Lung‑oxygen therapy (LTOT) is indicated for COPD when PaO2 meets which criterion?

• A. PaO2 ≤ 60 mmHg
• B. PaO2 ≤ 55 mmHg
• C. PaO2 ≤ 40 mmHg
• D. PaO2 ≤ 55 mmHg or ≤60 mmHg with cor pulmonale/polycythemia

Answer: (D)

LTOT is used in COPD for chronic hypoxemia because it improves survival and reduces complications from prolonged low oxygen levels. The key threshold is resting PaO2: if it is 55 mmHg or lower, LTOT is indicated. If the PaO2 is 60 mmHg or lower but there are end-organ effects of hypoxemia—such as cor pulmonale or polycythemia—LTOT is also indicated. That combination is why the best criterion is the statement that includes either PaO2 ≤ 55 mmHg, or PaO2 ≤ 60 mmHg with cor pulmonale/polycythemia. A PaO2 of 60 mmHg alone without these complications isn’t enough, and a PaO2 of 40 mmHg would meet hypoxemia thresholds but the standard emphasis for COPD LTOT is the rule described.