title: Comparison of frequency and time domain methods of assessment of cerebral autoregulation in traumatic brain injury.
abstract: The impulse response (IR)-based autoregulation index (ARI) allows for continuous monitoring of cerebral autoregulation using spontaneous fluctuations of arterial blood pressure (ABP) and cerebral flow velocity (FV). We compared three methods of autoregulation assessment in 288 traumatic brain injury (TBI) patients managed in the Neurocritical Care Unit: (1) IR-based ARI; (2) transfer function (TF) phase, gain, and coherence; and (3) mean flow index (Mx). Autoregulation index was calculated using the TF estimation (Welch method) and classified according to the original Tiecks' model. Mx was calculated as a correlation coefficient between 10-second averages of ABP and FV using a moving 300-second data window. Transfer function phase, gain, and coherence were extracted in the very low frequency (VLF, 0 to 0.05 Hz) and low frequency (LF, 0.05 to 0.15 Hz) bandwidths. We studied the relationship between these parameters and also compared them with patients' Glasgow outcome score. The calculations were performed using both cerebral perfusion pressure (CPP; suffix 'c') as input and ABP (suffix 'a'). The result showed a significant relationship between ARI and Mx when using either ABP (r=-0.38, P<0.001) or CPP (r=-0.404, P<0.001) as input. Transfer function phase and coherence_a were significantly correlated with ARI_a and ARI_c (P<0.05). Only ARI_a, ARI_c, Mx_a, Mx_c, and phase_c were significantly correlated with patients' outcome, with Mx_c showing the strongest association.
authors.affiliation: Division of Neurosurgery, Department of Clinical Neurosciences, Addenbrooke's Hospital, University of Cambridge, Cambridge, UK.
authors.forename: Xiuyun
authors.initials: X
authors.lastname: Liu
authors.affiliation: 1] Division of Neurosurgery, Department of Clinical Neurosciences, Addenbrooke's Hospital, University of Cambridge, Cambridge, UK [2] Institute of Electronic Systems, Warsaw University of Technology, Warsaw, Poland.
authors.forename: Marek
authors.initials: M
authors.lastname: Czosnyka
authors.affiliation: Division of Neurosurgery, Department of Clinical Neurosciences, Addenbrooke's Hospital, University of Cambridge, Cambridge, UK.
authors.forename: Joseph
authors.initials: J
authors.lastname: Donnelly
authors.affiliation: Division of Neurosurgery, Department of Clinical Neurosciences, Addenbrooke's Hospital, University of Cambridge, Cambridge, UK.
authors.forename: Karol P
authors.initials: KP
authors.lastname: Budohoski
authors.affiliation: Division of Neurosurgery, Department of Clinical Neurosciences, Addenbrooke's Hospital, University of Cambridge, Cambridge, UK.
authors.forename: Georgios V
authors.initials: GV
authors.lastname: Varsos
authors.affiliation: 1] Division of Neurosurgery, Department of Clinical Neurosciences, Addenbrooke's Hospital, University of Cambridge, Cambridge, UK [2] Service de Neurologie Vasculaire, Hôpital Rangueil, INSERM U1048 - Team 11 (I2MC-Toulouse), Université de Toulouse III, Toulouse, France.
authors.forename: Nathalie
authors.initials: N
authors.lastname: Nasr
authors.affiliation: Baylor College of Medicine, Texas Children's Hospital, Houston, Texas, USA.
authors.forename: Ken M
authors.initials: KM
authors.lastname: Brady
authors.affiliation: Department of Neurology, University Hospital, University of Freiburg, Freiburg, Germany.
authors.forename: Matthias
authors.initials: M
authors.lastname: Reinhard
authors.affiliation: Division of Neurosurgery, Department of Clinical Neurosciences, Addenbrooke's Hospital, University of Cambridge, Cambridge, UK.
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Hutchinson
authors.affiliation: Division of Neurosurgery, Department of Clinical Neurosciences, Addenbrooke's Hospital, University of Cambridge, Cambridge, UK.
authors.forename: Peter
authors.initials: P
authors.lastname: Smielewski
mesh_terms: D000293:Adolescent; D000328:Adult; D001783:Blood Flow Velocity; D001794:Blood Pressure; D001930:Brain Injuries / Q000000981:diagnostic imaging / Q000503:physiopathology; D002560:Cerebrovascular Circulation; D005260:Female; D006706:Homeostasis; D006801:Humans; D008297:Male; D008875:Middle Aged; D008955:Models, Cardiovascular; D012189:Retrospective Studies; D017585:Ultrasonography, Doppler, Transcranial