A PaO2/FiO2 ratio of less than 200 indicates which pathophysiological condition?

A PaO2/FiO2 ratio of less than 200 is indicative of Acute Respiratory Distress Syndrome (ARDS). This condition is characterized by severe hypoxemia and is classified according to the degree of respiratory failure. The PaO2/FiO2 ratio is a crucial metric used to differentiate between varying levels of respiratory distress.

In the context of ARDS, the key to understanding the significance of the ratio lies in the severity of lung impairment. A ratio below 200 signifies a more severe form of acute lung injury that meets the criteria for ARDS. It reflects a significant impairment in gas exchange, which can result from various factors such as pneumonia, sepsis, or trauma.

While Acute Lung Injury (ALI) is also associated with reduced PaO2/FiO2 ratios, it is typically classified with a ratio between 200 and 300. Therefore, a ratio of less than 200 specifically indicates ARDS rather than ALI, which is a critical distinction in clinical diagnosis and management.