This study compares two opposite strategies of weaning from Mechanical Ventilation. One of them is Low Pressure Support Ventilation during 30 minutes and the other is T-Tube for 2 hours. The aim of the study is to know witch one has a higher successful extubation rate.

The final stage of weaning from Mechanical Ventilation is known as Spontaneous Breathing Test (SBT). Some studies in the last 20 years have compared different strategies of weaning.

The SBT using T-Tube versus Low Pressure Support Ventilation (PSV) for 2 hours didn't show differences in successful extubation.

No difference in successful extubation rate were seen with the T-Tube for 30 or 120 minutes, or the Low PSV for 30 minutes or 2 hours For this reason the actual guidelines recommend to use T-Tube or Low PSV from 30 minutes to 2 hours with the same level of evidence.

Nevertheless, no studies have compared two opposite strategies like T-Tube for 2 hours (High work of breathing) versus Low PSV for only 30 minutes (Low work of breathing). Whereas the high work of breathing approach can be more specific for detecting more fitted patients, the low work of breathing method may reduce fatigue during SBT allowing more patients to be extubated.

We have designed a prospective, multicentric controlled and randomized study to compare this two opposite strategies of weaning: T-Tube for 120 minutes versus PSV 8 cmH2O for 30 minutes.

When patients show weaning criteria the randomly assigned SBT will be done.

We consider weaning criteria:

• Adequate cough
• Not too many respiratory secretions.
• Primary pathology solved.
• Clinical stability: Heart Rate (HR) < 140 bpm, Systolic Blood Pressure (SBP) 90-160 mmHg.
• Correct oxygenation: SatO2 > 90% with FiO2 < 0,4.
• Correct ventilatory pattern: Respiratory rate (RR) < 35 pm, Maximal Inspiratory Pressure (MIP) < -20 cmH2O, Tidal volume (TV) > 10 ml/kg, RR/TV < 100 pm/l.
• Adequate level of consciousness

Patients who succeed SBT will be extubated. Patients who fail SBT will be reconnected to the ventilator in the previous modality. These patients won't be randomized in future SBT.

We consider SBT failure:

Subjective Index:

• Neurological: Agitation or anxiety, Low level of consciousness.
• Increased work of breathing: accessory muscle use, dyspnea.

Objective Index:

• Hypoxemia: PaO2 < 60 mmHg or SatO2 < 90% with FiO2 > 50%.
• Tachypnea: RR > 35 pm.
• Hemodynamic instability: HR > 140 bpm, SBP > 180 mmHg, Arrhythmia.

Extubation failure will be registered within the first 72 hours after extubation.

We consider extubation failure:

• Respiratory acidosis: pH < 7,32, PaCO2 > 45 mmHg.
• Hypoxemia: SatO2 < 90% or PaO2 < 60 mmHg with FiO2 > 0,5.
• Deteriorating level of consciousness, Glasgow Coma Scale < 13.
• Uncontrolled agitation.
• Signs of fatigue.

Treatment of extubation failure will be decided by the attending physician: Reintubation, High Flow Oxygen therapy or Non Invasive Ventilation.

Reintubated patients won't be randomized in future SBT.

An interim analysis will be done when half of the simple is recruited.

Successful extubation will be analyzed by Kaplan-Meier survivial curves and logistic multivariable analysis with confounding variables.

Inclusion Criteria:

• More tan 18 years old
• More tan 24 hour of Mechanical Ventilation ready for weaning

Exclusion Criteria:

• Tracheostomy
• Non reintubation orders