When is humidification of inspired gas during mechanical ventilation considered mandatory?

Humidification of inspired gas is considered mandatory when an endotracheal or tracheostomy tube is present. This is due to the fact that these tubes bypass the natural humidifying structures of the upper airway, causing the inspired air to be delivered directly to the lower respiratory tract without the moisture normally added in the nasal passages and oral cavity.

In the absence of humidification, the dry gas can lead to complications such as mucosal irritation, thickening of secretions, increased risk of infection, and potential damage to the airway epithelia. Therefore, implementing humidification is crucial to maintain adequate airway moisture and function in patients who are mechanically ventilated with these artificial airways in place.

In contrast, other situations such as when a patient is awake or using a nasal cannula may not necessitate humidification to the same extent, as the body's natural airway structures are still functioning to provide adequate moisture. Similarly, the patient's tidal volume doesn't directly relate to the need for humidification when an artificial airway is in place.