Development of an intravenous oxygenator

[摘要] ENGLISH ABSTRACT: Patients in critical care with lung injuries need to be assisted with regards to breathing function, but current methods are not applicable for all situations. The most common method, Extracorporeal Membrane Oxygenation (ECMO) is an expensive procedure and requires trained staff to operate the equipment at all times. Lung injury may lead to the inability of the lungs to be perfused and the blood oxygenated by tracheal intubation, whereas mechanical ventilators can injure the lungs further. Especially at risk are preterm neonates, where congenital disorders or complications during birth render ECMO the only viable option. Respiratory Assist Catheters (RACs) could be used as an alternative because they do not place extra stress on the lungs, are easy to implement, cost-effective and are available for immediate use in clinical settings or in first aid situations. The development of such a device requires knowledge of possible oxygenation methods as well as the risks involved in implementing such a device. The possibility of oxygenating the blood via microbubbles by means of a RAC is promising due to the high gas transfer rates common in bubble oxygenators. It is the aim of this study to develop a prototype that could function as a RAC and to evaluate the feasibility of oxygenation by using microbubbles.The method used to design a prototype included selection of various materials and finalization of a design to be tested. The tests selected were in vivo tests and ex vivo tests using animal models to investigate the dissolution times of the microbubbles, as well as the physiological effects of an intravenously placed device. Measurements of oxygen saturation of the blood in arterial blood (SaO2), venous blood (SvO2) and pulmonary pressure allowed the oxygen transfer rates and risks involved to be evaluated, and also gave an indication regarding the formation dynamics of microbubbles in the blood. An in vitro test was also performed with the aim of determining the rate of dissolving of oxygen, and hence to give an indication regarding microbubble dissolution times. Mathematical simulations based on the dissolution rate of oxygen in venous blood confirmed the abovementioned results.The tests and simulations were analysed in order to evaluate the feasibility of intravenously oxygenating the blood using microbubbles. Approximate bubble dissolution times were an indicator of the feasibility of the concept and showed that very large bubble dissolution times renders intravenous bubble oxygenation unfeasible. These large dissolution times also lessen the possibility of implementing bubble oxygenation in an intravenous device.

[发布机构] Stellenbosch University