title: The oxygen reactivity index and its relation to sensor technology in patients with severe brain lesions.
abstract: BACKGROUND
  The oxygen reactivity index (ORx) has been introduced to assess the status of cerebral autoregulation after traumatic brain injury (TBI) or subarachnoid hemorrhage (SAH). Currently, there is some controversy about whether the ORx depends on the type of PbrO2-sensor technology used for its calculation. To examine if the probe technology does matter, we compared the ORx and the resulting optimal cerebral perfusion pressures (CPPopt) of simultaneously implanted Licox (CC1.SB, Integra Neuroscience, France) and Neurovent-PTO (Raumedic, Germany) probes in patients after aneurysmal SAH or severe TBI.
  
  
  METHODS
  Licox and Raumedic probes were implanted side by side in 11 patients after TBI or SAH. ORx and CPPopt were recorded continuously. The equivalence of both probes was examined using Bland-Altman analyses.
  
  
  RESULTS
  The mean difference in ORx was 0.1, with Licox producing higher values. The limits of agreement regarding ORx ranged from -0.6 to +0.7. When both probes' ORx values were compared in each patient, no specific pattern in their relationship was seen. The mean difference in CPPopt was 0 mmHg with limits of agreement between -16.5 and +16.4 mmHg.
  
  
  CONCLUSIONS
  Owing to the rather limited number of patients, we view the results of this study as preliminary. The main result is that Licox and Raumedic showed consistent differences in ORx and CPPopt. Therefore, ORx values of both probes cannot be interchanged and should not be viewed as equivalent. This should be taken into consideration when discussing ORx data generated by different PbrO2 probe types.
authors.affiliation: Department of Neurosurgery, Charité, Universitaetsmedizin Berlin, CVK, Augustenburger Platz 1, 13553, Berlin, Germany. julius.dengler@charite.de
authors.forename: Julius
authors.initials: J
authors.lastname: Dengler
authors.forename: Christin
authors.initials: C
authors.lastname: Frenzel
authors.forename: Peter
authors.initials: P
authors.lastname: Vajkoczy
authors.forename: Peter
authors.initials: P
authors.lastname: Horn
authors.forename: Stefan
authors.initials: S
authors.lastname: Wolf
mesh_terms: D001921:Brain / Q000098:blood supply / Q000378:metabolism; D001930:Brain Injuries / Q000378:metabolism*; D015331:Cohort Studies; D005260:Female; D006706:Homeostasis / Q000502:physiology*; D006801:Humans; D007427:Intracranial Pressure / Q000502:physiology; D008297:Male; D008875:Middle Aged; D008991:Monitoring, Physiologic / Q000295:instrumentation / Q000379:methods*; D010100:Oxygen / Q000378:metabolism*; D010313:Partial Pressure; D011237:Predictive Value of Tests; D012815:Signal Processing, Computer-Assisted / Q000295:instrumentation*; D013345:Subarachnoid Hemorrhage / Q000378:metabolism*; D015599:Trauma Severity Indices
chemical_list: D010100:Oxygen