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Ilias Tachtsidis " Experimental Measurements of Cerebral Haemodynamics
and Oxygenation and Comparisons with a Computational
Model: a Near-Infrared Spectroscopy Investigation" Ph.D Thesis,
University of London (2005)
Abstract
This thesis describes studies of cerebral oxygenation, autoregulation
and metabolism carried out on human volunteers and patients. These
studies are intended to aid both the development and the validation of a
new physiology based mathematical model of the cerebral circulation and
metabolism The thesis contains comparisons between the
experimentally derived data and predictions from this model.
The experimental studies involve the measurement of systemic and
cerebral haemodynamic parameters and their response to physiological
challenges. In particular, near-infrared spectroscopy (NIRS) is used to
monitor cerebral blood volume,oxygenation and flow. NIRS is a
non-invasive technique, which uses the differing optical absorption of
oxy- and deoxy- haemoglobin in the near infrared to monitor variations
in oxygenation and blood volume deep within the tissue. A 2 channel NIRS
instrument with spatially-resolved capabilities (NIRO 300, Hamamatsu
Photonics KK),was used to monitor cerebral changes in response to
physiological challenges such as hypercapnia, hypoxia and passive tilt
in healthy volunteers. Furthermore we studied patients with primary
autonomic failure with severe orthostatic hypotension undergoing a tilt
test. The main reason for using data from these patients is that a
comparatively minor physiological challenge (a 60° tilt) produces a
major drop in arterial blood pressure and cerebral haemodynamics.
The computational model, against which the experimental data is
compared, is being developed at UCL. The model is capable of accepting
experimentally determined data as an input and predicting changes in
other measured and non-measured parameters.The thesis describes the
model and illustrates its abilities using both theoretical and
experimental data, in particular examining the measured and predicted
changes in cerebral tissue oxygenation.
Finally, practical aspects of clinical data monitoring are addressed and
the capabilities and limitations of the cerebral modelling work are
discussed. The findings and conclusions of these studies should be
relevant to the wider mathematical, physiology and biomedical optics
community.h
Title Abstract, Contents etc.
Chapter 1 Introduction
Chapter 2 Anatomical and Physiological Background of the Cerebral
Circulation
Chapter 3 Computational Modelling of the Brain
Chapter 4 Near-Infrared Spectroscopy: Theory and Practical Aspects
Chapter 5 Model Predictions with Experimental Data during a CO2
Challenge
Chapter 6 Model Predictions with Experimental Data during a Hypoxic Challenge
Chapter 7 Changes in Cerebral Oxygenation and Haemodynamics
following a Postural
Change in Patients with Autonomic Failure and Postural Hypotension and
Control
Subjects
Chapter 8 Work in Progress
Chapter 9 Discussion
Appendix A,
Appendix B,
Appendix C
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