Most patients admitted to intensive care units require mechanical ventilation. Weaning from assisted/controlled ventilation begins when we recognize that the patient has recovered adeguately from acute respiratory failure.

If weaning is delayed, costs are increased, as are the risks of nosocomial pneumonia, cardiac-associated morbility, and death. On the other hand, weaning too soon often results in reintubation, which is associated with complications similar to those of prolonged ventilation.

The aim of this trial is to establish an evidence-based approach to weaning and to determine when a patient is ready to be weaned from mechanical ventilation, and what is the best weaning technique.

Inclusion Criteria:

1. Age higher than 18 yrs
2. PaO2/FiO2 greater or equal than 150 with PEEP equal or lower than 10, and minute ventilation lower than 15 l/min
3. Temperature lower than 38,5°C
4. Stable hemodynamics: HR 60-125 b/min, SBP 90-160 mmHg without or with dopamine lower than 10 gamma/Kg/min or dobutamine lower than 10 gamma/Kg/min, no acute arrythmias
5. Hb higher than 8 g/dl
6. GCS higher or equal than 9
7. The attending physician has to agree that the patient is in stable conditions and ready to be weaned from the ventilator

Exclusion Criteria:

1. presence of chronic neuromuscular diseases
2. need of surgical intervention within the next 72 hours
3. difficult tracheal intubation
4. tracheostomized patients