Low Power Pulse Oximeter Dynamic Sampling
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Solution Overview
Problem
Conventional pulse oximeters face challenges in reducing power consumption while maintaining functionality, especially in portable applications, as they cannot afford to miss critical events like patient oxygen desaturation, and existing sleep mode techniques are inadequate due to reliance on output parameters and increased processing overhead.
Innovation Solution
A low power pulse oximeter system that includes a sensor interface, signal processor, and sampling controller to dynamically adjust power consumption based on signal quality and physiological events, using mechanisms such as varying emitter duty cycles, intermittent detector front-end power-down, and data block time shifts to maintain performance within a predetermined power target.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If conventional sleep mode techniques are used to reduce power consumption, then power usage decreases, but critical events like oxygen desaturation may be missed
Solution Approach 1:
The system dynamically adjusts the sampling rate based on signal quality metrics and detected physiological events. During stable conditions, sampling occurs at lower rates to conserve power. When motion artifacts or desaturation events are detected, the system automatically increases sampling frequency to ensure accurate event detection, thus resolving the contradiction between power savings and reliability
Solution Approach 2:
The system continuously monitors signal quality and physiological parameters, using this feedback to adjust power consumption in real-time. The processor evaluates each data block and modifies sampling behavior accordingly, creating a closed-loop system that balances power efficiency with reliable event detection
2Reliability
If sampling rate is increased to ensure continuous monitoring of critical events, then event detection reliability improves, but power consumption increases
Solution Approach 1:
The system applies partial sampling action by processing complete data blocks only when necessary. Instead of continuously sampling at high rates, the system accumulates data in blocks and processes them selectively based on signal quality and event detection needs, reducing overall power consumption while maintaining reliability when critical events occur
3Measurement precision
If processor is kept active continuously to monitor physiological parameters, then measurement accuracy improves, but power consumption increases
Solution Approach 1:
The processor operates periodically rather than continuously, entering low-power states between data block processing intervals. The system maintains measurement precision by ensuring complete data blocks are processed with full computational resources, while reducing power consumption through periodic operation and strategic use of low-power modes during stable physiological conditions
4Use of energy by moving object
If emitter duty cycle is reduced to lower power consumption, then power efficiency improves, but signal quality may deteriorate
Solution Approach 1:
The emitter duty cycle is dynamically adjusted based on real-time signal quality assessment. During periods of good signal quality and stable physiological conditions, the duty cycle is reduced to conserve power. When signal quality deteriorates or physiological events are detected, the duty cycle increases to maintain adequate signal strength, thus resolving the contradiction between power efficiency and signal quality
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
The system effectively reduces average power consumption while ensuring continuous monitoring of critical events, providing a balance between power efficiency and functional reliability by adapting power usage based on real-time signal quality and physiological measurements.
Implementation Method 1
The sensor 110, which can be attached to an adult's finger or an infant's foot, has both red and infrared LEDs 112
Implementation Method 2
The photodiode 114 is positioned at the finger tip opposite the fingernail so as to detect the LED emitted light as it emerges from the finger tissues
Implementation Method 3
a ratio of detected red and infrared intensities is calculated by the signal processor 156, and an arterial oxygen saturation value is empirically determined based on the ratio obtained
Data Source
AI summary
A pulse oximeter may reduce power consumption in the absence of overriding conditions. Various sampling mechanisms may be used individually or in combination. Various parameters may be monitored to trigger or override a reduced power consumption state. In this manner, a pulse oximeter can lower power consumption without sacrificing performance during, for example, high noise conditions or oxygen desaturations.