Browsing by Author "Rodriguez, Reynaldo Adrian"
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- ItemRedesign and performance evaluation of a cardiac pulse duplicator(Stellenbosch : Stellenbosch University, 2017-12) Rodriguez, Reynaldo Adrian; Muller, Jacobus Hendrik; Dellimore, Kiran Hamilton; Stellenbosch University. Faculty of Engineering. Dept. of Mechanical and Mechatronic Engineering.ENGLISH ABSTRACT: The worldwide demand for prosthetic heart valve (PHV) replacements is increasing rapidly. Although developing countries have the largest demand due to the high incidence of rheumatic heart disease, the mismatch between the available resources and the cost of PHVs often renders them inaccessible in these locations. This raises the need for lower cost PHVs which calls for reduced development costs. A cardiac pulse duplicator (CPD) plays a crucial role in the PHV design process and CPDs built in-house can represent large savings over commercial alternatives. However, they are complex devices and without the appropriate level of expertise their development can result in a time consuming, expensive process which offsets any benefits derived from building it in-house. This thesis documents the redevelopment of a PHV testing device and the methods used to evaluate its performance, providing guidelines to assist those interested in developing a CPD. This was also done to enable the Biomedical Engineering Research Group at Stellenbosch University to test, in accordance to the ISO5840 standard, the PHV it developed. A literature survey confirmed the increasing importance of CPDs in PHV development and in a variety of other cardiovascular research topics but also indicated that there are no established guidelines to quantify or directly assess a CPD’s performance. Due to the difficulty of distinguishing between the hydrodynamic performance of the PHV and that of the device used to test it, the standardisation of methods to assess the performance of CPDs is proposed. The concept of fidelity is presented as a first step towards a means of quantifying CPD performance which can improve the quality of PHV test data. A high performance system was designed and implemented to control the motion of the pump used to generate pulsatile flow. Various other aspects of the CPD were designed and implemented or manufactured. This included control, acquisition and analysis software as well as a number of connected hydraulic elements making up a flexible platform for testing PHVs. Rigorous tests were devised to assess the performance of the CPD’s control system. Commercially available PHVs were tested to evaluate the electrical and hydrodynamic performance of the CPD. To compare the overall performance of the CPD to that of a widely cited counterpart, further tests were carried out so that the results obtained could be compared directly against those found in the literature. Analysis of the results showed the control system to be highly dynamic, accurate (0.019 ±0.006 mm deviation from setpoint at 70 bpm) and repeatable (2.426 ±1.335 mmHg RMSE cycle-to-cycle). The hydrodynamic performance achieved with the hydraulic components that were designed was satisfactory. The measured pressure data showed good agreement with published data for the available reference PHV, although some deviations were noted. These deviations were used to investigate some phenomena that ought to be taken into consideration during the design phase of CPDs. Some shortcomings present in the final implementation of the CPD were identified and recommendations made to address them. Despite its limitations and a cost of R 160 951, the CPD offers similar performance to a commercial system eight times this cost.