Which oxygen delivery and flow rate is typically recommended for a conscious passenger with suspected hypoxia at cabin altitude?

• A. 50% oxygen via nasal cannula at 4 L/min
• B. 100% oxygen via a tight-fitting mask at about 15 L/min if a non-rebreather mask is used; otherwise a tight-fitting mask with high-flow O2
• C. 21% oxygen via a simple mask at 2 L/min
• D. No supplemental oxygen

Answer: (B)

When a conscious passenger shows signs of suspected hypoxia at cabin altitude, the goal is to quickly raise the fraction of inspired oxygen to restore arterial oxygen levels. The most effective way to do this in flight is to deliver high-concentration oxygen using a non-rebreather mask with a reservoir at a high flow, typically around 15 L/min. This setup can provide near-100% oxygen to the passenger, which is crucial when ambient cabin pressure reduces the available oxygen.

If a non-rebreather mask isn’t available, the next best option is a tight-fitting mask with high-flow oxygen, because it still delivers a high FiO2 compared with other devices like a nasal cannula or a simple mask at low flow. The lower-flow devices deliver substantially less oxygen and may not adequately treat hypoxia in this setting.

So, the recommended approach is to give high-concentration oxygen with a non-rebreather mask at about 15 L/min (or, if that mask isn’t available, a tight-fitting mask with high-flow oxygen) to rapidly improve oxygenation.