<qa>  What is dyspnea experienced by 50 of mechanically ventilated patients?Although pain has been extensively studied in ICU patients, only a few studies have focused on dyspnea, which is experienced by 50 of mechanically ventilated patients. The purpose of the present study is to determine whether dyspnea in intensive care unit patients is associated with a higher length of stay in the ICU and a higher incidence of post traumatic stress disorders. 