Blood Pressure Sensor Using Pulse Transit Time Without Calibration
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Solution Overview
Problem
Conventional methods for measuring blood pressure using pulse transit time (PTT) require external calibration with a blood pressure cuff, which is invasive and less accurate for direct systolic blood pressure measurement.
Innovation Solution
A body-worn sensor system that measures PTT and optical waveforms without external calibration, using inflatable armbands and pressure sensors to apply pressure to the arm, allowing for continuous blood pressure measurement through pressure-dependent and pressure-free techniques, directly measuring systolic and diastolic blood pressures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional PTT measurement methods are used, then blood pressure can be measured, but external calibration with a blood pressure cuff is required which is invasive and less accurate
Solution Approach 1:
The system performs self-calibration by automatically determining the relationship between PTT and blood pressure using pressure-dependent measurements during inflation, eliminating the need for external calibration equipment and manual calibration procedures
Solution Approach 2:
The patent replaces the mechanical external blood pressure cuff with an integrated optical and electrical sensing system that measures blood pressure directly through non-contact methods, substituting mechanical compression with optical waveform analysis
2Productivity
If conventional cuff-based methods are used, then blood pressure measurement can be performed, but measurement time and variability increase
Solution Approach 1:
The system enables continuous blood pressure monitoring by continuously measuring PTT and optical waveforms during the inflation process, eliminating the need to wait for cuff deflation and manual reading, thus reducing measurement time and increasing productivity
3Ease of operation
If external calibration is used, then measurement can be performed, but patient comfort is reduced due to cuff application and removal
Solution Approach 1:
The patent replaces the mechanical cuff system with an integrated sensor system that uses optical and electrical measurements to determine blood pressure, eliminating the need for physical cuff application and removal while maintaining measurement reliability through direct waveform analysis
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 continuous, accurate measurement of blood pressure without external calibration, improving accuracy and comfort by directly measuring systolic blood pressure and indirectly determining diastolic pressure, reducing measurement time and variability compared to conventional cuff-based methods.
Implementation Method 1
Pulse oximetry is typically measured with a bandage or clothespin-shaped sensor that attaches to a patient's finger, and includes optical systems operating in both the red and infrared spectral regions. A photodetector measures radiation emitted from the optical systems that transmits through the patient's finger.
Implementation Method 2
These disposable sensors typically include an armband that features an inflatable air bladder coupled to a pressure sensor
Data Source
Figure 1A~1B
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AI summary
A method and apparatus for continuous measurement of blood pressure, based on pulse transit time, which does not require any external calibration. This technique, referred to herein as the 'composite technique', is carried out with a body- worn sensor that measures blood pressure and other vital signs, and wirelessly transmits them to a remote monitor. A network of disposable sensors, typically placed on the patient's right arm and chest, connect to the body sensor and measure a time-dependent electrical waveform, optical waveform, and pressure waveform. The disposable sensors typically include an armband that features an inflatable bladder coupled to a pressure sensor, at least 3 electrical sensors (e.g. electrodes), and an optical sensor (e.g., a light source and photodiode) attached to a wrist-worn band.