Optical Blood Pressure Measurement Without a Wearable Cuff
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Solution Overview
Problem
Existing non-invasive blood pressure measurement techniques lack accuracy and reliability for continuous monitoring without the use of a wearable cuff.
Innovation Solution
A system and method utilizing a light sensor to measure the intensity of light reflected from the skin at different wavelengths, analyzing pulse amplitudes to determine systolic and diastolic blood pressure based on applied force, combining optical and mechanical properties of blood.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If automated blood pressure measurement is implemented, then ease of operation is improved, but measurement precision deteriorates due to difficulty in detecting Korotkoff sounds
Solution Approach 1:
The patent replaces the mechanical/acoustic detection method (Korotkoff sound listening) with an optical detection method using light absorption. The blood pressure measurement apparatus uses a light source and light receiver to detect changes in light absorption by blood vessels during inflation and deflation, converting the measurement from acoustic to optical domain for improved automated detection accuracy
Solution Approach 2:
The patent introduces light as an intermediary medium between the blood vessel and the detection system. By measuring light absorption changes rather than directly detecting sound waves, the system creates an indirect measurement path that is more suitable for automated operation while maintaining or improving precision
2Reliability
If cuff inflation is performed to measure blood pressure, then measurement capability is improved, but discomfort to the user worsens due to arm numbness
Solution Approach 1:
The patent performs preliminary detection of the pulse wave at the measurement site before cuff inflation. By detecting the pulse wave in advance using light absorption changes, the system can determine appropriate inflation pressure levels and timing, allowing for more controlled inflation that maintains measurement reliability while reducing excessive pressure and user discomfort
Solution Approach 2:
The patent implements dynamic adjustment of cuff pressure based on real-time pulse wave detection. The system continuously monitors pulse wave characteristics during inflation and deflation, dynamically adjusting the pressure control to optimize measurement accuracy while minimizing discomfort, rather than using fixed pressure protocols
3Measurement precision
If pulse wave detection is performed before measurement, then measurement precision is improved, but measurement time increases
Solution Approach 1:
The patent merges the pulse wave detection function with the blood pressure measurement function into a single integrated process. The same cuff inflation/deflation cycle serves both to detect the pulse wave for positioning and to perform the blood pressure measurement, eliminating the need for separate detection and measurement phases that would increase total time
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
Enables accurate and reliable continuous non-invasive blood pressure measurement, providing comfort by avoiding the need for a wearable cuff and enhancing measurement precision through mechanical and optical analysis.
Implementation Method 1
detecting, by the light receiver, changes in light absorption by the blood vessel in response to inflation and deflation of the cuff
Data Source
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AI summary
There is provided an apparatus (100) for determining a blood pressure measurement for a subject (102). The apparatus (100) comprises a processor (104) configured to acquire, from a light sensor (106), measurements of an intensity of light (108) of a first wavelength range reflected from the skin (110) of the subject (102) for a range of forces at which the light sensor (106) is applied to the skin. The processor (104) is further configured to determine a pulse amplitude from the measurements of light intensity at the range of applied forces and analyze the determined pulse amplitudes to determine a systolic blood pressure measurement based on the applied force at which the pulse amplitude drops below a predefined threshold and/or an integral of the pulse amplitudes and/or a diastolic blood pressure measurement based on the applied force at which an initial rise in the pulse amplitude is identified.