What is a cannula used for? A comprehensive medical guide

October 1, 2025 •

4 min read

According to a study on emergency department patients, blood can safely be drawn from a newly inserted peripheral intravenous (IV) cannula, dispelling some previous safety concerns. What is a cannula used for in the broader medical context, and how do its applications extend beyond simple blood draws?

Quick Summary

A cannula is a versatile medical tube used to insert or remove fluids, administer medication or oxygen, and collect samples. They are used for intravenous therapy, oxygen delivery, cosmetic procedures, and more, with applications varying based on the type of cannula and the patient's needs.

Key Points

Core Function: A cannula is a thin tube inserted into the body to either administer or drain fluids, medication, and gases like oxygen.
Primary Types: The most common types are intravenous (IV) cannulas for vein access and nasal cannulas for oxygen delivery.
IV Uses: Intravenous cannulas facilitate blood transfusions, drug administration, and fluid delivery during surgery, emergency care, and long-term treatments like chemotherapy.
Nasal Uses: Nasal cannulas are used for oxygen therapy in patients with breathing difficulties, such as those with COPD, heart failure, or other respiratory conditions.
Beyond Medicine: Cannulas also have applications in cosmetic procedures, such as administering dermal fillers, and even in scientific research.
Key Distinction: A cannula is typically a smaller device inserted with a needle, while a catheter can be a larger tube for long-term access or drainage.
Potential Risks: Common complications include infection, phlebitis, and hematoma, though proper clinical practice minimizes these risks.

A cannula is a small, hollow tube, typically made of plastic, that is inserted into a body cavity, duct, or vessel for a variety of medical purposes. Its core function is to either allow for the delivery of substances into the body or the removal of fluids and gases. While the term is most often associated with intravenous (IV) therapy, different types of cannulas serve distinct, critical functions across modern healthcare.

Intravenous Cannulas: Accessing the Bloodstream

Intravenous (IV) cannulation is one of the most common hospital procedures and provides access to a patient's venous system. IV cannulas are essential for delivering medications, fluids, chemotherapy drugs, and blood products directly into the bloodstream. They also serve as a pathway for drawing blood samples without repeated needle sticks, which is particularly beneficial for patients requiring frequent testing. IV cannulas are differentiated by size, or gauge, which is indicated by a color-coded system. A lower gauge number corresponds to a larger diameter, allowing for a faster flow rate. For instance, a large orange or grey gauge (14-16G) is used for rapid fluid administration during trauma, while a smaller blue or yellow gauge (22-24G) is more suitable for delicate veins in pediatric or elderly patients.

Nasal Cannulas: Delivering Supplemental Oxygen

For patients with respiratory issues, a nasal cannula provides a non-invasive way to receive supplemental oxygen. The device consists of a flexible tube with two prongs that rest just inside the nostrils, and it is held in place by looping the tubing around the patient's ears and under the chin. A nasal cannula is widely used to treat conditions that cause low oxygen levels, such as COPD, heart failure, and sleep apnea. There are two main types:

Standard Nasal Cannula: Delivers oxygen at a lower flow rate, typically up to 4–6 liters per minute.
High-Flow Nasal Cannula (HFNC): Can deliver a significantly higher flow rate, up to 60 liters per minute, and can also warm and humidify the air, making it more comfortable for the patient. HFNC has proven effective for patients with severe respiratory distress, including those with COVID-19.

Draining and Cosmetic Cannulas

Beyond infusions and oxygen, cannulas are also specialized for other medical and cosmetic procedures:

Draining Cannulas: These are used to remove fluids or other substances from the body. During procedures like liposuction, a draining cannula is inserted to suction out fat, often connected to a trocar that punctures the tissue.
Dermal Filler Cannulas: In cosmetic procedures, a blunt-tipped cannula is used to inject dermal fillers. Unlike a sharp needle, the blunt end can be maneuvered under the skin with less trauma, reducing the risk of bruising, bleeding, and injury to blood vessels, which leads to better cosmetic results and a more comfortable patient experience.

Cannula vs. Catheter: A Comparison

Though sometimes used interchangeably, the terms 'cannula' and 'catheter' have distinct meanings in medical practice. Understanding the difference is crucial for clarity in a clinical setting.


Feature	Cannula	Catheter
Design	Typically a smaller, shorter tube. Often involves insertion over a sharp needle (stylet), which is then removed, leaving the flexible tube in place.	Generally a larger, longer tube. Can be inserted into a body opening or through a pre-existing lumen.
Insertion	Inserted via a needle puncture into a vessel (e.g., a peripheral vein) or cavity.	Can be inserted into a vessel or a naturally occurring opening like the urinary bladder.
Primary Use	Vascular access for short-to-medium term infusions, oxygen delivery.	Often used for long-term access, monitoring, or drainage from cavities (e.g., Foley catheter).
Flexibility	Peripheral IV cannulas are short and flexible.	Can be more flexible and longer, designed for deeper insertion.

Potential Complications and Patient Safety

Like any invasive medical procedure, cannula insertion carries potential risks, which healthcare providers take steps to minimize. In the case of IV cannulas, complications can include phlebitis (inflammation of the vein), hematoma (localized swelling of blood), infection at the insertion site, or accidental nerve damage. To reduce these risks, healthcare professionals follow strict protocols, including proper hand hygiene, using sterile equipment, and regular site monitoring. Patients should alert staff immediately if they experience pain, swelling, or redness around the cannula site.

Conclusion

The cannula is a deceptively simple yet indispensable tool in modern medicine, with a broad range of applications for delivering essential care. From the routine administration of IV fluids to specialized procedures like cosmetic injections and critical oxygen support, it plays a vital role in ensuring patient health and comfort. Its continued development, driven by patient safety and therapeutic efficacy, solidifies its status as a cornerstone of medical treatment across numerous disciplines. For more information on patient procedures and medical care, you may refer to publications from authoritative sources like the National Center for Biotechnology Information (NCBI).

Frequently Asked Questions

A nasal cannula is used to deliver supplemental oxygen to patients with respiratory distress or low oxygen levels. It is a lightweight, flexible tube with two prongs that fit into the nostrils, and it is commonly used for conditions like COPD and sleep apnea.

An intravenous (IV) cannula is used to gain access to a vein. Its purposes include administering fluids, medications, and blood transfusions directly into the bloodstream, as well as collecting blood samples for testing.

While sometimes used interchangeably, a cannula is typically a smaller tube inserted over a needle, with the needle then removed. A catheter, by contrast, can be a larger, more complex tube used for longer-term access or for draining cavities, such as the bladder.

Cannula insertion typically causes a brief, sharp pinch or discomfort when the needle enters the vein. However, once the cannula is properly positioned and secured, it should not cause ongoing pain. Any persistent discomfort should be reported to a healthcare professional.

Potential risks of IV cannulas include infection, phlebitis (vein inflammation), hematoma (bruising), and extravasation (fluid leaking into surrounding tissue). Proper hygiene and care protocols are followed to minimize these complications.

Healthcare guidelines often recommend that a peripheral IV cannula be electively replaced every 48-72 hours to reduce the risk of phlebitis and infection, or sooner if there are signs of complication.

To clean a nasal cannula, you can wash it in warm, soapy water. Some sources also suggest soaking it in a mixture of 10 parts water to 1 part vinegar to kill bacteria. After soaking, rinse it thoroughly with clean water and let it air dry completely.

Showering with an IV cannula is often possible, but requires careful protection of the site to prevent it from getting wet and potentially introducing infection. Your healthcare provider will give you specific instructions, which may involve covering the cannula with a waterproof dressing or bag.