Plethysmography Signal Processing for VAR-Robust Sleep Event Detection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional plethysmography methods struggle to accurately detect sleep-disturbing events due to the interference of venoarteriolar reflex (VAR) caused by hydrostatic pressure gradients, leading to false positives and negatives in sleep disorder detection.
Innovation Solution
A method and apparatus using conventional plethysmography probes to process signals for vasoconstriction events by deriving reference and baseline amplitude values, accounting for VAR effects, and employing classifiers to identify sleep-disturbing events based on magnitude measures of vasoconstriction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional plethysmography probes are used to detect sleep-disturbing events, then the detection process is simple and uses off-the-shelf equipment, but the detection accuracy deteriorates due to interference from venoarteriolar reflex (VAR) caused by hydrostatic pressure gradients
Solution Approach 1:
The patent introduces an intermediary processing layer between the raw plethysmography signal and the final detection output. This intermediary involves deriving a baseline-invariant version of the signal and calculating magnitude measures that compensate for VAR effects, allowing conventional equipment to achieve accurate detection without requiring complex hardware modifications
Solution Approach 2:
The patent transforms the raw plethysmography signal into a baseline-invariant representation by adjusting signal parameters. Specifically, it calculates magnitude measures based on reference and baseline amplitude values, changing the signal's mathematical properties to eliminate the confounding VAR effect while preserving sleep-event information
2Device complexity
If venoarteriolar reflex (VAR) effects are not accounted for, then the signal processing is simpler, but false positives and negatives increase in sleep disorder detection
Solution Approach 1:
The patent performs preliminary signal processing actions before final detection by first deriving the baseline-invariant version of the plethysmography signal and pre-calculating magnitude measures. This preliminary compensation for VAR effects ensures that subsequent detection algorithms operate on cleaned data, reducing false positives and negatives without requiring complex real-time adjustments during detection
3Measurement precision
If complex pressure-providing probes are used to reduce venous blood pooling, then the detection accuracy improves, but the device complexity and cost increase
Solution Approach 1:
The patent substitutes the mechanical approach (complex pressure-providing probes with internal and external membranes) with a signal processing approach. Instead of physically compensating for VAR effects through complex probe mechanics, the invention uses mathematical transformations on the signal to eliminate VAR interference, achieving the same detection accuracy with simple conventional probes
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 significantly reduces false positives and negatives in sleep-disturbing event detection, ensuring accurate and robust identification using off-the-shelf medical equipment.
Implementation Method 1
Optical plethysmography or photoplethysmography measures the arterial blood volume changes by shining light from one or more light sources, such as LEDs, onto an investigated volume and by detecting collected light corresponding to the light being reflected or transmitted in the investigated volume on a sensor
Implementation Method 2
Plethysmography, be it pneumatic-based or optics-based, is a measurement technique commonly used to monitor changes in blood volume in the macrovascular and the microvascular system of an individual
Implementation Method 3
Norepinephrine is released in the bloodstream and binds to adrenergic receptors in the arterioles in the investigated volume, which triggers an increase in muscle tension of the arterioles resulting in a reduction of the arteriole diameter
Implementation Method 4
due to the effect of gravity, when some part of the body is situated below heart level, a hydrostatic pressure gradient is automatically generated. Hydrostatic pressure gradients affect the venous system, an innately low-pressure system, causing venous distention also known as venous blood pooling
Data Source
Figure 1A~1B
Figure 2
Figure 3
AI summary
The present disclosure relates to a method and apparatus for detecting sleep-disturbing events from a signal indicative of a peripheral arterial tone of an individual, the signal being affected by a venoarteriolar reflex, wherein sleep-disturbing events are detected by: determining a vasoconstriction event from changes in the signal; deriving, a reference amplitude value and a baseline amplitude value for the vasoconstriction event, the reference amplitude value being different from the baseline amplitude value; relating the reference amplitude value for the vasoconstriction event to the baseline amplitude value for the vasoconstriction event, thereby obtaining a magnitude measure for the vasoconstriction event; and detecting, therefrom, a sleep-disturbing event.