American Board of Internal Medicine (ABIM) Certification Practice Exam

What is a primary indication for oxygen therapy in COPD patients?

1. Arterial PO2 less than or equal to 70 mm Hg

2. Persistent cough with mucus

3. Arterial PO2 less than or equal to 55 mm Hg

4. Age over 65 years

The correct answer is: Arterial PO2 less than or equal to 55 mm Hg

The primary indication for oxygen therapy in patients with chronic obstructive pulmonary disease (COPD) is based on specific arterial oxygen partial pressure (PO2) thresholds. Oxygen therapy becomes critical when the arterial PO2 is less than or equal to 55 mm Hg, which indicates severe hypoxemia. This low level of oxygen in the blood signifies that the body is not receiving adequate oxygenation, which can lead to significant complications such as pulmonary hypertension and right heart failure. By administering oxygen, the goal is to improve the patient's oxygen saturation, enhance organ function, and ultimately improve quality of life. In contrast, a PO2 of 70 mm Hg might suggest mild hypoxemia and doesn't typically warrant the initiation of long-term oxygen therapy. Persistent cough with mucus is a symptom of COPD but does not directly indicate the need for oxygen therapy. Finally, being over 65 years of age does not inherently require oxygen therapy, although older patients may have a greater prevalence of pulmonary diseases that could lead to the need for such interventions based on their oxygen saturation levels.