This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Airway, Subject name: Anaesthesia
Simple face mask (Hudson mask) can deliver maximum FiO2 of:- 
Select and explain. 
A. 0.6, B. 0.4, C. 0.8, D. 1
A: 0.6
Answer: A: 0.6 
Explanation: Simple facemask/ 'Hudson' mask These devices are used very commonly. They are variable performance devices and the maximum inspired oxygen concentration that can be achieved with these devices is up to 60%, but this is very dependent on the oxygen flowrate and the patient's respiratory pattern. The mask has side holes which are designed to allow indrawing of room air during inspiration