necessary exercise. However, the specific principles, energy characteristics, and effects on the human body, fundamental functions, operating sequences, safety measures, and taboos should be practiced by engineering skilled personnel. It is also necessary to practice dealing with treatment equipment and urgent situations.
3.4 Maintenance and repair: No matter what equipment is used for a long time, its functionality and safety will decrease accordingly. Therefore, regular maintenance, scheduled maintenance, and repair of problems should be carried out. Regular maintenance and check the safety and fundamental functions of the equipment before starting daily treatment. Admit whether the grounding is outstanding and conduct a proofreading. At the end of the assignment, check if there are any issues such as reduced functionality. Therefore, each device should be equipped with a daily operation, maintenance record book, and usage record book. Regular maintenance: In order to detect problems and reduce functionality in the early stage, it is necessary to regularly and specifically check for issues such as functionality and safety. Due to different equipment, the viewing items are also different, but generally it is about the appearance, mechanical characteristics, electrical characteristics, and electrical safety of the machines and parts. Problem repair: When there is a problem with the equipment, the first thing to clarify is whether it is an operational error or a problem with the equipment itself. If it is a problem with the device itself, it needs to be repaired. The repaired equipment should be calibrated according to the given skill instructions.
The safety concerns of handling medical equipment in the 3.5 system are a crucial task that concerns people's lives. Therefore, the handling department, clinical technicians, and engineering skilled personnel should pay attention to them, and there should be corresponding handling organizations and cross unit academic organizations to practice, exchange experiences, and improve academic level. The United States began using Biomedical Equipment Technicians to handle medical equipment several decades ago. In Japan, clinical engineering technicians are responsible for this task, and the organization is standardized from national level to local hospitals, with lively academic activities. Although most hospitals in China have medical equipment departments and engineering skilled personnel responsible for repair and maintenance, they are currently in a situation of fighting alone.
With the development of scientific skills, a variety of high-tech equipment has been applied in clinical practice. Therefore, establishing and improving a sophisticated and capable medical equipment handling and repair team is a very urgent mission.

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