Respiratory weaning is classified into simple weaning, difficult weaning and prolonged weaning. When the patient successfully completes the spontaneous breathing trial (SBT), weaning can then be started using one of the three ways: moving from assist control to higher levels of pressure support ventilation, using synchronized intermittent mandatory ventilation with an initial higher rate which can be decreased over time, and continuing full ventilatory support with intermittent trials of low levels of pressure support or continuous positive airway pressure (CPAP). The chapter outlines the role of tracheostomy and non-invasive ventilation in weaning. Proportional assist ventilation (PAV) is a form of synchronized partial ventilatory support in which the ventilator generates support in proportion to the patient's instantaneous effort. Adaptive support ventilation (ASV) is based on a computer-driven closed loop regulation system of ventilator settings which are responsive to changes in both the respiratory system mechanics and spontaneous breathing efforts.