A comparison of dynamic cerebral autoregulation across changes in cerebral blood flow velocity for 200 s

Abstract

Objectives: The dynamic interaction between blood pressure (BP) and cerebral blood flow velocity (CBFV) is not fully understood, especially for CBFV changes lasting longer than 50 s. The interaction between BP and CBFV is relatively well characterized for periods <50 s using transfer function (TF) estimations of phase, gain, and coherence. We used TF estimations to compare the phase and gain for periods >50 s with those for periods <50 s.Materials and Methods: BP and CBFV (of the middle cerebral artery) were simultaneously recorded in 23 healthy subjects (10 men, 13 women, mean age 35 ± 10 years) under normo- and hypocapnia (induced by hyperventilation). TF and coherence estimations were based on Welch's periodogram method with a windowing of 200 s (frequency resolution, 0.005 Hz, corresponding to a period of 200 s). Means of the phase, gain, and coherence were calculated over frequency periods of 0.005–0.02 Hz (sVLF), 0.02–0.07 Hz (VLF), 0.07–0.15 Hz (LF), and 0.15–0.40 Hz (HF) and analyzed using the t-test and Pearson correlation.Results: Compared with the VLF range, normo- and hypocapnia phases were slightly but significantly lower in sVLF, while gain and coherence were not different. Hypocapnia induced significant (mostly p < 0.01) phase increases and gain decreases as well as coherence decreases in all frequency ranges. The phase and gain correlated significantly (−0.87 < r > −0.99) (p < 0.001) and inversely in all frequency ranges <0.15 Hz under both respiratory conditions. In some instances, the phase indicated disturbed autoregulation.Conclusion: In the frequency range <0.15 Hz, the phase and gain correlate highly and linearly with high consistency. The phase, gain, and coherence were similar in sVLF and VLF ranges. The phase was slightly lower in the sVLF range than in the VLF range. Notably, the data suggest that autoregulatory failure may occur in healthy persons.

Reproducibility of dynamic cerebral autoregulation parameters: a multi-centre, multi-method study

“…Data analyses were performed by 14 participating centres on 44 datasets from 22 volunteers with two measurements each. The following dCA analysis methods were used: TFA (Reinhard et al, 2003a, Liu et al, 2005, van Beek et al, 2010, Gommer et al, 2010, Panerai, 2014, Mitsis et al, 2002, Zhang et al, 1998, Meel-van den Abeelen et al, 2014a, Muller et al, 2003, Muller and Osterreich, 2014, Panerai et al, 1998a, Laguerre expansion of 1 st -order Volterra kernels or finite impulse response models (Marmarelis, 2004, Marmarelis et al, 2013, Marmarelis et al, 2014b, Mitsis et al, 2004, Mitsis et al, 2009, wavelet analysis (Peng et al, 2010, Torrence and Webster, 1999, Grinsted et al, 2004, parametric finite-impulse response filter based methods (Panerai et al, 2000, Simpson et al, 2001, ARI anaysis (Panerai et al, 1998b), autoregressive moving average (ARMA) based ARI methods and variant ARI methods (Panerai et al, 2003), autoregressive with exogenous input (ARX) methods (Liu and Allen, 2002, Liu et al, 2003, Panerai et al, 2003 and correlation coefficient-like indices (Heskamp et al, 2013, Caicedo et al, 2016. A summary of the methods and corresponding references are given in Table 1.…”

Measuring cerebrovascular autoregulation in preterm infants using near-infrared spectroscopy: an overview of the literature

“…However, in the very-low-frequency range, contributions of other physiological variables (like PaCO 2 and sympathetic influence) take place, making interpretation of cerebrovascular autoregulation results more complex [72]. TFA values can be calculated in different frequency ranges: 0.005-0.02 Hz (sub-very low frequency), 0.02-0.07 Hz (very low frequency), 0.07-0.15 Hz (low frequency), and 0.15-0.40 Hz (high frequency) [73], although various authors use various definitions for the various ranges. Tsuji et al found a higher coherence score in the very-lowfrequency range for preterm infants with severe cerebral ultrasound abnormalities (grade 3-4 GMH-IVH or PVL) compared to infants with normal or minimal abnormal ultrasound findings [6].…”

Cerebral Autoregulation

“…More recently, there has been interest in the sub-very low frequency band, Müller and Osterreich (2014). Phase angles were found to be significantly lower in the sVLF (0.005-0.02 Hz) band, compared to the VLF (0.02-0.07 Hz) band (gain and coherence were unaltered), with hypocapnia resulting in significant phase increases and gain and coherence decreases in all frequency ranges.…”