Multi-Modal Pulse Rate Estimation Using ECG and PPG Signals
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Solution Overview
Problem
Existing methods for detecting cardiovascular pulse rates often face challenges due to differences in noise characteristics, availability, and quality of signals from various sensors, leading to inaccurate or uncertain pulse rate determinations, especially when signals are intermittently available.
Innovation Solution
A system and method that combine signals from multiple sensors, including continuously available and occasionally available sensors, using techniques like inertial filtering, Kalman filtering, and pattern matching to determine pulse rates, with the occasionally available signal serving as 'ground truth' when available, and updating estimates using the continuously available signal when intermittent.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple sensor signals are combined to improve pulse rate accuracy, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent combines signals from multiple sensors (photoplethysmographic sensor and electrocardiographic sensor) to determine pulse rate. The system merges the continuously available PPG signal with the occasionally available ECG signal, using the ECG as ground truth when available and the PPG as continuous monitoring, thereby improving measurement precision through multi-modal signal integration.
Solution Approach 2:
The patent introduces an intermediary processing system that mediates between the raw sensor signals and the final pulse rate determination. This intermediary system applies inertial filtering, Kalman filtering, and pattern matching algorithms to reconcile the different signal types, manage their intermittent availability, and produce accurate pulse rate estimates without requiring direct complex hardware integration.
2Productivity
If continuously available sensor signal is used for pulse rate monitoring, then productivity is improved, but measurement precision deteriorates due to noise and intermittent contact
Solution Approach 1:
The patent implements feedback mechanisms where the system continuously monitors the quality and availability of both PPG and ECG signals. When the ECG signal becomes available, it provides feedback to correct and recalibrate the PPG-based pulse rate estimates. The system uses this feedback to adjust filtering parameters and update the continuous monitoring algorithm, maintaining productivity while correcting precision degradation from noise and intermittent contact.
Solution Approach 2:
The patent applies preliminary signal processing actions to the continuously available PPG signal, including inertial filtering and adaptive noise reduction, before the ECG signal becomes available. These preliminary actions prepare the continuous signal for accurate pulse rate determination, and when ECG data arrives, the system uses it to validate and refine the preliminary estimates, thereby maintaining both continuous monitoring capability and 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
This approach enhances the accuracy and reliability of pulse rate determination by leveraging the strengths of both signal types, improving resolution and sensitivity while minimizing uncertainty, even with intermittent sensor contact or noise.
Implementation Method 1
A variety of cardiovascular parameters can be detected by illuminating blood in a portion of subsurface vasculature and detecting one or more properties of light responsively emitted from the portion of subsurface vasculature
Implementation Method 2
Cardiovascular parameters may additionally or alternatively be detected by detecting a biopotential between two or more locations of a body
Data Source
AI summary
Systems and methods are provided for determining the frequency of a cardiovascular pulse based on a first physiological signal that is continuously available and a second physiological signal that is less available and that is more accurate or otherwise improved relative to the first signal with respect to pulse rate estimation. When the second signal is available it controls the determination of the pulse rate. When the second signal is unavailable, the first signal is used to determine the pulse rate. This can include using the first signal to estimate the pulse rate until the second signal is available, at which point the pulse rate is estimated based on the second physiological signal. Alternatively, the first signal could be used to determine a number of candidate pulse rates, and the second signal could be used to select a pulse rate from the set of candidate pulse rates.