Article révisé par les pairs
Résumé : Abstract Cerebral hypoxia is an important cause of secondary brain injury. Improving systemic oxygenation may increase brain tissue oxygenation (PbtO 2 ). The effects of increased positive end-expiratory pressure (PEEP) on PbtO 2 and intracranial pressure (ICP) needs to be further elucidated. This is a single center retrospective cohort study (2016–2021) conducted in a 34-bed Department of Intensive Care unit. All patients with acute brain injury under mechanical ventilation who were monitored with intracranial pressure and brain tissue oxygenation (PbtO 2 ) catheters and underwent at least one PEEP increment were included in the study. Primary outcome was the rate of PbtO 2 responders (increase in PbtO 2  > 20% of baseline) after PEEP increase. ΔPEEP was defined as the difference between PEEP at 1 h and PEEP at baseline; similarly ΔPbtO 2 was defined as the difference between PbtO 2 at 1 h after PEEP incrementation and PbtO 2 at baseline. We included 112 patients who underwent 295 episodes of PEEP increase. Overall, the median PEEP increased form 6 (IQR 5–8) to 10 (IQR 8–12) cmH 2 O (p = 0.001), the median PbtO 2 increased from 21 (IQR 16–29) mmHg to 23 (IQR 18–30) mmHg (p = 0.001), while ICP remained unchanged [from 12 (7–18) mmHg to 12 (7–17) mmHg; p = 0.42]. Of 163 episode of PEEP increments with concomitant PbtO 2 monitoring, 34 (21%) were PbtO 2 responders. A lower baseline PbtO 2 (OR 0.83 [0.73–0.96)]) was associated with the probability of being responder. ICP increased in 142/295 episodes of PEEP increments (58%); no baseline variable was able to identify this response. In PbtO 2 responders there was a moderate positive correlation between ΔPbtO 2 and ΔPEEP (r = 0.459 [95% CI 0.133–0.696]. The response in PbtO 2 and ICP to PEEP elevations in brain injury patients is highly variable. Lower PbtO 2 values at baseline could predict a significant increase in brain oxygenation after PEEP increase.

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