Final answer:
The condition known as 'white out' lung with a PCWP less than 18 in a postsurgical patient is Acute Respiratory Distress Syndrome (ARDS), a severe lung condition characterized by inflammation and fluid accumulation in the alveoli.
Step-by-step explanation:
The condition referred to when a postsurgical patient has 'white out' lung on an X-ray and a pulmonary capillary wedge pressure (PCWP) less than 18 mmHg is commonly known as Acute Respiratory Distress Syndrome (ARDS). This serious lung condition leads to severe inflammation, increased permeability of lung capillaries, and fluid leakage into the alveoli, preventing proper oxygenation of the blood. 'White out' of the lung on a radiograph is indicative of this profound consolidation and fluid accumulation. ARDS can occur due to various direct or indirect lung injuries, including severe infections, trauma, or other inflammatory processes that injure the lung. It is not typically associated with an elevated PCWP, which would be more suggestive of cardiogenic pulmonary edema. In contrast, pneumonia is an infection of the lungs leading to inflammation and accumulation of fluids and white blood cells in the alveoli, marked by coughing and difficulty breathing. Pulmonary embolism refers to a blockage in one of the pulmonary arteries in the lungs most often caused by blood clots which travel to the lung from the legs or, occasionally, other parts of the body. However, 'white out' lung with normal PCWP is not descriptive of pulmonary embolism.