Cuff-less Blood Pressure Calibration via Mass Transit Time

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Solution Overview

Problem

Conventional blood pressure monitoring methods are cumbersome, invasive, and not suitable for frequent or ambulatory measurements, and cuff-less systems provide only relative values, necessitating a simple and accurate calibration process for absolute blood pressure estimation.

Innovation Solution

A calibration process for non-invasive, cuff-less blood pressure monitoring systems using a wearable device with a sensor assembly that detects mass transit time and heart rate, coupled with a user interface device and a reference monitor, allowing for fully automatic, semi-manual, or manual calibration protocols to achieve accurate absolute blood pressure measurements.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If conventional blood pressure monitoring methods (cuff-based oscillometric or auscultation methods) are used, then accurate absolute blood pressure values can be obtained, but the measurement process becomes cumbersome, invasive, and unsuitable for frequent or ambulatory measurements

Engineering Contradiction:

Improveaccuracy of blood pressure measurementVSAvoidconvenience for frequent and ambulatory measurements

Core Design Contradiction:

Measurement precisionVSEase of operation

Solution Approach 1:

The patent extracts the cuff component from the blood pressure measurement system, developing a cuff-less monitoring device that uses optical sensors (photoplethysmogram) and accelerometers to detect blood pressure-related signals without requiring inflation of a cuff, thereby eliminating discomfort and enabling frequent use

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent replaces the mechanical cuff-based oscillometric measurement system with an optical sensing system that uses photodetectors to measure blood volume changes and accelerometers to detect motion, enabling non-invasive and comfortable continuous monitoring

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Ease of operation

If cuff-less blood pressure monitoring systems are used, then ease of operation and suitability for frequent measurements are improved, but only relative values can be provided without absolute blood pressure values

Engineering Contradiction:

Improveconvenience for frequent and ambulatory measurementsVSAvoidaccuracy of absolute blood pressure value

Core Design Contradiction:

Ease of operationVSMeasurement precision

Solution Approach 1:

The patent implements a calibration process that establishes a relationship between the optical sensor signals and actual blood pressure values before continuous monitoring begins, using reference measurements to create a calibration curve that enables subsequent absolute blood pressure calculations from relative optical signals

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent uses feedback from the calibration process where reference blood pressure measurements (from a cuff-based device) are compared with simultaneous optical sensor readings, and this feedback is used to adjust and optimize the conversion algorithm that translates optical signals into absolute blood pressure values

Inventive Principle:

Principle #23Feedback

3Measurement precision

If a calibration process is implemented for cuff-less blood pressure monitoring, then absolute blood pressure values can be obtained, but the calibration process may introduce complexity and potential errors

Engineering Contradiction:

Improveaccuracy of absolute blood pressure valueVSAvoidcomplexity of calibration process

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent implements self-calibration capabilities where the device automatically performs calibration routines using built-in sensors and algorithms, reducing the need for manual intervention and specialist knowledge while maintaining calibration accuracy through automated quality checks and validation

Inventive Principle:

Principle #25Self-service

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 user-friendly calibration of cuff-less blood pressure monitoring systems, providing absolute values with reduced user interaction and minimizing errors, suitable for frequent and ambulatory measurements.

Implementation Method 1

A calibration process for non-invasive, cuff-less blood pressure monitoring systems using a wearable device with a sensor assembly that detects mass transit time and heart rate

Methodology Applied

Scientific EffectMass transit time measurement: Time of Flight

Data Source

PatentUS11185237B2Calibration methods for blood pressure devices

Publication Date: 2021.11.30 ROBERT BOSCH GMBH

AI summary

A method for calibrating a blood pressure monitoring system includes activating a reference monitor to perform a reference measurement of the blood pressure of a user as part of a calibration process. A wearable sensing device is activated to detect a parameter of user that is correlatable to the user's blood pressure. A processor of the user interface device processes the at least one parameter detected by the wearable blood pressure sensing device with reference to the reference measurement to determine a correlation factor that correlates the at least one parameter detected by the wearable blood pressure sensing device to the blood pressure of the user. The reference measurement includes an inflation phase, a measurement phase and a deflation phase. The processor is configured to only use the at least one parameter detected by the wearable blood pressure sensing device during the measurement phase in determining the correlation factor.