There is no recommendation for the management of the positive end-expiratory pressure (PEEP) during setting of a central venous catheter (CVC) in a ventilated patient. Several non-randomized studies have investigated the cross-sectional area (AST) ultrasound minor axis for different pressure levels by evaluating a single vessel every time or by not displaying the right or left side in the evaluation. Another study showed that there could be unpredictable size differences between the 2 subclavian veins.

In ventilated patient, the PEEP, which is intrathoracic, will result in a decrease of venous return and thus possibly a superior vena cava dilation, located outside the pleura, depending on their capacitance. Different pressure levels showed an increase of AST with the increase of intra-thoracic pressure on certain veins, in a heterogeneous and not randomized manner.

The primary purpose of the study is to measure the effect of PEEP (0, 5, 10 or 15 cm H2O) and the patient's position (supine or Trendelenburg strict -15-20 °) on the cross-sectional area of the jugular and subclavian veins.

There is no recommendation for the management of the positive end-expiratory pressure (PEEP) during setting of a central venous catheter (CVC) in a ventilated patient. Several non-randomized studies have investigated the cross-sectional area (AST) ultrasound minor axis for different pressure levels by evaluating a single vessel every time or by not displaying the right or left side in the evaluation. Another study showed that there could be unpredictable size differences between the 2 subclavian veins.

In ventilated patient, the PEEP, which is intrathoracic, will result in a decrease of venous return and thus possibly a superior vena cava dilation, located outside the pleura, depending on their capacitance. Different pressure levels showed an increase of AST with the increase of intra-thoracic pressure on certain veins, in a heterogeneous and not randomized manner.

The primary purpose of the study is to measure the effect of PEEP (0, 5, 10 or 15 cm H2O) and the patient's position (supine or Trendelenburg strict -15-20 °) on the cross-sectional area of the jugular and subclavian veins.

Inclusion Criteria:

• Any patient ventilated in intensive care is eligible.
• Age ≥ 18 years
• Patient with stable hemodynamic status and Mean Blood Pressure (< 65 mmHg)
• Patient with registered social security number

Exclusion Criteria:

• clinical sign for a central venous thrombosis (unilateral edema ...).during echography screening before inclusion
• presence of a central line for more than 48 hours.
• Anechoic patient (checked during echography screening)
• History of cervical spine surgery.
• IntraCranial HyperTension
• patient in shock with hemodynamic instability and not stabilized
• patient treated by noradrenaline > 1 µg/kg/min
• patient or relative's refusal
• protected patients ≥ 18 years, minors, pregnant women