A cannula needle is a stainless steel, hollow needle encased by a hollow plastic tube. The needle closely resembles a medical syringe tip, except that the needle isn't always attached to a plastic barrel for extracting fluids or tissue. These needles are blunt on one end and sharp on the other, with the sharpened end being formed into various shapes. Cannula needles are commonly used to insert medicines or fluids intravenously, to insert tracheotomy tubing or during liposuction.
The cannula needle is composed of two parts, the inner needle and the outer hollow tube. The needle can be removed from the tube after it is inserted for use, leaving behind the hollow tube. Eleven types of cannula needles exist, including those with bullet, probe, vet, lancet, deflected and pencil points. The other types are the bias grind, closed-end consistent wall, welded ball end, razor edge and trocar needle.
All of these types of cannula needles serve different purposes in areas such as veterinary medicine and body piercing. For instance, the trocar needle and cannula is most often used in human medicine to pierce the skin or body and remove fluid, remove gases, insert a catheter or take a biopsy. Also, the vet point cannula needle is used by veterinarians for similar purposes or to relieve gases that have built up in the stomachs of cows.
A cannula needle also varies in size, called a gauge. These needle sizes vary in diameter, and the gauge indicates the outer diameter of the needle in millimeters. Larger needles are indicated by smaller gauge sizes and vice versa. For instance, a 14-gauge cannula usually is 2 millimeters in diameter, and an 18-gauge needle usually is 1.2 millimeters in diameter. Depending on their applications, different sizes of needles are used.
In body piercing, many people work their way up to larger-sized piercings in steps. For instance, a small-gauge piercing is often placed in the skin with a small-gauge cannula. After the skin heals and the wearer is used to that size, he or she removes the piercing and replaces it with a piercing of a slightly larger size. This slowly stretches the skin until the wearer can insert very large-gauge piercings.
People who want to skip the multi-step process can simply punch a large hole in the skin to place a large-gauge piercing using a large-gauge cannula needle. This results in a large piercing without the time needed for the multi-step process. The one-punch method, however, can leave a large hole in the skin that can't close the way stretched skin might if the wearer changes his or her mind about the piercing.