Low eligibility rate

The purpose of this study is to understand the relationship between intracranial pressure and airway pressures during mechanical ventilation. This study is a single-center, prospective cohort study to be conducted at Beth Israel Deaconess Medical Center. The investigators will recruit patients with severe brain injury (GCS 8 or less) who receive intracranial pressure monitoring and mechanical ventilation as part of their routine medical care. The primary endpoint is the change in intracranial pressure as a function of positive end-expiratory pressure. There is only one study encounter with safety monitoring for up to 24 hours after. No additional follow up is required.

Inclusion Criteria:

- Patients with severe brain injury (GCS 8 or less) who receive both mechanical ventilation and intracranial pressure monitoring as part of their standard medical care will be considered eligible.

Exclusion Criteria:

• Patients with esophageal varices
• Patients with esophageal trauma
• Patients with recent esophageal surgery
• Patients with coagulopathy (Platelets < 80k or INR> 2 )
• Other contraindication for esophageal manometry
• Patients who are receiving PEEP greater than 15 cmH2O within 24 hours prior to enrollment
• Intracranial hypertension (defined as ICP greater than 20 mmHg) within 48 hours prior to enrollment
• Decompressive hemi-craniectomy

Cessation Criteria: Study related ventilator adjustments and measurements will be stopped at any point during the intervention and ventilator settings will be returned to the pre-intervention settings under the following conditions:

• If ICP increases above 20mmHg, regardless of the duration of the event.
• If systolic blood pressure decreases below 90mmHg, regardless of the duration of the event.
• If systolic blood pressure increases above 180mmHg, regardless of the duration of the event.