American Board of Internal Medicine (ABIM) Certification Practice Exam

What arterial PO2 level indicates severe resting hypoxemia in COPD patients?

1. 60 mm Hg or less

2. 55 mm Hg or less

3. 50 mm Hg or less

4. 65 mm Hg or less

The correct answer is: 55 mm Hg or less

In chronic obstructive pulmonary disease (COPD), arterial blood gas measurements are crucial for assessing the severity of hypoxemia. A partial pressure of oxygen (PO2) level of 55 mm Hg or less is indicative of severe resting hypoxemia. At this level, patients often experience significant clinical manifestations, including cyanosis, altered mental status, and other complications associated with inadequate oxygenation of tissues. A PO2 of 55 mm Hg or less suggests that the oxygen saturation in the blood is critically low, which may necessitate interventions such as supplemental oxygen or more advanced respiratory support. This threshold is particularly relevant for clinicians when evaluating the need for aggressive management of COPD and the potential for long-term oxygen therapy. While other levels such as 60 mm Hg or less and 50 mm Hg or less are relevant in clinical practice, the specific benchmark of 55 mm Hg clearly delineates a level of hypoxemia that warrants immediate attention and intervention in the context of COPD management.