The insulin patch pump for boluses

A patch device for giving an insulin bolus when needed is a small, single-use pump that sticks directly onto the skin [1]. This pump contains a reservoir of rapid-acting insulin and a thin cannula [2]. It has no tubing visible on the outside and no screen.

The role of this type of pump is to replace the insulin injections at meals and the correction ones [1]. Once you have filled the pump with insulin, you apply it to the skin and activate it. Then you can give yourself a dose of insulin by pressing two buttons on the body of the device [2]. In this way, a single device covers the insulin needed for meals for up to four days (96 hours) [1].

The main difference from an ordinary pump is that this device delivers boluses only. An ordinary pump sends insulin semicontinuously (every few minutes), through the basal rates programmed into it, and adds boluses for meals and corrections when needed [3]. The bolus patch device does not provide any basal insulin flow and stays inactive between presses [1]. The second difference concerns the controls.

An ordinary pump has a battery, which drives a small motor that pushes a piston. It generally has a screen and settings that you decide together with your medical team [4]. The bolus patch device works purely mechanically, with no battery and without any prior programming [1]. You give the insulin dose by pressing directly on the pump, and its size is fixed by the manufacturer [2]. There are also patch pumps that deliver a fixed basal rate, with the option of giving a manual bolus as well. Those belong to a different category, that of patch pumps for basal insulin.

The device is useful above all if you have type 2 diabetes, you already give yourself a daily injection of basal insulin and you additionally need insulin at meals [5]. A pump dedicated only to boluses can help you cover the mealtime doses without any more pen pricks [2]. The daily basal insulin injection remains necessary, though [5]. The approved indication is not limited to type 2 diabetes. It covers adults with diabetes who need insulin at meals or correction doses, whatever the type of diabetes.

It also suits the following situations:

• you find it hard to inject yourself in front of other people [1];
• you often skip the lunchtime dose [2];
• you want a simple treatment, without a technology that is harder to learn [4].

You do need, however, to see well (glasses are enough), to be able to fill the reservoir and to keep measuring your blood glucose. The decision to use this type of pump is one you can take together with your medical team [3].

No, the device has no basal insulin function. The bolus patch device delivers insulin only on demand, that is, only when you press the buttons. Between presses it sends nothing, so it does not automatically cover your basal need [1].

Basal insulin remains covered by the daily injection of long-acting insulin [5]. The two complement each other, the long-acting insulin working between meals and at night, while the bolus device steps in at meals. There are also patch pumps that deliver a fixed basal insulin flow, but those belong to a different category [6].

The bolus is triggered by pressing at the same time two buttons on the edges of the device [2]. You squeeze them fully, all the way down, between your fingers, until you hear and feel a click. That click confirms that the standard dose, set by the manufacturer, has been delivered [7].

You have to press both buttons because this avoids doses given by mistake, through clothes rubbing or through an accidental press [7]. For a larger dose you repeat the press and count the clicks. You can do this discreetly, without taking the device out from under your clothes [1].

In type 2 diabetes the body responds more weakly to insulin, and the doses needed are generally larger [8]. A pen with 0.5-unit steps or an ordinary pump allows doses in fractions of a unit. In type 2 diabetes, however, such a fine adjustment generally does not change the way blood glucose behaves, so the step by which the meal bolus is increased or decreased can be larger. A pump designed only for boluses generally has a delivery of two units set for each click, which is precise enough for type 2 diabetes [7]. In type 1 diabetes a much finer adjustment is needed, which this device cannot offer. Even so, the bolus patch pump is not forbidden in this case. The manufacturer also indicates it for adults with type 1 diabetes who give themselves basal insulin separately [4].

In type 2 diabetes some of your own insulin secretion is generally preserved, which can partly make up for the basal insulin need. The basal insulin comes separately, from the injection, so if the device comes off or runs empty you will still have the cover given by the basal insulin. In this way, the risk of starting to produce ketone bodies is much lower compared with a classic pump used in type 1 diabetes [9]. This cover applies only to the basal insulin, though, so a detached or empty device leaves meals without insulin and glucose rises. The device has no screen and gives no alarms, so you are the one who checks it: if the patch has come off the skin or if your blood glucose stays high after a meal, replace the device. Until then, give the mealtime dose with the injection pen. If vomiting, difficulty breathing or drowsiness appear, go to the emergency room straight away.

With each full press of the two buttons the device releases two units of insulin [7]. For six units you press three times, and for ten units you press five times [2]. You count in twos, which makes the arithmetic fairly easy.

A full reservoir holds up to 200 units, an amount that covers meals for several days (up to 96 hours) [2]. Before the first dose you prime it, that is, you press a few times (see the manufacturer's instructions), in order to fill the cannula with insulin [7]. Your doses are set in even numbers, because the minimum step is two units.

No. The device has no bolus calculator and in fact has nothing electronic in it [4]. The bolus pump does not know how much you have eaten and does not know your blood glucose value, so setting the insulin dose is strictly your responsibility [1]. Hypoglycemia means a blood glucose below 70 mg/dL (3.9 mmol/L): you take 15 g of fast-acting carbohydrate and recheck after 15 minutes. The complete steps are on the pages about what hypoglycemia is and about how to treat it.

The doses for each meal are generally set with your medical team, as a fixed number of presses for various situations. You then adjust them according to your blood glucose and the amount of carbohydrates you have eaten [5]. The device does not record your doses, so it is useful to write down the number of clicks.

Yes, the bolus pump was created for exactly this combination [5]. You give your daily basal insulin injection just as you usually do, and the device takes care of the mealtime doses. The two treatments complement each other: the long-acting insulin works between meals and overnight, while the device covers the meals. Their effects add up over time, so the doses are set together with your medical team.

In practice this approach greatly reduces the number of pricks. You will have one injection a day for the basal insulin and a single insertion every few days for the device [2]. Your medical team sets the doses for each of them, and you can then adjust them separately, according to your blood glucose readings [10].

Yes, it is much simpler. There are no basal rates to program, no menus to work through, no battery to charge and no alarms to interpret [4]. What you have to learn is essentially filling it with insulin and pressing the buttons [1].

Simplicity comes at a price, however:

• you have no fine adjustment of the doses [7];
• you get no basal insulin from the device [1];
• you have no bolus calculator [4];
• you cannot download the data for your medical appointments.

A full pump gives you much more control, but it also asks more attention from you in order to learn how to use it [11].