Wearable PPG Blood Pressure Sensing Without Inflatable Cuffs
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Solution Overview
Problem
Traditional blood pressure cuffs rely on inflating a bladder to constrict arteries and listening for heartbeats, which is cumbersome and less accurate for continuous monitoring, especially during activities.
Innovation Solution
A biometric monitoring device with a PPG sensor and force sensor that measures blood volume pulses and pressure variations, allowing for continuous blood pressure estimation by manually applying variable pressure with user guidance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a traditional blood pressure cuff with air bladder is used, then blood pressure measurement is achieved, but the device is cumbersome and unsuitable for continuous monitoring during activities
Solution Approach 1:
The patent replaces the mechanical air bladder system with a combination of PPG sensor and force sensor. The PPG sensor detects blood volume changes optically, while the force sensor measures applied pressure mechanically. This substitution eliminates the need for inflation/deflation mechanisms and enables continuous monitoring during physical activities.
Solution Approach 2:
The invention extracts the core measurement function from the traditional cuff system. Instead of using the entire air bladder mechanism, it isolates the essential measurements (blood volume pulse via PPG and applied pressure via force sensor) and processes these separately to determine blood pressure, thereby simplifying the device for continuous wear.
2Measurement precision
If an air bladder is inflated to constrict arteries, then blood pressure can be measured, but the process is complex and requires pumping mechanisms
Solution Approach 1:
The patent replaces the complex mechanical inflation system with electronic sensing. The force sensor directly measures the pressure applied by the cuff, while the PPG sensor measures blood volume changes. The processor combines these measurements to calculate blood pressure, eliminating pumps, valves, and inflation mechanisms entirely.
Solution Approach 2:
The invention introduces a processor as an intermediary that combines data from the PPG sensor and force sensor. This processor integrates the blood volume pulse information with the applied pressure measurement to compute blood pressure values, replacing the need for mechanical pressure regulation systems.
3Measurement precision
If a pressure sensor is placed in the air path, then heart beat signals can be detected, but the system requires continuous air pressure maintenance
Solution Approach 1:
The patent replaces the air-based pressure transmission system with direct electronic sensing. The force sensor measures pressure directly without requiring an air medium, and the PPG sensor detects blood volume changes optically. This eliminates air leaks and pressure maintenance requirements, enabling indefinite continuous operation.
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 continuous blood pressure monitoring by correlating blood volume pulse amplitude with applied pressure, facilitating precise systolic and diastolic readings without the need for inflation.
Implementation Method 1
a photoplethysmogram (PPG) sensor comprising a light emitter and a light detector configured to generate PPG sensor data representing blood volume pulses
Implementation Method 2
a force or pressure sensor located and oriented with respect to the PPG sensor to generate variable force or pressure data when a user wearing the fixing structure presses the PPG sensor against a location of the user's body
Data Source
AI summary
A wearable device is wearable on an appendage of a user and includes a force-sensitive display screen to generate force data when a force is applied to the force-sensitive display screen, a photoplethysmogram (PPG) sensor, and one or more processors. The PPG sensor is positioned below an external surface of the force-sensitive display screen and generates PPG sensor data when the force is applied to the force-sensitive display screen. The one or more processors are configured to: determine, from the PPG sensor data and the force data, a variation of PPG blood volume pulse amplitude with a variation in pressure applied to the appendage, and calculate an estimate of blood pressure of the appendage from the variation of PPG blood volume pulse amplitude with the variation in the pressure applied to the appendage.