American Board of Internal Medicine (ABIM) Certification Practice Exam

In the context of ARDS, what is the upper limit of the acceptable PaO2 range?

1. 50 mm Hg

2. 80 mm Hg

3. 100 mm Hg

4. 150 mm Hg

The correct answer is: 80 mm Hg

In the context of Acute Respiratory Distress Syndrome (ARDS), maintaining an appropriate arterial oxygen partial pressure (PaO2) is crucial for patient management. The upper limit of the acceptable range for PaO2 is considered to be around 80 mm Hg. This is because excessively high PaO2 levels can lead to oxygen toxicity and may cause further lung injury. In ARDS, the goal is to optimize oxygen delivery while minimizing potential harm from over-oxygenation. Maintaining PaO2 around 80 mm Hg is often sufficient to ensure adequate tissue oxygenation while reducing the risk of complications associated with hyperoxia, such as oxidative stress and damage to the pulmonary and systemic vasculature. Values above 80 mm Hg may not provide additional benefits and can lead to the aforementioned risks, thus making 80 mm Hg the upper limit of the acceptable PaO2 range in this clinical scenario. Options indicating higher values might not align with the clinical guidelines aimed at preventing oxygen toxicity, which is particularly important in the fragile environment of ARDS, where lung protection strategies are paramount.