Small Clinics
Types of Cannula: IV, Nasal and Other Cannulas with Sizes and Uses
Learn the types of cannula, from IV and nasal to arterial and tracheostomy, with IV cannula sizes, colour codes, parts and which size to use for adults.
A cannula is a thin, flexible tube inserted into a vein, artery, body cavity or airway to deliver or remove fluids or gases. The main types of cannula are IV (intravenous) cannulas, nasal cannulas for oxygen, arterial cannulas, tracheostomy cannulas and specialised surgical cannulas.
This guide explains each type, the parts and sizes of an IV cannula, which size is used for adults and blood transfusion, and how a cannula differs from a catheter.
What Is a Cannula?
In medical terms, a cannula is a hollow tube placed into the body so that fluids, medicines or oxygen can be given, or fluids removed, without repeated punctures. The word most often refers to the IV cannula, a short plastic tube that sits inside a vein for days at a time.
Cannulas are used in almost every hospital setting, from emergency rooms and operating theatres to wards, ICUs and day-care clinics. They are also used at home for oxygen therapy.
Other Names: Vigo, Venflon and IV Catheter
In India, an IV cannula is often called a "vigo" or "venflon". Venflon is a brand name from BD Venflon, and both words are used informally for any IV cannula. Internationally, the same device is usually called a peripheral IV catheter.
So a vigo, a venflon and an IV cannula are the same type of device. Only the brand or local name differs.
Different Types of Cannula
There is no single official count, but cannulas are usually grouped by where they go and what they do.
| Type | Where it goes | Used for |
| IV (peripheral) cannula | A vein, usually in the hand or arm | Fluids, medicines, blood transfusion, contrast |
| Nasal cannula | Just inside the nostrils | Oxygen therapy |
| Arterial cannula | An artery, often at the wrist | Continuous blood pressure monitoring, arterial blood samples |
| Tracheostomy cannula | Through the neck into the windpipe | Keeping the airway open |
| ECMO and cardiac bypass cannulas | Large veins and arteries | Circulating blood through an external machine |
| Karman cannula | The uterus | Manual vacuum aspiration |
| Suction cannula | Mouth, throat or surgical field | Removing secretions or fluid |
Types of IV Cannula
IV cannulas are the most common type. Each one has a flexible plastic tube over a fine steel needle. The needle guides the tube into the vein and is then withdrawn, leaving only the soft tube in place.
IV Cannula Designs
| Design | Features | Commonly used for |
| Without port or wings | Simple, straight design | Short procedures, some paediatric use |
| With wings | Flat wings for securing to the skin | Most ward use |
| With port and wings | Extra injection port for giving medicines without disconnecting the drip | Routine adult care in many Indian hospitals |
| Safety IV cannula | A clip or shield covers the needle tip after use | Reducing needlestick injuries among staff; see safety IV cannulas |
| Neonatal and paediatric cannula | Very small sizes, often without a port | Newborns and infants |
Peripheral Cannulas and Central Venous Catheters
A peripheral IV cannula sits in a small vein near the surface, usually in the hand or forearm. It is used for short-term treatment, typically a few days.
For longer treatment or medicines that irritate small veins, such as some chemotherapy drugs or parenteral nutrition, clinicians use a central venous catheter. This is a longer tube placed into a large vein in the neck, chest or groin, or threaded from the arm (a PICC line). Although sometimes called a "central cannula", it is a different device, placed by trained clinicians under strict sterile conditions.
Parts of an IV Cannula
| Part | What it does |
| Protective cover | Keeps the needle and catheter sterile until use |
| Introducer needle | Fine steel needle with a bevelled tip that guides the catheter into the vein; removed after insertion |
| Catheter (cannula tube) | Flexible plastic tube that stays in the vein |
| Catheter hub | Luer connector at the end of the tube, where an IV set, extension line or syringe attaches |
| Flashback chamber | Clear chamber that fills with blood when the needle enters the vein, confirming placement |
| Wings | Flat tabs that help secure the cannula to the skin |
| Injection port and cap | One-way valve for giving medicines without disconnecting the drip; kept capped when not in use |
| Luer plug (stopper) | Seals the hub when no line is attached |
| Safety clip or shield | On safety cannulas only; covers the needle tip after withdrawal |
IV Cannula Sizes, Colour Codes and Flow Rates
IV cannula size is measured in gauge (G). The higher the gauge number, the thinner the cannula, so a 24G cannula is much smaller than an 18G. Cannulas are colour coded by gauge so staff can identify the size at a glance.
| Gauge | Colour | Approx. flow rate (mL/min) | Typical uses |
| 14G | Orange | 240 to 330 | Trauma, major surgery, rapid fluid or blood replacement |
| 16G | Grey | 180 to 240 | Trauma, major surgery, rapid fluids |
| 18G | Green | 80 to 105 | Blood transfusion, surgery, rapid fluids, CT contrast |
| 20G | Pink | 55 to 65 | Routine adult IV fluids and medicines, blood transfusion |
| 22G | Blue | 30 to 40 | Smaller or fragile veins, older adults, children |
| 24G | Yellow | 18 to 24 | Children, infants, very fragile veins |
| 26G | Violet | about 13 to 15 | Newborns |
Flow rates are approximate. They vary with cannula length and manufacturer, so check the packaging. For a detailed chart, see our guide to IV cannula sizes and colour codes.
Which Cannula Size to Use
The general rule is to use the smallest cannula that can deliver the treatment needed. Smaller cannulas are more comfortable and cause less damage to the vein.
- For adults: 20G and 22G are the most common sizes for routine fluids and medicines. 18G is used when faster flow is needed.
- For blood transfusion: 18G or 20G is usually used in adults; a 22G may be used when veins are small, as per local policy. Blood is given through a blood transfusion set.
- For emergencies and major surgery: 14G or 16G (large bore) allows rapid fluid or blood replacement.
- For children and infants: 22G to 24G, and 26G for newborns.
- For older adults with fragile veins: 22G or 24G is often chosen.
Common Cannula Sites
Peripheral cannulas are usually placed in veins on the back of the hand or the forearm. The inner elbow (antecubital area) is also used, especially in emergencies, though it is less comfortable for longer use because the arm bends there. In infants, veins in the hand, foot or scalp may be used.
Sites are usually avoided on an arm with an injury, infection, a dialysis fistula or lymphoedema. The choice of site is always made by the clinician placing the cannula. For clinicians, our guide explains how IV cannulation is performed.
Types of Nasal Cannula
A nasal cannula is a light plastic tube with two short prongs that sit just inside the nostrils and deliver oxygen. The patient can talk, eat and drink while wearing it. Nasal cannulas are available in adult, paediatric and infant sizes.
| Type | Oxygen flow | Typically used for |
| Standard (low-flow) nasal cannula | Usually up to about 4 to 6 litres per minute | Mild to moderate low oxygen levels, ward and home use |
| High-flow nasal cannula (HFNC) | Up to about 60 litres per minute, heated and humidified | Respiratory distress in hospital, often in ICU or HDU |
| Home or portable nasal cannula | Low flow, connected to a portable cylinder or concentrator | Long-term oxygen therapy at home |
At higher flows, a humidifier is often used to stop the nose and mouth drying out.
Nasal Cannula vs Nasal Catheter
A nasal cannula has two short prongs that rest just inside the nostrils. A nasal catheter is a single, longer tube passed further into one nostril towards the back of the nose. Nasal cannulas are more comfortable and are used far more often today; nasal catheters are used less commonly, sometimes in children or in low-resource settings.
Other Types of Cannula
| Type | What it is | Where it is used |
| Arterial cannula | A short cannula placed in an artery, usually at the wrist | ICU and theatres, for continuous blood pressure readings and repeated blood gas samples |
| Tracheostomy tube and inner cannula | A tube in the windpipe; the removable inner cannula can be cleaned or replaced to keep it clear. See tracheostomy tubes | Long-term airway support |
| ECMO and bypass cannulas | Large-bore cannulas placed in major vessels | Heart surgery and ECMO for severe heart or lung failure |
| Karman cannula | A flexible plastic cannula used with a vacuum syringe. Read more about the Karman cannula | Gynaecology, manual vacuum aspiration |
| Suction cannula | A rigid tube attached to suction tubing | Clearing secretions from the mouth or blood from a surgical field |
| Liposuction cannula | A long blunt cannula | Cosmetic surgery |
A "three-way cannula" is in fact a three-way stopcock, a valve attached to a cannula or line so more than one infusion can be given.
Cannula vs Catheter: What Is the Difference?
The two terms overlap. A catheter is any tube inserted into the body to deliver or drain fluid, such as urinary catheters or central venous catheters. An IV cannula is technically a short catheter placed over a needle, which is why it is also called a peripheral IV catheter.
| Feature | IV cannula | Catheter (general) |
| Typical length | Short, a few centimetres | Short to very long, depending on type |
| Placement | A small peripheral vein, using a needle | Veins, arteries, bladder, heart and other sites |
| Usual duration | Short term, a few days | Hours to weeks or longer |
| Examples | Peripheral IV cannula, arterial cannula | Urinary catheter, central venous catheter, cardiac catheter |
Benefits of Using a Cannula
- Fewer needle pricks: one cannula can be used for many doses and infusions instead of repeated injections.
- Soft tube in the vein: once the needle is removed, only flexible plastic stays in the vein, so the patient can move their arm more freely.
- Continuous access: fluids, medicines and blood can be given over hours or days.
- Quick access in emergencies: a cannula already in place saves time if urgent medicines are needed.
- Extra doses without disconnecting: a port allows medicines to be added while a drip is running.
Cannula Care and Safety
These points apply to healthcare staff caring for patients with a cannula.[MR10]
- Secure it well with a sterile dressing or cannula fixators so it does not move or slip out.
- Check the site regularly for redness, pain, swelling or leakage, which can signal phlebitis or fluid leaking into the tissue. Remove the cannula if these appear.
- Keep the line clear by flushing according to local protocol.
- Use accessories correctly: a three-way stopcock can help when several infusions are needed.
- Record the insertion date and replace or remove the cannula as per hospital policy, or when it is no longer needed.
- Handle needles safely: never reinsert the needle into the catheter, as it can cut the tube. Discard used needles immediately in a sharps container; safety cannulas reduce needlestick risk.
Conclusion
The main types of cannula are IV cannulas, nasal cannulas, arterial cannulas, tracheostomy cannulas and specialised surgical cannulas. IV cannulas are the most widely used, and their size, from 14G to 26G, is chosen to match the patient's veins and the treatment needed.
Knowing the types, parts and sizes of a cannula helps healthcare teams choose the right device and use it safely.
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