Tissue oxygenation index as a measure of cerebral autoregulation

The clinical importance of cerebral autoregulation has resulted in a significant body of literature that attempts both to model the underlying physiological processes and to estimate the mathematical relationships between clinically measurable variables. The primary measurement variable used thus far has been Cerebral Blood Flow Velocity (CBFV). However, this has important drawbacks as a measure of cerebral autoregulation. We have thus investigated a new measurement variable: Tissue Oxygenation Index, which is measured using Near Infra-Red Spectroscopy. We show, using a model, that this provides another measure of cerebral autoregulation and illustrate its performance with a clinical example. It is hoped that this will lead to a greater understanding of the nature of cerebral autoregulatory processes on a global level.