Using an infusion set that works well is one of the most important steps in achieving success on a pump. If a particular set causes skin irritation, falls off when you swim or sweat, gets blocked or dislodged, or leaks insulin back to the skin surface, significant control problems may occur. For a satisfying pump experience, you want the infusion set you wear to be comfortable, reliable and easy to use.
An infusion set is the non-glamorous, funny-looking piece of plumbing needed to deliver insulin, and is often the most overlooked ingredient for success on a high-tech insulin pump system. Its role is to allow insulin to flow from a reservoir in the pump through an infusion line into an infusion set with a Teflon tube or metal needle held in place beneath the skin by an adhesive backing on the skin. Small but important, the infusion set is the weakest link in pumping and often makes or breaks the wearer’s ability to control their glucose.
Patch pumps applied directly to the skin are making headway, and they have the advantage of no infusion set to cause problems. But if they become loose from their adhesion, the plumbing and glucose control problems are identical.
Not all sets have an optimal design nor will one set work well for everyone. When selecting an infusion set, consider how much body fat you have, which sites on your body are best to use, how your clothing choices affect site selection, if your activity level limits you to certain sites, how easily you can detach the pump for bathing or other activities, and whether you really need a device to aid you in inserting your infusion set.
Unless your MD, NP, or PA prescribes a particular set, the infusion set shipped with a new pump is likely to be one manufactured exclusively for your pump company. This set may or may not be the best choice for you. In the box that accompanies your pump are usually two or three samples of other sets to try. Go further than this if possible and try other sets, especially if the initial sets cause problems. Ask your diabetes educator to help you choose from the two dozen sets that are available. Wear different infusion sets before deciding which one is comfortable, easy to use, stays in place, and seldom or never leads to a loss of control. Fortunately, there are many alternative sets to choose from.
Metal and Teflon versions: Today’s straight-in metal sets or slanted metal sets offer fine gauge needles that are comfortable, reliable, and often the easiest to insert. Teflon sets are inserted through the skin using a similar metal needle with a Teflon tube around it. The metal needle inserter is removed after insertion, leaving only the Teflon cannula under the skin. Generally, the longer the Teflon cannula, the more reliable it is. Slanted Teflon sets tend to be the most reliable. Reliability of the straight-in Teflon sets varies by brand. Unfortunately, slanted sets are more difficult to use with automatic inserters, while straight-in sets tend to be easier to use with automatic inserters. Slanted sets are often more successful when inserted by hand.
An infusion set that is not placed deep enough may hurt when a larger bolus is given because the nerves are close to the top of the skin. This is more likely to occur with one of the slanted sets, which are designed to be inserted at a 30-60 degree angle into the skin (90 degrees is straight in). Adjust the slant on a slanted set for your padding in the insertion area so the set is angled enough to go further under the skin.
An infusion set can also be too long and hurt when shifting the body because it is hitting the muscle. This is more likely when placed into the arm or leg of a thin person or a small child. If this occurs, choose a shorter needle or cannula.
Site location: Infusion sets can be inserted in the abdomen, hips, upper buttocks, outer thighs, or back of the arms. The sites should be rotated to allow use of a larger area of the body while avoiding overuse of any one area. The skin real estate required for an infusion set is relatively small and more adaptable to bending and twisting of the body than the larger base of a patch pump that must remain stable on the skin. This allows infusion sets to be placed in a wider variety of skin areas compared to patch pumps.
Tubing Length: Infusion sets have different tubing lengths. The tubing connects the reservoir to the infusion set. Most infusion tubing is 12” (30.5 cm), 23” or 24” (60 cm), 31” (80 cm) or 40” or 43” (110 cm) in length. Shorter tubing works better for small children and those who wear their pump close to the site while longer tubing works well for those who are taller. Tubing is sold with the infusion set and cannot be purchased separately. So ordering an infusion set might look like 24 inch, 6 mm “brand” (straight-in) set or 40 inch, 17 mm “brand” (slanted) set.
Cannula/Needle Length: Typical cannula/needle lengths for straight-in sets are 6 mm (about ¼ “) recommended for infants, 8 mm or 9 mm (slightly less than 1/3” ) for a child, 10 mm (about1/3”) for an adult, and 12 mm (½”) for larger adults. Slanted sets come in 13 mm (about ½”) and 17 mm (a little more than ½”) that serve similar functions with the depth of insertion controlled to fit the skin area of an individual physiognomy.
Needle Gauge: Gauge is a standard way to measure the diameter of a needle or cannula. A higher number for the gauge means a needle is smaller in diameter. For example, a 28 gauge needle is smaller than a 25 gauge needle. Smaller needles are usually considered more comfortable.
Connection: Most infusion sets have a standard threaded luer lock connection to the reservoir at the pump end of the line. A standard connection allows you to choose from among about 20 different infusion sets that can be used on most pumps. The reservoir for the Medtronic Paradigm has a proprietary connection that cannot be used with luer lock infusion sets. If you want to try a luer lock, Applied Diabetes Research offers “Fifty50” 1.8ml and 3.0ml reservoirs that work with the Paradigm series of insulin pumps. These reservoirs allow any infusion set with a standard luer connector to be used in the Paradigm pumps.
Disconnect: Most sets give you the ability to disconnect the infusion tubing at or near the infusion set. This allows you to disconnect for showering, sports, etc. Just the adhesive, connection hub and cannula or needle remain behind on the skin.
Away-from-body disconnect is a good option for people who prefer to leave their line taped down when they detach. Rather than disconnecting right at the infusion site, you can disconnect a few inches away from your body where you can see and feel the tubing better. About a 4-inch tail is left behind with the cannula, connection hub and adhesive. Be careful that the tail doesn’t get caught on anything. For example, Sof Set, Rapid D, and Sure T have a tail on them.
Inserter: An inserter is a spring-loaded device that helps insert the cannula when it is held against the skin at the site, simplifying the insertion process for those who are needle phobic or have dexterity problems. An inserter can also aid insertion in difficult-to-reach places, such as the upper hips, sides of the abdomen or arms. Inserters generally work much better with straight-in sets than with slanted ones. Some inserters can be used repeatedly to put sets in. Others are built in to a set and are disposed of after one use, adding to expense and medical waste. With current patch pumps, the inserter is thrown away after one use as is the whole insulin delivery device, which also contributes to medical waste.
How long to wear a set: Pump companies recommend that a set be worn two to three days before changing it for a new one. Some pumpers push the margins and vie for bragging rights to the “longest use of an infusion set” title. These thrifty and resourceful users have been known to extend use to six or seven days. Although less expensive, extended use of a set may cause skin irritation or scarring and increase the risk of infection. Protect the skin so you can repeat use of a variety of sites on a rotation basis.
Set movement: Any movement, tugging or twisting applied to the Teflon or metal needle makes the set more likely to detach or, as more commonly occurs, to loosen and allow insulin to tunnel back to the surface of the skin. Some sets, like the Rapid-D metal set and Sof-Set, have a separate connection a few inches from where they attach to the skin. This allows an adhesive, like IV3000 or Tegaderm, to be placed over the set so it is well anchored to the skin.
Critical information: In most sets, the infusion line detaches at the infusion site. If this line is not anchored, movement of the line while dressing, moving or sleeping can easily loosen the Teflon tubing under the skin. All infusion lines need to be anchored by taping the infusion line to the skin near the infusion set. Anchor the line by taping a short piece of one-inch tape (Durapore, Micropore, Hypafix, etc) over the line or lay tape over a circle of the tubing against the skin close to the infusion set to prevent movement of the Teflon when changing clothes, bending over, or turning over in bed.
Anchoring the infusion set or infusion line in these ways keeps tugs on the line from loosening the infusion set. This single step lets you receive the expected dose of insulin and prevents many headaches and unexplained highs.
How to recognize infusion set problems: Do you have unexplained highs? Does this happen frequently? Do the highs correct when you change your infusion set? If you answer yes to any of these, be sure to anchor your infusion line with tape or consider changing to a different type of infusion set. Loose sets cause the glucose to start rising for no apparent reason.
Set problems are often blamed on “scarring” or “poor absorption.” We are aware of only one research study that has looked at whether scarring affects control. Dr. Louise Conwell and her associates in the Department of Pediatrics at the University of Toronto studied skin changes in 50 children and adolescent pump patients and conducted ultrasound scans in 8 of them. They found frequent but minor skin changes (average severity score of 6.3 in a range of 0 to 69 that had no relation to A1c levels. Infusion sets inserted at 90 degree produced the least skin changes. Skin changes were most severe in thinner subjects. Less than 5% of the patients considered stopping CSII because of skin concerns. LS Conwell, E Pope, et al.
Preventing occlusions: For many pumpers, occlusions or blockages of the line are rare. For others they are relatively common. More than one blockage of your insulin delivery a month can raise your A1c level. An occlusion causes a complete stop of insulin through the infusion tubing, but before this happens a significant amount of insulin is lost inside the tubing over many hours before the complete blockage occurs. Fortunately pumps alarm when they sense an occlusion. However, when a basal rate is low, as with a small child, it may take longer for insulin to precipitate onto the inside of the tubing, normally near its connection with the Teflon cannula. This partial occlusion may not be enough of a blockage to trigger an alarm, but it can create a high blood glucose.
To prevent occlusions, avoid stopping the pump for any reason (let it run when you are showering, etc), and avoid inserting the infusion set with lotion on your hands or body that can enter the line. It is better to never stop a pump, because this may increase the risk for occlusions and is not really effective for avoiding or treating a low blood glucose. Use a temp basal reduction to keep the insulin flowing rather than stopping a pump for sports or other situations where less basal delivery is needed.
Allergies to infusion sets: Your choice of metal or Teflon should take into account any allergies you have. Metal needles are made of stainless steel, which can contain as much as 8 to 12% nickel. People allergic to either of these should avoid metal needles.
Soft cannula sets are made of Teflon, are latex free and contain no PVC (polyvinyl chloride). A person may be allergic to the adhesive in the dressing or the glue in the infusion set.
If you experience redness, itchiness or pain around your insertion site, try other products to rid yourself of symptoms.
Bleeding from the site: Bleeding from the site after the set is inserted requires immediate attention. When this happens, no insulin is being delivered and the blood glucose has either started to rise or will soon. Bleeding may be caused by nicking a blood vessel when you insert the set or by movement of the set afterwards which can open a vessel. You need to change the set immediately if blood appears in the infusion line or a lump (hematoma or pool of blood) can be felt under the skin, usually within 1 to 6 hours after inserting a new set.
Reliability is the most desirable feature for any infusion set. Most infusion sets work well, but problems like a tendency to detach, the Teflon cannula crimping during insertion, or a series of unexplained high blood glucoses caused by set failure may not be apparent until a set is worn for some time. A particular infusion set may cause a skin rash or irritation while another may not. A trial run with various sets is likely to pick up most of these problems. Do not continue to wear a set that causes problems. You have many good choices so find a set that works well for you.
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