Aim.To evaluate the functioning of an implantable pediatric axial pump «DON-3» for bypassing the left ventricle of the heart in experiments on sheep.Materials and methods. Five sheeps at the age of 12–18 months performed paracorporeal installation of the children’s axial pump «DON-3» according to the scheme «left ventricle – aorta».Results.A technique was developed and 5 chronic experiments were conducted on sheep to assess the model of the children’s axial pump «DON-3». The duration of the experiments in this series averaged 9 ± 5 days. The main indicators of hemodynamics, acid-base balance were within the norm. Conducted morphological and histological studies of the kidneys, liver and lungs did not reveal the presence of zones of ischemia and thromboembolism.Conclusion.The results of this series of experiments showed satisfactory results, suggesting further research on the development of prototypes of a pediatric pump for clinical practice.
Continuous-flow ventricular-assist devices are widely used to support patients with advanced heart failure, because continuous-flow ventricular-assist devices are more durable, have smaller sizes and have better survival rates for patients compared to the pulsatile-flow ventricular-assist devices. Nevertheless, continuous-flow ventricular-assist devices often cause complications such as gastrointestinal bleeding, haemorrhagic stroke, and aortic insufficiency and have a negative impact on the microcirculation for both long-time implantable and short-time extracorporeal systems. The aim of this study is the evaluation of the pulsatile-flow generation method in continuous-flow ventricular-assist device without pump speed changes. The method may be used for short-time extracorporeal continuous-flow mechanical circulatory support and long-time implantable mechanical circulatory support. A shunt with a controlled adjustable valve, that clamps periodically, is connected in parallel to the continuous-flow ventricular-assist device. We compared the continuous-flow ventricular-assist device operating with and without the shunt on the mock circulation loop. The continuous-flow ventricular-assist device–shunt system was connected according to the left ventricle–aorta circuit and worked in phase with the ventricle. Heart failure was simulated on the mock circulation circuit. Rotaflow (Maquet Inc.) was used as the continuous-flow pump. Haemolysis studies of the system for generating a pulse flow were carried out at a flow rate of 5 L/min and a pressure drop of 100 mm Hg. To compare the haemodynamic efficiency, we used the aortic pulsation index Ip, the equivalent energy pressure and the surplus haemodynamic energy. These indexes were higher in the pulsatile mode ( Ip – 4 times, equivalent energy pressure by 7.36% and surplus haemodynamic energy – 10 times), while haemolysis was the same. The normalised index of haemolysis was 0.0015 ± 0.001. The results demonstrate the efficiency of the pulsatile-flow generation method for continuous-flow ventricular-assist devices without impeller rotation rate changes.
The use of extracorporeal circulation systems (cardiopulmonary bypass pumps, ECMO) can lead to brain and coronary artery microembolism, which significantly reduces postoperative rehabilitation and often leads to severe complications. Microembolism occurs when oxygen or air microbubbles (MBs) enter the arterial system of patients. Existing CPB pumps come with built-in bubble trap systems but cannot remove bubbles in the circuit. ECMO devices have arterial filters but cannot reliably filter out <40 μm bubbles in a wide flow range. We have proposed an alternative method that involves the use of an efficient dynamic bubble trap (DBT) for both large and small bubbles. The design includes development of two DBT variants for hemodynamic conditions of adult and pediatric patients. The device is installed in the CPB pump and ECMO outlet lines. It provides sufficient bubble separation from the lines in a blood flow of 3.0–5.0 L/min for adults and 0.5–2.0 L/min for children. The developed computer models have shown that MBs smaller than 10 μm can be filtered. The use of this device will greatly reduce the likelihood of air embolism and provide the opportunity to reconsider the concept of expensive arterial filters.
A channel centrifugal pump has been developed which have calculated parameters during the nominal operating mode based on 3-dimensional computer simulation (flow rate 5 l/min, pressure drop 100 mm). In addition, pump’s operating conditions in ECMO mode are considered at high pressure drops of 200–300 mm Hg with a speed of rotor up to 3500 rpm. Simulation result was a creation of a new channel- type centrifugal pump with shear stress that do not exceed the allowable threshold of 150 Pa, and also minimizing stagnation and flow recirculation zones. The obtained data were also the result of use design of rotor with constant cross-section channels formed along a logarithmic curve and ensuring minimum turbulence due to the minimum outlet angle of the flow.
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