What is the hallmark of severe ARDS?

The hallmark of severe Acute Respiratory Distress Syndrome (ARDS) is identified by a PaO2/FiO2 ratio of less than 100 mmHg. This measurement reflects the degree of hypoxemia a patient experiences, and in the context of ARDS, it indicates significant impairment in gas exchange due to lung injury.

When the PaO2/FiO2 ratio drops below 100 mmHg, it suggests that the patient is facing critical respiratory failure, which necessitates immediate and aggressive management, often including mechanical ventilation. This level of hypoxemia is consistent with the severe form of ARDS, indicating the lungs are severely compromised in their ability to oxygenate blood.

In comparison, a PaO2/FiO2 ratio ranging from 200-300 mmHg characterizes mild to moderate ARDS, while a ratio greater than 300 mmHg suggests that the condition is not severe. Therefore, understanding these values is crucial for the effective clinical assessment and management of patients with ARDS.