Hand Arterial Structure Estimation via Pulse Transit Time
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Solution Overview
Problem
Existing methods for monitoring cardiovascular health, particularly in the hand, suffer from poor performance due to movement artefacts and the difficulty in accurately measuring pulse wave behavior at bifurcations, leading to unreliable clinical assessments.
Innovation Solution
A wrist pulse measurement device and digit pulse measurement device are used to compare the arrival times of waveform features, calculating pulse transit times and velocities to estimate the arterial structure of the hand, with adjustments for biometric factors like height, weight, and hand size, and normalization of pulse signals based on the number of arteries present.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If ECG or PPG techniques are used to measure pulse signals in smartwatches and smartphones, then personal fitness and telemedicine monitoring is enabled, but measurement reliability deteriorates due to movement artefacts
Solution Approach 1:
The measurement system is segmented into multiple independent pulse measurement locations (wrist and multiple digits). By distributing sensors across different body parts, the system can isolate and identify movement artefacts affecting specific locations, thereby improving overall measurement reliability while maintaining portability
Solution Approach 2:
The system uses feedback by comparing pulse signals from multiple locations to identify and correct for movement artefacts. When artefacts are detected in one location, the system can use signals from other locations as reference to maintain accurate cardiovascular monitoring
2Reliability
If manual compression tests (Allen's test) are performed to assess arterial circulation, then circulation abnormalities can be detected, but measurement precision deteriorates due to manual operation variability
Solution Approach 1:
Manual mechanical compression and visual assessment in Allen's test is replaced with automated optical sensors (PPG) that objectively measure pulse signals. This substitution eliminates operator variability and provides precise, quantifiable data on arterial circulation and pulse wave behavior
Solution Approach 2:
The manual Allen's test procedure is copied and automated using electronic sensors that replicate the compression and measurement functions. The system captures pulse waveforms digitally, allowing for precise analysis of arterial structure and blood flow without manual intervention variability
3Loss of information
If pulse wave behavior at bifurcations is measured to understand cardiovascular dynamics, then insights into reflected waves can be obtained, but measurement difficulty increases due to complex vascular geometry
Solution Approach 1:
The measurement approach transitions from single-location to multi-location sampling along the arterial path. By measuring pulse waves at the wrist and multiple digit locations, the system captures the propagation and reflection of pressure waves through the vascular bifurcation network, providing comprehensive insights into wave behavior without requiring direct measurement at complex bifurcation points
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
This approach provides a more accurate and reliable estimation of arterial structure, reducing the risk of cardiovascular events by minimizing measurement errors and improving the detection of atypical arterial conditions.
Implementation Method 1
A PPG reading can be obtained through optronics, normally a light-emitting diode (LED) and a photodiode pair operating in green, red or infrared wavelength ranges. The LED illuminates the skin and then the amount of light either transmitted or reflected is measured by the photodiode.
Data Source
AI summary
An apparatus for determining the arterial structure of the hand of a subject, the apparatus comprising a wrist pulse measurement device configured to measure wrist pulse signals at the wrist of the subject, a digit pulse measurement device configured to measure digit pulse signals at the digits of the hand, the apparatus being configured to compare the arrival time of one or more waveform features in a wrist pulse signal and the arrival time of the corresponding feature in two or more digit pulse signals in order to determine a pulse transit time for each of the one or more waveform features, thereby estimating the arterial structure of the hand.