In control: methodological and clinical aspects of cerebral autoregulation and haemodynamics

Cerebral autoregulation (CA) is a key mechanism to protect the brain against excessive fluctuations in blood pressure (BP) and maintain cerebral blood flow. Analysing the relationship between spontaneous BP and cerebral blood flow velocity (CBFV) using transfer function analysis is a widely used technique to quantify CA in a non-invasive way. The objective of this review was to provide an overview of transfer function techniques used in the assessment of CA. For this review, 113 publications were included. This literature showed that there is no gold standard for the execution and implementation of the transfer function. There is a high diversity in settings and criteria used for transfer function analysis. Notable is also the high number of studies which report little on the settings. This disparity makes it difficult to replicate or compare the results of the different studies and further hinders the opportunity to make a distinction between intact and impaired CA in different patient groups. More research on the effects of different implementation techniques on outcomes for CA and optimization of the transfer function analysis is urgently needed. Furthermore, the results of this review show that international guidelines should be created to inform the minimal description of the applied technique and the interpretation of transfer function outcomes in scientific research.