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Autoregulation in a Simulator-Based Educational Model of Intracranial Physiology

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Abstract

Objective.To implement a realistic autoregulation mechanism toenhance an existing educational brain model that displays in real-time thecerebral metabolic rate (CMRO2), cerebral blood flow (CBF),cerebral blood volume (CBV), intracranial pressure (ICP), and cerebralperfusion pressure (CPP). Methods.A dynamic cerebrovascular resistance(CVR) feedback loop adjusts automatically to maintain CBF within a range ofthe CPP and defines autoregulation. The model obtains physiologic parametersfrom a full-scale patient simulator. We assumed that oxygen demand andarterial partial pressure of carbon dioxide (CO2 responsivity) arethe two major factors involved in determining CBF. In addition, our brainmodel increases oxygen extraction up to 70% once CBF becomes insufficient tosupport CMRO2. The model was validated against data from theliterature. Results.The model's response varied less than 9%from the literature data. Similarly, based on correlation coefficients betweenthe brain model and experimental data, a good fit was obtained for curvesdescribing the relationship between CBF and PaCO2 at a meanarterial blood pressure of 150 mm Hg (R2 = 0.92) and 100 mm Hg(R2 = 0.70). Discussion.The autoregulated brain model, withincorporated CO2 responsivity and a variable oxygen extraction,automatically produces changes in CVR, CBF, CBV, and ICP consistent withliterature reports, when run concurrently with a METI full-scale patientsimulator (Medical Education Technologies, Inc., Sarasota, Florida). Once themodel is enhanced to include herniation, vasospasm, and drug effects, itsutility will be expanded beyond demonstrating only basic neuroanesthesiaconcepts.

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Authors and Affiliations

  1. Department of Anesthesiology, University of Florida College of Medicine; the Departments of Electrical and Computer Engineering, Mechanical Engineering, and Engineering Science, University of Florida College of Engineering; the University of Florida Brain Institute; and Shands Hospital at the University of Florida, Gainesville, Florida, U.S.A

    W. James Thoman, Dietrich Gravenstein, Jan van der Aa & Samsun Lampotang

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  1. W. James Thoman
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  2. Dietrich Gravenstein
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  3. Jan van der Aa
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  4. Samsun Lampotang
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Thoman, W.J., Gravenstein, D., van der Aa, J. et al. Autoregulation in a Simulator-Based Educational Model of Intracranial Physiology. J Clin Monit Comput 15, 481–491 (1999). https://doi.org/10.1023/A:1009998606087

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