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Modellbasierte CO_2 Regelung für die Anästhesie


T. Geyer

no. 8840, Term Project at the Automatic Control Lab, ETH Zürich, WS 98/99.

During general anesthesia, the mechanical ventilation must be controlled continuously and adjusted in order to maintain a suitable arterial carbon dioxide tension ($P_{a_{CO_2}}$). Even though there exist recommendations for initial settings of the respiratory parameters to achieve a certain $P_{a_{CO_2}}$ it will usually be necessary to individually adjust these parameters during anesthesia for two reasons: First there is a broad variability among different individuals and it is not likely that the initial parameter settings will result in the exact desired $P_{a_{CO_2}}$. Secondly, physiological parameters such as carbon dioxide ($CO_2{}$) production and the ratio of alveolar ventilation to pulmonary diffusion may change during anesthesia and surgery and thus adjustment of the respirator parameters might be necessary. The actual $P_{a_{CO_2}}$ can be measured directly by analyzing the arterial blood gases which is very time consuming and costly. Indirect non-invasive estimates for $P_{a_{CO_2}}$ can be obtained through monitoring of the end-tidal (expired) $CO_2{}$ fraction ($F_{E_{CO_2}}$). A possible control variable is the ventilation of the lung represented by the respiratory minute volume (MV). Increasing the ventilation of the lung will decrease $F_{E_{CO_2}}$ and vice versa. In the past a fuzzy controller adjusting $P_{a_{CO_2}}$ has already been derived and implemented. In clinical studies it showed satisfactory performance comparable to the one of an anesthetist. In this paper a model-based controller (LQG) is derived with improved performance.

Further Information

Type of Publication:

(13)Semester/Bachelor Thesis

A.M. Zbinden

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% Autogenerated BibTeX entry
@PhdThesis { Xxx:1999:IFA_486
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