The first three questions I posed have to do with food and adjusting the algorithmâs response.
The meal entry screen has 4 fields
- amount (grams of carb)
- the time the food is to be eaten
this is pre-filled to the current time, but you can scroll the wheels to change it to a time in the past or future in case you already started eating, or youâre planning to eat it at some time in the future.
- the food type, which has 3 buttons: lolly pop, taco, or pizza
these are shortcuts that correspond with âdigestion timeâ which means how fast the food will turn into carbs in the bloodstream. The lolly pop sets the time to 30 minutes, and is used for any kind of sugary fast carbs. The taco button sets the time to 3 hours, which is representative of a typical mixed meal containing carbs, protein, and fat. The pizza button sets the time to 5 hours, which is useful for slow-digesting foods. These 3 buttons just change the time displayed on the 4th line to three convenient pre-set values.
- absorption time
this shows the time if you pressed one of the 3 buttons, or is pre-filled with 3 hours if you didnât, and you can scroll it in half hour increments from 1/2 hour to 8 hours. This isnât intended to be some scientific measurement, itâs just a knob that enables you to tell the algorithm whether to give the meal bolus rapidly, or spread out over more time. Kind of like a âsquare waveâ or âextendedâ bolus on a traditional pump, but more adjustable.
If you donât enter anything other than the grams of carb, it just acts like a traditional pump, so you arenât required to use all the fancy features and answer lots of questions with lots of button presses. For example, if I just want to eat a 50g sandwich, I type the following:
press the "meal" button
50
press the "continue" button [it shows the recommended bolus which you can change]
press the "save and deliver" button
That was 5 button presses. On my old t:slim it was something like 14 button presses to get it done.
If you notice that your BG is rising too fast or is topping out too soon, suggesting that the meal bolus wasnât right, itâs possible to change what you originally entered. Loop saves the data for all of todayâs meals in a table. The meal grams, time eaten, and absorption time are stored as a line in that table. Itâs easy to tap on a line to bring up the food entry screen pre-filled with the numbers from the table, but you can edit any of them, for example to change the grams, or the absorption time, or even the eating time. As before, the continue button goes to the bolus amount screen, which will show any additional bolus that the algorithm suggests based on the new information and the amount of insulin and remaining carbs in your system. As always, you can accept the suggestion or change it to whatever you want. And it shows a graph of your estimated BG over the next 5 hours based on all the food and insulin the algorithm knows about, so you will see if it thinks you already have too much insulin and maybe should consider eating some extra carbs to avoid going low.
If dealing with extra insulin resistance or insulin sensitivity, you press the âcustom presetâ button. This is a bit like âexercise modeâ on a traditional pump, but much more adjustable. Here thereâs a slider showing overall insulin needs, pre-set to 100%, but you can adjust it anywhere from 10% of normal to 200% of normal. There are also fields for target BG range in case you want your BG to run higher (or lower) than usual; start time; and duration of this override (in 15 minute intervals for up to a day, or âenable indefinitelyâ if you donât know how long it will take for your insulin sensitivity to return to normal.
You set the kind of insulin in DIY Loop because the algorithm uses the actual published insulin absorption curves for Humalog, Novolog, Apidra, Fiasp, and Lyumjev. This enables the algorithm to be more accurate than it would be if it just used a âduration of insulin actionâ setting like the 2 or 3 hours that we used to put into traditional pumps to try to get them to dose more aggressively.
If you take a manual bolus by syringe or by Afrezza inhaler, thereâs a screen to enter that information so that the algorithm can take that into account when deciding itâs automatic insulin corrections every 5 minutes.