Acute lung injury/acute respiratory distress syndrome (ALI/ARDS) is a common problem faced by patients in the intensive care unit (ICU). The etiology of ALI is multifactorial and depends on the clinical situation; frequently ALI is the manifestation of bilateral pneumonia, transfusion reactions, or aspiration. This chapter presents a case study of a 26-year-old female who was admitted for confusion, continuing headache, nausea, and vomiting. There are two different etiological categories of ALI: direct lung injury and indirect lung injury. Direct lung injury tends to include pneumonia and aspiration along with inhalational injury and pulmonary contusions. Indirect injury etiology includes sepsis, trauma, blood transfusions, and pancreatitis. The use of positive end expiratory pressure (PEEP) and low tidal volume ventilation in the neurosurgical population is problematic, as a key component of ventilator management in this population is appropriate CO2 removal.