What oxygen flow rate is used in emergencies?

• A. 5 litres per minute via nasal cannula
• B. 15 litres per minute via non-rebreather mask
• C. 2 litres per minute via rescue mask
• D. 25 litres per minute via mask

Answer: (B)

In emergencies, the aim is to raise oxygen levels quickly with a device that can deliver a high concentration of oxygen and keep exhaled air from being re-inhaled. A non-rebreather mask with a reservoir delivers a high FiO2 when used at a high flow, typically around 10–15 litres per minute. This flow keeps the reservoir full and the one-way valves closed during inspiration, so most of the air inhaled comes from the oxygen reservoir rather than from room air. That combination gives the highest possible oxygen concentration with a simple mask, which is crucial in acute hypoxaemia.

Lower flow rates or less capable devices don’t provide enough oxygen rapidly. A nasal cannula at 5 litres per minute supplies a relatively modest FiO2 and isn’t sufficient for emergencies needing rapid, high oxygen delivery. A rescue mask at 2 litres per minute would under-deliver oxygen, and a flow like 25 litres per minute via a standard mask isn’t typical or safe with that equipment. So the best choice in an emergency is delivering oxygen at about 15 litres per minute through a non-rebreather mask to ensure the quickest, highest concentration oxygen delivery.