PPG-LDV Blood Pressure Sensing for Motion-Robust Accuracy
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Solution Overview
Problem
Existing methods for determining blood pressure, particularly systolic and diastolic blood pressure, are limited by sensitivity to movement, ambient light, and reduced accuracy in individuals with low vascular distensibility, such as the elderly or those with hypertension.
Innovation Solution
A system combining information from a PPG sensor for blood volume and an LDV sensor for blood speed, utilizing a model to predict and enhance the quality of blood pressure measurements, including a Windkessel model or neural network, to improve accuracy across various user groups.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If PPG sensor is used to measure blood pressure, then the measurement can be obtained continuously, but the sensitivity deteriorates when vascular distensibility is decreased
Solution Approach 1:
The patent combines PPG sensor data (blood volume information) with LDV sensor data (blood flow speed information) to determine blood pressure. This merging of two different measurement approaches compensates for the limitations of PPG alone in patients with reduced vascular distensibility, as LDV provides complementary blood flow velocity data that is less affected by vascular stiffness.
Solution Approach 2:
The patent changes from relying solely on PPG waveform parameters to using a combination of PPG blood volume parameters and LDV blood flow speed parameters. By introducing the blood flow speed parameter from LDV, the system overcomes the parameter degradation that occurs in patients with low vascular distensibility.
2Measurement precision
If PPG sensor is used for blood pressure determination, then continuous monitoring is possible, but sensitivity to movement and ambient light reduces measurement accuracy
Solution Approach 1:
By combining PPG and LDV sensors, the system benefits from the complementary nature of the two measurement methods. LDV measures blood flow speed based on Doppler shift, which is less susceptible to ambient light interference, while PPG provides blood volume information. The combination allows continuous monitoring while mitigating the harmful effects of movement and light sensitivity.
3Measurement precision
If combined PPG and LDV system is used, then measurement accuracy is improved, but device complexity increases
Solution Approach 1:
The patent integrates both PPG and LDV sensing capabilities into a single wearable device that can perform multiple functions: continuous blood pressure monitoring, blood flow speed measurement, and blood volume assessment. This multi-functionality justifies the increased complexity by providing comprehensive physiological monitoring from one device.
Solution Approach 2:
The patent introduces a controller as an intermediary component that receives data from both PPG and LDV sensors, processes the combined information, and determines blood pressure. This intermediary structure manages the complexity by centralizing the data fusion and calculation logic, making the system more manageable despite having multiple sensors.
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 robust and accurate blood pressure measurements, including systolic and diastolic, by leveraging the complementary strengths of PPG and LDV sensors, reducing sensitivity to vascular distensibility and motion artifacts.
Implementation Method 1
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
Implementation Method 2
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
Data Source
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.