title: A noninvasive estimation of cerebral perfusion pressure using critical closing pressure.
abstract: OBJECTIVE
  Cerebral blood flow is associated with cerebral perfusion pressure (CPP), which is clinically monitored through arterial blood pressure (ABP) and invasive measurements of intracranial pressure (ICP). Based on critical closing pressure (CrCP), the authors introduce a novel method for a noninvasive estimator of CPP (eCPP).
  
  
  METHODS
  Data from 280 head-injured patients with ABP, ICP, and transcranial Doppler ultrasonography measurements were retrospectively examined. CrCP was calculated with a noninvasive version of the cerebrovascular impedance method. The eCPP was refined with a predictive regression model of CrCP-based estimation of ICP from known ICP using data from 232 patients, and validated with data from the remaining 48 patients.
  
  
  RESULTS
  Cohort analysis showed eCPP to be correlated with measured CPP (R = 0.851, p < 0.001), with a mean ± SD difference of 4.02 ± 6.01 mm Hg, and 83.3% of the cases with an estimation error below 10 mm Hg. eCPP accurately predicted low CPP (< 70 mm Hg) with an area under the curve of 0.913 (95% CI 0.883-0.944). When each recording session of a patient was assessed individually, eCPP could predict CPP with a 95% CI of the SD for estimating CPP between multiple recording sessions of 1.89-5.01 mm Hg.
  
  
  CONCLUSIONS
  Overall, CrCP-based eCPP was strongly correlated with invasive CPP, with sensitivity and specificity for detection of low CPP that show promise for clinical use.
authors.affiliation: Division of Neurosurgery, Department of Clinical Neurosciences, Addenbrooke's Hospital, University of Cambridge, United Kingdom;
authors.forename: Georgios V
authors.initials: GV
authors.lastname: Varsos
authors.affiliation: Division of Neurosurgery, Department of Clinical Neurosciences, Addenbrooke's Hospital, University of Cambridge, United Kingdom;
authors.forename: Angelos G
authors.initials: AG
authors.lastname: Kolias
authors.affiliation: Division of Neurosurgery, Department of Clinical Neurosciences, Addenbrooke's Hospital, University of Cambridge, United Kingdom;
authors.forename: Peter
authors.initials: P
authors.lastname: Smielewski
authors.affiliation: Baylor College of Medicine, Texas Children's Hospital, Houston, Texas;
authors.forename: Ken M
authors.initials: KM
authors.lastname: Brady
authors.affiliation: Department of Neurosurgery, Red Cross Hospital, Athens, Greece;
authors.forename: Vassilis G
authors.initials: VG
authors.lastname: Varsos
authors.affiliation: Division of Neurosurgery, Department of Clinical Neurosciences, Addenbrooke's Hospital, University of Cambridge, United Kingdom;
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, United Kingdom;
authors.forename: John D
authors.initials: JD
authors.lastname: Pickard
authors.affiliation: Division of Neurosurgery, Department of Clinical Neurosciences, Addenbrooke's Hospital, University of Cambridge, United Kingdom;|Institute of Electronic Systems, Warsaw University of Technology, Warsaw, Poland.
authors.forename: Marek
authors.initials: M
authors.lastname: Czosnyka
mesh_terms: D000293:Adolescent; D000328:Adult; D001783:Blood Flow Velocity / Q000502:physiology*; D001794:Blood Pressure / Q000502:physiology; D002560:Cerebrovascular Circulation / Q000502:physiology*; D006259:Craniocerebral Trauma / Q000000981:diagnostic imaging / Q000503:physiopathology*; D005260:Female; D006801:Humans; D007427:Intracranial Pressure / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D008991:Monitoring, Physiologic; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D017585:Ultrasonography, Doppler, Transcranial; D055815:Young Adult
keywords: ABP = arterial blood pressure; AUC = area under the curve; CBF = cerebral blood flow; CPP = cerebral perfusion pressure; CVR = cerebrovascular resistance; CrCP = critical closing pressure; FV = flow velocity; GCS = Glasgow Coma Scale; GOS = Glasgow Outcome Scale; ICP = intracranial pressure; IQR = interquartile range; MCA = middle cerebral artery; ROC = receiver operating characteristic; TAU = time constant of the cerebrovascular arterial bed; TBI = traumatic brain injury; TCD = transcranial Doppler; cerebral perfusion pressure; critical closing pressure; eCPP = noninvasive estimator of CPP; nICP = noninvasive estimator of ICP; noninvasive model; transcranial Doppler ultrasonography; vascular disorders