Title page for ETD etd-09192005-161652

Document Type Doctoral Thesis
Author Steyn, Johan Daniel
URN etd-09192005-161652
Document Title Is the absorption of anaesthetic agents non linear?
Degree PhD (Anaesthesiology)
Department Anaesthesiology
Advisor Name Title
Prof J M Hugo Committee Chair
  • isoflurane
  • enflurane
  • anaesthesia
  • anaesthetics
  • absorption physiology
Date 2003-09-01
Availability unrestricted
Knowledge of the absorption of inhalation anaesthetic agents is essential if one is to safely administer them. Despite many years of research in linear science, no model has been described that can reliably predict inhalation agent uptake. To date no published investigation has looked for non¬linearity in the absorption process. The aim if this research project was to determine if the absorption of anaesthetic agents is non-linear, using isoflurane and enflurane as examples.

To detect non-linearity, four conditions must be met:

  • Sensitivity to initial conditions,
  • Fractal Dimension of the attract or,
  • Invariant probability distribution of the attractor, and
  • Detection of an underlying dynamical process.

Ten measured time series for both isoflurane and enflurane absorption were measured. These were then compared with ten noise signals, with similar standard deviations, means and number of points in the series.

Calculated Lyapunov exponents tested sensitivity to initial conditions. The dimension of the attractor was calculated using the following statistics, each giving an approximation of the fractal dimension. Approximate entropy, information entropy, correlation dimension and fractal dimension (box counting method). The Invariant probability distribution of the attractor was tested for using non-linear forecasting. Detection of an underlying dynamical process was determined by the method of surrogate data.

Each of the four conditions required have been met with statistical significance ( p< 0.05) and acceptable statistical power (>0.8). It is therefore concluded that the absorption of both isoflurane and enflurane are non-linear processes. The implications and implementations in anaesthesia practice are discussed.

© 2003 University of Pretoria. All rights reserved. The copyright in this work vests in the University of Pretoria. No part of this work may be reproduced or transmitted in any form or by any means, without the prior written permission of the University of Pretoria.

Please cite as follows:

Steyn, JD 2003, I the absorption of anaesthetic agents non linear?, PhD thesis, University of Pretoria, Pretoria, viewed yymmdd < http://upetd.up.ac.za/thesis/available/etd-09192005-161652/ >


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