Gated PPG Monitoring via ECG Triggering for Power Reduction
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Solution Overview
Problem
Wearable vital sign monitors face significant power consumption challenges due to continuous SpO2 measurement, limiting their operating time, especially since SpO2 measurement requires high power for LED operation, while ECG signals consume less power, making it a bottleneck for extended operation.
Innovation Solution
The gated physiological monitoring system operates the PPG monitoring device based on timing information from another physiological monitoring device, such as an ECG system, to capture selected portions of the PPG waveform, reducing unnecessary LED power consumption by duty-cycling and using a trans-impedance amplifier with a switch to integrate current signals efficiently, thereby minimizing energy usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If continuous PPG monitoring is performed to obtain SpO2 measurements, then measurement precision is improved, but power consumption increases significantly
Solution Approach 1:
The patent implements periodic action by gating the PPG measurement process to specific time windows triggered by ECG R-waves. Instead of continuous monitoring, the system periodically activates the PPG LED and ADC only during relevant cardiac cycles, reducing power consumption while maintaining measurement precision through selective sampling of critical waveform portions.
Solution Approach 2:
The system performs preliminary action by using the ECG monitoring to predict and prepare for upcoming PPG measurement opportunities. The ECG R-wave detection provides advance timing information that allows the PPG system to be pre-positioned and activated only when necessary, avoiding continuous operation and reducing overall power consumption.
2Measurement precision
If continuous PPG monitoring is performed to capture full waveform, then measurement precision is improved, but duration of action is reduced
Solution Approach 1:
The patent applies the extraction principle by isolating and capturing only the critical portions of the PPG waveform that are necessary for SpO2 and heart rate estimation. Instead of continuously recording the full waveform, the system extracts specific time segments around ECG-triggered events, reducing data volume and power consumption while maintaining measurement precision for vital parameters.
Solution Approach 2:
The system extends operating time by implementing periodic measurement cycles triggered by ECG events. The PPG monitoring operates in discrete periodic intervals rather than continuously, allowing the battery to last longer while still capturing sufficient waveform data for accurate SpO2 and heart rate calculation during each active period.
3Measurement precision
If high power is supplied to LED for SpO2 measurement, then measurement precision is improved, but power consumption increases
Solution Approach 1:
The patent reduces energy loss by operating the PPG LED in periodic bursts synchronized with ECG-triggered measurement windows. The LED is activated only during these brief periodic intervals rather than continuously, significantly reducing total energy consumption while maintaining sufficient light intensity for accurate SpO2 measurement during active periods.
Solution Approach 2:
The system applies partial action by providing high power to the LED only during the specific time periods when measurements are actually taken, rather than maintaining high power continuously. This partial activation during critical measurement windows achieves the necessary measurement precision while dramatically reducing overall energy loss.
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 power consumption of the PPG monitoring device, allowing for extended operation of wearable vital sign monitors by focusing energy use on critical waveform portions for SpO2 and heart rate estimation, enhancing energy autonomy and reducing design complexity.
Implementation Method 1
a photodetector to detect the light and convert the light into a current signal
Implementation Method 2
The trans-impedance amplifier can be configured to output a voltage signal during a measurement frame
Implementation Method 3
SpO2 measurement requires high power for LED operation
Data Source
AI summary
Gated physiological monitoring systems and methods are described that utilize a photoplethysmogram (PPG) monitoring device and another (different) physiological monitoring device, where the PPG monitoring device is operated based on timing information obtained from the other physiological monitoring device. In some implementations, control circuitry can be configured to operate the PPG monitoring device based on timing information from a physiological waveform detected by the physiological monitoring device. For example, the control circuitry can operate the PPG monitoring device to capture one or more selected portions of a measured PPG waveform that can then be used to estimate the full PPG waveform or portions of interest.