DynamicISF (DynISF)

Dynamic ISF was added in AAPS version 3.2 and requires Objective 11 to be started before Dynamic ISF can be activated. Select Dynamic ISF in the Config Builder > AAPS to activate. Dynamic ISF is recommended only for advanced users that have a good handle on their AAPS« controls and monitoring.

To use Dynamic ISF effectively, AAPS« database requires a minimum of five (5) days of the user’s AAPS data.

Dynamic ISF adapts the user’s insulin sensitivity factor (ISF) dynamically based on the user’s:

  • Total Daily Dose of insulin (TDD); and

  • current and predicted blood glucose values.

Dynamic ISF uses Chris Wilson’s model to determine ISF instead of a user’s static Profile’s settings for ISF.

The Dynamic ISF equation implemented is: ISF = 1800 / (TDD * Ln (( glucose / insulin divisor) +1 ))

SMB/AMA - an example of a user’s Profile with static ISF as set by the user and utilized by SMB and AMA.

Static ISF

Dynamic ISF - an example of a user’s ISF subject to change as determined by Dynamic ISF.

Dyn ISF

The implementation uses the above equation to calculate current ISF and in the oref1 predictions for IOB, ZT and UAM. It is not used for COB. Further discussion can be found here: https://www.youtube.com/watch?v=oL49FhOts3c.

TDD (Total Daily Dose)

TDD will use a combination of the following values:

  1. 7 day average TDD;

  2. the previous day’s TDD; and

  3. a weighted average of the last eight (8) hours of insulin use extrapolated out for 24 hours.

The TDD used in the above equation is weighted one third to each of the above values.

Insulin Divisor

The insulin divisor depends on the peak of the insulin used and is inversely proportional to the peak time. For Lyumjev this value is 75, for Fiasp, 65 and regular rapid insulin, 55.

Dynamic ISF Adjustment Factor

The Adjustment Factor allows the user to specify a value between 1% and 300%. This acts as a multiplier on the TDD value and results in the ISF values becoming smaller (i.e. more insulin required to move glucose levels a small amount) as the value is increased above 100% and larger (i.e. less insulin required to move glucose levels a small amount) as the value is decreased below 100%.

The Adjustment Factor can be located in ‘Preferences’ > AAPS:

Factor ISF

Future ISF

Future ISF is used in the dosing decisions that oref1 makes. Future ISF uses the same TDD value as generated above, taking the Adjustment Factor (discussed above) into account. It then uses different glucose values dependent on the case:

  • If levels are flat, within +/- 3 mg/dl, and predicted BG is above target, a combination of 50% minimum predicted BG and 50% current BG is used.

  • If eventual BG is above target and glucose levels are increasing, or eventual BG is above current BG, current BG is used.

Otherwise, minimum predicted BG is used.

Enable TDD based sensitivity ratio for basal and glucose target modification

This setting replaces Autosens, and uses the last 24h TDD/7D TDD as the basis for increasing and decreasing basal rate, in the same way that standard Autosens does. ערך זה שנחשב נמצא בשימוש גם כדי להתאים את ערך המטרה, אם האפשרויות להתאמת ערך המטרה עם הרגישות מופעלות. Unlike Autosens, this option does not adjust ISF values.

CAUTION - Automations or Profile Percentage Increase

Automations should always be used with care. This is particularly so with Dynamic ISF.

If Dynamic ISF is in operation, users should reconsider enabling any temporary Profile increase as an Automation rule or similarly activating a Profile Percentage which may create Dynamic ISF to be overly aggressive in correction bolusing and could cause hypoglycemia.