A motor-driven artificial pump and its transcutaneous energy transmission (TET) system are discussed. The artificial pump consists of a high-speed DC brushless motor driving a ball screw and magnetic coupling mechanism between the blood pump and ball screw. The ball screw transfers high-speed rotary motion into low-speed rectilinear motion by a single component. Magnetic coupling enables active blood filling without applying an excess negative pressure to the pump. The transcutaneous transformer is formed from a pair of concave/convex ferrite cores. This design minimizes lateral motion of the external core. Information on motor voltage is transmitted through the skin by infrared pulses. The motor voltage is regulated by controlling the duty ratio of the square pulse supplied to the primary coil. Pump flow of 5.6 l/min was obtained with a mean outlet pressure of 100 mm Hg at a drive rate of 100 b.p.m. under preload of 15 mm Hg. >

Development of an implantable motor-driven assist pump system

https://digitalcommons.lsu.edu/cgi/viewcontent.cgi?article=5019&context=gradschool_dissertations

Bio-implantable microdevices and structures for functional electrical stimulation applications

Recent years have seen a huge increase in the number and scope of therapeutic procedures involving mechanical devices and the heart. Diseases of the heart which can now be treated using devices fall into four categories: valvular disease, abnormalities of cardiac innervation, congenital malformations and myocardial disease.

The Pathology of Artificial Hearts and Ventricular Assist Devices

This dissertation describes the development of microstructures and devices for applications in functional electrical stimulation. A nerve cuff electrode design has been developed for applications in neural electrical stimulation and recording, which addresses limitations with existing cuff electrodes. The developed clip-on micro-cuff electrode design consists of a naturally closed cuff with inner diameter in the micro-scale or above. A novel pinch-hinge feature allows a user to easily open the cuff and place it on target nerve tissue for stimulation or recording purposes. Upon release of the pinch-hinge, the cuff assumes its normally closed nature. The device conducts and reads electrical signals in the amplitude and frequency range of typical neural signals. A typical clip-on cuff device with 800 µm inner diameter is opened to its maximum extent by a relatively low force of less than 0.8 N, offering an alternative to other designs requiring application of a force for cuff closure. For applications involving gastric muscle stimulation, a novel gastric pacing electrode is fabricated in biocompatible silicone elastomer. In response to physiological temperature of about 37 ˚C, polyethylene glycol embedded inside the device body melts due to which the structure changes from a more rigid state initially to a more flexible state. This is expected to reduce tissue penetration during and after electrode implantation. A comprehensive piece-wise discrete element equivalent circuit model has been developed to represent an electrode-neural tissue interface. This model addresses internal aspects of both the tissue and the electrode surface and is an improvement over previous models. The equivalent circuit is employed in conjunction with electronic circuit simulation software to study the electrical response of an axon to external stimulus. Simulation results broadly correlate with practical observations reported by others. Lastly, a new percutaneous access device functioning as an interface between implants and the external world is reported here. The device made of silicone elastomer incorporates stress concentration features and shows promise for improved robustness and reliability. The device also incorporates micro-scale porous structures to allow for tissue in-growth to facilitate anchoring of the device. 

The Pathology of Artificial Joints.- Pathology of Injected Polytetrafluoroethylene.- The Pathology of Bioprosthetic Heart Valves and Allografts.- Mechanical and Other Problems of Artificial Valves.- The Pathology of Artificial Hearts and Ventricular Assist Devices.- Pathology of Cardiac Pacemakers and Central Catheters.- The Pathology of Vascular Grafts.- The Pathology of Intra-uterine Contraceptive Devices.

The Pathology of devices

Vegetative endocarditis and thromboembolism are the two leading pathologic findings and causes of death in calves receiving total artificial hearts (TAH). Percutaneous access devices (PAD) for the pneumatic drive lines often become infected and may serve as the nidus of infection of the vegetative lesions. Observations of 80 calves living with TAHs revealed that most infections began at the dorsal surface of the PAD. Chronic skin ulceration or acute, traumatic avulsion can result in PAD separation from the skin and bacterial implantation. Evaluation of 58 necropsy specimens from calves with TAHs demonstrated improper flange positioning in 76% of the PAD and gross infection in 57%. A new implantation technique and design of PAD have resulted in better flange position and less irritation at the skin/device interface. Necropsies of 11 animals with the new PAD have shown a reduction in superficial infections.

Percutaneous Access Devices in Calves Receiving an Artificial Heart

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Percutaneous Access Devices in Calves Receiving an Artificial Heart