title: Assessment of zero drift in the Codman intracranial pressure monitor: a study from 2 neurointensive care units.
abstract: OBJECTIVE
  Intraparenchymal monitoring devices play an important role in the daily management of head injury and other critically ill neurosurgical patients. Although zero drift data exist for the Camino system (Camino Laboratories, San Diego, CA), only in vitro data exist for the Codman system (Codman and Shurtleff, Inc., Raynham, MA). The aim of this study was to assess the extent of zero drift for the Codman intracranial pressure (ICP) monitor in patients being monitored in 2 neurointensive care units.
  
  
  METHODS
  This was a prospective study conducted at 2 neurointensive care units. Eighty-eight patients who required ICP monitoring and who presented to the 2 neurosurgical departments, Center 1 (n = 48) and Center 2 (n = 40), were recruited for participation. The duration of ICP monitoring was noted, as was the resultant pressure reading in normal saline on removing the ICP monitor (zero drift).
  
  
  RESULTS
  The median absolute zero drift for the group was 2.0 mm Hg (interquartile range, 1-3 mm Hg). The median time in situ was 108 hours (interquartile range, 69-201 hours). There was a positive correlation between the drift and time of the probe spent in situ (Spearman's correlation coefficient = 0.342; P = 0.001). Of the readings, 20 and 2% showed a drift greater than 5 and 10 mm Hg in magnitude, respectively.
  
  
  CONCLUSIONS
  These data demonstrate that a small amount of zero drift exists in ICP monitors and that this drift increases with time. The wide range in the data demonstrates that some drift readings are quite excessive. This reinforces the school of thought that, although ICP readings contribute significantly to the management of neurosurgical patients, they should be interpreted carefully and in conjunction with clinical and radiological assessment of patients.
authors.affiliation: Academic Neurosurgery Unit, University of Cambridge and Cambridge University NHS Foundation Trust, Addenbrooke's Hospital, Cambridge, England, UK. yahia27@hotmail.com
authors.forename: Yahia Z
authors.initials: YZ
authors.lastname: Al-Tamimi
authors.forename: Adel
authors.initials: A
authors.lastname: Helmy
authors.forename: Seb
authors.initials: S
authors.lastname: Bavetta
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Price
mesh_terms: D000328:Adult; D001930:Brain Injuries / Q000503:physiopathology; D004868:Equipment Failure; D005260:Female; D006801:Humans; D007362:Intensive Care Units; D019586:Intracranial Hypertension / Q000175:diagnosis* / Q000503:physiopathology; D007427:Intracranial Pressure / Q000502:physiology*; D008297:Male; D008991:Monitoring, Physiologic / Q000295:instrumentation*; D014160:Transducers, Pressure