Electrical and Electronic Engineering - Theses
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ItemComprehensive circulatory management of seriously ill patients with a closed-loop system( 1989)The objective of this project was to develop a closed-loop computer system to assist intensive care staff manage multiple drug and fluid infusions for the treatment of seriously ill patients with circulatory failure. The system was to be designed specifically for clinical application, forming an integral part of an intensive care system. The treatment of circulatory failure can present a complex management problem with the need for multiple, concurrently administered drug and fluid infusions. Hence a major part of this work involved the design of the control algorithm which determines the infusion to be adjusted, the amount it needs to be adjusted and the timing of the adjustment. The design of the algorithm is complicated by the range of circulatory responses to an adjustment of a drug infusion. In addition, there is currently no reliable means of continuously monitoring important haemodynamic variables such as cardiac output and pulmonary artery wedge pressure. It was therefore deemed appropriate to prepare a multivariable control strategy based on the control actions of clinical staff using expert system techniques. This required interaction with skilled clinical staff to identify general rules which they use when managing drug and fluid infusions for patients in shock. The practical implementation of this computer system required specific attention to patient safety and user interface. Therefore the architecture of the developed system contains a safety net to ensure a safe recovery path for all possible alarm conditions. All displayed information including alarm and advisory messages are presented in a clear and concise format. The trials of this computer system were set in stages to validate the system's knowledge base and to promote the progressive evolution of the system architecture. At first the computer system operated as a multi variable monitoring station. The knowledge base was embedded in the system architecture. Advisory modes of operation were implemented to assist in the validation of the knowledge base. The final and desired mode of operation automated the adjustment of multiple concurrently administered drug and fluid infusions. Progress through these development phases was facilitated by the analysis of data recorded by the system. Initial clinical trials have demonstrated the clinical utility of this system. In addition, the system reliably produced stable closed-loop control under difficult management conditions. Therefore the contribution of this study is a closed-loop computer system which satisfies the initial objective. Ample scope exists for the continued development of this system. Insights gained through its continued use will contribute to its refinement. New intensive care equipment can be incorporated into the system. This will see the system develop in sophistication and versatility.