Support different insulin strengths

Copied to new issue as per @Sjoerd-Bo3's request:

Working with U-200 I started wondering if it'd be worthwile to implement different insulin strengths. You keep the same settings/profiles in Trio and you bolus and log the same amounts of insulin and carbs, but the system will take care of the different insulin strength in the background.

Is your feature request related to a problem? Please describe.

Currently, Trio does not support different insulin strengths (U-200, U-400), which means users need to manually adjust their profiles and settings when switching from U-100 insulin. This can lead to confusion, inaccuracies in insulin delivery, and inconsistent data in Nightscout and other reports. Moreover, when using dynamic features it may take a while to catch-up.

The problem stems from the fact that pumps only "speak" U-100 and bases its "units" off of that assumption. However, 1 unit of insulin is a universal standard that is not tied to the insulin potency per ml. 1 unit in U-400 is still 1 unit, not 0.25U; you just get 75% less juice out of the pen as its more potent per ml. But as we cannot get the pump to speak U-200 or U-400: we need another way around this. Currently U-200/U-400 users compensate for this problem by "lying" to their pump and reducing their "units" being delivered by for example 50%. This also finds its way to Nightscout reports and Apple Health, giving a skewed view of how many units the user is actually consuming .

Describe the solution you'd like

Implement support for different insulin strengths (U-200, U-400) in the Trio app. The system should automatically adjust insulin delivery based on the selected insulin strength while keeping user settings and profiles consistent. Specifically:

a) When set to U-200 mode, reduce insulin output on the pump by 50% relative to U-100.
b) When set to U-400 mode, reduce insulin output on the pump by 75% relative to U-100.
c) When set to any such mode, warn the user that (basal) profile adjustments need to be sent to the pump (confirm). (Note: the profile in-app stays the same, the app sends the relatively adjusted/recalculated profile to the pump in the background.)
d) Multiply the remaining units available in the reservoir to reflect the correct amount (e.g., an Omnipod Dash starting from 50U would show 100U in U-200 mode).

So what you see as the user is when you want X amount of units: you always get that exact same amount of units regardless of the insulin strength; also in reports, Apple Health and Nightscout. 1U is always 1U - we're using the unit as the standard for measurement (how it should be and what is being done in medicine) rather than the different potency per ml and compensating for it in the profiles/delivery. As such, we just ensure the amount of milliliters required to deliver that amount of units are reduced in the background to account for the pump only 'speaking' U-100. On the pump itself, if it has a display, this will confusingly look like reducing "units", but we're just compensating for its dumbness. (Eg; if we want 2U on U-200 mode: we tell the U-200 filled pump, which always thinks it has U-100 in it, to inject "1U" to compensate for the higher insulin strength. And 2U/hr of basal will be set to 1U/hr on the pump. (But we know the truth and log it properly as 2U in this example).)

Describe alternatives you've considered

a) Manually changing profiles and settings when switching insulin strengths, which is prone to error, increases user burden and results in erroneous logs/reports as the user is technically "lying" about the amount of units they take. (Eg: at the endo's office in your NS repot they'll suddenly see 50% fewer units, whilst that's not actually true at all.)_
- b) Continuing to use U-100 insulin, which may not be feasible for all users due to availability or specific medical needs._

Additional context

This feature ensures consistency and accuracy in insulin delivery and reporting across different insulin strengths. It aligns with how Eli Lilly pens manage higher potency insulin, ensuring user settings remain the same while adjusting the insulin delivery in the background. Key benefits include:

a) Consistency in insulin units delivered, regardless of strength.
b) Simplified bolus calculations and profile management.
c) Consistent data in Nightscout and other reporting tools.
d) Cross-compatibility of settings with different insulin types and strengths.

The reasoning behind it is that this leads to:

a) Consistency. It is similar to using Humalog/Lyumjev pens with increased potency. With the pens Eli Lily provides, 1U on the dial is still 1U injected - this doesn't change. The mechanism reduces the insulin (in ml) administered, not the user. So with U-200 when you inject 100 units, it injects only 0.5ml instead of the 1.0ml it would've been on U-100. This ensures the user doesn't have to change anything, the only thing that changes for the user is that the pen lasts twice as long.
b) Prevents confusion when you have to do the maths yourself whilst coming from U-100 and are used to doing bolus calculations in your head or correcting quickly.
c) Keeps Nightscout output consistent so for analysis you don't have to multiply it by 2 or 4 for the interpreter (e.g., endo) to understand it. Plus some added bonuses if the care team hates U-200/U-400.
d) Keeps settings cross-compatible with any insulin type and strength, nothing changes; you just have more units available to work with (a 200U Omnipod becomes 400U or 800U).
e) Makes tuning work better and cross-compatible between different insulin types as it has the same data to work with, only minor tweaks may be necessary after switching to a different concentration.
f) It's actually more correct. Artificially "reducing" the units you're delivering in the profile and for bolus and basal is technically lying to the system. You're not suddenly actually using 50%-75% fewer units of insulin; you're still using the same amount of units. You just have to "lie" about that because the pump isn't capable of speaking U-200/U-400, but this lie finds its way to all your settings, reports, the algorithm, etc. It becomes more confusing to analyze those reports as well when every delivery you see must be multiplied by 2 or 4 to get to the true amount of units delivered.

Possible negative effects:

Possible negative effects I couldn't directly find any, especially as Eli Lily chose the exact same strategy with their pens. (Reduce output in millilitres, rather than making the user reduce their number of units - they chose to use the unit as the standard rather than the units per ml as well.) The current negatives are you have to maually change profile and manually remember it and the nightscout, AT and AS data get's "tainted" when you switch insulins. If it's as easy as switching in-app from U-100 to U-200 when you switch insulin type: that's easier and probably safer. However, there are some potential caveats that may require a solution/warnings:

a) The stored settings on the pump will be different than what the app shows, such as the basal rates. Whilst the app in this setup will show the same basal rates + ISF + I:C as on U-100, we do instruct the pump in the background to deliver 50% less on U-200 and 75% less on U-400. So 1U/hr basal will be 0.5U/hr shown on the pump with U-200 and 0.25U/hr shown with U-400. An in-app warning above/next to the basal rates (and other factors) plus a clear explanation in the docs is a good idea for starters. People must also be made aware that if for whatever reason they manually bolus directly from their pump (e.g., Medtronic), they need to remember to do the maths themselves; this is of paramount importance!
b) The minimum bolus delivery (and minimum basal per hour) is different and is a hardware limitation. Eg: if 0.05 is the minimum, on U-200 that'd be equivalent to 0.1U and on U-400 that'd be equivalent to 0.2U minimum.
c) People using other software to generate reports from data stored on their pump, such as Glukoo or Tidepool, may see their insulin administration is reduced by 50% or 75% compared to what is shown in-app and in Nightscout. With the current supported pumps, that's likely not an issue (as they cannot be read with such tools to my knowledge); but it may be a problem in the future. It's important to point that out and/or get in touch with the developers of such tools to allow setting insulin strength.

Technical Details

This feature involves adjusting the Trio app’s insulin delivery calculations and display settings based on the selected insulin strength. It also requires clear documentation and in-app warnings to inform users about the adjusted delivery rates on the pump.

User Impact

Medium – This feature will improve the ease of use and accuracy of insulin delivery for users switching between different insulin strengths.

nightscout / Trio