Features of Control and Formation of The Blood Flow of A Two-Chambered Pulsating Blood Pump by External Valves
Development of blood pumps, that are able to provide artificial circulation with the most approximate to the physiological parameters of blood circulation, is still relevant. However, recent studies show that pulsatile flow during cardiopulmonary bypass can prevent the development of unwanted complications. Used standard roller and centrifugal pumps are structurally laminar flow pumps and their use in pulsating mode is impractical. The volumetric pulsating blood pump created by us is recommended for use in perfusion systems for artificial blood circulation.
MATERIALS AND METHODS
The dual chamber blood pump is a hybrid of a roller pump, a ventricular assist device and a centrifugal pump. It lacks any moving parts in the blood stream, which excludes hemolysis. The volumetric blood pump consists of two rigid chambers and internal polyurethane blood bags with inlets and outlets. The rigid chambers are connected by a reversible roller pump that cycles pressurized inert fluid from one chamber to another. Accordingly, the blood bags alternately in antiphase are filled and emptied with blood. The inlets and outlets of the bags are equipped with four external electromechanical valves that switch automatically and ensure continuous blood circulation. The valves located on the output lines have the ability to operate in a pulsating mode by periodically clamping and releasing the arterial line by them. Software control makes it possible to arbitrarily adjust the percentage systole-diastolic ratio, pulsation frequency, and also place the systole pulse of the electromechanical valve between the R waves of the cardiogram. The mechanical part of the external valve consists of a body made of light metal (dimensions 5x3x8 cm), inside which there is a microservomotor that drives a piston that closes the vascular line.
RESULTS AND DISCUSSION
Bench tests have confirmed the simplicity and convenience of the location of external valves on the blood lines and the reliability of their operation under various load conditions:
• Pulsation from 10 to 300 beats/min;
• Possibility of synchronization by cardiogram;
• The possibility of displacement of the pulse of the beginning of the systole of the external valves;
• The ability to control the duration of systole.
A two-chambered blood pump with external valves was tested in six experiments on 30 kg anesthetized sheep. Two experiments each were performed on cardiopulmonary bypass, extracorporeal cardiopulmonary resuscitation, and "ex vivo" preservation of an isolated transplants, and the pump parameters were evaluated.In all cases, pulsatile perfusion was performed. Depending on the experimental model, the pulsation frequency was maintained within 60-100 BPM, flow rate of pump - from 80 ml/min to 150 ml/min, the temperature – 34-38O C. Under these conditions, almost all hemodynamic parameters remained within the physiological norms. In particular, the mean AP was 70 mmHg. with a systolic-diastolic gradient of 36 mmHg, CVP - 3 mmHg. and pressure in the portal vein - 8 mmHg.
Software control of external electronic-mechanical valves makes it possible to operate the two-chambered blood pump easily and simply, while creating optimal hemodynamic parameters that are as close as possible to physiological norms. Such pump can be successfully used for cardiopulmonary bypass in cardiac surgery, during extracorporeal cardiopulmonary resuscitation, as well as in the preservation of isolated organs.
Keywords - External Valve, Pulsatile Flow,Volumetric Blood Pump.