Assessment of Cerebral Autoregulation Dynamics in Diabetics Using Time-Domain Cross-Correlation Analysis

The main purpose of this paper is to apply time-domain cross-correlation analysis to assess the cerebral autoregulation (CA) dynamics in diabetics with autonomic neuropathy. Continuous and spontaneous arterial blood pressure (ABP) and cerebral blood flow velocity (CBFV) were acquired from 10 normal subjects, 10 diabetics without autonomic neuropathy and 10 diabetics with autonomic neuropathy (sex and age matched) with the Finapres device and the transcranial Doppler ultrasound (TCD) for periods of approximately 5 minutes in both supine and tilting positions. Cross-correlation function (CCF) was calculated through a 64-beat wide moving window. Mean CCF patterns were received for each subject and for the whole group. Mean arterial blood pressure (MABP) and mean cerebral blood flow velocity (MCBFV) signals were bandpass filtered in three different frequency ranges, the very low-frequency range (VLF, 0.015-0.04 Hz), low-frequency range (LF, 0.04-0.15 Hz) and high-frequency range (HF, 0.15-0.40 Hz), before applying CCF for the purpose of studying the effect of different bandwidths on the resulting mean CCFs. Results indicated that the CCF values fluctuated seriously in VLF range of each group. It might show that relation between MABP and MCBFV is uncertain in VLF range. On the other hand, maximum CCF indices in HF range were closer to origin and it indicates that CA is less efficient in this range. Cross-correlation analysis revealed that correlation between MABP and MCBFV in LF range for the group of normal subjects in supine position is the highest among these three groups. It might indicate that CA operates more effectively in normal subjects than diabetics in LF range. Hence, cross-correlation analysis could be a useful method to evaluate the CA dynamics in clinical practice.