 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. 