Multi-Path Photoplethysmography Patch for Hematocrit Monitoring
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Solution Overview
Problem
Current remote monitoring technologies for patients, particularly vulnerable populations like dialysis patients, lack accurate and non-invasive methods for monitoring critical metrics such as hemoglobin and hematocrit levels, leading to high hospitalization and mortality rates due to reliance on subjective data and infrequent blood draws.
Innovation Solution
A system using a patch with a matrix of light emitting diodes and photodetectors to measure optical signals from the skin, processing AC and DC components of these signals to calculate ratio-of-ratios, which are then used to determine hematocrit concentration and other biological metrics, enabling more frequent and accurate monitoring.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple optical paths are used to improve measurement precision, then the device complexity increases
Solution Approach 1:
The optical measurement system is segmented into multiple independent optical paths, each with its own light source and detector pair. This allows the complex measurement task to be divided into simpler sub-measurements that can be processed independently and then combined to achieve higher overall measurement precision for biological metrics.
Solution Approach 2:
The patent transitions from single-point optical measurement to multi-point spatial measurement by implementing multiple optical paths at different locations. This dimensional expansion from 1D to 2D/3D measurement space enables more comprehensive sampling of the target tissue, improving measurement accuracy while providing spatial distribution information.
2Reliability
If multiple optical paths with multiple light sources and detectors are implemented, then the device complexity increases
Solution Approach 1:
The multiple light sources and detectors are designed to serve multiple functions: each optical path can independently measure different biological metrics (hemoglobin concentration, oxygen saturation, hematocrit), and the system can adaptively select which paths to use based on signal quality and measurement requirements, enhancing reliability without proportionally increasing complexity.
Solution Approach 2:
The system dynamically adjusts operational parameters such as light source wavelength selection, detection sensitivity settings, and path selection based on real-time signal characteristics. This parameter optimization allows the system to maintain high reliability across varying physiological conditions while managing device complexity through adaptive control rather than fixed complex hardware.
3Measurement precision
If AC and DC components are separately processed to calculate ratio-of-ratios, then the measurement precision improves, but the processing complexity increases
Solution Approach 1:
The signal processing system extracts and separates the AC (pulsatile) and DC (baseline) components from the optical detection signals. By isolating these distinct physiological information carriers, the system can apply different processing algorithms to each component, improving measurement precision for different biological metrics while managing complexity through targeted processing rather than comprehensive analysis of the entire signal.
Solution Approach 2:
The ratio-of-ratios calculation serves as an intermediary processing step that transforms the separated AC and DC components into a standardized metric that can be used across multiple biological measurements. This intermediary representation simplifies subsequent analysis and comparison, reducing overall system complexity despite the intermediate processing step.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach allows for continuous, non-invasive monitoring of blood metrics, reducing the need for frequent hospital visits and improving patient safety by providing objective data for clinicians, thereby reducing hospitalization and mortality risks.
Implementation Method 1
A plurality of light emitting diodes (LEDs) arranged on the substrate to form a R×C matrix
Implementation Method 2
a row of C photodetectors (PDs) disposed on the substrate substantially in parallel with R rows of LEDs extending to form C columns substantially co-linear with each photodetector
Data Source
AI summary
Systems and methods for monitoring blood flow metrics using a patch of a flexible substrate configured to attach to an area of skin over a blood vessel. The patch includes a plurality of light sources arranged on the substrate to form a matrix and a row of photodetectors disposed on the substrate substantially in parallel with the rows of LEDs. The patch includes an optical signal interface configured to drive each light source and to input an intensity signal at one of the photodetectors. The intensity signals are used to determine AC and DC components corresponding to each optical path. AC to DC component ratios are calculated for each optical path and used to determine ratio-of-ratio values. At least a subset of the ratio-of-ratio values are used to determine a biological metric or a cross-sectional area of the blood vessel.