Mechanical Ventilation in Severe Brain Injury: The Effect of Positive End Expiratory Pressure on Intracranial Pressure

Mechanical Ventilation in Severe Brain Injury: The Effect of Positive End Expiratory Pressure on Intracranial Pressure

Mechanical Ventilation in Severe Brain Injury: The Effect of Positive End Expiratory Pressure on Intracranial Pressure

The purpose of this study is to collect physiologic data from patients with severe brain injury who require mechanical ventilation in order to describe the impact of ventilation, specifically positive end expiratory pressure (PEEP), on intracranial pressure (ICP).

Intracranial Hypertension, Critical Illness, Brain Injuries, Lung Injury, Respiratory Failure, Positive-Pressure Respiration, Intrinsic

Enrolled patients will receive a sequential, step-wise increase in positive end-expired pressure from 5 cmH2O to 15 cmH2O. Intracranial pressure, transpulmonary pressure, vitals, and mechanical ventilator data will be measured at each increment. PEEP will be increased by increments of 5 cmH2O. The mode of mechanical ventilation (pressure or volume control), inspiratory time and fraction of inspired oxygen (FIO2) will be determined by the critical care team caring for the patient. In the event that PEEP is set > 5 cmH2O, measurements will be obtained from that starting point and increased to a maximum of 15 cmH2O. The physiologic measurements will be obtained at regular intervals (within 5 minutes at each PEEP level) throughout the PEEP titration period.

Intracranial pressure will be measured and recorded using the existing intracranial pressure monitoring device placed previously as part of the patient's routine care. The association between positive end expiratory pressure and intracranial pressure will be analyzed as the primary outcome.

Transpulmonary pressure will be measured and recorded using an esophageal balloon catheter placed for research purposes. The association between transpulmonary pressure change with titration of PEEP and intracranial pressure will be analyzed as a secondary outcome.

Cerebral hemodynamic information will be recorded and calculated. The association between positive end expiratory pressure and cerebral hemodynamics will be analyzed as a secondary outcome.

Inclusion Criteria: Patients with severe brain injury (GCS 8 or less) Receiving mechanical ventilation Receiving intracranial pressure monitoring Exclusion Criteria: Esophageal varices Esophageal trauma Recent esophageal surgery Coagulopathy (Platelets < 80k or INR> 2 ) Other contraindication for esophageal manometry Already receiving PEEP > 15 cmH2O at enrollment Intracranial hypertension (defined as ICP > 20 mmHg) Decompressive hemi-craniectomy