Measuring Capillary Transit Time Heterogeneity for Oxygen Extraction
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Solution Overview
Problem
Current measurement techniques fail to accurately assess oxygen and nutrient extraction by tissues despite normal blood flow, due to neglecting capillary transit time heterogeneity, leading to impaired tissue function and disease progression in conditions like diabetes and hypertension.
Innovation Solution
A system that measures blood flow and capillary transit time heterogeneity through direct and indirect in-vivo methods, using models to estimate oxygen extraction capacity, accounting for the linear dependence of substance extraction on plasma concentration and incorporating capillary bed characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional measurement techniques are used to assess blood flow, then blood flow measurement is obtained, but oxygen extraction capacity cannot be accurately assessed
Solution Approach 1:
The patent segments the blood flow measurement into two distinct components: mean transit time (representing average blood flow) and transit time heterogeneity (representing distribution variability). This segmentation allows the system to capture both the overall flow and the microvascular distribution characteristics that affect oxygen extraction, resolving the contradiction by preventing information loss about capillary heterogeneity while maintaining blood flow measurement capability.
2Reliability
If only mean blood flow is measured, then measurement simplicity is maintained, but tissue hypoxia cannot be detected in diseases with normal blood flow
Solution Approach 1:
The patent introduces a new parameter - transit time heterogeneity - alongside the traditional mean transit time measurement. By adding this parameter, the system can detect tissue hypoxia in conditions like diabetes and hypertension where mean blood flow appears normal but microvascular distribution is impaired. The heterogeneity parameter provides the additional diagnostic capability needed to improve reliability without requiring complete system redesign.
3Measurement precision
If capillary transit time heterogeneity is neglected, then measurement simplicity is maintained, but extraction capacity assessment becomes inaccurate
Solution Approach 1:
The patent uses transit time heterogeneity as an intermediary parameter that connects blood flow characteristics to oxygen extraction capacity. Rather than directly measuring extraction capacity (which would require complex multi-modal imaging), the heterogeneity parameter serves as a mediator that, when combined with mean transit time, allows accurate extraction capacity assessment through established physiological relationships. This intermediary approach improves measurement precision while avoiding the complexity of direct extraction measurement.
Data Source
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AI summary
The present invention relates to a system for measuring a micro-vascular flow distribution of a tissue portion of a mammal comprising means (101) for measuring a first indicator (MTT) for the blood flow through acapillary bed, means (102) for measuring a second indicator (CTTH) of heterogeneity of the blood flow in said capillary bed, and a first processor (110) arranged for using the first and the second indicator to estimate an extraction capacity (EC) of a substance from the blood in said capillary bed.