What is a Heart Lung Machine?

The artificial heart-lung machine is also called extracorporeal circulation device, which is composed of oxygenator, blood pump and auxiliary equipment. It extracts venous blood from the venous system, performs oxygenation in vitro, and then returns the oxygenated blood to the arterial system through a blood pump to achieve cardiopulmonary bypass. It is mainly used for cardiopulmonary bypass, assisted breathing of lung transplantation, macrovascular surgery and adjuvant treatment of acute respiratory failure.

The artificial heart-lung machine is also called extracorporeal circulation device, which is composed of oxygenator, blood pump and auxiliary equipment. It extracts venous blood from the venous system, performs oxygenation in vitro, and then returns the oxygenated blood to the arterial system through a blood pump to achieve cardiopulmonary bypass. It is mainly used for cardiopulmonary bypass, assisted breathing of lung transplantation, macrovascular surgery and adjuvant treatment of acute respiratory failure.

Chinese name

Artificial heart lung machine

Foreign name

ArtificialCardiopulmonary Machine

Management category

Class III

Category Name

Artificial cardiopulmonary equipment

Structure and principle of artificial heart-lung machine

Artificial heart-lung machine is when the heart patient undergoes surgery, the patient's heart and lungs stop working. The artificial heart (blood pump) and artificial lung (oxygenator) are used to replace the normal heart and lung work to maintain the patient and vital signs stable. The transition equipment belongs to Class III medical devices ^[1] . The principle is to insert the inferior vena cava or right atrium of the patient with a vena cava cannula. After the patient's blood is temperature-adjusted through a venous duct, it is drained into the artificial lung for oxygenation, so that the patient's venous blood becomes arterial blood, and then The artificial heart is pumped into the patient's arterial system to maintain the stability of the patient's blood circulation and internal environment, so that the tissues and organs of the human body are fully perfused to ensure the functions of the patient's various organs. At the same time, it provides a quiet, bloodless field for cardiac surgery ^[2] .

How an artificial heart-lung machine works

The structure of the heart-lung machine mainly includes the following parts ^[3] :

1. Oxygenator. The oxygenator is an important part of the heart-lung machine. Its main function is to exchange gas, so that carbon dioxide is expelled during the oxygen contraction of the blood, temporarily replacing the function of the human lung. The conditions that a high-quality oxygenator should meet are: ideal oxygenation of blood and carbon dioxide emission, good temperature change effect, small precharge, light blood destruction, small transmembrane pressure difference, convenient operation, and easy exhaust.

2. Blood pump. A heart-lung machine usually has 4 to 5 blood pumps. The requirements for the blood pump are: the function of each pump head is single, one of which replaces the ventricular stroke function of the main pump, and the other pump heads are used for blood respiration, ventricular decompression and exhaustion in the surgical field during surgery, and the heart. Perfusion of cardioplegic fluid, etc .; can perform stepless speed regulation, large flow adjustment range, high accuracy, and satisfactory results can be obtained in the adjustment of very small flow; constant stroke volume, will not affect the flow due to changes in vascular resistance of the body And always maintain one-way flow; the damage to the blood is slight in a certain period of time; the console is simple to operate and has a backup emergency system.

3. Micro plug filter. Artificial heart-lung machines produce small solid or gas emboli during extracorporeal circulation, which may block blood vessels and damage tissues and organs, especially the brain and lungs. Therefore, filter devices such as blood filters, gas filters, and leukocyte filters must be used during extracorporeal circulation.

4. Thermostat: Used for the rise and fall of the patient's body temperature during cardiopulmonary bypass and the temperature change of the cardiac arrest fluid.

5. Tubing and intubation. In extracorporeal circulation surgery, the appropriate tube type and intubation radius are selected according to the weight and condition of the patient. Requirements for pipes and intubations: good transparency, moderate wall thickness, good elasticity and toughness, not easily deformed by the influence of temperature, smooth inner wall of the pipe, low blood flow resistance, stable chemical properties, non-toxic, Good blood compatibility. The main materials used are non-toxic polyvinyl chloride, silicone rubber, and polyurethane.

6. Vital signs monitoring device. These auxiliary devices can monitor patients' ECG, arteriovenous pressure, nasopharyngeal temperature, anus temperature, etc. during extracorporeal circulation, and have special software to record and print related data. Guide the management of extracorporeal circulation according to the monitoring results, such as: continuous arteriovenous blood oxygen saturation monitoring, activated whole blood coagulation time monitoring, blood gas electrolyte monitoring, and cerebral oxygen saturation monitoring.

Development history of artificial heart-lung machine

The development of artificial heart-lung machines is roughly divided into three stages ^[4] .

The first stage was the stage of exploration and formation from the early 19th century to the early 20th century. The earliest Le Gallceis substitutes the heart for arterial blood injection, and allows all parts of the body to survive, building the foundation of modern extracorporeal circulation.

In 1868, Ludwig et al. Oscillated defibrinated blood without increasing oxygen in the air, relying on this blood to study muscle metabolism. The effects of hypoxia in blood on metabolism were explored.

In 1882 Schroder delivered air to the blood bank, creating air bubbles to increase the oxygen in the blood, and this was the beginning of artificial heart and lungs.

In 1895, the world's first artificial heart (blood pump) appeared as a two-plate compressed rubber ball.

In 1915, Richards et al. Hung the cloth under a glass tube with many small holes, and developed an artificial lung called a barrier type.

The second phase was the early experimental phase from 1915 to 1953. During this period, more than 30 forms of artificial heart (blood pump) and more than 10 artificial lungs (oxygenator) have appeared. Gibbon first combined a blood pump and an oxygenator in 1937 to form an artificial heart-lung machine.

The third stage is the development and improvement stage after 1953. In 1953, Gibbon used a barrier oxygenator to perform an open-heart cardiopulmonary repair operation for an 18-year-old girl and achieved success, which opened the prelude to the development of an artificial heart-lung machine.

China began the development of artificial heart-lung machines in 1956, and Shanghai Type and artificial heart-lung machines were produced by Shanghai Medical Equipment Factory. In June 1958, the Fourth Military Medical University performed an open-loop repair of ventricular septal defect for a 6-year-old boy with extracorporeal circulation and achieved a complete success. In July, Shanghai Thoracic Surgery Hospital used a domestic artificial heart-lung machine for a 9-year-old girl. Open heart surgery has also been successful, beginning a new period of clinical use of artificial heart and lungs in China.

Artificial heart-lung machine extended reading

[1] Fan Xiang, Wan Yiyi. Interpretation and prospect of the main standard clauses of GB 12260-2005 "Rolling blood pump for artificial heart-lung machine" [J]. Medical Equipment, 2017, 30 (14): 48-49.

[2] He Tianfu. Artificial Heart-Lung Machine and Prospect [J]. Guangdong Medical Journal. 1982, (10): 39-41.

[3] Zhang Luo. Research on artificial heart-lung machine design [D]. Beijing University of Technology, 2016.

[4] Zhang Quanfu, Wei Jingyi. Management of artificial heart-lung machine and prevention of accidents [J]. Jiangsu Medicine, 1988 (4).

[5] Tang Chengzuo, Fan Qingfu. Artificial Heart-Lung Machine [J]. Shanghai Biomedical Engineering. 2006, (27): 247-249.