A Concept for Direct Control of Rotary Blood Pump Speed by Inlet Pressure

Heart failure remains a major health problem for the world. Heart transplantation is the most effective treatment for end stage heart failure. A major problem with heart transplantation is finding adequate numbers of appropriate donors. The lack of donor numbers in the world creates a significant clinical need for blood pumping devices. The ability of ventricular assist devices to relieve the consequences of less than terminal heart failure further creates a need for assist therapy. Current new ventricular assist devices are built around continuous flow technology. These nonpulsatile assist devices have had major clinical success in relieving symptoms and increasing patient survival. However they have a control issue as opposed the first generation pulsatile Ventricular Assist Devices (VADs) in that their output is sensitive to pressure difference, not primarily to inlet pressure. We have developed a rotodynamic blood pump speed management concept that results in a pump that responds to inlet pressure in a Starling law-like manner without active electronic controls or pressure sensors. The long term goal of this project is to develop a VAD system which responds as the natural human heart does. The pump speed is controlled by an adjunct electromechanical inlet conduit. The inlet conduit has 2 integrated cylinders. The inner cylinder is the blood flow pathway, and is flexible in order to expand/collapse in response to inlet blood pressure. The outer cylinder is used as the coil of a tank circuit. There is also a ferrofluid reservoir which is connected to the space between the 2 cylinders. The majority of ferrofluid is in the reservoir when inlet pressure is high, but ferrofluid flows into the core of the coil when inlet pressure is low. The inductance of the coil varies in response to the volume of the ferrofluid within the core. Therefore the natural frequency of the tank circuit varies and the impedance of the tank circuit changes. The control circuit is connected in series with the motor leads. Thus the voltag

A Concept for Direct Control of Rotary Blood Pump Speed by Inlet Pressure

Heart failure remains a major health problem for the world. Heart transplantation is the most effective treatment for end stage heart failure. A major problem with heart transplantation is finding adequate numbers of appropriate donors. The lack of donor numbers in the world creates a significant clinical need for blood pumping devices. The ability of ventricular assist devices to relieve the consequences of less than terminal heart failure further creates a need for assist therapy. Current new ventricular assist devices are built around continuous flow technology. These nonpulsatile assist devices have had major clinical success in relieving symptoms and increasing patient survival. However they have a control issue as opposed the first generation pulsatile Ventricular Assist Devices (VADs) in that their output is sensitive to pressure difference, not primarily to inlet pressure. We have developed a rotodynamic blood pump speed management concept that results in a pump that responds to inlet pressure in a Starling law-like manner without active electronic controls or pressure sensors. The long term goal of this project is to develop a VAD system which responds as the natural human heart does. The pump speed is controlled by an adjunct electromechanical inlet conduit. The inlet conduit has 2 integrated cylinders. The inner cylinder is the blood flow pathway, and is flexible in order to expand/collapse in response to inlet blood pressure. The outer cylinder is used as the coil of a tank circuit. There is also a ferrofluid reservoir which is connected to the space between the 2 cylinders. The majority of ferrofluid is in the reservoir when inlet pressure is high, but ferrofluid flows into the core of the coil when inlet pressure is low. The inductance of the coil varies in response to the volume of the ferrofluid within the core. Therefore the natural frequency of the tank circuit varies and the impedance of the tank circuit changes. The control circuit is connected in series with the motor leads. Thus the voltag

The potential of a tesla type device as a non pulsatile blood pump

A review of the published work on pumps designed to assist a failing biological heart has been made and discusses the different types of pump presently on the market with the characteristics of each. The materials used to make these pumps are also discussed, together with some of the methods of output control. The application to the patient is described together with the advantages and disadvantages. A Tesla type pump appeared to offer an alternative solution to those problems listed above. This is not a new design but appeared to offer advantages if applied to the application of pumping blood from outside the body. One of these was that at a constant speed, the pump supplied constant fluid pressure irrespective of the delivery. It also appears that the pump can give fluid shear stress levels that are less than the amount that will seriously damage blood components. A prototype pump has been built and tested. The pump achieved the performance target delivery of 10 I/min at a differential pressure of 200 mm Hg. This was considered to be greater than the average performance produced by existing blood pumps but the maximum performance that could be produced by the human heart under extreme conditions. The pump reached a maximum speed of about 4000 rev/min with a maximum power consumption of about 120 Watts. The results indicate that this type of pump is a potential blood pump in terms of the delivery and pressures achieved. The characteristic performance figures are within the envelope of published theoretical results. The pump tested here needs further development to improve the hydraulic performance. Recommendations are made for the direction of future work to improve the pump efficiency and flow patterns, biocompatibility and methods of production. Controls and power supply also need improvement

Study of a bi-directional axial flow blood pump

This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.A common treatment for circulatory disorders is the application of rotary blood pumps to locally increase blood flow to required levels. Existing devices tend to support flow from inlet to outlet and in that direction only. This thesis presents a bi-directional pump that may enable ventricle assist devices (VAD) to support blood flow to the organs during systole, when rotating in one direction, and to increase coronary perfusion during diastole, when rotating in the other. For each flow direction blade profiles were designed and tested for performance. Both designs were merged to obtain a symmetric profile to provide flow support in both directions. This initial bi-directional design was optimised using computational fluid dynamics modelling. The model was set to accelerate to a maximum forward rotational speed of 8,000 rpm, change rotational direction after 300 ms and accelerate to 2,400 rpm whilst rotating backwards. Experimental testing was carried out to validate the computational results. In the forward direction, the pump was predicted to deliver 39 cm3 compared to 19 cm3 in the backward direction. Pressure heads reached maxima of 2.2 kPa in forward and 0.16 kPa in backward direction. Analysis of wall shear stress profiles at the blades’ surface showed that the maximum was 140 Pa lasting less than 300 ms in the forward direction, whilst in the backward direction this was approximately 23 Pa lasting for 700 ms. A design for the bi-directional blades is established and characterised computationally and experimentally. Analysis of the blade pressure profiles confirmed generation of pressure rise in both directions. The computational results for wall shear stress were predicted to be below the accepted limits of haemolysis. Recirculation zones were found at the outlet in the backward rotating direction. Future work may reduce those by using guide vanes at either side of the rotor

Design and development of a pulsatile axial flow blood pump as a left ventricular assist device

This thesis was submitted for the award of Doctor of Philosophy and was awarded by Brunel University LondonEach year all over the world, Millions of patients from infants to adults are diagnosed with heart failure. A limited number of donor hearts available for these patients results in a tremendous demand of mechanical circulatory support (MCS) system, either in the form of total artificial heart (TAH) or a ventricular assist device (VAD). Physiologically MCS are expected to provide heart; a time to rest and potential recovery by unloading the ventricle, while maintaining the adequate peripheral as well as coronary circulation. Existing ventricular assist devices (VAD) have employed either displacement type pulsatile flow pumping systems or continuous flow type centrifugal/rotodynamic pumps systems. Displacement type devices produce a pulsatile outflow, which has significant benefits on vital organ function and end organ recovery. Continuous flow devices are small and can be placed within body using minimal invasive procedures, in addition they reduces infection as well as mechanical failure related complications. Despite availability of success stories for both types of pumping systems, the selection of the either of them is an ongoing debate. This thesis aims to merge the advantages of displacement pumps (pulsatile flow) and axial-flow pumps (continuous flow) into a novel left vertical assist device (LVAD), by designing a novel minimal invasive, miniature axial-flow pump producing pulsating outflow for the patients having early heart failure and myocardial infarction as a Bridge-To-Recovery (BTR) or Bridge-To-Decision (BTD) device. The design of VAD, the experimental setup and dedicated control system were developed for the in vitro evaluation of pulsatile flow. Computational fluid dynamics (CFD) had been employed for the detail investigation of pulsatile flow. In addition, CFD was also applied to optimize the pulse generation for low haemolysis levels. Outcome of the study produces comprehensive understanding for the generation of pulsatile flow using an axial flow pump. Further, it provides the means of generating a controlled pulse that can regulate flow rate for varying heart rate within low haemolysis levels

Flow Visualization Studies in the Novacor Left Ventricular Assist System CRADA PC91-002, Final Report

This paper discusses a series of experiments to visualize and measure flow fields in the Novacor left ventricular assist system (LVAS). The experiments utilize a multiple exposure, optical imaging technique called fluorescent image tracking velocimetry (FITV) to hack the motion of small, neutrally-buoyant particles in a flowing fluid