December 2014

Description of the pod in the OmniPod Insulin Pump

By Kathy Jean Schultz

The Omnipod Insulin Pump is a system consisting of two separate devices used by diabetic people for automatic insulin injection into the body. The two devices are the pod, and the Personalized Diabetes Manager.

The Omnipod is a microprocessor–controlled insulin-delivery system. The pod is attached to the skin near the user’s stomach, or wherever insulin injections are comfortable.

The pod is lightweight and disposable, and is worn for 3 days and then replaced. It is encased in water-tight flexible material and secured to the body with adhesive.

The pod operates like a human pancreas and releases small amounts of insulin all the time, night and day. The pod is wirelessly linked to and operated by the Personalized Diabetes Manager, or PDM, a hand-held electronic unit the size of a cellphone.

The pod’s PDM is programmed by the user’s health care professional. The data in the PDM is synchronized with the user’s baseline blood glucose levels and eating schedule. A user’s PDM is wirelessly linked to the pod. The PDM can be attached to a belt or carried in a case.

There is just one part makes up the outside of the pod, and that is its white, water-tight housing. The pod when resting on its skin-side base is slightly oval-shaped on three sides and straight on the fourth side.

The pod measures 3.9 centimeters by 5.2 centimeters by 1.5 centimeters (1.5 inches by 2 inches by .6 inches). The pod weighs 25 grams, or less than one ounce, when its insulin reservoir is empty. Figure 1 shows a pod, next to a PDM.

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Figure 1. The PDM, left, and the pod, right

Users can wear the pod anywhere they take injections, including on the arm, thigh or back. Because the pod is applied directly to the body, and there are no needles or tubing, users don’t have to take it off to shower, play sports or be intimate. Figure 2 shows how the pod’s adhesive keeps it attached to the skin.

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Figure 2.

Eight parts make up the inside of the pod, which is shown in Figure 3.

  1. automated cannula insertion system
  2. base of the water-tight housing
  3. insulin reservoir
  4. adhesive
  5. drive mechanism
  6. angled infusion set
  7. electronic circuitry
  8. 2 batteries

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Figure 3.

Description of Parts and their Functions

Materials inside the pod are proprietary and copyrighted but possess 3 properties: metal-like properties, soft rubbery properties, or plastic-like properties.

Automated cannula insertion system. The 1-inch long, soft plastic automated cannula insertion system lies at the flat end of the base, and extends toward the center of the base. It is attached to the insulin reservoir on one end and to the insertion mechanism at its other end.

The insertion end encloses a tiny needle inside the soft flexible cannula. The cannula is inserted under a user’s skin at a 45-degree angle and then retracted within five-1000ths of a second.

When a user is ready to attach a fresh pod, she or he removes the adhesive, fills the reservoir with insulin through an opening on the oval end, and sticks the pod onto the skin. By following the PDM screen directions and pressing specific buttons on the PDM, the user activates the insertion mechanism, which quickly drives both the insertion needle and the soft cannula into the tissue under the skin. (Figure 4.)

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Figure 4.

The insertion needle punctures the skin and stiffens the cannula during the insertion process. When it reaches its forward limit of travel, the insertion mechanism retracts and withdraws only the needle, leaving the cannula in place at the infusion site. The cannula enters the patient’s tissue at a 45-degree angle, to a depth of 6.5 mm. The cannula is then ready to conduct insulin infusion.

Base of the water-tight housing. The housing is attached to the pod around the perimeter of the base, on the side that sticks to the skin.

Insulin reservoir. The plastic-like insulin reservoir is a vial positioned on the flat end of the base to the left of the insertion system. It has a capacity of 85 to 200 deliverable units of insulin. The pod requires a minimum of 85 units of insulin to begin operation.

Adhesive. The adhesive is latex-free and acrylic-based. It is the same shape as the base and slightly larger, extending out from the pod on all sides.

Drive mechanism. The drive mechanism is a .5-inch long plastic plunger that forces insulin inside the insertion system when programmed to do so by the PDM.

Angled infusion set. The .5-inch long angled infusion set is positioned in the center of the base and near the rounded end of the base. The function of the set is to propel the cannula into the skin, and the insulin through the cannula.

By following directions on the PDM screen and pressing specific PDM buttons, the user activates the insertion set, which drives both the insertion needle and the soft cannula into the tissue just under the skin’s surface.

Electronic circuitry. The metal wire electronic circuitry is located to the right of the insertion system near the round side of the base, when the base is attached to the skin. Its function is to power insulin delivery by enabling wireless communications from the matching PDM.

The pod can be operated up to 5 feet away from the PDM, although most users keep the PDM in a pocket, belt case, or garter designed for the upper arm or leg. The circuitry enables the pod using secure, bidirectional radio frequency.

Batteries. Two AAA alkaline batteries fit into the squared end of the base to the right of the insertion system.

Theory of Operation

The pod in the Omnipod system keeps users’ blood glucose level steady between meals and while they sleep via wireless programming of insulin injection from the pod’s matching PDM.

Images by OmniPod

Copyright 2014 by Kathy Jean Schultz