In this study, the investigators aimed to study the role of medical gas humidification during noninvasive mechanical ventilation.

The medical gases are usually dry and cold thus when they are used during invasive mechanical ventilation they must be conditioned. No data are present on the necessity to condition the medical gases during non invasive mechanical ventilation. In this study the investigators studied the humidity and the temperature of the medical gases with and without any conditioning during non invasive mechanical ventilation in a group of healthy subjects and critically ill patients.

Inclusion Criteria:

• Critically ill patients requiring non invasive mechanical ventilation

Exclusion Criteria:

• Comatose patients