title: Traumatic brain injury: increasing ICP attenuates respiratory modulations of cerebral blood flow velocity.
abstract: In vitro experiments have suggested that respiratory oscillations (R waves) in cerebral blood flow velocity are reduced as soon as the intracranial pressure-volume reserve is exhausted. Could R waves hence, provide indication for increasing ICP after traumatic brain injury (TBI)? On days 1 to 4 after TBI, 22 sedated and ventilated patients were monitored for intracranial pressure (ICP) in brain parenchyma, Doppler flow velocity (FV) in the middle cerebral arteries (MCA), and arterial blood pressure (ABP). The analysis included the transfer function gains of R waves (respiratory rate of 9-20 cpm) between ABP and FV (GainFv) as well as between ABP and ICP (GainICP). Also, the index of the intracranial pressure-volume reserve (RAP) was calculated. The rise of ICP (day 1: 14.10 ± 6.22 mmHg; to day 4: 29.69 ± 12.35 mmHg) and increase of RAP (day 1: 0.72 ± 0.22; to day 4: 0.85 ± 0.18) were accompanied by a decrease of GainFv (right MCA; day 1: 1.78 ± 1.0; day 4: 0.84 ± 0.47; left MCA day 1: 1.74 ± 1.10; day 4: 0.86 ± 0.46; p < 0.01) but no significant change in GainICP day 1: 1.50 ± 0.77; day 4: 1.15 ± 0.47; p = 0.07). The transfer of ventilatory oscillations to the intracerebral arteries after TBI appears to be dampened by increasing ICP and exhausted intracranial pressure-volume reserves. Results warrant prospective studies of whether respiratory waves in cerebral blood flow velocity may anticipate intracranial hypertension non-invasively.
authors.affiliation: Department of Neurology, University Hospital Aachen, Aachen, Germany. Electronic address: chaubrich@ukaachen.de.
authors.forename: Christina
authors.initials: C
authors.lastname: Haubrich
authors.affiliation: Department of Neurology, Alfried-Krupp-Krankenhaus Essen, Germany.
authors.forename: Rolf R
authors.initials: RR
authors.lastname: Diehl
authors.affiliation: Institute of Biomedical Engineering and Instrumentation, Wroclaw University of Technology, Poland.
authors.forename: Magdalena
authors.initials: M
authors.lastname: Kasprowicz
authors.affiliation: Department of Neurology, Tübingen University, Germany.
authors.forename: Jennifer
authors.initials: J
authors.lastname: Diedler
authors.affiliation: Department of Academic Neurosurgery, Addenbrooke's Hospital, Cambridge, UK.
authors.forename: Enrico
authors.initials: E
authors.lastname: Sorrentino
authors.affiliation: Department of Academic Neurosurgery, Addenbrooke's Hospital, Cambridge, UK.
authors.forename: Piotr
authors.initials: P
authors.lastname: Smielewski
authors.affiliation: Department of Academic Neurosurgery, Addenbrooke's Hospital, Cambridge, UK.
authors.forename: Marek
authors.initials: M
authors.lastname: Czosnyka
mesh_terms: D001783:Blood Flow Velocity; D001794:Blood Pressure; D001930:Brain Injuries / Q000503:physiopathology*; D002560:Cerebrovascular Circulation; D006801:Humans; D007427:Intracranial Pressure; D012119:Respiration
keywords: Cerebral blood; Flow velocity; Head injury; Intracranial pressure; Intracranial pressure–volume reserve; Respiratory oscillations