Pulse Oximeter Optical CRT Estimation After Tissue Compression
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Solution Overview
Problem
The manual method of compressing living tissue and visually checking skin color change for capillary refill time (CRT) lacks quantification and is prone to measurement errors.
Innovation Solution
A pulse oximeter that emits lights of different wavelengths, detects their intensity changes, calculates pulsation rate and percutaneous arterial oxygen saturation, and estimates CRT based on these changes to return to predetermined thresholds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If manual compression and visual checking method is used, then the measurement process is simple and easy to operate, but the measurement precision and quantification are insufficient
Solution Approach 1:
The patent replaces the manual mechanical compression method with an automated compression mechanism that applies controlled compression force to the tissue. This mechanical automation substitutes the operator's hand compression, providing consistent and quantifiable compression while enabling optical detection systems to measure CRT parameters objectively through light absorption changes in the tissue.
Solution Approach 2:
The patent introduces light as an intermediary substance to detect tissue perfusion status. By shining light through the compressed tissue and measuring the transmitted or absorbed light intensity, the system converts the biological process of capillary refill into an optical signal that can be precisely measured and quantified, eliminating the subjectivity of visual assessment.
2Measurement precision
If pulse oximeter with multiple calculations is used, then the CRT estimation accuracy is improved, but the computational load and device complexity increase
Solution Approach 1:
The patent makes the pulse oximeter's light detection system perform multiple functions: it detects both the standard pulse oximetry parameters (oxygen saturation, heart rate) and the CRT-specific parameters (compression-induced changes in light absorption). By using the same hardware for multiple measurement purposes, the system achieves accurate CRT estimation without adding separate dedicated equipment, thus managing device complexity while improving measurement precision.
Solution Approach 2:
The patent combines the CRT measurement function with the existing pulse oximetry measurement functions into a single integrated system. The compression mechanism, light detection, and processing algorithms are merged to simultaneously provide traditional SpO2 monitoring and novel CRT assessment, reducing overall system complexity compared to having separate devices for each function.
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
Provides a quantified and accurate estimation of CRT, reducing computational load and device complexity, enhancing convenience and portability.
Implementation Method 1
light having a wavelength absorbed by a blood is incident on a living tissue such as a fingertip, and an intensity of the light transmitted through the living tissue is measured
Data Source
AI summary
A pulse oximeter includes a light emitting device that emits a first light and a second light, a light detecting device that outputs a first signal and a second signal respectively corresponding to an intensity of the first light and an intensity of the second light after interacting with a tissue of a subject, a processing device that calculates a pulsation rate of at least one of the first signal and the second signal, calculates a percutaneous arterial oxygen saturation of the subject, and estimates a capillary refill time of the tissue based on a time taken for at least one of the pulsation rate and the percutaneous arterial oxygen saturation, which change along with compression on the tissue, to return to a predetermined threshold range with respect to each value before the compression, and an output device that outputs information indicating the capillary refill time.