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.

Intensive care unit (ICU) patients are continuously exposed to various unpleasant sensations that are as many sources of discomfort. If, growing attention has been given to the detection and treatment of pain, very little attention has been given to dyspnea. However, there is growing evidence suggesting that dyspnea is frequent and severe in mechanically ventilated ICU patients. In mechanically ventilated ICU patients, dyspnea is independently associated with anxiety and mechanical ventilation itself. Indeed, an optimization of ventilator settings alleviates dyspnea in 35% of patients.

Various arguments suggest that dyspnea contributes to the dark experience of ICU and participates to the genesis of post traumatic stress disorders. In addition, dyspnea is associated with a longer duration of mechanical ventilation.

Large multicentre studies are however lacking. The aims of the present multicentre study are 1) to quantify the prevalence of dyspnea in a large population of ICU mechanically ventilated patients, 2) to examine the link between the level of dyspnea and the occurrence of adverse events in the ICU, 3) 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 disorder associated symptoms.

Inclusion criteria:

• Invasive mechanical ventilation in the ICU for > 24 hours
• Remaining stay in the ICU estimated > 24 hours

Exclusion criteria :

• RASS <-2 or >+2
• Delirium (defined according to CAM-ICU)
• Severe cognitive impairment or severe psychiatric disease
• Patient who does not understand French
• Severe depthless
• Age <18 years

The aims of the present multicentre study are 1) to quantify the prevalence of dyspnea in a large population of ICU mechanically ventilated patients, 2) to examine the link between the level of dyspnea and the occurrence of adverse events in the ICU, 3) 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 disorder associated symptoms.