A PICC is a long, slender, small, flexible tube that is inserted into a peripheral vein, typically in the upper arm, and advanced until the catheter tip terminates in a large vein in the chest near the heart to obtain intravenous access. It is similar to other central lines as it terminates into a large vessel near the heart. However, unlike other central lines, its point of entry is from the periphery of the body the extremities. And typically the upper arm is the area of choice.
A PICC line provides the best of both worlds concerning venous access. Similar to a standard IV, it is inserted in the arm, and usually in the upper arm under the benefits of ultrasound visualization. Also, PICCs differ from peripheral IV access but similar to central lines in that a PICCs termination point is centrally located in the body allowing for treatment that could not be obtained from standard periphery IV access. In addition, PICC insertions are less invasive, have decreased complication risk associated with them, and remain for a much longer duration than other central or periphery access devices.
Using ultrasound technology to visualize a deep, large vessel in the upper arm, the PICC catheter is inserted by a specially trained and certified PICC nurse specialist. Post insertion at the bedside, a chest x-ray is obtained to confirm ideal placement.http://picclinenursing.com/picc_why.html
And here's a picture of where the PICC goes