title: Differences in mortality based on worsening ratio of partial pressure of oxygen to fraction of inspired oxygen corrected for immune system status and respiratory support.
abstract: OBJECTIVE
  To define the relationship between worsening oxygenation status (worst PaO(2)/FiO(2) ratio in the first 24 hours after intensive care unit admission) and mortality in immunosuppressed and immunocompetent ICU patients in the presence and absence of mechanical ventilation.
  
  
  METHODS
  Retrospective cohort study.
  
  
  METHODS
  Data were extracted from the Australian and New Zealand Intensive Care Society Adult Patient Database.
  
  
  METHODS
  Adult patients admitted to 129 ICUs in Australasia, 2000-2010.
  
  
  METHODS
  In hospital and ICU mortality; relationship between mortality and declining PaO(2)/FiO(2) ratio by ventilation status and immune status.
  
  
  RESULTS
  457 750 patient records were analysed. Worsening oxygenation status was associated with increasing mortality in all groups. Higher mortality was seen in immunosuppressed patients than immunocompetent patients. After multivariate analysis, in mechanically ventilated patients, declining PaO(2)/FiO(2) ratio in the first 24 hours of ICU admission was associated with a more rapidly rising mortality rate in immunosuppressed patients than non-immunosuppressed patients. Immunosuppression did not affect the relationship between oxygenation status and mortality in non-ventilated patients.
  
  
  CONCLUSIONS
  Immunosuppression increases the risk of mortality with progressively worsening oxygenation status, but only in the presence of mechanical ventilation. Further research into the impact of mechanical ventilation in immunosuppressed patients is required.
authors.affiliation: Alfred Hospital, Melbourne, VIC, Australia. lachlan.miles@gmail.com
authors.forename: Lachlan F
authors.initials: LF
authors.lastname: Miles
authors.forename: Michael
authors.initials: M
authors.lastname: Bailey
authors.forename: Paul
authors.initials: P
authors.lastname: Young
authors.forename: David V
authors.initials: DV
authors.lastname: Pilcher
mesh_terms: D000368:Aged; D001315:Australia / Q000453:epidemiology; D015331:Cohort Studies; D005260:Female; D006723:Hong Kong; D017052:Hospital Mortality; D006801:Humans; D007154:Immune System Diseases / Q000097:blood* / Q000401:mortality* / Q000503:physiopathology / Q000628:therapy; D007362:Intensive Care Units / Q000706:statistics & numerical data; D008297:Male; D008875:Middle Aged; D009520:New Zealand / Q000453:epidemiology; D010100:Oxygen / Q000097:blood*; D010313:Partial Pressure; D012121:Respiration, Artificial / Q000706:statistics & numerical data*; D012189:Retrospective Studies
chemical_list: D010100:Oxygen