Omnipod IOB Question

[Lorraine]

@Terry4

Does the Omnipod use a simple linear IOB calculation so that it computes an insulin duration of say, 4 hours, at a 25% insulin used every hour?

Yes! Before there was IOB on the Omnipod, I was doing quick math in my head all the time. It was tolerable, but you’re right - multiple boluses complicates it.

[Dragan1]

@ClaudandDaye

So, that’s the changes we’ve made lately and, like I said, I couldn’t be more happy with the results we’re seeing. We are staying between the comfort zone (80 - 180) over 90% of the time.

That’s just phenomenal, congratulations! So happy to hear about your excellent results!

@ClaudandDaye

We also made another change in creating a temp basal preset that adds an additional 50% more for 3.5 hours after each meal onto whatever his current basal regimen is. This has helped us practically eliminate the spikes. What this “can” cause; however, if we’re not paying attention, is hypoglycemia. So we carefully watch him post-prandial and, after he “levels off” and starts going down, we turn off that temp basal preset. Also, if we see him going below a certain level that we’re comfortable with (under 150), we suspend insulin until the “down arrow, or 45 degree arrow down” stops, then we resume the basal.

Nice “surfing,” well done! What you’ve described above is what some closed-loop systems are attempting to do automatically - they use temp basal rates not only to adjust for activities, sickness, or such, but to make meal-bolus corrections based on CGM data. In a manual system, such as the current OmniPod, using temp basals for meals is just fine, except for one small problem, which is related to your question about IOB. IOB calculations on the PDM take only boluses into account, and are completely ignoring basal and temp basal rates. If you wanted to stick to the conventional bolus/basal model the PDM assumes, you could use extended boluses instead of temp basals. Lets say you give a 1U meal bolus together with a 50% temp basal increase from 0.2U/h to 0.3U/h for 2 hours. This temp basal amounts to (0.3U/h-0.2U/h)*2h = 0.2U of extra insulin for that meal. In this example, you could reproduce exactly the same effect by issuing a 0.2U bolus extended over 2 hours. Then, just as you may abort a temp basal based on CGM reading, you may terminate an extended bolus at will. An advantage compared to what you are doing is that the PDM would take the extended bolus into account in its IOB calculations.