A study of the variability of cerebral autoregulation using modelling techniques

Liu, Jia (2006) A study of the variability of cerebral autoregulation using modelling techniques. University of Southampton, Doctoral Thesis.

Abstract

Cerebral autoregulation is defined as a mechanism that maintains cerebral blood flow at a relatively constant level despite changes of cerebral arterial blood pressure over a wide range.  Impaired autoregulation, which may lead to ischemia and hyperaemia in the brain, is associated with pathosphysiological conditions including intracranial tumours, head injury, hypertension and space-occupying lesions in the brain.  Therefore, assessing and monitoring cerebral autoregulation is important to guide the treatments of patients suffering from such conditions.  Although great efforts have been made to develop methods for assessing autoregulation using mathematical models and signal processing techniques, the assessment of autoregulation still suffers from large variability which is not yet fully understood.  In addition, there is currently no ‘gold’ standard for assessing cerebral autoregulation for clinical applications.  In this thesis, methods for assessing cerebral autoregulation are investigated and evaluated using linear modelling approaches, showing that the phase difference between cerebral blood flow velocity and blood pressure is a reliable indicator of autoregulation.  A method is suggested for identifying signal characteristics which are suitable for the assessment of autoregulation. Finally, a method of tracking the time-varying cerebral autoregulation caused by inhaling CO₂ is proposed to show the variability of autoregulation.  The dynamics of cerebral autoregulation in response to the changes in CO₂ is similar to the dynamics of cerebral blood flow under the same CO₂ condition in the cerebral arteries.

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