Blood Pressure Estimation Using Neck Pulse Transit Time
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Solution Overview
Problem
Existing blood pressure estimation methods using pulse wave transit time are unstable and inaccurate due to the need for precise positioning of the pulse wave sensor over the carotid artery, which is difficult to maintain, especially in varying positions or for individuals with thick necks, and can lead to inaccurate measurements and potential health risks.
Innovation Solution
A blood pressure estimating device that measures pulse wave transit time at an arteriole or capillary near the carotid artery, using an electrocardiographic electrode and photoplethysmographic sensor to detect signals without direct contact over the carotid artery, and estimates blood pressure after a stable transit time is achieved, regardless of sensor position.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the pulse wave sensor is positioned directly over the carotid artery to obtain accurate pulse wave transit time information, then measurement precision is improved, but device complexity and ease of operation deteriorate due to the difficulty of locating and maintaining precise positioning
Solution Approach 1:
The patent uses the bifurcated portion of the carotid artery as an intermediary landmark to locate the measurement position. Instead of directly seeking the carotid artery which requires expert palpation skills, the device positions the sensor at the bifurcation point (where internal and external carotid arteries branch from the common carotid artery), which is easier to identify and provides a stable reference point for consistent measurements.
2Reliability
If the sensor position is fixed at the carotid artery bifurcation to ensure measurement stability, then reliability is improved, but adaptability deteriorates for individuals with thick necks or varying anatomical structures
Solution Approach 1:
The patent employs a universal positioning method based on the bifurcated portion of the carotid artery that can be applied to all individuals regardless of neck thickness or anatomical variations. The bifurcation point serves as a consistent anatomical landmark that is accessible and identifiable in all users, making the measurement system universally applicable while maintaining reliability across diverse populations.
3Measurement precision
If strong pressure is applied to position the sensor accurately over the carotid artery, then measurement precision is improved, but object-affected harmful factors increase due to potential plaque dislodgement and cerebral infarction risk
Solution Approach 1:
The patent converts the potential harm of strong pressure application into a benefit by using the bifurcated portion as a positioning landmark that requires minimal pressure for accurate sensor placement. The bifurcation point provides natural anatomical cues that enable precise positioning without excessive force, thereby eliminating the risk of plaque dislodgement while maintaining measurement quality.
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
The device provides stable and accurate blood pressure estimation by measuring pulse wave transit time at an arteriole or capillary, ensuring consistent measurements even with positional deviations, and reducing the risk of health complications.
Implementation Method 1
a photoplethysmographic sensor 20 to detect a photoplethysmographic signal
Implementation Method 2
an electrocardiographic electrode 15 to detect an electrocardiographic signal
Data Source
AI summary
A signal processor of a blood pressure estimating device includes a pulse wave transit time acquirer that acquires a pulse wave transit time based on a pulse wave signal detected by a photoplethysmographic sensor and an electrocardiographic signal, a time measurer that measures a time elapsed from when acquisition of the pulse wave transit time is started, and a blood pressure estimator that estimates a blood pressure based on a predetermined relationship between the pulse wave transit time and the blood pressure. The photoplethysmographic sensor is in contact with a neck of a user at a position not directly over a carotid artery when the pulse wave transit time is acquired, and the blood pressure estimator estimates the blood pressure after the measured elapsed time has become a predetermined time or more.