By Donna Rice, MBA, BSN, RN, CDE, and Kay Sweeney, PhD, RD, CDE | March 17, 2008 12:00 am
When a person uses an insulin pump to control his diabetes, one of the decisions he has to make is what model of infusion set to use. Pumps are often an excellent choice for people who use insulin and seek tight control of their diabetes but need some flexibility in their diabetes regimen.
Most insulin pumps require the use of an infusion set to deliver insulin from the pump to the user. An infusion set consists of a length of thin plastic tubing, a very thin stainless steel or Teflon cannula that is inserted just under the skin, and a plastic connector that joins tubing and cannula together. The connector is generally mounted on an adhesive patch that is stuck to the skin at the insertion site to help keep the cannula in place. The connector allows a person to disconnect from his pump temporarily (for swimming, intimate situations, etc.) without removing the infusion set.
Insulin infusion sets come in a variety of styles to suit individuals’ unique needs and preferences. In addition to having either a Teflon or steel cannula, infusion sets may be designed to have the cannula inserted straight into the subcutaneous tissue or at an angle. Some cannulas can only be inserted manually, while others can be inserted either manually or with an insertion device. All infusion sets offer a variety of tubing lengths.
A “soft” cannula is a thin, flexible needle made of the synthetic substance Teflon that is inserted into the subcutaneous tissue via a steel introducer needle. The introducer needle is then removed and only the soft cannula is left in place. Soft cannula sets are popular because they are comfortable to wear and they can remain inserted for up to 72 hours. One disadvantage of the soft cannula, however, is that its flexibility can potentially lead to kinking, which disrupts the flow of insulin into the body. If a disruption is not detected, it can lead to dangerously high blood glucose levels. Users of soft cannulas, therefore, need to know how to troubleshoot and immediately change their infusion sets if kinking occurs.
A steel cannula is a thin metal needle that is inserted into the subcutaneous tissue; steel cannulas should stay in place for no longer than 48 hours. One advantage of using a metal cannula is that it is durable and will not kink, assuring a continuous flow of insulin into the body. Metal cannulas are also very useful for people who are allergic to Teflon. The disadvantages of using a metal cannula are that it can cause discomfort during movement or physical activity and that it requires more frequent site changes.
There are two options for inserting a cannula. A person can choose manual insertion, which means that he simply pushes the needle into his subcutaneous tissue as if giving himself an injection, or he can use a spring-loaded insertion device that automatically inserts the needle into the tissue. The manual method is useful for people who like to control the speed of the insertion; it allows them to prepare themselves psychologically for the task and to achieve a gradual and less forceful insertion. People who are lean often prefer manual insertion.
Many people, however, prefer using an insertion device. These devices are definitely helpful for people who have arthritis, Parkinson disease, or any other condition that affects fine motor skills, as well as for people who have a needle phobia. Insertion devices also allow the pump user to insert a cannula more easily into harder-to-reach infusion sites, such as the buttocks or the back of the arm. The disadvantages of using an insertion device include the added expense (though it is usually covered by insurance, and some devices are reusable) and the additional education needed to learn to use it correctly. Another disadvantage is that the user cannot control the depth or the exact angle of insertion.
Both insertion methods work effectively, so it is entirely up to the user to decide which works best for him.
Infusion sets come in two varieties with regard to the angle at which the cannula is inserted into the skin: straight (90Â°) or angled (10Â° to 45Â°). A 90Â° set means the needle is inserted at a right angle, or straight into the skin. This option allows for use of a shorter needle, which many people view as an advantage. The disadvantage, however, is that a shorter needle can become dislodged more easily. Also, kinks in a soft cannula are more common with a 90Â° infusion set.
“Angled” infusion sets are popular among people who are physically active and lean. They allow a person to insert the needle into the subcutaneous tissue at different angles ranging from 10Â° to 45Â°. The major disadvantage with this type of set is that the introducer needle is longer and may therefore be less appealing for people with needle phobia.
Most manufacturers provide infusion sets with a variety of lengths of tubing. Your preference may depend on where on your body you insert your infusion set and whether you wear the pump itself inside or outside of your clothing. Also, the physical setup of areas, such as the bathroom, where pump users carry out their daily routines often determines what tubing length they choose.
Different areas of the body generally absorb the rapid-acting insulin analogs used in pumps at similar rates. However, people may find slight variations from one body area to another and should keep this in mind if they notice otherwise unexplained fluctuations in their blood glucose levels after changing infusion areas.
The most comfortable place to insert an infusion set for most pump users is the abdominal area, which also has the most consistent absorption rate. During pregnancy it is still appropriate to insert in the abdomen as long as the subcutaneous tissue can be pinched up.
Other infusion sites include the outer thighs, backs of the arms, hips, and buttocks. The thighs and arms usually have slower absorption rates than the abdominal area, but the rates may accelerate with increased activity. The backs of the arms can be a difficult to use if dexterity is an issue. Many people choose the hips and buttocks as their infusion sites since these areas tend to have more subcutaneous fat and may be more comfortable, especially for people who are very active or don’t have much body fat in general.
When selecting an infusion site, avoid bony areas and places where the infusion set might be constricted, such as areas that will be covered with tight-fitting clothing. Also avoid areas that contain scar tissue, superficial (visible) blood vessels, body piercings, or tattoos. It is also important to stay two inches away from the navel.
Proper infusion site care is essential for preventing infections. Good technique starts with cleanliness. All equipment should be stored unopened in the manufacturer’s original packaging until use. Washing hands and the area of insertion with soap will help prevent bacteria from gaining a foothold. One way to insure that the insertion area is clean is to change infusion sites immediately after a shower. It is also imperative that blood glucose levels be checked 1—2 hours after insertion to make sure that insulin is being delivered unimpeded.
Even with impeccable site care, infection can occur, and it is important to recognize the signs of infection so you can respond quickly. Signs and symptoms of infection include redness, swelling, pain, warmth in the area, a lump under the skin, fever, pus, and elevated blood glucose levels. Medical care is always recommended, so contact your health-care team at the first sign of any suspected infection. Antibiotic treatment may be necessary, and more serious infections may require surgical incision and drainage.
Each time an infusion set is changed, the new set should be inserted at least two inches from the previous site, and an insertion site should not be used again for 7—10 days. Any rotation pattern that helps you remember where to insert next can work effectively. Some people use the “clock method,” in which sites are rotated in a circle from “12 o’clock” to “3 o’clock” to “6 o’clock” to “9 o’clock,” while others rotate from side to side. The important thing is not how it is done but that it is done. Meticulous site rotation can prevent serious complications (such as infection, breakdown of skin, and poor absorption of insulin) down the road.
An infusion set should be changed immediately if marked high blood glucose levels occur and are not corrected by a bolus dose of insulin. If ketones are detected in the blood or urine or there are signs of infection, insulin delivery may be impeded, and it is imperative that the infusion set be removed and a new set inserted at a different location.
It is often not necessary to use more than the adhesive patch that is part of the infusion set to keep it in place. However, people who are very active or who tend to perspire a lot may require additional tape or other adhesive products to keep the set in place. Different tapes and dressings have different looks (transparent, white, or colored), and certain ones may adhere better in wet conditions (due to perspiration, swimming, showering, etc.) or may be more comfortable for people with sensitive skin. People with skin sensitivities and/or adhesion problems may also benefit from skin barrier preparations, which are liquids that are applied to the skin to form a barrier between the skin and tape or dressing while also helping it adhere better. Tape removers dissolve tape and adhesives before the infusion set is removed, reducing damage to the skin. However, tape removers can potentially cause skin irritation and should be avoided if there is any skin breakdown at the infusion site.
Trial and error is the best way to determine which products work best, and more than one product may be used in combination to provide maximal adhesion with minimal irritation. Talk to your health-care provider about options currently on the market.
Some manufacturers’ pumps are compatible only with their own infusion set systems, while others are compatible with a variety of product lines. The availability and universality of supplies may be a consideration in your pump selection, so it is wise to check on this prior to making your final pump decision. Usually an insurance company that covers a certain insulin pump will cover compatible infusion sets, but because coverage varies greatly it is important to check on this issue as well. Insurance companies usually cover 30 days’ worth of infusion sets at one time.
When choosing infusion sets and tubing lengths for children who use insulin pumps, comfort and security are issues to consider. The buttocks seem to be one of the most comfortable infusion sites for children since they have the largest amount of fatty tissue. Also, because a child cannot see this area, it is less likely that he will tamper with or remove the infusion set. Products and techniques for numbing the insertion site are also available and can be useful for both children and adults with needle phobia.
It is a well-known fact that tight control of blood glucose levels can prevent or delay the progression of long-term diabetes complications. There are many treatment choices for achieving this level of control, and finding the option that best fits your lifestyle usually requires trial and error and most of all, patience and perseverance.
When choosing an insulin pump infusion set, don’t go it alone: Team up with a diabetes educator who can help you sort through the available products and teach you proper infusion set techniques and care.
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