title: Oxygen tolerance in patients with acute respiratory failure.
abstract: OBJECTIVE
  To search for a threshold of pulmonary oxygen toxicity in patients with acute respiratory failure.
  
  
  METHODS
  Retrospective study over a 10-year period.
  
  
  METHODS
  Three intensive care units of two university hospitals.
  
  
  METHODS
  Seventy-four patients with acute respiratory failure ventilated continuously with a FIO2 > or = 0.9 for at least 48 h were selected.
  
  
  METHODS
  Information regarding status, scoring, diagnosis and therapeutic interventions upon admission and ICU course were extracted from the patients' charts.
  
  
  RESULTS
  We found that total exposure [mean (standard error of the mean)] to a FIO2 of 0.9 (TE 90) or more was 5.6 (1.1) days in the 17 survivors (S) versus 5.9 (0.5) days in the 57 non-survivors (D) (NS). Total exposure time to a FIO2 more than 0.5 (TE 50) was 16.5 (2.6) days in S and 11.2 (1) days in D (p < 0.05). The PaO2/FIO2 ratio became significantly higher in S only 5 days after beginning FIO2 of 0.9 or more. Hypoxemia was not frequent at the time of death, whereas in 70% of the non-survivors there were at least three organ failures in the last 48 h. In univariate analysis, the duration of exposure to FIO2 of 0.9 or more was not different in survivors and non-survivors, and the average total duration of exposure to FIO2 of more than 0.5 was even longer in survivors. In multivariate analysis, exposure shorter than 10 days to FIO2 more than 0.5 and exposure longer than 4 days to a FIO2 of 0.9 or more were significantly associated with death. However, despite a larger exposure to a FIO2 of 0.9 or more during the last 5 years of the study, the trend moved towards a higher survival rate during this period compared with the first 5 years of the study.
  
  
  CONCLUSIONS
  Thus, our data provide circumstantial evidence that the lungs of patients with acute respiratory failure might exhibit some relative resistance to prolonged oxygen exposure. Therefore, it might be worthwhile carrying out a prospective study of different FIO2 strategies in such patients.
authors.affiliation: Service de réanimation médicale, CHU, Besançon, France.
authors.forename: G
authors.initials: G
authors.lastname: Capellier
authors.forename: P
authors.initials: P
authors.lastname: Beuret
authors.forename: G
authors.initials: G
authors.lastname: Clement
authors.forename: F
authors.initials: F
authors.lastname: Depardieu
authors.forename: C
authors.initials: C
authors.lastname: Ract
authors.forename: J
authors.initials: J
authors.lastname: Regnard
authors.forename: D
authors.initials: D
authors.lastname: Robert
authors.forename: F
authors.initials: F
authors.lastname: Barale
mesh_terms: D016009:Chi-Square Distribution; D004361:Drug Tolerance; D006801:Humans; D016015:Logistic Models; D010100:Oxygen / Q000633:toxicity*; D010102:Oxygen Inhalation Therapy / Q000706:statistics & numerical data; D012121:Respiration, Artificial / Q000706:statistics & numerical data; D012128:Respiratory Distress Syndrome / Q000401:mortality / Q000503:physiopathology / Q000628:therapy*; D012189:Retrospective Studies; D018709:Statistics, Nonparametric; D017741:Survivors / Q000706:statistics & numerical data; D013997:Time Factors
chemical_list: D010100:Oxygen