American Board of Internal Medicine (ABIM) Certification Practice Exam

What arterial PO2 level indicates the need for supplemental oxygen in patients with COPD?

1. 50 mm Hg

2. 55 mm Hg

3. 60 mm Hg

4. 65 mm Hg

The correct answer is: 55 mm Hg

In patients with Chronic Obstructive Pulmonary Disease (COPD), supplemental oxygen therapy is often indicated when the arterial partial pressure of oxygen (PO2) falls below a certain threshold, which generally signifies inadequate oxygenation. A PO2 level of 55 mm Hg is associated with significant hypoxemia, and it is at this level that supplemental oxygen is usually recommended to mitigate the risk of hypoxic damage and improve patient outcomes. In the context of COPD, maintaining adequate oxygen saturation is crucial, as many patients may have baseline desaturation due to their underlying lung disease. When the arterial PO2 is at 55 mm Hg, it indicates that the patient is likely experiencing severe respiratory distress and possible organ dysfunction due to insufficient oxygen. Providing supplemental oxygen can help to elevate the arterial PO2 into a safer range, ensuring that vital organs receive the necessary oxygenation. While PO2 levels of 50 mm Hg and lower may also suggest the need for oxygen therapy, the standard practice often considers the 55 mm Hg threshold as a critical point at which intervention should definitely occur. A level of 60 mm Hg, although it may suggest a degree of hypoxemia, is often seen as being on the edge of acceptable range and might not trigger an immediate