Well, let’s see if I can clearly explain.
Since you’ve lived with diabetes and insulin dosing long-term, I’ll start by examining a typical manual insulin dosing scheme that most of us started on.
We take insulin for two main reasons. First, we use it to metabolize our meals and counteract unhealthy blood glucose rise. This is called bolus insulin.
Second, we need to metabolize the glucose called glycogen that is steadily pulsed from the liver. One can do this taking a long acting insulin like Tresiba or by using an insulin pump to provide a basal rate drip of insulin around the clock.
So what cognitive process do we step through to calculate insulin dose sizes? Usually, with meals, we consider the carbohydrate content of what we intend to eat and base our insulin dose on grams of carbohydrates.
For example, if our meal contains 50 grams of carbs and our insulin to carb ratio is 1:10, then we’d take 5 units of insulin (50/10=5).
The basal insulin is taken via a pen/syringe or a pump basal rate.
Sometimes we need to correct high blood sugar using an extra bolus of insulin. We calculate the size of this dose using something called an insulin sensitivity factor or ISF. This is a personal customized amount in mg/dL (or mmol/L) that one unit of insulin will drop your glucose level.
What does this have to do with Loop, an automated insulin dosing system? The short answer is that Loop takes over much of the cognitive load doing the tasks I listed above.
Every five minutes, Loop examines the current blood sugar as measured by the CGM and decides whether to add or withhold insulin. Loop then sets a temporary basal rate that is increased or decreased from the pump programmed basal rate. In other words, Loop modulates the pump basal rate.
No matter how diligent the person with diabetes may be, it’s impossible to pay attention every five minutes to your ever changing blood glucose levels.
When dosing insulin, there are only two levers we control: dose size and timing. Dose timing is a big deal. I’m reminded of the bit of wisdom contained in the saying, “a stitch in time saves nine.” A well timed insulin dose will do the most work with the smallest amount of insulin. Anyone who has struggled to correct a very high BG will attest that it takes a lot more insulin to correct high glucose than it does to prevent it.
Loop’s ability to pay attention and act dynamically and appropriately every five minutes, even while you sleep, is what makes it a huge improvement over manual insulin treatment.
Does this make things any clearer?