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Choosing an Infusion Set
Everything You Always Wanted to Know About Sets (But Were Afraid to Ask)
Part 2: Choosing an Infusion SET
As background information for what follows, we suggest you first check out Part 1: What is an Infusion Set?
Just like most things with diabetes, there are few right or wrong choices when it comes to infusion sets; the “best” infusion set for your child is the one that best matches your child’s physical needs, and your family’s values and preferences. With that in mind, there are a variety of factors to consider when choosing an infusion set.
What Factors Should I Consider When Choosing an Infusion Set?
- Fixed (Steel*) or Flexible (Plastic) cannula?
The benefit of a fixed cannula, which is made of metal, is that it will not bend (like a flexible cannula may), so you know that the insulin is getting in under the skin where the body can use it (as long as it’s inserted properly, of course, and the pump is working as it should). This often makes a fixed cannula a good choice for small children, for whom reliability may be a priority (as small variations in insulin delivery can have large effects in little bodies). Also, if your child has a sensitivity or allergy to the components of some flexible cannulas (such as Teflon), a metal cannula may be the solution.
(*refers to stainless steel; different manufacturers use different metals, including nickel)
The downside of its unyielding nature, however, is that a fixed cannula can be less comfortable, particularly if the infusion site is bumped. For this reason, a fixed/metal cannula may not be the best choice for very lean individuals, including athletes (who tend to have minimal subcutaneous “fatty” tissue), as the cannula is more likely to contact muscle tissue. This can be uncomfortable and problematic in terms of insulin absorption.
The main benefit of a flexible cannula is comfort; wearers typically do not feel it at all once it’s on. As a result, this is the most common cannula-type used by insulin pumpers. However, because the cannula is flexible, it can bend or kink upon insertion and/or when the cannula comes in contact with muscle, which interrupts the flow of insulin, resulting in high blood glucose and the potential for ketones to develop. Because of this potential for unreliability, a flexible cannula may not be the best choice for very young children (for whom a small interruption in insulin may have a bigger effect).
For individualized information on appropriate cannula types, please discuss with your/ your child’s diabetes health care team.
- Cannula length
The length of the cannula varies between different makes and models of infusion sets, from 6 to 13mm long for flexible cannulas. Since the goal is to infuse the insulin into the layer of fat below the skin (i.e. subcutaneous tissue) where it is absorbed most effectively, without going so deep as to encounter the muscle below, the length of cannula (combined with the angle of insertion, described next) should ideally match the depth of an individual’s subcutaneous fat layer. The shorter cannula length is appropriate for most people (teens, adults, and little ones), perhaps even necessary for leaner individuals and for children; a longer cannula length may be a wise choice for individuals with a high BMI (Body Mass Index), and for those who typically deliver very large boluses. Of course, personal preference is an important factor, too.
For individualized information on appropriate cannula length, please discuss with your/ your child’s diabetes health care team.
- Angled or 90-degree insertion?
Some infusion sets are inserted straight down into the skin (at 90); others are inserted at an angle (between 20 and 45 down from the surface of the skin). Which is most appropriate depends largely on the amount of subcutaneous, “fatty” tissue an individual has – if there is little depth to the fat layer right below the skin, then an angled set may be best, as the depth of insertion can be manipulated to keep the end of the cannula in the fat layer as desired, while avoiding the layer of muscle below the fat. For this reason, small or lean individuals (including athletes, who tend to have minimal subcutaneous “fatty” tissue) may feel an angled infusion set is a good match for their needs.
The main drawback of an angled infusion set is that it uses up more “real estate” – more linear space is affected when a cannula of a given length sits in the tissue for a few days, which means a longer space of tissue needs to heal, so the next set needs to be placed further over on the skin than if the cannula was inserted at 90. If you find that you are having trouble finding enough viable infusion sites, angled sets may not be the best match for your needs.
- Tubing Length:
The length of tubing can vary from 60cm (23”) to 110 cm (43”) and beyond. So how long should your tubing be? A pumper once advised me that the ideal tubing length is one in which, if the pump is worn in the pants pocket or on the belt, it will be long enough so that your pants can hit the floor when you go to bathroom, but short enough to not snag it on door handles and knobs all the time. This aspect of “short enough” is especially true for younger children, and anyone else who tends to forget to tuck their tubing in. This factor likely isn’t a deal-breaker – pick the infusion set or sets that work best for you based on the above factors first, and you will likely find your preferred brand and model of infusion set is available in a variety of tubing lengths to meet your needs.
- Serter or Manual?
Some infusion sets have a matching housing assembly which automatically inserts the infusion set – just load the spring and press a button, and the serter will do the rest. Other infusion sets are inserted manually. Which type is best depends largely on preference.
Some people prefer not to see the introducer needle/metal cannula. If it is a deal-breaker for you to have automatic insertion for this reason, you may want to narrow your research to those sets which have this option (either as a pre-constructed, disposable inserter, or as a re-usable inserter into which you load each disposable infusion set). Infusion sets that come with a disposable inserter standardizes and simplifies insertion, so may be a good choice for when your child is learning to insert their own infusion sets as you hand over diabetes care tasks.
Manual insertion infusion sets may be a good match for those who don’t mind seeing the needle, don’t want to fuss with a serter, springs and buttons, and/or want to reduce the amount of garbage/recycling that diabetes creates in their lives.
If you want to reduce your environmental footprint, you may want to focus your research on infusion sets that are inserted manually, or with a reusable serter.
- Connector type:
Some infusion sets have a type of universal connector called a “Luer”, or Luer-lock. If your pump uses this type of connection, you will have the greatest breadth and depth of options of infusion sets to choose from.
Medtronic pumps uses a proprietary infusion set connector that was specifically designed to work with their own pump reservoir. If your child’s pump uses this type of connector, your choices of infusions sets are limited to those manufactured by Medtronic. This is not typically a problem, as they offer a wide-range of infusion sets with a choice on the above features. However, it could become problematic if you need to explore alternate manufacturers because of an allergy, for example.
- Omnipod’s infusion sets are also proprietary, in a sense, since there is NO connector – the pod IS the infusion set.
- Other Factors:
There is also a range of options regarding colour (pink, blue, grey, for example), one-handed insertion/disconnection, reversibility of the connector, and protection of the introducer needle after insertion. For more on these options and others, your best bet is to talk to your diabetes educator or an online diabetes supplier that carries pump supplies.
The above information was reviewed for content accuracy by clinical staff of the Alberta Children’s Hospital Diabetes Clinic.
This material has been developed from sources that we believe are accurate, however, as the field of medicine (in particular as it applies to diabetes) is rapidly evolving, the information should not be relied upon, as it is designed for informational purposes only. It should not be used in place of medical advice, instruction and/or treatment. If you have specific questions, please consult your doctor or appropriate health care professional.
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