Which ARDS severity category has the highest PaO2/FiO2 ratio?

Mild ARDS is characterized by a PaO2/FiO2 ratio ranging from 200 to 300 mmHg. This category indicates a less severe impairment in gas exchange compared to the other ARDS severity categories. In contrast, moderate and severe ARDS exhibit progressively lower PaO2/FiO2 ratios, with moderate ARDS ranging from 100 to 200 mmHg and severe ARDS being below 100 mmHg.

The significance of the PaO2/FiO2 ratio is that it serves as a quantitative measure of the extent of hypoxemia and reflects the degree of lung injury. Since mild ARDS has the highest ratio, it indicates a better preserved ability for oxygen transfer in comparison to the more severe forms of ARDS, which can lead to significant oxygenation failure. Thus, understanding the implications of these categories helps in assessing the severity of ARDS and guiding treatment decisions effectively.