Physiologic Sensor Using Dual-Wavelength LED for Tissue Oxygen Monitoring
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Solution Overview
Problem
Current medical technologies lack an objective, reliable, and non-invasive method to monitor tissue-level oxygen delivery, leading to potential tissue damage and misperceptions in critical care, as existing methods cannot accurately determine if tissues receive sufficient or excessive oxygen.
Innovation Solution
Development of physiology index (PI) sensors using 660+/−10 nm and 850+/−10 nm LED emitters to detect optical signal intensity divergence through skin tissue, providing an index of oxygen delivery rate that is neither too low nor too high, and configured for wearable, non-invasive use with calibration methods to accommodate skin variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of information
If blood oxygen metrics and pulse oximetry are used to monitor oxygen levels, then oxygen saturation information is obtained, but tissue-level oxygen delivery information is lost
Solution Approach 1:
The patent uses light as an intermediary to indirectly measure tissue oxygen delivery. By shining light through tissue and analyzing the absorbed and scattered light patterns, the system obtains tissue-level oxygen delivery information without directly contacting or invading the tissue, thus preserving information while maintaining measurement precision.
Solution Approach 2:
The patent replaces invasive mechanical measurement methods (such as arterial blood gas sampling) with optical measurement. Light interaction with tissue provides non-invasive access to tissue oxygen delivery metrics that previously required mechanical intrusion into the body.
2Measurement precision
If invasive methods are used to measure tissue oxygen, then accurate tissue-level data is obtained, but patient safety and comfort are compromised
Solution Approach 1:
The patent substitutes optical measurement for invasive mechanical measurement. Light passes through tissue and is detected on the other side, providing accurate tissue oxygen delivery data without penetrating or damaging tissue structures.
Solution Approach 2:
Light serves as a non-harmful intermediary that carries information about tissue oxygen delivery. The light interacts with chromophores in the tissue and emerges with modified properties that reveal tissue oxygen status, eliminating the need for invasive probes or sensors within the tissue.
3Loss of information
If multiple separate measurements are taken to assess oxygen status, then comprehensive information is gathered, but integration and interpretation complexity increases
Solution Approach 1:
The patent merges multiple oxygen assessment metrics into a single integrated optical measurement system. By measuring light absorption and scattering at multiple wavelengths simultaneously, the system derives tissue oxygen delivery, blood oxygen saturation, and perfusion information from one unified measurement process rather than separate tests.
Solution Approach 2:
The optical measurement system performs multiple functions simultaneously: it measures tissue oxygen delivery, blood oxygen saturation, and tissue perfusion. This multi-functional approach provides comprehensive oxygen status information through a single device and measurement protocol.
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 PI sensors effectively monitor tissue oxygen delivery, preventing tissue injury by providing real-time, objective feedback on oxygen levels, enabling precise regulation of breathing gas oxygen fraction and improving patient safety in critical care and everyday applications.
Implementation Method 1
the optical signal intensity from the 850+/−10 nm light, after it has diffused through skin tissue, has been found to diminish in intensity more rapidly than the signal from the 660+/−10 nm light after it has similarly diffused through skin tissue
Implementation Method 2
the optical signal intensity from the 850+/−10 nm light, after it has diffused through skin tissue
Data Source
AI summary
Physiologic sensors and methods of application are described. These sensors function by detecting recently discovered variations in the spectral optical density at two or more wavelengths of light diffused through the skin. These variations in spectral optical density have been found to consistently and uniquely relate to changes in the availability of oxygen in the skin tissue, relative to the skin tissue's current need for oxygen, which we have termed Physiology Index (PI). Current use of blood gas analysis and pulse oximetry provides physiologic insight only to blood oxygen content and cannot detect the status of energy conversion metabolism at the tissue level. By contrast, the PI signal uniquely portrays when the skin tissue is receiving ‘less than enough oxygen,’‘just the right amount of oxygen,’ or ‘more than enough oxygen’ to enable aerobic energy conversion metabolism. The PI sensor detects one pattern of photonic response to insufficient skin tissue oxygen, or tissue hypoxia, (producing negative PI values) and a directly opposite photonic response to excess tissue oxygen, or tissue hyperoxia, (producing positive PI values), with a neutral zone in between (centered at PI zero). Additionally, unique patterns of PI signal response have been observed relative to the level of physical exertion, typically with a secondary positive-going response trend in the PI values that appears to correspond with increasing fatigue. The PI sensor illuminates the skin with alternating pulses of selected wavelengths of red and infrared LED light, then detects the respective amount of light that has diffused through the skin to an aperture located a lateral distance from the light source aperture. Additional structural features include means of internally excluding light from directly traveling from the light emitters to the photodetector within the sensor. This physiology sensor and methods of use offer continuous, previously unavailable information relating to tissue-level energy conversion metabolism. Several alternative embodiments are described, including those that would be useful in medical care, athletics, and personal health maintenance applications.