 The efficacy and safety parameters that will be monitored include sedation levels, heart rate, blood pressure and ventilation indicators. Once subjects have met site-specified respiratory criteria, they will undergo tracheal extubation. The dexmedetomidine infusion may be continued during and after extubation if further sedation is required post-extubation. The continuous infusion of dexmedetomidine must be administered for a minimum of 6 hours and a maximum of 24 hours. Sedation levels, heart rate, blood pressure, respiratory rate, ventilator settings, SpO2 and if available transcutaneous carbon dioxide TcCO2 andor arterial blood gases ABG will be monitored and recorded in the peri-extubation period. 