CGM Lag Compensation Using Weighted Rate-of-Change Filtering
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Solution Overview
Problem
Existing analyte monitoring systems, such as continuous glucose monitoring (CGM) systems, experience a lag between interstitial fluid (ISF) and blood glucose levels, leading to inaccurate glucose level measurements, particularly during fast excursions.
Innovation Solution
A method of lag compensation that calculates analyte point and rate-of-change estimates using a series of uncompensated measurements, applying weighted coefficients based on scaled rates-of-changes from multiple time periods to correct for the lag, utilizing a combination of FIR LTI models to improve accuracy during fast glucose changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If ISF glucose measurements are used for monitoring, then continuous monitoring capability is achieved, but time lag behind blood glucose occurs
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the lag compensation factor based on the rate of change of ISF glucose measurements. When the rate of change is high (indicating fast glucose excursions), a larger compensation factor is applied to correct the lag. This transforms the static measurement approach into a dynamic one that adapts to changing physiological conditions, resolving the contradiction between continuous monitoring and measurement accuracy.
2Ease of operation
If simple lag compensation is applied, then implementation ease is maintained, but accuracy during fast glucose excursions deteriorates
Solution Approach 1:
The patent implements dynamics by making the lag compensation factor variable rather than fixed. The compensation factor is dynamically adjusted based on the calculated rate of change of ISF glucose measurements. This dynamic approach allows the system to automatically increase compensation during fast glucose excursions while maintaining simplicity during stable conditions, thereby resolving the contradiction between implementation ease and accuracy during fast changes.
3Measurement precision
If multiple scaled rates-of-changes are used for compensation, then measurement accuracy is improved, but computational complexity increases
Solution Approach 1:
The patent applies partial action by using a limited number of scaled rates-of-changes (typically two or three) rather than attempting to account for all possible historical data points. This selective approach provides sufficient compensation accuracy for clinical purposes while keeping the computational burden manageable. The system uses only the necessary number of previous measurement points to achieve adequate lag compensation without excessive computational complexity.
Data Source
AI summary
Methods comprising applying a first analyte point measurement filter comprising: receiving, from an in vivo analyte sensor, at least a first, second, and third uncompensated analyte measurement at a first, second and third reference time; determining a first scaled rate-of-change by multiplying a first weighting coefficient and a first rate-of-change, the first rate-of-change computed between the first uncompensated analyte measurement at the first initial reference time to the second uncompensated analyte measurement at the first prior reference time; determining a second scaled rate-of-change by multiplying a second weighting coefficient and a second rate-of-change, the second rate-of-change computed between the first uncompensated analyte measurement at the first initial reference time to the third uncompensated analyte measurement at the second prior reference time; and calculating a first filter lag-compensated point measurement based on the sum of the first uncompensated analyte measurement, the first scaled rate-of-change, and the second scaled rate-of-change.