American Board of Internal Medicine (ABIM) Certification Practice Exam

In patients with severe acute respiratory distress syndrome, what FiO2 level should be targeted?

1. Less than 0.4

2. Less than 0.5

3. Less than 0.6

4. Less than 0.7

The correct answer is: Less than 0.6

In patients with severe acute respiratory distress syndrome (ARDS), targeting an FiO2 level of less than 0.6 is crucial for managing oxygenation without exposing the patient to excessive oxygen toxicity. High levels of supplemental oxygen can lead to complications such as lung injury and absorption atelectasis, especially in individuals with compromised lung function. The rationale for targeting an FiO2 below 0.6 stems from evidence suggesting that maintaining oxygen saturation levels (such as SpO2) between 90% and 96% is generally adequate to ensure tissue perfusion while mitigating the risks associated with higher FiO2 levels. Additionally, lower oxygen requirements encourage the use of lung-protective ventilation strategies, which are essential in ARDS management. By keeping the FiO2 below this threshold, clinicians can balance the need for adequate oxygen delivery with the potential adverse effects of prolonged exposure to high oxygen levels, making this approach particularly beneficial for patients suffering from severe ARDS.