Posture-Aware Pulse Wave Transit Time Measurement
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Solution Overview
Problem
Existing pulse wave transit time measurement devices fail to accurately account for posture changes during prolonged measurements, leading to inaccuracies in blood pressure fluctuation monitoring.
Innovation Solution
A pulse wave transit time measurement device that classifies and corrects time serial data based on user posture, using electrocardiographic and photoplethysmographic signals, along with an acceleration sensor, to determine fluctuations in pulse wave transit time with higher accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of moving object
If pulse wave transit time is measured continuously for several hours to monitor blood pressure fluctuations, then the duration of measurement is extended, but measurement precision deteriorates due to posture changes during sleep
Solution Approach 1:
The patent segments the continuous measurement data into distinct posture-based categories (supine, lateral, sitting) using the acceleration sensor. By dividing the measurement period into posture-specific segments, the system can accurately identify and exclude measurements taken during posture transitions, thereby maintaining measurement precision throughout extended monitoring periods.
Solution Approach 2:
The patent implements a feedback mechanism where the acceleration sensor continuously monitors posture and provides real-time information to the measurement system. This feedback loop allows the system to dynamically adjust which measurements are considered valid based on current posture, preventing inaccurate measurements from compromising the overall precision of long-term blood pressure monitoring.
2Device complexity
If posture changes are not considered in pulse wave transit time measurement, then the measurement system remains simple, but measurement precision deteriorates due to posture-induced fluctuations
Solution Approach 1:
The patent merges the acceleration sensor functionality with the existing pulse wave transit time measurement system. By combining posture detection and blood pressure monitoring into a single integrated system, the patent achieves high measurement precision without requiring separate complex systems, thus balancing device complexity with measurement accuracy.
Solution Approach 2:
The acceleration sensor serves multiple functions: it detects posture changes, identifies measurement validity, and provides context for interpreting pulse wave transit time data. This multi-functionality allows the system to maintain simplicity while significantly improving measurement precision through comprehensive posture-aware monitoring.
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 and accurate measurement of pulse wave transit time fluctuations even when posture changes, improving the estimation of blood pressure fluctuations.
Implementation Method 1
an electrocardiographic detection unit (i.e., an ECG detection unit) both set on a subject
Implementation Method 2
a pulse wave detection unit (PPG detection unit) both set on a subject
Implementation Method 3
detecting the posture and the motion of the subject from detected data
Data Source
AI summary
A pulse wave transit time measurement device includes a pulse wave transit time calculator that calculates a pulse wave transit time based on a peak time difference between an electrocardiographic signal and a pulse wave signal, a posture classifier that classifies time serial data of the pulse wave transit time based on a posture detected by an acceleration sensor, and a fluctuation identifier that sets a reference posture from among classified postures, corrects, in conformity with the reference posture, the time serial data of the pulse wave transit time classified into the posture different from the reference posture, and determines fluctuations in the pulse wave transit time based on the time serial data of the pulse wave transit time in the reference posture and the time serial data of the pulse wave transit time having being corrected.