- Title
- On the automated monitoring and control of extracorporeal membrane oxygenation
- Author
- Kazdan, David
- Degree
- Doctor of Philosophy, Case Western Reserve University,
Biomedical Engineering, 1992.
- Advisor
- Kenneth A. Loparo
- Pages
- 230p.
- Abstract
- Extracorporeal membrane oxygenation (ECMO) is a well-established cardiopulmonary support technique, used most frequently intraoperatively (short-term) and in the neonatal intensive care unit setting (for up to two weeks). The device serves as an artificial lung outside the body, separating a flowing blood phase from a flowing gas phase by an O2 and CO2 permeable membrane, dialyzing oxygen into the blood and carbon dioxide out. Blood is usually moved through the device by a pump placed between the venous cannula and the ECMO dialyzer. ECMO units are prone to degradation of gas transfer performance over time. These changes are due to blood protein deposition on the membrane, sticking or waterlogged areas, and so on. Previously published methods for monitoring such degradation are clinically unwieldy, depending on measurements of oxyhemoglobin saturation and therefore working only when the ECMO-outlet blood is desaturated. A quality-monitoring method is presented here which uses inlet and outlet oxygen tension measurements to compute continuously a figure of merit corresponding to membrane diffusivity, even when the device is being operated in a condition of outlet oxyhemoglobin saturation. The method uses a parameter estimation from a one-dimensional ECMO oxyg en transfer model, which is derived here. Numerical simulations and laboratory experiments on a mockup ECMO are presented. This monitoring method is intended to assist in timely ECMO changes during long-term therapy, reducing the need for emergent changes and minimizing patient time spent on undercapacity units. Acid/base chemistry control of the ECMO patient is also examined. A gain-scheduled, "principle-based" but model-independent controller is developed which uses a forward-computable, two-input, two-output control of either arterial or venous oxygen saturation and pH. The controller uses minimally invasive sensors (none in an oxygen-only control form) and is adaptable to current hardware. Variations in control strategy of some special blood chemistry pathologies and the use of the controller in automatic therapy logging are discussed. Simulations are presented using developed circulation models of patients with venoarterial and arteriovenous ECMO; they indicate adequate response times and noise insensitivity over a wide range of plant and controller parameters. Experimental examination of control is discussed
- Subject Headings
- Engineering, Biomedical
- Keywords
- Extracorporeal membrane oxygenation (ECMO),; monitoring
Document number: case1060019332.
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