Which feature is characteristic of non-vented masks?

Non-vented masks are designed with a specific feature that distinguishes them from vented masks, and that is their ability to provide pure ventilation during both the inspiratory and expiratory phases of breathing. The characteristic of having both an inspiratory and expiratory line allows for effective ventilation without the risk of rebreathing exhaled gases. This design typically involves a one-way valve system that ensures that the air exhaled by the patient does not mix with the air they breathe in, which is critical for maintaining adequate oxygenation and preventing carbon dioxide retention.

This feature is particularly important in clinical scenarios where controlled and effective ventilation is necessary, as it maximizes the efficiency of the noninvasive ventilation therapy provided through these masks. In contrast, other options either misrepresent the function of non-vented masks or inaccurately describe other types of ventilation systems. Non-vented masks do not typically rely solely on tidal volume monitoring or require external oxygen supplementation specifically as a defining characteristic, nor do they involve pressure monitoring as a primary feature.