Why is high-flow oxygen avoided in certain patients?

• A. It can cause oxygen toxicity or suppress the hypoxic drive in CO2-retaining patients
• B. It has no adverse effects and is always preferred
• C. It reduces blood pressure
• D. It causes dehydration

Answer: (A)

High-flow oxygen isn’t always harmless because certain patients rely on low oxygen levels to drive their breathing. In chronic CO2-retaining patients, like some with COPD, the body’s normal stimulus to breathe comes more from a drop in oxygen than from rising CO2. Providing them with high oxygen can lessen or eliminate that drive, leading to hypoventilation, rising CO2 (hypercapnia), and possible respiratory failure. There’s also a risk of oxygen toxicity from prolonged exposure to very high oxygen levels, which can cause oxidative stress and absorption atelectasis, further impairing gas exchange. That combination is why we target safer, room-to-moderate oxygen levels rather than always using high-flow oxygen.