What Is It, Different Types, and More
Author:Nikol Natalia Armata, MD
Editors:Alyssa Haag,Emily Miao, PharmD,Kelsey LaFayette, DNP, ARNP, FNP-C
Illustrator:Jessica Reynolds, MS
Copyeditor:David G. Walker
What is a cannula?
A cannula refers to a small tube that is inserted into a body cavity, duct, or vessel for medical purposes. There are two main types of cannulas: intravenous (IV) cannulas and nasal cannulas. IV cannulas consist of short, flexible tubing that are placed into a vein and are usually used for blood transfusions, blood draws, administration of medication, and providing fluids. On the other hand, nasal cannulas are a simple yet effective device for delivering oxygen. They consist of a flexible tube with two protruding tips that sit inside the nostrils to deliver oxygen. They can be useful if the individual is experiencing difficulty breathing as nasal cannulas can decrease the work required to breathe and the strain on the heart, therefore treating hypoxia or hypoxemia.
What are the different types of cannulas?
The two main types of cannulas are the IV and nasal cannulas. Each type has several different subtypes.
What are types of IV cannulas?
IV cannula subtypes include the peripheral IV cannula, the central IV cannula, and the draining cannulas. There are also several sizes of intravenous cannulas. The most common sizes range from 14 to 22 gauge. The higher the gauge number, the smaller the cannula. Different sized cannulas move liquid through them at different rates.
Peripheral IV Cannulas
Medical professionals typically use peripheral IV cannulas in the emergency room and during surgery in order to provide necessary fluids or to insert contrast when taking a radiological image. These cannulas are for short-term use and may be taped to the skin to prevent them from moving.
Central IV Cannulas
Medical professionals may use a central line cannula for an individual who needs long-term treatments that require weeks or months of IV medication or fluids. For example, an individual receiving chemotherapy might require a central IV cannula for the intravenous infusion of the drugs. Central IV cannulas can quickly deliver medication and fluids into the body via the jugular, femoral, or subclavian vein. They can get easily infected; therefore, if any signs of infection (e.g. erythema, swelling, induration, fever) occur, they are typically removed.
Health care providers use draining cannulas to drain fluids or other substances from the body. They can be used in procedures such as extracorporeal membrane oxygenation (ECMO), which is typically only used in critically ill patients with severe pulmonary and/or cardiac failure. In ECMO, blood is drained from the venous system, oxygenated, and then returned to the body. Sometimes draining cannulas might be used during liposuction. In that case, the cannula is connected to a trocar, which is a sharp metal or plastic instrument that can puncture tissue and remove fluid from or insert fluid into a body cavity or organ.
IV Cannula Insertion
When inserting an IV cannula in an individual’s vein (usually in their arm), the patient is asked to lie or sit down with one of their arms exposed and extended by their side. The healthcare professional performing the procedure will choose the insertion point, which is usually in the individual's non-dominant arm or hand. Then, the area is thoroughly cleaned with an antiseptic while a tourniquet is tied above the desired insertion point. When ready, the healthcare professional will insert the IV cannula into a vein. The needle is only required to puncture the skin and vein. Once the cannula is placed in the vein, the needle is withdrawn as the cannula slides over the needle and into the vein. The cannula is then secured in place with medical tapes, such as a wrap or a special bandage.
What are types of nasal cannulas?
A standard nasal cannula consists of lightweight plastic tubing that is inserted just inside an individual’s nostrils. The oxygen flow in a standard nasal cannula is lower than in other types, such as high flow nasal cannula (HFNC). The nasal cannula allows breathing through the mouth or nose, is available for all age groups, and is adequate for short or long-term use. Unlike the numbered sizes of intravenous cannulas, nasal cannulas are available in sizes for adults, children, and infants. Regular flow nasal cannulas provide only up to 4–6 liters per minute of supplemental oxygen. The delivered oxygen percentage varies, depending on the rate and depth of the individual’s breathing. When cannulas are used at higher flow rates (i.e. greater than 4 L/min), the airway mucosa may dry, so a humidifier may be used to help prevent drying of the nasal and oral mucous membranes.
High-flow Nasal Cannula (HFNC)
High-flow nasal cannula therapy systems (HFNCs) offer an increased flow rate of oxygen compared to standard nasal cannulas. HFNCs deliver oxygen at a flow rate of up to 60 liters per minute. The latest models of HFNCs can also heat the gas to 98.6°F (37°C) to ensure the individual can breathe easily. Some individuals prefer the HFNC because it is lighter, more comfortable, and does not irritate their airways as much as a standard nasal cannula. In fact, HFNC was highly effective for individuals with COVID-19 who experienced respiratory distress.
At-home Nasal CannulasNasal cannulas can be portable to give an individual the independence of receiving oxygen therapy at home. The procedure for fitting a nasal cannula for home is very similar to insertion of a nasal cannula at the hospital; however, a home nasal cannula will attach to a portable oxygen supply. The healthcare provider may instruct the individual on how to use the equipment and how often to refill the oxygen supply.
Nasal Cannula Insertion
When inserting a nasal cannula, the individual may be asked to sit up straight (if possible) to expand their lungs fully. The flow meter is then inserted into a power source and attached to a nozzle. The flow meter is turned on and assessed to ensure oxygen is coming through properly. The healthcare provider may then place the nasal cannula into the individual’s nose with the two prongs of the cannula placed just inside the individual’s nostrils. The extended tubes are then looped around the individual’s ears and a plastic slider is set under the chin so it stays in place. Finally, the flow rate may be evaluated every 4-8 hours in order to assess the individual's oxygen levels and how they are responding to oxygenation.
What are the most important facts to know about cannulas?
Cannulas are small, plastic tubes inserted into a body cavity, duct, or vessel, and they serve various purposes. There are two main types of cannulas: intravenous (IV) cannulas and nasal cannulas. IV cannulas can be placed into a vein for blood transfusions, blood draws, administration of medication, and providing fluids. Different subtypes of IV cannulas (i.e. peripheral, central line and draining cannulas) are each used for specific reasons. Nasal cannulas are also very useful devices as they provide oxygen to individuals who are having difficulty breathing. The oxygen flow can vary and is significantly increased when using high flow nasal cannulas.
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Resources for research and reference
Cannula. In ScienceDirect. Retrieved August 29, 2022, from https://www.sciencedirect.com/topics/medicine-and-dentistry/cannula
Intravenous cannula (IV). In Healthy WA. Retrieved August 29, 2022, from https://www.healthywa.wa.gov.au/Articles/F_I/Intravenous-cannula-IVOxygen Therapy: Nasal Cannula or Oxygen Mask - CE. (2021). In Elsevier. Retrieved August 28, 2022, from https://elsevier.health/en-US/preview/oxygen-therapy-nasal-cannula-or-oxygen-mask