Pneumothorax occurs when air leaks between the lung and the chest wall, causing the lung on the affected side to collapse, reducing the ability to breathe.

In patients with neurological impairment such as those with traumatic brain injury, the goal of ventilation is to optimize oxygen saturation, limit ventilator-related injury, and ensure ventilation (CO2 removal). Equally important is to avoid secondary brain injury, including problems associated with positive pressure ventilation: hypoxia, hypotension, excessive or prolonged hypercapnia, and increased intracranial pressure.