What is the rationale for selecting the lowest FiO2 to maintain SpO2 88–92% in COPD patients?

• A. To avoid CO2 retention due to hypoxic drive suppression
• B. To eliminate all risk of hyperoxia
• C. To prevent dehydration
• D. To reduce heart rate

Answer: (A)

In COPD with chronic CO2 retention, the body’s drive to breathe is often more dependent on low oxygen levels (peripheral chemoreceptors) than on CO2 levels. If you give too much oxygen, this hypoxic drive can be blunted, leading to hypoventilation and CO2 buildup (hypercapnia) with a risk of respiratory failure. By titrating oxygen to the lowest FiO2 that still keeps SpO2 in the 88–92% range, you provide enough oxygen for tissue needs while preserving enough ventilatory drive to avoid CO2 retention. This balance helps prevent acidosis and deterioration in ventilation.

The other ideas aren’t the primary rationale here. Dehydration isn’t directly addressed by oxygen levels, and reducing heart rate isn’t the goal of COPD oxygen therapy. While avoiding excessive oxygen is important, the key concept is preserving hypoxic drive to prevent CO2 retention rather than simply eliminating hyperoxia risk.