This study compares the short-term effects of a new humidification system (Hygrovent Gold) and two other humidification devices (heated and moisture exchanger and heated humidifier) on respiratory pattern and work of breathing, during invasive ventilation.

Three humidifying devices are commonly and indifferently used during mechanical ventilation, but their impact on respiratory mechanics and, eventually, mechanical ventilation efficacy, particularly in patients highly dependent from mechanical ventilation, are not superimposable.

It has already been described that heated and moisture exchangers (HME), increasing dead space, can negatively affect ventilatory function and gas exchange, in comparison to heated humidifiers (HH).

The Hygrovent Gold, mainly because of its position between the tracheostomy and the Y-piece of the ventilatory circuit and its structure, may lead to analogous or even worse effects, determining and increase in inspiratory resistances and dead space and consequently an increase in the work of breathing.

Inclusion Criteria:

• Chronic hypercapnic respiratory failure (PaCO2 of 45 mmHg or more)
• Long-term mechanical ventilation via tracheostomy
• Clinical stability

Exclusion Criteria:

• Non collaborative subjects
• Acute respiratory failure
• Haemodynamic instability
• Encephalopathy