Multimodal PPG Sensor for Neonatal SpO2 Reliability
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Solution Overview
Problem
Existing pulse oximetry technologies face challenges in obtaining reliable SpO2 measurements in newborns due to spatial and temporal variations in skin physiology, leading to movement artefacts and inaccurate readings, which can be critical in neonatal care where timely monitoring is essential.
Innovation Solution
A photoplethysmography device with a multimodal measurement system that combines DC light ratio analysis at different wavelengths, capacitive sensing, pressure sensing, and lens-based opto-spatial reduction to determine the reliability of SpO2 measurements, ensuring proper sensor placement and contact pressure, thereby improving measurement accuracy and reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the sensor is placed on the neonate's skin with sufficient contact pressure to ensure reliable measurement, then measurement reliability is improved, but skin blanching may occur
Solution Approach 1:
The system continuously monitors the PPG signal quality and provides feedback to adjust the contact pressure dynamically. When the sensor detects poor signal quality, it automatically increases contact pressure; when signal quality is adequate, it reduces pressure to prevent skin blanching. This closed-loop control resolves the contradiction between ensuring reliable measurement and avoiding skin damage.
Solution Approach 2:
The contact pressure is made dynamic rather than static. The system adjusts the pressure in real-time based on signal quality metrics, transitioning between different pressure states as needed. This dynamic adjustment allows the system to optimize between measurement reliability and skin safety at any given moment.
2Measurement precision
If the sensor placement is optimized for accurate SpO2 measurement, then measurement precision is improved, but movement artefacts may occur due to improper fit
Solution Approach 1:
The system uses feedback from the PPG signal to continuously monitor placement quality. When movement or improper fit is detected through signal degradation, the system provides feedback to adjust the sensor position or contact pressure, thereby maintaining both precision and reliability despite neonatal movement.
Solution Approach 2:
The system performs preliminary assessment of signal quality upon initial placement and continuously monitors during measurement. This preliminary and continuous monitoring allows for early detection of placement issues and corrective action before inaccurate measurements are recorded, maintaining both precision and reliability.
3Reliability
If multiple measurement modalities are integrated to improve measurement reliability, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent combines multiple measurement modalities (PPG, DC light ratio, capacitance, pressure sensing) into a single integrated sensor unit. By merging these functions into one cohesive device with shared processing and control systems, the overall complexity is managed more effectively than separate devices would be, while still achieving improved reliability through multi-modal measurement.
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 combined modalities enhance the accuracy and reliability of SpO2 measurements by correctly positioning the sensor on the neonate's skin, reducing movement artefacts and providing contextual information for adjusting the sensor's fit, leading to more trustworthy and precise readings.
Implementation Method 1
a light emitter and a light detector configured to detect the light from the light emitter after it has been attenuated by tissue comprising blood vessels
Implementation Method 2
When the cardio pulse arrives, more light is absorbed in the increasing blood volume and, as a result, the level of light detected is reduced. The time-varying optical signal that is detected is called the Photoplethysmogram (PPG)
Implementation Method 3
By measuring a PPG at different wavelengths, a level of oxygen saturation in the haemoglobin can be detected due to the different absorption coefficient of Hb (de-oxygenated haemoglobin) and HbO2 (oxygenated haemoglobin) as a function of wavelength
Data Source
AI summary
A device is disclosed comprising: an optical physiological sensor and a further measurement system. The optical physiological sensor comprises a light emitter and a light detector configured to detect the light from the light emitter after it has been attenuated by tissue comprising blood vessels. The optical physiological sensor is configured to determine the value of a physiological parameter from the detected light. The further measurement system is configured to determine when the value of the physiological parameter is likely to be reliable. The further measurement system comprises at least one measurement subsystem, each measurement subsystem employing a different measurement modality that is also different to a measurement modality used to determine the value of the physiological parameter.