Table 4. The advantages and disadvantages of common types of ventilation interface.

Aspect	Nose mask	Nose-mouth mask	Helmet
Oral leakage	–	+	+
Volume monitoring	–	+	–
Initial response of blood gases	0	+	0
Speaking	+	–	0
Expectoration	+	–	–
Risk of aspiration	+	0	+
Aerophagy	+	0	0
Claustrophobia	+	0	0
Dead space (compressible volume)	+	0	–
Noise and limitation of hearing	+	+	–

+, advantage; o, neutral; –, disadvantage