Organ Perfusion Monitoring via DC Reflectance Intensity
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Solution Overview
Problem
Current methods for monitoring organ perfusion, such as ultrasound, pulse oximetry, and photoplethysmography, are limited by operator dependence, mechanical instability, and sensitivity to motion and low perfusion, leading to inaccurate oxygen saturation measurements and unreliable perfusion monitoring.
Innovation Solution
A system using multiple wavelengths in the visible and infrared spectra to measure slow, long-term changes in tissue reflectance or transmittance, combined with a time multiplex technique and a flexible sensor design, allowing for robust and continuous monitoring of organ perfusion with reduced noise sensitivity and increased measurement volume.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If pulse oximetry is used to monitor organ perfusion, then oxygen saturation can be measured, but the measurement becomes unreliable at low perfusion values and is sensitive to mechanical motion
Solution Approach 1:
The patent changes the measurement parameter from pulse-based amplitude changes to DC-level reflectance intensity changes. By measuring the absolute reflectance intensity rather than pulsatile changes, the system remains reliable at low perfusion values where pulse amplitude is diminished. The system uses multiple wavelengths to measure reflectance intensity at each wavelength and processes these DC-level signals to determine perfusion status.
Solution Approach 2:
The patent extracts the DC component (steady-state reflectance intensity) from the AC component (pulsatile changes) of the optical signal. By focusing measurement on the DC level rather than the AC pulsations, the system eliminates sensitivity to mechanical motion that affects pulse detection while maintaining perfusion monitoring capability through intensity-based measurements.
2Measurement precision
If photoplethysmography is used to monitor perfusion, then volumetric changes can be detected, but the system remains sensitive to mechanical instability and produces false pulse detections
Solution Approach 1:
The patent extracts and measures the DC component of the optical signal representing steady-state reflectance intensity, separate from the AC pulsatile component. By processing the DC level information rather than relying solely on AC pulse detection, the system achieves reliable perfusion monitoring without false pulse detections caused by mechanical instability.
Solution Approach 2:
Instead of detecting perfusion through pulse waveform analysis (AC component), the patent inverts the approach by measuring reflectance intensity at the DC level. This inversion from pulse-based to intensity-based measurement eliminates false pulse detections while maintaining volumetric change detection capability through multiple wavelength analysis.
3Device complexity
If a limited number of wavelengths are used in oximetry, then the device complexity is reduced, but the robustness of perfusion monitoring decreases
Solution Approach 1:
The patent changes the measurement approach from relying on pulse amplitude ratios at limited wavelengths to measuring DC reflectance intensity at multiple wavelengths. By using multiple wavelengths to capture spectral characteristics of tissue chromophores at the DC level, the system achieves robust perfusion monitoring that is less susceptible to mechanical motion and low perfusion conditions.
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 provides more accurate and reliable perfusion monitoring with improved sensitivity and the ability to measure larger tissue volumes, minimizing the impact of mechanical instability and motion, enabling continuous monitoring of transplanted organs postoperatively.
Implementation Method 1
The transmitting section contains transmitters with light-emitting diodes, which irradiate the monitored tissue by radiation of multiple wavelengths
Implementation Method 2
the receiving section with receivers with photosensitive sensors, which detect the radiation reflected from the monitored tissue
Implementation Method 3
monitoring the amplitude of quasi-periodic changes in the reflectance or transmittance of the monitored tissue caused by the varying concentrations of oxyhemoglobin and deoxyhemoglobin during a heart cycle
Data Source
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AI summary
The system for monitoring the blood supply to a transplanted organ uses its spectral characteristics to monitor the organ's status and, based on the evaluation of the measured results, it robustly classifies blood supply failure regardless of the local variability of blood perfusion. The proposed system is based on the measurement of slow changes in the intensity of the radiation reflected from the organ at several wavelengths in the visible and near-infrared spectral range. The state of the organ perfusion is evaluated on the basis of a common classification of slow changes and amplitudes of pulsations of the measured signals. The measurement accuracy is therefore not affected by the intensity of the perfusion, as is the case of pulse oximetry, but the pulse changes in the reflected light intensity can be evaluated. The modulation and demodulation technique applied to the measuring signals significantly increases the useful signal-to-noise ratio, thus allowing for a reduction in the overall system input power and increasing the distance between the sensors while maintaining high measurement accuracy. Due to this and due to the special mechanical concept of the sensor, the system allows to monitor a larger volume of tissue. The system also has low energy demands, making it suitable for battery operation.