Abstract
Background and Aims
Intra-individual variability in insulin absorption after subcutaneous (SC) infusion may impair glycemic outcomes and has not been widely studied in the hybrid closed-loop (HCL) setting. Our aim was to ascertain the intra-individual variability in SC insulin absorption by means of a previously validated model (Schiavon et al., IEEE 2018) during a standardized HCL meal study.
Methods
Ten youths with T1D (age=20.9±3.7 y; BMI=23.6±4.5 kg/m2; TDD= 50.6±16.3 U/day) underwent two consecutive, standardized meal studies (70g carbohydrate breakfast and lunch meals) on the same day during DiAs HCL (CGM: Dexcom G4 Platinum with software 505; Insulin pump: Tandem t:slimTM) treatment. Pre-meal insulin bolus was determined based on subjects’ insulin to carbohydrate ratio and was delivered at the beginning of each meal. Plasma insulin aspart concentrations were measured every 10min for 4h during each meal and were used to estimate, for each subject and for each meal, a set of SC insulin absorption parameters (Figure A). The primary metric to assess intra-individual variability of model-derived parameters was the between-meals coefficient of variation (CV %).
Results
As shown in Figure B, mean values of model parameters have been similar between meals (p=NS); however mean intra-individual variability (CV) ranged from 34-94%, with the highest CV for the model parameter representing the direct absorption of non-monomeric insulin to plasma (ka1).
Conclusions
Our preliminary results suggest high intra-individual variability in SC insulin absorption during HCL treatment and underline the importance of optimizing insulin delivery algorithms to account for such variability to improve treatment outcomes.
