Tracheal Pulse Rate Detection via Adaptive Filtering
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Solution Overview
Problem
Current methods for detecting sleep apnea using sound signals are limited by noise from snoring and patient movements, which hinder precise pulse rate computation, essential for diagnosing the condition.
Innovation Solution
A method involving sound-sensing means placed on the trachea, using adaptive filtering, lowpass filtering, and intercorrelation to extract pulse rate from sound signals, generating a temporal series of pulse rates and correcting for noise and anomalies, thereby correlating respiratory sounds with pulse rate variations to diagnose sleep apnea.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If sound signals are used to detect pulse rate, then the number of sensors is reduced, but measurement precision deteriorates due to noise from snoring and movements
Solution Approach 1:
The patent extracts the useful signal (heart sounds) from the noisy respiratory signals by using adaptive filtering to separate the cardiac component from the respiratory component, thereby obtaining accurate pulse rate information from a single microphone channel
Solution Approach 2:
The patent introduces an adaptive filter as an intermediary processing stage between the microphone and pulse rate calculation, which acts as a mediator to eliminate noise and extract the hidden cardiac information from the respiratory sound signals
2Measurement precision
If adaptive filtering is applied to extract pulse rate, then measurement precision improves, but device complexity increases due to additional processing steps
Solution Approach 1:
The patent uses adaptive filtering with dynamic adjustment of filter coefficients based on the changing characteristics of respiratory and cardiac signals, allowing the system to automatically adapt to varying noise conditions and maintain high measurement precision
Solution Approach 2:
The patent changes the parameters of the filter (coefficients, order, cutoff frequencies) dynamically during signal processing to optimize the extraction of pulse rate information under different physiological conditions and noise environments
Data Source
AI summary
A method is proposed for determining a pulse rate through a sound-sensing means placed on an individual's trachea, the method comprising a preliminary step for recording sound signals for a lengthy duration, wherein it comprises subsequently the following steps: filtering digital signals representative of the sound signals by using an adaptive filter, applying a lowpass filter to the signals obtained in order to select the signals comprised in a specified passband, selecting a first temporal portion of filtered digital signals of a specified duration, intercorrelation with a temporal portion of filtered digital signals that follows the first temporal portion in time and is of a same duration, searching (4.6) for the intercorrelation, computing the time interval corresponding to this temporal position and computing the corresponding pulse rate throughout the recording duration, to obtain a temporal series of pulse rates S1.