Correlations of optic nerve sheath diameter with intracranial pressure, positive end-expiratory pressure and patient positioning in patients with severe traumatic brain injury on a mechanical ventilator in the ICU

Objectives

This study aims to assess the effect of different PEEP levels and patient positioning on optic nerve sheath diameter (ONSD) as a surrogate marker for intracranial pressure (ICP) in patients with severe TBI on mechanical ventilation.

Design

A prospective interventional study assessing the effects of PEEP and patient positioning on ONSD in ventilated TBI patients.

Setting

The aim of this study was to explore how alterations in the PEEP and patient position influence the optic nerve sheath diameter (ONSD), which is a marker of the ICP. Eighty patients on ventilators with TBIs were placed in three different positions with the bed's head end at 0°, 30°, and 45° angles.

Interventions

The ONSD was assessed using an ultrasound probe at PEEP of 0, 3, and 5 cm H₂O in all three positions.

Variables of interest

ONSD, ICP and PEEP.

Results

The study findings indicate that no statistically significant alteration in the ONSD observed at different PEEP levels or various patient positions. Although there was an increase in the ONSD when the PEEP was increased from 0 to 5 cm H₂O, this increase did not reach statistical significance. Notably, the most notable changes in ONSD were observed at the 30-degree patient position when the PEEP increased from 0 to 5 cm H₂O (6.12 ± 0.38 vs. 6.23 ± 0.40), with a p value of 0.07, indicating a trend toward significance.

Conclusion

The study results suggest that the application of PEEP up to 5 cm H₂O did not lead to significant changes in the ONSD, suggesting a degree of safety in its application for patients with TBI.