Effect of propofol on sleep quality of critically ill patients

INTERVENTION: Each patient will be studied on two consecutive nights (from 9:00 pm to 7:00 am). In each patient two nights polysomnography studies will be performed with or without propofol in random order. Propofol will be administered via continuous infusion. The rate (mc/Kgr/min) of sedation will be such as to achieve a score of 3 on the Ramsay Scale (response to commands) with no changes in the infusion rate during the study time. Single doses of sedatives or changes in the rate of infusion of sedatives will be not permitted during the study or for 4 hours before the study. Patients in whom the requirements for sedation as judged by the primary physician increased during the night will be excluded for further study and the study will be terminated at that point. The Ramsay Scale will be re‐evaluated at the beginning (9:00pm) at the middle (2:00pm) and end (7:00am) of the study. Patients will be followed up until their discharge from the hospital. CONDITION: Critically ill patients ; Not Applicable PRIMARY OUTCOME: 1. Effect of propofol on sleep quality, measured immediately after each study night; 2. Sleep architecture, scored manually by an expert physician not involved in the study.; 3. Central apnoeas, arousals and awakenings, defined using standard criteria; 4. Total sleep fragmentation, calculated as the sum of arousals and awakenings per hour of sleep SECONDARY OUTCOME: Not provided at time of registration INCLUSION CRITERIA: 1. Critically ill patients, on mechanical ventilation for at least 48 hours, haemodynamically stable 2.Ventilated on assist mode 3. No respiratory distress 4. Aged between 18 and 85 years, inclusive, either sex