What is a Cannula?

Cannula: Uses and types

Cannulas are important in clinical settings such as their nose, or a vein. Doctors use them to drain fluid, administer medication, or provide oxygen. There are many types of the cannula, such as a nasal cannula, that run under the nose to deliver oxygen. Blood is to be drawn during critical conditions using an arterial cannula. It is mainly used for the radial artery. This article will describe what cannulas are and explain the difference between IV and nasal cannulas. There are different types of cannula having different sizes.

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What is Cannula?

The term cannula refers to a tiny plastic tube that is placed into a body cavity using a needle to puncture a vein or blood vessel. It is then left in place for simple access to withdraw or inject anything into the vessel.

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The Three Different Types Of Cannulas

A cannula can extend its length by half or more depending on the length of the tubing. Cannula size differs depending on the procedure and the comfort levels of the patient. So, an injector should always keep these considerations in mind before using any of these cannulas on a patient.

1. Intravenous Cannula

The most commonly-used cannula in medical settings is the venous cannula. By using a peripheral IV cannula, doctors and nurses can insert intravenous fluid, medication, and other compounds directly into the blood via the vein, rather than waiting for the patient to ingest them orally.

While the insertion of the IV cannula is a relatively common procedure, the injection itself does not come without the risk of complication. Problems with the tubing, the infusion, the intravenous line, and even errors in the cannulation site can occur with the insertion of different IV cannula.

There should be a distinction made between a peripheral IV cannula and a central line IV cannula. A peripheral IV cannula is only injected in a vein located on the extremities and limbs of the body. It is done mainly for intravenous medication and extraction of blood samples. A central line IV cannula is always placed in major vein systems of the body, like the jugular vein, femoral vein, or axillary vein. Both IV catheter types can come in different sizes that can determine the overall flow rate of the medicine/blood that goes through the tube, and the attending physician should always be careful to never misjudge the cannula size required for their patient.

USES: Cardiopulmonary bypass, cardiac surgery extraction and deployment of medicines directly into the patient’s veins.

Types of Cannula

2. Nasal Cannula (Oral nasal cannula)

The high-flow nasal cannula differs from the standard cannula used in IV treatments in its role in oxygen therapy, where the delivery of supplemental oxygen, measurement of airflow into the patient’s nose and mouth, or the delivery of medications like anesthetics is crucial to a procedure’s success.  Instead of the artery, it will be commonly inserted into the nostrils and mouth. The length of the nasal cannula is usually longer than the arterial cannula.

The efficacy of a nasal cannula isn’t measured in the fluid flow rate. But, the speed at which it can deliver supplemental oxygen and other air-based medication into the patient’s system measures its efficacy. For procedures like a tracheostomy, this type of catheter is critical for helping the patient receive oxygen directly to their lungs safely and efficiently.

3. Microcannula

The blunt-tip microcannula has quickly emerged as an alternative to traditional hypodermic needle treatment, especially for procedures like the injection of dermal filler. Unlike other cannulas, the microcannula is a needle-like injection tool that can penetrate the skin via a single incision point.

It does not have an inner cannula or outer cannula, as its primary use is to deliver filler materials (sometimes with varying fluid flow rates) to injection sites around the face and skin. They are incompatible with blood transfusion procedures despite their needle-like appearance. Thus, microcannula liposuction techniques have steadily been rising as a less painful and more efficient way of extracting fat.

The significant advantage of the microcannula of the standard hypodermic needle is that the patient experiences less overall trauma with microcannula use compared to needles. The use of the blunt-tip cannula is fast becoming a necessity as more non-invasive methods of aesthetic improvements are sought out by patients.

Dermatologists and doctors should always take the right precautions before the insertion of any of these cannulas into their patients, as complications from improper cannula use can range from mildly debilitating to life-threatening. If possible, consult with the manufacturers of the cannula for recommendations on their best use.

Types of Cannula

Different types of cannula have different colours, lengths, flow rates, and importantly different uses. It is good to note that the bigger the cannula size, the smaller the number.

For instance, a cannula size of 16G is larger in diameter than a cannula size of 22G. The “G” in cannula size stands for “Birmingham gauge”. This gauge is used to show the thickness of different hypodermic needles. In this post, we will explain all the different types of IV cannulas by size, colour, and estimated flow rate.

Types of Cannula

Cannula size 14G

The cannula colour is Orange. It has a flow rate of 10.3l/hr for blood (290ml/minute), 16.2l/hr for plasma, and 13.5l/hr for crystalloids. The length is 45 mm, and the outside diameter of 2.10 mm.

Uses- Emergency blood transfusion, fluid replacement, surgeries, and trauma cases.

Cannula Size 16G

The 16G cannula colour is Medium Grey in colour. It has a flow rate of 7.1L/hr for blood, 10.8l/hr for plasma, and 9.4l/hr for crystalloids. The length is 45, while the outside diameter is 1.70 mm.
Uses- Emergency blood transfusion, intravenous fluid replacement, surgeries. The uses are similar to the 14G.

Cannula size 17G

Comes in White colour, with a length of 45, a flow rate of 130 ml/min, and an outside diameter of 1.50 mm.

Uses: For rapid fluid replacement, blood transfusion, surgery, and trauma.

Cannula size 18G

This cannula size is Deep green in colour. The flow rate is 2.7l/hr for blood (90ml/minute), 4.8l/hr for plasma, and 4.1l/hr for crystalloids. It has a length of 45, and an outside diameter of 1.50 mm.

Uses-Blood transfusions, fluid replacement, large fluid volume, trauma cases, parenteral nutrition, stem cell harvesting, and major surgeries.

Cannula size 20G

20G cannula comes in pink colour. It has a length of 32 mm. The flow rate is 1.9l/hr for blood (60ml/minute), 3.2l/hr for plasma, and 2.9l/hr for crystalloids. The outside diameter is 1.00 mm.

Uses: For transfusion of blood and intravenous fluids, the most commonly used cannula in clinical settings.


Cannulas are flexible tubes attached to a person’s body that can introduce or drain different things. A doctor or nurse can use an IV cannula to introduce medication or take blood.

IV cannulas can reduce the need for needle pricks. Cannulas make it easier to deliver medications or fluids to a person’s body. Nasal cannulas can help a person who has difficulty in breathing by providing them with more oxygen.

Cannulas are generally safe. There is a minor risk of infections and the formation of blood clots in IV cannulas.

Keep reading for more!

Team MBD

Reference: Cannula – an overview | ScienceDirect Topics

1 Response

  1. Yaseer Jamal says:

    Very useful content in our life

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