• PaO2 ≥ 60 mmHg (8 kPa) with FiO2 of ≤ 0.35 • Alveolar-arterial PO2 gradient < 350 mmHg

Weaning is the process of gradual discontinuation of mechanical ventilation. Strictly speaking, it refers to a process of slow decrease in level of support from the ventilator and gradual increase of proportion of spontaneous ventilation by patient. 1) Does this patient need weaning? Patients with normal conscious state, respiratory mechanics and stable haemodynamics do not need weaning. Patients with chronic pulmonary disease with recent deterioration of respiratory mechanics or underlying neuromuscular problems may benefit from weaning. 2) Is the patient ready for weaning? z Precipitating factors for respiratory failure are under control z Sedation is not required z Normal conscious state z Adequate cough and gag reflexes z Stable haemodynamics requiring minimal or no vasopressor or inotropes 3) Parameters used to predict weaning success