Novel technology of non-invasive cerebrovascular autoregulation monitoring

A novel technology for non-invasive cerebrovascular autoregulation (CA) status monitoring is presented. This fully non-invasive CA monitor is based on ultrasonic time-of-flight (TOF) measurement of cerebral blood volume pulsations within the brain parenchyma, processing of volumetric waves, and calculation of CA estimation indexes without using any additional arterial blood pressure (ABP) measurements. The CA status is estimated by extracting informative and reference slow waves from non-invasively measured TOF signals and by calculating Pearson's correlation coefficient between these waves as a CA index. The analysis of the signal extracted from the envelope of noninvasively measured pulse waves showed good agreement between this signal and ABP waves (r=0.68). Consequently, it shows that this signal might be used instead of ABP waves as a reference signal for calculation of the CA estimation indexes. Comparative invasive versus non-invasive CA monitoring study of 11 traumatic brain injury patients showed that correlation between invasively measured CA index and fully non-invasively measured CA index (no arterial line) was r=0.75. The proposed innovative CA real-time monitoring method gives us new possibilities to perform estimation of the CA status from intracranial waves only as well as to exclude the ABP line's errors and artifacts from the measurement results.