title: The role of lung function in brain tissue oxygenation following traumatic brain injury.
abstract: OBJECTIVE
  Previous studies have demonstrated that periods of low brain tissue oxygen tension (PbtO2) are associated with poor outcome after head trauma but have primarily focused on cerebral and hemodynamic factors as causes of low PbtO2. The purpose of this study was to investigate the influence of lung function on PbtO2 with an oxygen challenge (increase in fraction of inspired oxygen [FiO2] concentration to 1.0).
  
  
  METHODS
  This prospective observational cohort study was performed in the neurointensive care unit of the Level 1 trauma center at San Francisco General Hospital. Thirty-seven patients with severe traumatic brain injury (TBI) undergoing brain tissue oxygen monitoring as part of regular care underwent an oxygen challenge, consisting of an increase in FiO2 concentration from baseline to 1.0 for 20 minutes. Partial pressure of arterial oxygen (PaO2), PbtO2, and the ratio of PaO2 to FiO2 (the PF ratio) were determined before and after oxygen challenge.
  
  
  RESULTS
  Patients with higher PF ratios achieved greater PbtO2 during oxygen challenge than those with a low PF ratio because they achieved a higher PaO2 after an oxygen challenge. Lung function, specifically the PF ratio, is a major determinant of the maximal PbtO2 attained during an oxygen challenge.
  
  
  CONCLUSIONS
  Given that patients with TBI are at risk for pulmonary complications such as pneumonia, severe atelectasis, and adult respiratory distress syndrome, lung function must be considered when interpreting brain tissue oxygenation.
authors.affiliation: Department of Neurosurgery, University of California, San Francisco, California, USA.
authors.forename: Guy
authors.initials: G
authors.lastname: Rosenthal
authors.forename: J Claude
authors.initials: JC
authors.lastname: Hemphill
authors.forename: Marco
authors.initials: M
authors.lastname: Sorani
authors.forename: Christine
authors.initials: C
authors.lastname: Martin
authors.forename: Diane
authors.initials: D
authors.lastname: Morabito
authors.forename: Michele
authors.initials: M
authors.lastname: Meeker
authors.forename: Vincent
authors.initials: V
authors.lastname: Wang
authors.forename: Geoffrey T
authors.initials: GT
authors.lastname: Manley
mesh_terms: D000328:Adult; D000368:Aged; D001784:Blood Gas Analysis; D001921:Brain / Q000378:metabolism; D001930:Brain Injuries / Q000378:metabolism* / Q000503:physiopathology* / Q000628:therapy; D015331:Cohort Studies; D005260:Female; D006801:Humans; D007427:Intracranial Pressure / Q000502:physiology; D008168:Lung / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D010101:Oxygen Consumption / Q000502:physiology*; D010102:Oxygen Inhalation Therapy