What Does a Cannula Look Like? A Guide to Medical Appearance and Variations

October 5, 2025 •

4 min read

A staggering one billion peripheral intravenous lines, a type of cannula, are used globally each year, making them one of the most common invasive medical procedures. But what does a cannula look like? The answer depends on its type, with appearances ranging from a simple oxygen tube to a complex, color-coded vascular access device.

Quick Summary

The appearance of a cannula varies widely based on its function, from the flexible, two-pronged nasal device for oxygen to the rigid, color-coded IV tube for delivering fluids into a vein.

Key Points

Intravenous Cannulas: These are flexible plastic tubes with color-coded hubs, used to access peripheral veins for medication and fluid administration.
Nasal Cannulas: A simple, lightweight device consisting of clear tubing and two nasal prongs, designed for delivering supplemental oxygen.
Color-Coding System: The color of an IV cannula's hub signifies its gauge (size), with specific colors representing different diameters and flow rates.
Blunt-Tip Microcannulas: Used primarily in cosmetic procedures, these have a flexible shaft and a non-sharp tip to minimize trauma during injection.
Central Line Cannulas: These appear longer and often have multiple ports because they are inserted into larger, central veins for long-term treatment.
Cannula vs. Catheter: While often used interchangeably, a cannula is typically smaller and inserted over a needle, whereas a catheter can refer to a broader range of draining or vascular devices.
Appearance Indicates Use: The specific design and components of a cannula, including its wings, ports, and material, are all determined by its intended medical application.

A cannula is a thin, tubular medical device used to drain or deliver fluids, administer medication, or provide oxygen. While the word comes from the Latin for "little reed," the modern medical tool has evolved into many forms, each with a distinct appearance tailored to its specific purpose. Understanding these visual differences is key to distinguishing between the devices used for different medical procedures.

The Appearance of an Intravenous (IV) Cannula

When most people think of a cannula, they are picturing the peripheral intravenous (IV) cannula. This device is used to access a vein, typically in the arm or hand, for short-term fluid and medication administration. Its appearance is distinct and includes several key components:

Flexible Plastic Sheath: The main body of the cannula is a thin, flexible plastic tube (often made of Teflon or polyurethane) that remains inside the vein after insertion.
Needle (Stylet): At the core of the cannula is a sharp, hollow needle, or stylet, used to puncture the skin and vein during insertion. This needle is removed immediately after the flexible plastic sheath is properly positioned.
Flashback Chamber: A clear or translucent chamber at the back of the device allows the healthcare provider to see blood enter, confirming successful venous access.
Hub and Wings: A plastic hub is located at the top of the cannula for connecting to an IV line. Some IV cannulas also feature small plastic "wings" on either side, which are designed to be taped to the skin for stabilization.
Injection Port: Many IV cannulas include an injection port, a small opening on the side that allows for the administration of medication without needing a separate needle stick.
Color-Coded Hub: A standardized, color-coded system is used on the hub to indicate the gauge, or diameter, of the cannula. The higher the gauge number, the smaller the diameter. For example, a common 20-gauge cannula is pink, while a smaller 22-gauge is blue.

The Color-Coding System for IV Cannulas

The color of an IV cannula's hub is a quick visual indicator of its size and flow rate. This helps medical professionals select the appropriate size for a given procedure.

Orange (14G): Very large, used for rapid fluid administration in emergencies.
Gray (16G): Large, also for rapid fluid or blood transfusions.
Green (18G): Standard for blood transfusions and fast IV fluids.
Pink (20G): A routine choice for general IV fluids and medications.
Blue (22G): Used for general infusions, especially in patients with smaller or more fragile veins.
Yellow (24G): Smallest common size, often used for pediatric or geriatric patients.

The Appearance of a Nasal Cannula

Unlike an IV cannula, a nasal cannula is a non-invasive device used to deliver supplemental oxygen to patients with respiratory issues. Its appearance is far simpler and more visible, consisting of:

Clear, Lightweight Tubing: The entire device is made of soft, clear plastic tubing that is comfortable for long-term wear.
Two Nasal Prongs: At one end, the tubing splits into two short, curved prongs. These are designed to rest just inside the nostrils to deliver oxygen.
Adjustable Slider: A small plastic ring or slider is positioned on the tubing that runs under the chin. This can be tightened to secure the tubing in place.
Long Oxygen Line: The single, long tube connects the cannula to an oxygen source, such as a wall outlet in a hospital or a portable oxygen tank.

Other Types of Cannulas and Their Unique Appearances

Beyond the common IV and nasal varieties, other cannulas have specialized forms:

Central Line Cannulas

Longer and Multi-Lumen: Unlike a short peripheral IV, a central line cannula is much longer and is inserted into a major vein (like the jugular or subclavian) for long-term access. It often has multiple lumens, or channels, allowing for the simultaneous administration of different medications or fluids.

Blunt-Tip Microcannulas

Blunt and Flexible: Primarily used in cosmetic procedures, these cannulas have a flexible shaft and a rounded, blunt tip. This design is intended to navigate through tissue layers and inject dermal fillers with minimal trauma, swelling, and bruising compared to a sharp needle.

Tracheostomy Cannulas

Curved Tube: Designed for patients with a tracheostomy (an opening in the neck to the trachea), these cannulas are short, curved, and often feature an inner cannula for easy cleaning.

A Visual Comparison of Cannulas


Cannula Type	Common Appearance	Primary Use	Key Differentiating Feature
Intravenous (Peripheral)	Short, flexible plastic tube with a color-coded hub, wings for taping, and a small injection port.	Administering fluids, medication, or drawing blood in a peripheral vein.	The color-coded plastic hub indicating gauge.
Nasal	Clear, lightweight plastic tubing with two soft prongs for the nostrils and a line that loops over the ears.	Delivering supplemental oxygen therapy to a patient.	The two prongs that sit in the nose.
Blunt-Tip Microcannula	Long, flexible tube with a blunt, rounded tip and a single injection port.	Injecting dermal fillers in cosmetic procedures with reduced trauma.	The non-pointed, flexible tip.
Central Line	Longer, often multi-lumen tube with a larger hub, inserted into a major vein.	Long-term IV access for medications, fluids, and monitoring central pressures.	The length and multiple connection ports.

Conclusion

In medicine, a cannula’s appearance is not arbitrary; it is a direct reflection of its function and the environment in which it is used. From the color-coded hubs of intravenous access devices to the simple, two-pronged design for oxygen delivery, each visual characteristic serves a practical purpose. By understanding the distinctive look of these tools, patients and caregivers can better comprehend their role in medical care, from routine medication delivery to complex, long-term therapeutic needs. For further information on the indications for different cannulas, refer to resources such as Medscape's overview on intravenous cannulation.

Frequently Asked Questions

An IV cannula is a short, flexible plastic tube with a hard, color-coded hub, often with wings for securing it to a limb. A nasal cannula is a clear, lightweight tube with two soft prongs that fit into the nostrils.

IV cannulas are color-coded to indicate their size, or gauge. This provides a quick visual reference for healthcare professionals to select the appropriate cannula for the patient's needs and the required flow rate.

Using the standardized color system, remember that a lower gauge number means a larger diameter. For example, a gray 16G is much larger than a yellow 24G.

A standard nasal cannula has soft, clear tubing that extends from the prongs, loops over the ears, and connects with an adjustable plastic slider under the chin to keep it secure.

No. While most IV cannulas are inserted using a needle (stylet) that is then removed, some, like blunt-tip microcannulas, are designed to be inserted through a pre-made entry point to avoid further trauma. Nasal cannulas are not inserted with a needle at all.

A peripheral IV cannula is a shorter tube inserted into a peripheral vein, like in the arm. A central line is a much longer, often multi-lumen tube inserted into a large vein in the neck, chest, or groin for long-term access.

No. Cannulas are specifically designed for their function. A nasal cannula is for oxygen delivery, while an IV cannula is for administering fluids and medication into the bloodstream. They have completely different designs and insertion methods.