Dermal Glucose Sensing has a Shorter Time Lag Relative to Blood Glucose: Implications for Hypoglycemia Detection and Time in Range

Introduction: Current continuous glucose monitors (CGM) sensing glucose in the subcutaneous tissue have a significant time lag (τ). This delay could result in severe hypo/hyperglycemia and lower time in range (TIR). Dermal sensing can greatly reduce time lag. Methods: In a clinical study conducted at two US-based clinical centers, subjects with type 1 diabetes mellitus (DM) wore a novel dermal CGM + Abbott-Libre 3 or Dexcom-G7. All were compared to a YSI-glucose analyzer. Time lag kinetics for all sensors were modeled using the two-compartment model and compared to published data. Time lag data and its potential effect on TIR were also analyzed. Results: Data from 55 subjects showed fast kinetics for the dermal CGM. In total, 93% of the Laxmi sensors had a τ of 0-2 minutes, whereas commercial CGMs had a varying distribution of τ (−10 to 10+ minutes). This reduction in τ by 10 minutes has profound effects on errors in insulin administration in both open-loop and in a proportional-integral-derivative (PID) model of automated insulin delivery (AID). To evaluate the effect of tau on TIR, we used an in silico PID controller in a well-accepted model (UVA type 1 diabetes simulator) over a variety of conditions. We observed that tau greatly affects TIR and the distribution of the time out of range parameters. Conclusion: Dermal sensing has a time lag close to 0. Individuals with DM can have lower glucose targets with a system that eliminates fear of hypoglycemia, resulting in higher TIR and better control of DM.