bg_ISF

There are indications that higher glucose levels require a stronger ISF. This observation is supported by successful users of AAPS who have defined automation rules that enhance the profile at elevated glucose levels. However, a drawback is the presence of sudden jumps in ISF at switch points with no further or minor adaptations in between.

In the context of AutoISF, a polygon is employed to establish a relationship between glucose and ISF, allowing for interpolation between data points. While the current implementation is hard-coded, users have the flexibility to apply weights for easy customization to suit individual needs. In principle, the polygon itself can be edited, and the .apk can be rebuilt if a different shape is desired. The prospect of developing a graphical user interface (GUI) for this purpose was initially deemed challenging, especially before confirming whether the results justify the effort. However, this approach enables users to approximate the formula used in DynamicISF for the ISF dependency on glucose.

Two weighting factors come into play based on whether glucose is below or above the target range:

lower_ISFrange_weight: Applied below the target, weakens ISF the more this weight is increased; a value of 0 disables this contribution, resulting in a constant ISF below the target. This weight is less critical when the loop is likely running at a TBR of 0, and a starting value of around 0.2 is recommended.

higher_ISFrange_weight: Employed above the target, strengthens ISF the more this weight is increased; a value of 0 disables this contribution, resulting in a constant ISF above the target. It is advisable to start with a weight of 0.2 and carefully observe reactions and check the SMB tab before further adjustments.

The resulting formula is expressed as:

bg_ISF=1+xxx_ISFrange_weight × glucose_polygon_Lookup

In a special case where bg_ISF < 1 indicating a scenario below the target, ISF will be weakened. In such cases, there is no need to assess the remaining effects. Only positive acceleration suggests a milder weakening, signaling a forthcoming rise in glucose levels.