Development of a guidance and Intra-Arterial flow monitoring catheter

[摘要] ENGLISH ABSTRACT: This thesis entails the development and testing of devices that can aid inguiding a needle into a blood vessel. Furthermore, a concept flow meter isalso developed and tested. Physicians often have difficulty placing a needle inblood vessels. For a number of procedures access to blood vessels are required.Investigating methods to ease this process is thus beneficial to the medicalfield. Likewise, measuring blood flow is also of importance in the medicalfield. Measuring blood flow to the brain can prevent brain ischemia, whichcan lead to death of brain tissue.Near infrared (NIR) light is used to guide the needle towards a blood vessel.Two optic fibre strands are placed inside the needle, one to transmit NIR lightand one to receive reflected light. The reflected light, when pointing at blood,is different from other tissue types. The in vitro and in vivo tests both showedthat there is a statistically significant difference (p < 0.001) in reflected lightwhen pointing at and away from a blood vessel.Electrical impedance is used to determine when the needle enters a bloodvessel. A sine wave is generated and passed through biological tissue. Themeasured impedance is different for blood and other tissue types. It was foundthat when a signal of 29.85 kHz was used, there was a statistically significantdifference (p < 0.001) between blood and muscle and blood and fat.The flow meter works on the principle of thermal convection. The conceptdevice that is developed, has an ambient temperature sensor and a secondtemperature sensor wrapped in a heating coil. In the presence of fluid flow, heatis carried away from the heater by thermal convection, causing a temperaturedrop. The device was tested in vitro in distilled water flow and blood flow atflow rates between 0.1 ml/s and 0.45 ml/s. Both the fluids had high variancesin the temperature difference between the ambient and heater temperature. Byremoving the offsets, clear trends become visible. For the distilled water tests,a fit in the tested flow region was obtained with a coefficient of determinationof R2 = 0:9801. The blood tests however were more erratic and the best fitthat could be obtained had a coefficient of determination of R2 = 0:6056. Inboth cases however, CFD results indicate that this method is a viable methodif some of the flow meter design aspects are improved.The results indicate that a combination of the aforementioned technologiescan be used to guide a needle into a blood vessel and measure flow rate. Whilefurther investigation is required to make this a product in the medical practice,the investigation in this thesis serves as a basis for future clinical trials in thedevelopment of a guidance and intra-arterial flow monitoring catheter.

[发布机构] Stellenbosch University