Oscillometric Signal Artifact Removal via Frequency Domain Segmentation
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Solution Overview
Problem
Current non-invasive blood pressure monitoring systems face challenges in accurately determining blood pressure due to artifact contamination, particularly from patient movements, which can render oscillometric data useless and require additional data collection, increasing measurement time and patient discomfort.
Innovation Solution
A method involving the conversion of oscillometric data to the frequency domain, followed by filtering using band pass filters centered around the fundamental and harmonic frequencies of the heart rate, with additional artifact bands to calculate energy ratios and determine the quality of the blood pressure reading, allowing for improved artifact removal and data processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If oscillometric data is collected to determine blood pressure, then blood pressure measurement is achieved, but artifact contamination from patient movements degrades measurement accuracy
Solution Approach 1:
The patent segments the frequency spectrum into multiple bands (first frequency band containing fundamental frequency, second frequency band containing harmonic frequencies, third frequency band for artifacts). By dividing the signal processing into distinct frequency segments, the system can selectively filter artifact frequencies while preserving physiological signal frequencies, thereby improving measurement accuracy despite patient movement artifacts.
Solution Approach 2:
The patent extracts and removes artifact components from the oscillometric signal by identifying frequency bands contaminated by patient movements and excluding these from the blood pressure calculation. The system separates the harmful artifact frequencies from the useful physiological frequencies and eliminates their influence on the measurement result.
2Reliability
If additional data collection is performed to overcome artifact contamination, then measurement reliability may improve, but measurement time and patient discomfort increase
Solution Approach 1:
The patent performs preliminary frequency domain analysis and artifact identification during the initial data collection phase. By pre-identifying artifact-contaminated frequency bands and adjusting the filtering strategy beforehand, the system avoids the need for repeated measurements, thereby maintaining high reliability without extending measurement time or increasing patient discomfort.
Solution Approach 2:
The patent replaces mechanical/time-based artifact rejection (repeating measurements) with frequency-domain signal processing. Instead of collecting additional data over time to overcome artifacts, the system uses spectral analysis and frequency band filtering to eliminate artifacts from the existing data, achieving reliable measurements faster.
3Measurement precision
If frequency domain filtering is applied to remove artifacts, then measurement accuracy improves, but processing complexity increases
Solution Approach 1:
The patent simplifies the frequency domain processing by segmenting the spectrum into a limited number of discrete frequency bands (first, second, and third bands) with specific purposes. This segmentation approach makes the complex frequency domain filtering more manageable by organizing it into structured, repeatable steps rather than continuous complex processing.
Solution Approach 2:
The patent changes the processing domain from time domain to frequency domain, enabling artifact removal through frequency-based filtering. This parameter change (domain transformation) allows the system to target specific artifact frequencies without affecting physiological frequencies, improving accuracy while the structured band approach keeps processing complexity manageable.
Data Source
AI summary
A system and method for processing oscillometric data from a plurality of pressure steps to determine the blood pressure of a patient. A heart rate monitor connected to the patient acquires the patient's heart rate. A time-to-frequency domain converter receives oscillometric data and converts the oscillometric data into the frequency domain. Based upon the calculated heart rate, the system and method filters the frequency domain oscillometric signal with pass bands centered at the fundamental frequency and at least one fundamental frequency. The energy of the frequency domain signal within the pass bands is compared to at least a portion of the energy of the frequency domain oscillometric signal outside of the pass bands. Based upon the comparison, the signal determines whether the signal at the current pressure step should be utilized in calculating the blood pressure of the patient.