Correlation of Positive End-Expiratory and Intracranial Pressure Using the Ultrasonographic-Guided Measurement of Optic Nerve Sheath Diameter in Traumatic Brain Injury Patients.

Abstract

In brain injury patients, positive end-expiratory pressure (PEEP) may potentially increase the intracranial pressure (ICP). ICP can be noninvasively assessed from the sonographic measurement of the optic nerve sheath diameter (ONSD). Herein, we aim to evaluate the association between PEEP and ICP via measuring ONSD in traumatic brain injury (TBI) patients. TBI patients with age ≥18 years, severe brain injury (GCS 8 or less), receiving mechanical ventilation, initial PEEP ≤4 mmHg and no history of severe cardiopulmonary disease were included in this study. Patients with intracranial hypertension (defined as ICP >20 mmHg) and already receiving PEEP >15 cm H2O at enrollment were excluded from the study. ONSD measurement was performed when hemodynamic parameters were most stable. Variables included central venous pressure, invasive blood pressure, heart rate, saturation, and ventilator parameters. The ONSD and ICP did not increase significantly while PEEP increased from 0-5 cm and 5-10 cm H2O. However, ONSD and ICP significantly increased when PEEP increased from 10-15 cm H2O. There was no significant difference noted while comparing measurements of optic nerve sheath (ONS) diameter in both eyes at all PEEP values in cases as well as control patients. Mean arterial pressure (MAP) decreased with an increase in PEEP value. Highly significant decrease occurred in MAP change from PEEP 10-15 in cases (P < 0.001) and control (P < 0.001). The PEEP up to 10 cm H2O can be safely applied in patients with TBI. In addition, the increment of PEEP might further increase the oxygenation, at the cost of ICP accentuation.