title: Accuracy of non-invasive ICP assessment can be increased by an initial individual calibration.
abstract: OBJECTIVE
  In a formerly introduced mathematical model, intracranial pressure (ICP) could be non-invasively assessed using cerebral blood flow velocity (FV) and arterial blood pressure (ABP). The current study attempts to check whether the accuracy of the non-invasive ICP assessment (nICP) improves after an initial individual calibration by implanted ICP probes.
  
  
  METHODS
  Thirteen patients with brain lesions (35-77 years, mean: 58 +/- 13 years) were studied. FV, ABP and ICP signals were recorded at days 1, 2, 4 and 7. nICP was calculated and compared to ICP. In the first recording of each patient the (invasively assessed) ICP signal was used to calibrate the nICP calculation procedure, while the follow-up recordings were used for its validation.
  
  
  RESULTS
  In 11 patients 22 follow-up recordings were performed. The mean deviation between ICP and the original nICP (+/- SD) was 8.3 +/- 7.9 mmHg. Using the calibrated method this deviation was reduced to 6.7 +/- 6.7 mmHg (P < 0.005).
  
  
  CONCLUSIONS
  Initial individual calibration of nICP assessment method significantly improves the accuracy of nICP estimation on subsequent days. This hybrid method of ICP assessment may be used in intensive care units in patients with initially implanted ICP probes. After removal of the probes, ICP monitoring can be continued using the calibrated nICP assessment procedure.
authors.affiliation: Department of Neurology, Medical Centre Chemnitz, Dresdner Str. 178, 09131 Chemnitz, Germany. B.Schmidt@skc.de
authors.forename: B
authors.initials: B
authors.lastname: Schmidt
authors.forename: M
authors.initials: M
authors.lastname: Weinhold
authors.forename: M
authors.initials: M
authors.lastname: Czosnyka
authors.forename: S A
authors.initials: SA
authors.lastname: May
authors.forename: R
authors.initials: R
authors.lastname: Steinmeier
authors.forename: J
authors.initials: J
authors.lastname: Klingelhöfer
mesh_terms: D000328:Adult; D000368:Aged; D001783:Blood Flow Velocity / Q000502:physiology; D001930:Brain Injuries / Q000503:physiopathology*; D002138:Calibration; D002560:Cerebrovascular Circulation; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007427:Intracranial Pressure / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D008955:Models, Cardiovascular; D017063:Outcome Assessment, Health Care; D010363:Pattern Recognition, Automated / Q000379:methods; D017585:Ultrasonography, Doppler, Transcranial