It is an observational study in order to define if there are common polysomnographic sleep features within the following three groups of wake critically ill patients on mechanical ventilation in ICU: the group of septical patients, the group of patients with chronic obstructive pulmonary disease in exacerbation and the group of surgical patients without sepsis.~15 patients will be included in each group. They will undergo polysomnographic sleep monitoring during up to 24 hours.~Polysomnograms will be studies then in order to find out if there are common sleep characteristics within the homogeneous patient groups of critically ill.
15 patients with sepsis, 15 patients with COPD and 15 surgical patients will undergo polysomnographic sleep monitoring up to 24 hours in order to define if there are common sleep features within the groups