PPG and LDV Blood Pressure Sensing for Low Vascular Distensibility
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Solution Overview
Problem
Existing methods for determining blood pressure, particularly systolic and diastolic blood pressure, are inaccurate for individuals with low vascular distensibility, such as the elderly or those with hypertension, and are sensitive to motion and ambient light, limiting their effectiveness.
Innovation Solution
A system combining photoplethysmography (PPG) and laser Doppler velocimetry (LDV) sensors to provide simultaneous measurements of blood volume and speed, using a model to integrate these signals for improved blood pressure estimation, reducing sensitivity to vascular distensibility and motion artifacts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If PPG sensor is used to measure blood pressure, then the measurement can be obtained non-invasively, but the measurement accuracy deteriorates for individuals with low vascular distensibility
Solution Approach 1:
The patent combines PPG sensor data with LDV sensor data to measure both blood volume and blood flow speed simultaneously. This merging of two different sensing approaches compensates for the limitations of PPG alone in individuals with low vascular distensibility, thereby maintaining non-invasive measurement while improving blood pressure measurement accuracy.
Solution Approach 2:
The patent changes from relying solely on blood volume parameters (PPG) to incorporating both blood volume and blood flow speed parameters (LDV). By measuring additional physiological parameters, the system overcomes the reduced sensitivity of PPG in individuals with stiff vessels, where blood volume changes are minimal.
2Device complexity
If PPG sensor is used for blood pressure determination, then the device can be simple and portable, but the measurement becomes sensitive to motion and ambient light
Solution Approach 1:
By combining PPG and LDV sensors, the system creates a more robust measurement that is less susceptible to motion and ambient light interference. The LDV component provides complementary information that helps distinguish true physiological signals from artifacts caused by motion or lighting conditions.
3Device complexity
If single sensor (PPG) is used for blood pressure measurement, then the device complexity is low, but the measurement accuracy for systolic and diastolic blood pressure is insufficient
Solution Approach 1:
The patent merges data from PPG and LDV sensors to simultaneously determine both systolic and diastolic blood pressure with improved accuracy. The combination of blood volume and blood flow speed measurements provides sufficient information to extract both pressure parameters, overcoming the limitations of single-sensor approaches.
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
The combined system provides more accurate blood pressure measurements across a wider range of individuals, including those with low vascular distensibility, by leveraging the complementary strengths of PPG and LDV to enhance measurement robustness and accuracy.
Implementation Method 1
information related to a blood volume, e.g. obtained from a photoplethysmography (PPG) sensor
Implementation Method 2
information relating to a blood speed, e.g. obtained from a laser Doppler velocimetry (LDV) sensor
Data Source
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AI summary
A system and a method for determining a physiological parameter of a body comprising blood perfused tissue, the system comprising a first sensor configured to receive first radiation from the blood perfused tissue and, based on the received first radiation, provide first information relating to an amount of blood in the tissue, such as from an absorption of the first radiation in the tissue, a second sensor configured to receive second radiation from the blood perfused tissue and, based on the received second radiation, provide second information relating to a speed of blood in the tissue, such as from Doppler shift of the second radiation, a controller configured to determine the physiological parameter from the first information and the second information.