title: A method for estimating zero-flow pressure and intracranial pressure.
abstract: BACKGROUND
  It has been hypothesized that the critical closing pressure of cerebral circulation, or zero-flow pressure (ZFP), can estimate intracranial pressure (ICP). One ZFP estimation method used extrapolation of arterial blood pressure as against blood-flow velocity. The aim of this study was to improve ICP predictions.
  
  
  METHODS
  Two revisions have been considered: (1) the linear model used for extrapolation is extended to a nonlinear equation; and (2) the parameters of the model are estimated by an alternative criterion (not least squares). The method is applied to data on transcranial Doppler measurements of blood-flow velocity, arterial blood pressure, and ICP from 104 patients suffering from closed traumatic brain injury, sampled across the United States and England.
  
  
  RESULTS
  The revisions lead to qualitative (eg, precluding negative ICP) and quantitative improvements in ICP prediction. While moving from the original to the revised method, the ±2 SD of the error is reduced from 33 to 24 mm Hg, and the root-mean-squared error is reduced from 11 to 8.2 mm Hg. The distribution of root-mean-squared error is tighter as well; for the revised method the 25th and 75th percentiles are 4.1 and 13.7 mm Hg, respectively, as compared with 5.1 and 18.8 mm Hg for the original method.
  
  
  CONCLUSIONS
  Proposed alterations to a procedure for estimating ZFP lead to more accurate and more precise estimates of ICP, thereby offering improved means of estimating it noninvasively. The quality of the estimates is inadequate for many applications, but further work is proposed, which may lead to clinically useful results.
authors: Applied Physics Laboratory, University of Washington, Seattle, WA 98195, USA. marzban@stat.washington.edu
authors: Caren
authors: C
authors: Marzban
authors: Paul R
authors: PR
authors: Illian
authors: David
authors: D
authors: Morison
authors: Anne
authors: A
authors: Moore
authors: Michel
authors: M
authors: Kliot
authors: Marek
authors: M
authors: Czosnyka
authors: Pierre D
authors: PD
authors: Mourad
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D062186:Arterial Pressure / Q000502:physiology; D002560:Cerebrovascular Circulation / Q000502:physiology*; D003627:Data Interpretation, Statistical; D005260:Female; D015600:Glasgow Coma Scale; D016489:Head Injuries, Closed / Q000503:physiopathology; D006801:Humans; D007427:Intracranial Pressure / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D017711:Nonlinear Dynamics; D012189:Retrospective Studies; D012212:Rheology; D017585:Ultrasonography, Doppler, Transcranial; D055815:Young Adult