Non-linear association between arterial oxygen tension and survival after out-of-hospital cardiac arrest: A multicentre observational study

Nicole Mckenzie, Judith Finn, Geoffrey Dobb, Paul Bailey, Glenn Arendts, Antonio Celenza, Daniel Fatovich, Ian Jenkins, Stephen Ball, Janet Bray, Kwok M. Ho

Research output: Contribution to journalArticleResearchpeer-review


BACKGROUND: Studies to identify safe oxygenation targets after out-of-hospital cardiac arrest (OHCA) have often assumed a linear relationship between arterial oxygen tension (PaO2) and survival, or have dichotomised PaO2 at a supra-physiological level. We hypothesised that abnormalities in mean PaO2 (both high and low) would be associated with decreased survival after OHCA. METHODS: We conducted a retrospective multicentre cohort study of adult OHCA patients who received mechanical ventilation on admission to the intensive care unit (ICU). The potential non-linear relationship between the mean PaO2 within the first 24 -hs of ICU admission and survival to hospital discharge (STHD) was assessed by a four-knot restricted cubic spline function with adjustment for potential confounders. RESULTS: 3764 arterial blood gas results were available for 491 patients in the first 24-hs of ICU admission. The relationship between mean PaO2 over the first 24-hs and STHD was an inverted U-shape, with highest survival for those with a mean PaO2 between 100 and 180 mmHg (reference category) compared to a mean PaO2 of <100 mmHg (adjusted odds ratio [aOR] 0.50 95% confidence interval [CI] 0.30, 0.84), or >180 mmHg (aOR 0.41, 95% CI 0.18, 0.92). Mean PaO2 within 24 -hs was the third most important predictor and explained 9.1% of the variability in STHD. CONCLUSION: The mean PaO2 within the first 24-hs after admission for OHCA has a non-linear association with the highest STHD seen between 100 and 180 mmHg. Randomised controlled trials are now needed to validate the optimal oxygenation targets in mechanically ventilated OHCA patients.

Original languageEnglish
Pages (from-to)130-138
Number of pages9
Publication statusPublished - Jan 2021


  • Arterial blood gas analysis
  • Arterial oxygen tension
  • Cerebral performance category
  • Emergency medical services
  • Neurological outcome
  • Out-of-hospital cardiac arrest
  • Post-resuscitation care
  • Survival

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