Proportional Assist Ventilation vs Pressure Support Ventilation

Inclusion Criteria: * Tracheotomized or endotracheally intubated and mechanically ventilated patients transferred or scheduled to be transferred to the RACU. * Age 18 years or older. Exclusion Criteria: * Patients who are weaned from ventilatory support within the first 72 hours of transfer to the RACU. Even though these patients had been randomized, they will be excluded. They will be considered in the intention to treat analysis but the final outcome analysis will be performed after their exclusion. * High spinal cord injury * Immunosuppressed patients receiving chemotherapy or radiation therapy (\< 2 months after chemotherapy or radiation therapy). * Neuromuscular/ neurological disease of a progressive nature resulting in chronic ventilator dependence. * High risk of mortality within 3 months (severe neurological damage and cancer patients in terminal stages of the disease). * Patients unable to trigger the ventilator for any reason. * Any patient who is not considered a candidate for weaning from ventilatory support * Patients consented for another interventional study. * Patients requiring more than 30 days to wean once randomized will be excluded. They will be considered in the intention to treat analysis but the final outcome analysis will be performed after their exclusion.