PPG Sensor Patch Signal Processing for SpO2 Accuracy
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Solution Overview
Problem
Photoplethysmography (PPG) signal quality is compromised by noise and skin pigmentation, particularly in patients with highly pigmented skin and high body mass index (BMI), affecting the accuracy of oxygen saturation (SpO2) estimation.
Innovation Solution
A system comprising a PPG sensor patch with a processor that uses reflectance red and infrared data, an electrocardiogram (ECG) sensor, accelerometer, and bioimpedance sensor to filter out noise, verify peaks, and calculate an optical ratio for precise SpO2 estimation, while adjusting light intensity and force for optimal signal quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If PPG sensors are used for detecting oxygen saturation, then SpO2 estimation can be obtained, but signal quality decreases for patients with highly pigmented skin and high BMI
Solution Approach 1:
The system dynamically adjusts PPG signal processing parameters including AC/DC component thresholds, peak detection criteria, and signal filtering parameters based on real-time signal quality assessment. This allows the system to adapt to varying skin pigmentation and tissue characteristics, maintaining measurement precision across diverse patient populations.
Solution Approach 2:
The patent introduces multiple intermediary processing steps including noise filtering, peak verification through secondary sensors (ECG, accelerometer, bioimpedance), and signal quality indexing. These intermediaries mediate between the raw PPG signal and final SpO2 calculation, improving reliability by eliminating false peaks and noise artifacts that particularly affect highly pigmented skin.
2Measurement precision
If PPG sensors are placed on the patient's chest, then heart rate detection is achieved, but noise from movement and respiration increases
Solution Approach 1:
The system segments the PPG signal into AC (pulsatile) and DC (baseline) components, allowing separate processing and analysis. This segmentation enables the system to isolate the cardiac signal from respiratory and motion artifacts, maintaining heart rate detection accuracy despite chest placement challenges.
Solution Approach 2:
The patent combines data from multiple sensors (PPG, ECG, accelerometer, bioimpedance) to verify heartbeats and eliminate false detections. By merging information from these complementary sensors, the system achieves robust heart rate detection that overcomes the noise challenges inherent in chest-mounted PPG sensors.
3Measurement precision
If multiple sensors are added to verify peaks and filter noise, then SpO2 estimation accuracy improves, but device complexity increases
Solution Approach 1:
The system implements multi-functional sensors and processing algorithms that serve multiple purposes. For example, the peak detection algorithm simultaneously identifies cardiac peaks, verifies them against multiple sensors, and assesses signal quality. This universal approach improves SpO2 accuracy without proportionally increasing device complexity.
Solution Approach 2:
The system uses the PPG signal itself and its relationship with other physiological signals (ECG, accelerometer, bioimpedance) to automatically verify peaks and filter noise. The algorithms self-adjust based on signal characteristics, reducing the need for complex external verification systems while maintaining high measurement precision.
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
Improves PPG signal quality and accuracy of SpO2 estimation by filtering noise and adapting to skin conditions, enhancing the reliability of oxygen saturation measurements.
Implementation Method 1
Photoplethysmography (PPG) sensors may be used for detecting and monitoring a patient's heart rate
Implementation Method 2
compute an oxygen saturation percentage (SpO2%) by computing an optical ratio of the red data and the IR data
Implementation Method 3
a photoplethysmography (PPG) sensor for providing reflectance red data and infrared (IR) data
Data Source
AI summary
The present disclosure relates to systems and processes for optimizing the detection of a patient's heartbeats, which may be useful in detection of the patient's oxygen saturation, as well as systems and processes for improving and optimizing the PPG signal quality of those patients with highly pigmented skin. In various embodiments, the process may comprise the steps of: receiving, from a radio, red data, infrared (IR) data, and a series of heartbeats associated with a time period; computing a series of peaks of the red data and IR data for the time period; computing a subset of the red data and IR data; estimating an oxygen saturation percentage (SpO2%) for the patient by computing an optical ratio of the red data and IR data included in the subset; and displaying on a computer screen the estimated SpO2% for the patient.