Effect of Intrathoracic Pressure Regulation on Traumatic Brain Injury

Inclusion Criteria: * ≥15 years of age * intubated and mechanically ventilated on a volume controlled mode * head injury or other intracranial pathology with ICP of ≥15 mmHg * arterial line in place * SpO2 ≥95% * MAP \>60 * in ICU or about to undergo neurosurgery with planned placement of an ICP monitor * inclusion presents no significant delays to planned emergent neurosurgery * prior written informed consent Exclusion Criteria: * cardiac or pulmonary injury impacting intrathoracic pressure * confirmed pneumothorax or hemothorax * PaO2/FiO2 \<300 * 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 or pulmonary vascular disease * congestive heart failure