The ultrasound-guided positioning of a PICC involves the ultrasound identification of a vein (1) of adequate internal caliber (at least three times the external diameter of the catheter), (2) of not excessive depth (not more than 2.5 -3 cm from the skin surface) , (3) located in the middle third of the arm (Dawson's green zone).
The location of the emergency site in the green zone in fact allows a better clinical result in terms of dressing stability and low infectious risk.