The physiological and clinical considerations of centrifugal and axial pumps as ven- tricular assist devices (VADs) demands limitations on the power, size and geometry of the impellers. A typical pump design method is to rely on the characteristics of previously designed pumps with known performance using empirical equations and nondimensional parameters based on uid dynamics similarity law. Such data are widely available for industrial pumps operating in Reynolds number region of 108. VADs operate in Re < 106 and therefore the similarity concept does not apply between the industrial diagrams and the medical application of small pumps. The present dissertation employs a parametric approached analytical model to in- vestigate more than 150 axial and centrifugal pumps. The design parameters are optimised using the response surface methodology. The effect of different design parameters on the performance, force analysis and hemocompatibility of the pumps is thoroughly investigated by modelling the haemolysis through a power-law equation. The results show an explicit and consistent relationship between the number of blades, outlet width, outlet angle and the hemocompatibility of the device. Centrifu- gal pumps showed signi cantly lower probability of blood complications compared to axial pumps. The evaluation of the design characteristics helps pump designers to select their parameters accordingly for a low probability of blood complications. Furthermore, experimental techniques are employed to test more than 70 pumps in different conditions of flow, pressure and rotational speed. The experimental results validate the numerical simulations and create a database of empirical equations and data points for small axial and centrifugal pumps. The specifi c speed and speci fic diameters of the pumps are plotted on an ns − ds diagram to enable preliminary design of small pumps for VADs suitable for different stages of congestive heart failure (CHF).

Heart failure (HF) affects an estimated 5.8 million Americans, accounting for near 250,000 deaths each year. With shortages in available donor hearts, mechanical circulatory support (MCS) has emerged as a life-saving treatment for advanced stage HF. With growth in MCS use, a clinical and developmental need has emerged for a standard characterization and evaluation platform that may be utilized for inter-device comparison and system training. The goal of this research was to harness SynCardia's total artificial heart (TAH) to meet this need. We first sought to characterize the TAH in modern physiological terms - i.e. hemodynamics and pressure-volume loops. We then developed a model of HF using the TAH and mock circulatory system operating in a reduced output mode. We demonstrated that MCS devices could be incorporated and evaluated within the HF model. Finally, we characterized the operational envelope of SynCardia's Freedom (portable), Driver operating against varying loading conditions. Our results describe the hemodynamic envelope of the TAH. Uniquely, the TAH was found not to operate with time-varying elastance, to be insensitive to variations in afterload up to at least 135 mmHg mean aortic pressure, and exhibit Starling-like behavior. After transitioning the setup to mimic heart failure conditions, left atrial pressure and left ventricular pressure were noted to be elevated, aortic flow was reduced, sensitivity to afterload was increased, and Starling-like behavior was blunted, consistent with human heart failure. The system was then configured to allow ready addition of ventricular assist devices, which upon placement in the flow circuit resulted in restoration of hemodynamics to normal. Lastly, we demonstrated that the Freedom Driver is capable of overcoming systolic pressures of 200 mmHg as an upper driving limit. Understanding the physiology and hemodynamics of MCS devices is vital for proper use, future device development, and operator training. Characterization of the TAH affords insight into the functional parameters that govern artificial heart behavior providing perspective on differences compared to the human heart. The use of the system as a heart failure model has the potential to serve as a valuable research and teaching tool to foster safe MCS device use.

Mechanical Circulatory Support (MCS) improves the health-related quality of life (HRQOL) for patients with end-stage heart failure (HF) (Friedrich & Bohm, 2007). Religious and spiritual practices positively influence health and well-being for cardiac patients (Ai, Park, Huang, Rodgers, & Tice, 2007; Blackhall, & Koenig, 1998). The purpose of this study was to examine the impact of spiritual well-being (SWB) and religious well-being (RWB) and coping styles and methods (CSM) on health related quality of life (HRQOL) of patients with MCS. This exploratory repeated measures study used Spearmans’ rho and Wilcoxons’ Signed Rank tests for correlation and comparison analyses. The study population included patients with left ventricular assist devices (HMII) and total artificial hearts (TAH). Patients were assessed pre and post MCS implant. Patients reported an increase in the use of faith practices for coping (prayer and meditation), providing evidence for spiritual growth after MCS. SWB, RWB, and CSM, and their corresponding subscales were positively related to HRQOL revealing medium to large correlation coefficients and variances. Post MCS, the TAH patients’ mean scores decreased for SWB and RWB (religious comfort) and increased for RWB (religious strain), indicating some spiritual distress. The internal locus of control for TAH patients increased with significance. HMII patients reported a significant increase in adaptive coping and “God” locus of control. The results suggest that early spiritual assessment with MCS patients may promote more timely and effective responses to maladaptive and dysfunctional coping. Patients who use their faith to cope (in distress or not) may also benefit from an increase in emotional and spiritual attention. Spiritual care providers who are knowledgeable about the MCS assessment, surgery, and recovery process could then provide interventions that build resilience and mediate improved outcomes through supportive and directed counseling. The results of this study inform the future development of interdisciplinary plans of spiritual and emotional care for this patient population and for other chronic illness populations. Further examination may reveal how SWB, RWB and CSM improve HRQOL as well as highlight the unique support needs of HMII and TAH patients.

No description available.