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Oxygen Cannulas

Cannulas are the most common oxygen accessory used by people needing oxygen therapy. Like oxygen systems, though, there are differences among cannula styles and applications that can be misunderstood. For this issue, we’ll go over some of the different cannula types and styles, and discuss how the choice of cannula can impact your oxygen therapy.

Single Lumen Cannulas are the most common style of nasal cannula. A ‘lumen’ in this case refers to the internal area of tubing that is utilized to transport gases or liquids. So a single lumen cannula can be described as a cannula that utilizes ONE tube to get oxygen from the oxygen device to the nasal interface.

It will have one connector that attaches to the oxygen device’s oxygen port, and the tubing length will typically be either 4 feet or 7 feet, though other lengths may be available.

Dual Lumen Cannulas may also be called demand cannulas as they are designed specifically for oxygen systems that require separate channels for sensing a breath and for delivering oxygen, thus they have TWO lumens. In addition to having two tubes that connect to the device, when you look at the nasal interface of the cannula, you will either see the interface itself bisected into two sections or the individual nasal prongs divided into two sections (as is seen at left). One section will lead to the delivery tube and the other

will lead to the sensing tube. You should never use a single lumen cannula with a device requiring a dual lumen cannula, and vice versa.

Standard single and dual lumen cannulas are typically designed to be used with oxygen devices that can deliver flow between 0 and 6 liters per minute (LPM). Oxygen systems that deliver flow at rates greater than 6 LPM should be used with a high flow cannula instead of a standard cannula. A high flow cannula is a cannula type that has a wider diameter lumen so that oxygen flow

can move more easily through the cannula without the smaller diameter restriction of the standard cannula. High flow cannulas can be used with oxygen flow rates ranging from 6 to 15 LPM, and will often have “HF” in their name as well as being a different color than a standard cannula. If you use a pulse device, whether it is a portable oxygen concentrator (POC), conserving regulator, or liquid portable system with pulsing capability, make sure to check the manual to determine if the device specifies use of a high flow cannula – sometimes pulse oxygen devices deliver their pulses at high flow rates, so using a standard cannula with that device may result in added restriction to the delivered flow that lowers how much oxygen you receive per pulse.

(Note: To confuse matters, the term high flow nasal cannula may also refer to a type of nasal cannula used in heated, humidified high flow oxygen therapy. These cannulas look more like CPAP nasal pillows in appearance, and are specifically designed to be used with a heated humidification system, and NOT standard home oxygen therapy equipment.)

Kinking

Kinking is a common problem in nasal cannula tubing. When a tube becomes kinked, the lumen becomes obstructed and oxygen flow passing through the tube may be highly restricted or even blocked altogether. This may cause your concentrator to alarm, or your pulse oxygen device to not sense your breath and deliver oxygen properly. Since kinking is a common issue, cannula lumens are often reinforced with anywhere from 3 to 6 ‘channels’ to help support the cannula structure and prevent kinking. Take a look inside the connector end of one of your cannulas and see if you can see these channel structures – if you can, you know your cannula is designed to help prevent kinking. Some cannulas will not have this reinforcement – these are usually called smooth bore cannulas – but they will have thicker outer walls instead. Kinking can also occur if extension tubing is coupled with the cannula and the oxygen user is moving around a lot, dragging the long lengths of tubing with them. In these cases, an oxygen swivel connector is recommended over a straight connector to help prevent kinks and tangles.

Sometimes cannulas can be too rigid and kink resistant for oxygen users to comfortably use – perhaps the tubing that rests over the ears and goes to the nose rests on the face no matter how much you try to keep it away, leaving marks and irritating the skin. Some manufacturers will provide specialized cannula packages that include ear/cheek pads or soft tubing wrap accessories that the cannula can be used with. Manufacturers may also design soft cannulas that are ‘memory resistant’ or ‘memory free’. Soft cannulas are designed with a softer, lighter material that will not recoil when stretched out, leaving the cannulas with a looser, more comfortable fit, though they may be more prone to kinking.

Nasal Prong Shapes

Cannulas will have a variety of nasal prong shapes, which may or may not impact user comfort. Nasal prongs are the portion of the cannula that fit into the nostrils. Typical cannulas will have curved prongs, so that the oxygen flow can be better directed toward the upper nasal airway when the cannula is placed in the nose. It is important for users to pay attention when they are putting a cannula with curved nasal prongs into their nose – the curve should align with the natural curvature of the nasal cavity rather than run up against the inside of the nostril. Some cannulas, though, are designed with straight nasal prongs and so proper orientation once placed in the nose is not as important. The nasal prongs themselves may also be tapered, straight or flared. Tapered nasal prongs will be widest at the base of the prong, whereas flared nasal prongs will be widest at the end of the prong. Flared cannulas may be preferred for those who have larger diameter nostrils and may have trouble triggering their pulse device, whereas tapered cannulas may be ideal for those with smaller diameter nostrils. Many patients can get nasal irritation due to the cannula prongs touching and rubbing up against the inside of the nose. If non-oil based lubricant or sprays do not help alleviate this discomfort, some people may clip the nasal prongs off (sometimes all the way down to the base), so the cannula just sits under the nose with shorter prongs. While I can’t outright recommend this approach, some oxygen users do this regularly when they get new cannulas.

Speaking of new cannulas, there is a wide variety of opinions on when the right time to switch out an old cannula for a new one is. My recommendation is usually every 30 days, though if you’ve been sick or you notice any damage to the cannula, the cannula should be swapped out sooner rather than later. Cleaning the cannula can be done with mild soap and water and/or vinegar and water, with special attention paid to the areas in contact with your nose and face, and then the cannula can be hung up to dry. When it comes down to it, if you are questioning whether to replace your cannula, it is probably time to actually replace your cannula!

Oxygen Cannula Terms

Single Lumen Cannula: Most common style of nasal cannula; utilizes one tube to get oxygen from oxygen device to the nose

Dual Lumen Cannula: Also called demand cannula; utilizes two tubes: one to sense a breath, one and to deliver oxygen

High Flow Cannula: Used with flow rates greater than 6 LPM, often have “HF” in its name and is a different color than standard cannula

Kinking: Common problem of tubing; kinking obstructs oxygen flow in tube

Nasal Prongs: The portion of cannula that fits into nostrils; typically curved to follow anatomy of nose; others are straight.

Prongs may be tapered or flared.