A: A midline is 3 to 8 inches long and is usually inserted in or near the bend of the arm; the tip of the catheter should end before the shoulder. This type of catheter does not require an X-ray after insertion and can be used for most antibiotics and other therapies lasting two to four weeks.

A PICC line, or peripherally inserted central catheter, is also inserted in or near the bend of the arm, but its tip goes past the shoulder and stops just outside the heart. A PICC requires a chest X-ray after insertion to make sure that the tip is in the correct place. This type of catheter can be inserted by a nurse or a doctor, either at the doctor's office or another place that has easy access to an X-ray facility.

PICCs can remain in place for a year and sometimes longer without complication. There is no maximum time that they can remain inserted, as long as there are no complications with the insertion site or the catheter itself. They are used for TPN (or total parenteral nutrition, a very rich liquid nutrient), IV antibiotics that can be irritating to the inside of a small vein, chemotherapy, and any other therapies lasting longer than four weeks.