Purpose: Severe traumatic brain injury is a leading cause of mortality and morbidity, and these patients are frequently intubated in the prehospital setting. Cerebral perfusion and intracranial pressure are influenced by the arterial partial pressure of CO 2 and derangements might induce further brain damage. We investigated which lower and upper limits of prehospital end-tidal CO 2 levels are associated with increased mortality in patients with severe traumatic brain injury. Methods: The BRAIN-PROTECT study is an observational multicenter study. Patients with severe traumatic brain injury, treated by Dutch Helicopter Emergency Medical Services between February 2012 and December 2017, were included. Follow-up continued for 1 year after inclusion. End-tidal CO 2 levels were measured during prehospital care and their association with 30-day mortality was analyzed with multivariable logistic regression. Results: A total of 1776 patients were eligible for analysis. An L-shaped association between end-tidal CO 2 levels and 30-day mortality was observed (p = 0.01), with a sharp increase in mortality with values below 35 mmHg. End-tidal CO 2 values between 35 and 45 mmHg were associated with better survival rates compared to < 35 mmHg. No association between hypercapnia and mortality was observed. The odds ratio for the association between hypocapnia (< 35 mmHg) and mortality was 1.89 (95% CI 1.53–2.34, p < 0.001) and for hypercapnia (≥ 45 mmHg) 0.83 (0.62–1.11, p = 0.212). Conclusion: A safe zone of 35–45 mmHg for end-tidal CO 2 guidance seems reasonable during prehospital care. Particularly, end-tidal partial pressures of less than 35 mmHg were associated with a significantly increased mortality.

Original languageEnglish
Pages (from-to)491-504
Number of pages14
JournalIntensive care medicine
Issue number5
Early online date2023
Publication statusPublished - May 2023


  • Carbon dioxide
  • Critical care
  • Endotracheal intubation
  • Traumatic brain injury
  • Ventilation

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