title: Increasing Intracranial Pressure After Head Injury: Impact on Respiratory Oscillations in Cerebral Blood Flow Velocity.
abstract: Experiments have shown that closed-box conditions alter the transmission of respiratory oscillations (R waves) to organ blood flow already at a marginal pressure increase. How does the increasing intracranial pressure (ICP) interact with R waves in cerebral blood flow after head injury (HI)?Twenty-two head-injured patients requiring sedation and mechanical ventilation were monitored for ICP, Doppler flow velocity (FV) in the middle cerebral arteries, and arterial blood pressure (ABP). The analysis included transfer function gains of R waves (9-20 cpm) from ABP to FV, and indices of pressure-volume reserve (RAP) and autoregulation (Mx). Increasing ICP has dampened R-wave gains from day 1 to day 4 after HI in all patients. A large impact (ΔGain /ΔICP right: 0.14 ± 0.06; left: 0.18 ± 0.08) was associated with exhausted reserves (RAP ≥0.85). When RAP was <0.85, rising ICP had a lower impact on R-wave gains (ΔGain /ΔICP right: 0.05 ± 0.02; left: 0.06 ± 0.04; p < 0.05), but increased the pulsatility indices (right: 1.35 ± 0.55; left: 1.25 ± 0.52) and Mx indices (right: 0.30 ± 0.12; left: 0.28 ± 0.08, p < 0.05). Monitoring of R waves in blood pressure and cerebral blood flow velocity has suggested that rising ICP after HI might have an impact on cerebral blood flow directly, even before autoregulation is impaired.
authors.affiliation: Department of Neurology, University Hospital Aachen, Aachen, Germany. ch723@cam.ac.uk.
authors.forename: Christina
authors.initials: C
authors.lastname: Haubrich
authors.affiliation: Department of Neurology, Alfried-Krupp-Krankenhaus Essen, Essen, Germany.
authors.forename: Rolf R
authors.initials: RR
authors.lastname: Diehl
authors.affiliation: Institute of Biomedical Engineering and Instrumentation, Wroclaw University of Technology, Wroclaw, Poland.
authors.forename: Magdalena
authors.initials: M
authors.lastname: Kasprowicz
authors.affiliation: Department of Neurology, Tübingen University, Tübingen, 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: Division of Neurosurgery, Department of Clinical Neurosciences, University of Cambridge, Cambridge, UK.
authors.forename: Piotr
authors.initials: P
authors.lastname: Smielewski
authors.affiliation: Division of Neurosurgery, Department of Clinical Neurosciences, University of Cambridge, Cambridge, UK.
authors.forename: Marek
authors.initials: M
authors.lastname: Czosnyka
mesh_terms: D001783:Blood Flow Velocity; D001794:Blood Pressure; D002560:Cerebrovascular Circulation / Q000502:physiology*; D006259:Craniocerebral Trauma / Q000150:complications / Q000503:physiopathology*; D005583:Fourier Analysis; D006706:Homeostasis; D006801:Humans; D019586:Intracranial Hypertension / Q000209:etiology / Q000503:physiopathology*; D007427:Intracranial Pressure; D020768:Middle Cerebral Artery / Q000000981:diagnostic imaging* / Q000503:physiopathology; D008991:Monitoring, Physiologic; D012121:Respiration, Artificial / Q000379:methods*; D017585:Ultrasonography, Doppler, Transcranial