What Is a Cannula? - Definition & Placement

Instructor: Ian Lord

Ian has an MBA and is a real estate investor, former health professions educator, and Air Force veteran.

In this lesson, we will identify and describe two types of cannulas: nasal and intravenous. We will also examine how providers place these types of cannulas into the patient's body.

Cannulas

Chris is a pack-a-day smoker with COPD exacerbation in the emergency department of his local hospital. His healthcare team decides he needs supplemental oxygen and intravenous (IV) rehydration. His therapy will happen with the aid of cannulas, which are tubes placed in the patient's body to administer medication or to draw off fluids. The word cannula originates from the Latin term for 'little reed.' Let's take a look at nasal and IV cannulas and how they are placed on Chris.

Nasal Cannula

A nasal cannula will help Chris breathe a little easier. It is made up of tubing with two small prongs that fit into the patient's nostrils. The device allows supplemental oxygen to mix with regular air, delivering more oxygen to the patient than is normally present in the environment.

The prongs fit into the nose, while the rest of the tubing wraps behind the patient's ears then down below the jaw in front of the throat. Wrapping the tubing behind the ears helps keep tension on the prongs so they stay in the nostrils, and placing the tubing in front relieves pressure and prevents kinking in the tubing. The other end of the tubing connects with a flow meter to an oxygen source. The flow meter controls the rate of oxygen flow from 1-5 liters per minute.

Nasal cannulas may cause mild discomfort or nosebleeds in some cases. One common problem is that the forced oxygen flow dries out the nasal passages. While oxygen is not flammable, it can feed a fire and make it much worse quickly. Exposure of the compressed-oxygen canister to heat also poses an explosion risk. Patients and others nearby should never smoke or use any kind of fire source like candles near oxygen therapy equipment.

Intravenous Cannula

Chris's rehydration will happen with the aid of an IV cannula. An IV cannula looks and functions very differently from a nasal cannula. The IV cannula itself is a small flexible tube that surrounds a trocar needle used to puncture the skin. The cannula has a fitting that can be connected to more tubing or a port for medication administration once the needle has been removed. Aside from aiding in hydration and administering medication, a cannula can also be used to obtain blood samples for testing.

To place an IV cannula, the nurse first sanitizes the area of skin over a vein with an antiseptic wipe. IV cannulas are often placed in the veins of the arm or the hand. The needle is inserted into the vein at a shallow angle. When a flash of blood appears in the clear part above the trocar, the cannula is in the vein. The trocar is removed while the cannula remains behind. The cannula is taped to the skin so that it doesn't move or come out inadvertently.

Throughout the process, the nurse should adhere to proper aseptic technique by taking active steps to avoid contaminating the IV site. These include: hand washing, wearing gloves, using aseptic wipes on the IV site, using sealed and unexpired IV equipment, and not contaminating the site with a potential germ exposure.

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