Safety of Optimal PEEP in NSICU Patients

Study Overview
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Brief Summary
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The investigators aim to demonstrate that use of transpulmonary pressure to guide PEEP management is safe in patients with possible elevations of intracranial pressure.

Detailed Description
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Purpose: To establish safety of titrating PEEP based on transpulmonary pressure as measured by an esophageal balloon in mechanically ventilated neurosurgical patients. Participants: Adult patients admitted to the Neuro ICU at UNC Hospital and requiring mechanical ventilation who have an intracranial pressure monitoring device in place. Procedures (methods): All enrolled patients will have esophageal balloons placed with measurement of transpulmonary pressures. All patients will have baseline measurements recorded of intracranial pressure, cerebral perfusion pressure, and cerebral autoregulation. PEEP will then be titrated based on transpulmonary pressure measurements with recording of physiological measurements over the next hour. At the conclusion of the hour, all patients will be returned to their prior ventilator settings.

Official Title
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Evaluating Safety of Transpulmonary Pressure Guided PEEP Management in Neurocritical Care Patients

Conditions
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Respiratory Failure, Intracranial Hypertension

Intervention / Treatment
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* Device: Esophageal Balloon catheter


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Adult patients (age >/= 18) admitted to the Neuro ICU of UNC Hospital requiring mechanical ventilation and with ICP monitoring in place. Exclusion Criteria: Pneumothorax or pneumomediastinum Life expectancy < 24 hours or expected to require mechanical ventilation for < 24 hours Condition that precludes placement of an esophageal balloon [esophageal or nasopharyngeal pathology preventing insertion of the esophageal balloon catheter (esophageal ulcerations, tumors, diverticulitis, bleeding varices or in patients with sinusitis, epistaxis or recent nasopharyngeal surgery), severe thrombocytopenia (platelet count < 30) or coagulopathy (INR > 3 or on oral anticoagulants). Pre-enrollment ICP > 20 mm Hg Pre-enrollment CPP < 60 mm Hg Planned change in the external ventricular drain set point during the pre-intervention, intervention or post-intervention periods Incarceration Variation in ICP of > 2 cm H2O in the hour prior to intervention.
Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Other
Intervention Model: Single Group Assignment
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: Esophageal Balloon catheter<br>All patients will have an esophageal balloon catheter inserted into their nare while upright (head of bed > 30 degrees) to a depth slightly more than the estimated distance from the lower sternum to the back of the ear (typically around 60 cm). Gastric positioning will be confirmed with abdominal compression testing and the catheter then retracted 10 - 20 cm into the lower esophagus. Placement will be confirmed with the presence of cardiac oscillations on the esophageal probe. The probe will then be secured to the patient's nasal opening using tape. | Device: Esophageal Balloon catheter<br>* Pressures [Esophageal Pressure (Pes), Airway Pressure (Paw), and Transpulmonary Pressure (Ptp)] are measured directly through the ventilator. The waveforms of Paw, Pes, and Ptp will be visualized on the ventilator. Ptp is obtained from Paw - Pes. All patients will have baseline measurements recorded of ICP, CPP, and MAP. PEEP will be increased on the ventilator to achieve a Ptp between 0 and +2 cm H2O (Optimal PEEP). Measurements of Intracranial pressure (ICP), cerebral perfusion pressure (CPP), and mean arterial pressure (MAP) will be repeated 5 minutes after the change in PEEP.<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Change in ICP Value | The Intracranial pressure (ICP) value after intervention will be considered equivalent to the ICP before intervention if the 95% upper bound of the change is lower than the non-inferiority margin of 4 mm Hg. | Within 5 minutes of catheter placement | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Change in Cerebral Perfusion Pressure (CPP) | Cerebral perfusion pressure is equal to the mean arterial pressure (MAP) minus the intracranial pressure (ICP). The initial CPP is calculated by measuring CPP immediately before changing ventilator settings. The post-intervention CPP is measured 5 minutes after ventilator setting change is made. The difference between the initial CPP and the post-intervention CPP reflects the change in CPP. | Immediately before and 5 minutes after ventilator setting change | 
| Change in Mean Arterial Pressure | Mean Arterial Pressure (MAP) is the average arterial pressure in one cardiac cycle measured through an arterial line. | Immediately before and 5 minutes after ventilator setting change |