Acoustic Bubble Detection in Dialysis Expansion Chambers
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Solution Overview
Problem
Current dialysis machines lack effective detection systems for air microbubbles in the blood, which can lead to serious patient complications, and existing safety systems are costly, hardware-intensive, and limited in sensitivity, failing to detect microbubbles that can cause ischemic issues.
Innovation Solution
An apparatus and method that utilize pressure sensors and the ideal gas law to monitor blood levels in expansion chambers, determining the volume of air without additional hardware, enabling reliable detection of air ingress and automatic patient safety interventions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional bubble sensors are used to detect air in blood, then they can reliably detect bubbles of predetermined size, but they fail to detect micro-bubbles of air dissolved in the blood
Solution Approach 1:
The patent replaces traditional mechanical/optical bubble sensors with an acoustic resonance-based detection system. The system uses acoustic waves to excite resonance in air bubbles within the blood, and detects the resulting acoustic signals to identify both macro-bubbles and micro-bubbles. This substitution of mechanical sensing with acoustic field-based detection enables sensitivity to micro-bubbles that were previously undetectable.
Solution Approach 2:
The system changes the detection parameter from optical/mechanical properties to acoustic resonance properties. By monitoring acoustic impedance changes and resonance frequencies of bubbles in the blood, the system can detect micro-bubbles based on their acoustic signature rather than their visual or mechanical presence, thereby improving detection sensitivity across all bubble sizes.
2Reliability
If additional safety hardware (bubble sensors, level sensors) is added to detect air and monitor blood levels, then patient safety is improved, but the cost and device complexity increase significantly
Solution Approach 1:
The acoustic resonance detection system serves multiple functions: it detects air bubbles in the blood, monitors blood volume levels in expansion chambers, and provides alarm signals. By integrating these detection capabilities into a single acoustic-based system rather than requiring separate sensors for each function, the patent reduces overall device complexity while maintaining comprehensive patient safety monitoring.
Solution Approach 2:
The system utilizes the existing acoustic environment and blood flow dynamics within the dialysis machine to enable self-detection. The acoustic resonance method leverages the natural acoustic properties of bubbles and blood without requiring external power-intensive sensors or complex hardware additions, allowing the system to monitor itself using minimal additional components.
3Measurement precision
If traditional safety systems are implemented to detect air bubbles, then they can signal the presence of bubbles, but they generate false positives and cannot distinguish micro-bubbles from normal blood components
Solution Approach 1:
The system continuously monitors acoustic resonance signals and compares them against threshold values and patterns characteristic of actual air bubbles. By implementing feedback mechanisms that analyze the frequency, amplitude, and temporal characteristics of acoustic signals, the system can distinguish true bubble presence from noise or normal blood flow variations, thereby reducing false positives while maintaining high detection accuracy.
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
This solution allows for reliable detection of air microbubbles and prevention of air infusion into the patient, reducing false positives and enhancing patient safety without requiring additional hardware, thus addressing the limitations of existing systems.
Implementation Method 1
at least a pressure sensor (13, 14) associated to the expansion chamber (11, 12) and configured such as to enable determining pressure values internally of the expansion chamber (11, 12)
Implementation Method 2
determine a magnitude that is representative of a blood level (L) in the expansion chamber (11, 12), as a function of the average value (Pavg) of the pressure (P(t)), of the estimated volume variation value (ΔV) and the estimated pressure variation value (ΔP) in the expansion chamber (11, 12)
Data Source
AI summary
An apparatus is described for extracorporeal blood treatment, comprising a treatment unit, an extracorporeal blood circuit and a fluid evacuation line. The apparatus comprises a control unit connected to a pressure sensor and a blood pump, the blood pump generating a variable flow with a constant component and a variable component. The control unit receives, from the pressure sensor, a plurality of values and calculates the average pressure value, acquires an estimated value of volume variation in the expansion chamber connected to the variable flow component, calculates, as a function of the pressure values, an estimated value of pressure variation in the expansion chamber that is representative of an oscillating pressure component and determines a representative magnitude of a blood level in the expansion chamber as a function of the average pressure value, the estimated value of volume variation and the estimated pressure variation in the expansion chamber.