Development and Implementation of a DSP Based Air Detector System to Prevent Embolism During Hemodialysis Therapy

This thesis describes the design of a DSP based air detector system to prevent air embolism during Hemodialysis, which is a treatment option for kidney failure disease. Hemodialysis consists of removing blood from the body, filtering and treating the blood to remove toxic substances such as wastes and fluids, reestablishing proper chemical levels in the blood and returning the processed blood to the body. The functions of hemodialysis are performed through the use of a dialyzer, which is also known as an artificial kidney. During hemodialysis small air bubbles may infiltrate the tubing used during the therapy and combine to form larger air bubbles that are harmful to the patient. If an air bubble is large enough and enters the patient\u27s circulatory system, the blood flow can be blocked and the patient can die by embolism. Most of the hemodialysis instruments in use today are equipped with air detection systems, which are based on analog design and digital microcontroll ers. This thesis presents a design method based strictly on DSP technology. The Motorola DSP 56824EVM was considered suitable for this biomedical application since its performance parameters include high-speed, multi-signal control capability, reliability and stability. These performance parameters are considered to be the most important when designing biomedical instruments dealing with human beings\u27 life and safety. The objective of this research was the development and implementation of a DSP algorithm for the detection and measurement of the sizes of air bubbles in a fluid. In addition the algorithm had to possess the capability, when appropriate, to initiate protective and awareness measures such as triggering a tube clamp as well as activating visual and audio alarms. The air detection was accomplished by means of a commercial air detector module, which was based on piezo ceramic and ultrasound sensing. The function of the tubing clamp was to stop the fluid flow in the tubing and prevent an air bubble from entering the patient\u27s circulatory system. A secondary goal of this research was to exploit the capability of the DSP 56824EVM and demonstrate its suitability for biomedical applications