| Ventricular assist device (VAD) is a set of apparatus used to assist the failing heart and reestablish normal circulation. Blood pump is the core component of VAD. With the development of heart surgery, different kinds of blood pumps came into being. As there are few domestic research work on blood pump, we together with Xi'an Jiao Tong university designed and made this small disposable pushing-plate pump driven by electromagnetic power. The homodynamic characteristics of this pump were also tested in mock experimental table. The results show the principle of this electromagnetic pushing-plate pump is practicable; the blood pump functions well and can provide sufficient volume and pressure to meet physiological need; the control system is simple and easy to maneuver; it can also achieve disposable use. The study includes two parts: Part I Design of the electromagnetic blood pump The whole system: The whole system of this electromagnetic pushing-plate pump is composed of 3 parts: the control system. the main body of the pump and drainage tracts. Through control system, we can adjust the working voltage and frequency, thus alters the volume. The main body of the pump is connected with drainage tracts so we can test the homodynamic characteristics of it in mock experimental table. Internal structure of the pump The body of the blood pump is made of stainless steel, while the wave propagation pipe is made of medical plastics. There are springs surrounding the pipe to add stability and flexibility. In both sides of the pipe there is a heart valve. 8y pushing-plate the magnetic motor connects with the body of blood pump, and between them are holders. The inner parts of the blood pump which may future contact blood are made from stainless steel, valves etc, which have good biocompatibility. The main body of the blood pump is 35 cm long, and the diameter of the inlet and outlet tract are 1.2 cm. Control system The control system consists 5 parts: the power, fixed control software, driving circuit, adverse circuit, and the control panel. The 24v DC power (transformed from 220v alternating current) is adopted. Control software is fixed into the main board of the system. Through driving circuit and adverse circuit, signals are transmitted to the coils, thus adjusting the working voltage and frequency. There are 4 basic buttons on the control panel charging different frequency: 0.2. 4. 20 30 Hz. Also there are 3 buttons in charge of the adjustment of the voltage. Principle of the blood pump The blood pump adopts oscillating motor as its driven source. The motor contains moving coils and closed magnetic field. When alternating electric currents pass through the coils, they periodically vibrate at a certain balanced place. thus the WPPs are pressed, resulting in the pressure alteration inside. Because of the two fixed heart valves. only unidirectional flow is allowed. thus the whole device functions as a pump. Test of the blood pump without load Using oscillometer to test the blood pump without load. Examining the wave shape of different working frequency (0.2. 4. 20 Hz). Results show this oscillating motor can output 0.2.. 4.. 20.. 30 Hz current as formerly designed. and the working voltage is adjustable from 5% to 4500 at each frequency; The whole control system functions well and has good practicability. |
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