A central (Hickman) line is a long, hollow tube made from silicone rubber. The central line is inserted under the skin of the chest into a vein. The space in the middle of the tube is called the lumen.
At the end of the tube outside the body the lumen has a special cap to which a drip line or syringe can be attached. Sometimes there is also a clamp to keep the tube closed when it is not being used. A central line can be used to give treatments such as chemotherapy, antibiotics and intravenous fluids. It can also be used to take samples of your blood for testing.
Definition from Macmillan website:Hickman line