Non-invasive ventilation application in neurocritical care with risk of pneumocephalus is controversial. Non-invasive ventilation-related increased intrathoracic pressure increases intracranial pressure via direct transmission of intrathoracic pressure to the intracranial cavity. In addition, increased thoracic pressure decreases venous return to the heart and increases vena jugularis interna pressure, thereby increasing cerebral blood volume. Pneumocephalus is one of the major concerns after non-invasive ventilation application in head/brain trauma patients. Non-invasive mechanical ventilation may be performed in limited conditions in head trauma/brain surgery with appropriate and close monitoring. High-flow nasal cannula oxygen therapy can provide higher FiO(2) as manifested by a larger increase in PaO2/FiO(2) ratio and provide the theoretical basis in pneumocephalus because augmenting the PaO2 more effectively would accelerate nitrogen (N-2) washout. As a result, non-invasive mechanical ventilation may be performed in limited manner in head trauma/ brain surgery with appropriate and close monitoring.