Effect of Intrathoracic Pressure Regulation on Decreased Cerebral Perfusion (4hour)

Inclusion Criteria:

• ≥18 years of age

• intubated and mechanically ventilated on a volume controlled mode

• head injury or other intracranial pathology and compromised cerebral perfusion

• arterial line in place or alternative with continuous pressure monitoring

• SpO2 ≥90%

• mean arterial pressure >55

• admission to ICU or about to undergo neurosurgery with planned placement of aninvasive intracranial pressure monitor

• inclusion presents no significant delays to planned emergent neurosurgery

• prior written informed consent

Exclusion Criteria:

• cardiac or pulmonary injury

• confirmed pneumothorax or hemothorax

• serious neck injury resulting in neck swelling with jugular venous compression

• evidence of ongoing uncontrolled bleeding

• respiratory disease such as COPD, interstitial lung disease, or other parenchymal orpulmonary vascular disease

• marked hypertension at time of device use defined as systolic blood pressure >180 mmHg

• congestive heart failure

• women with positive serum or urine pregnancy test or breast feeding