Dialysis Disconnection Monitor Using Pressure Pulse Cross-Correlation
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Solution Overview
Problem
Current methods for detecting disconnection in a venous return line of an extracorporeal blood circuit are unreliable, often resulting in undetected blood loss due to false negatives or false positives, and require additional apparatus like moisture sensors, which can fail in sudden movements or noisy electrical backgrounds.
Innovation Solution
A dialysis system with a disconnection monitor that uses a pressure transducer to generate a pulse signal and cross-correlates it with a cardiac reference signal to detect disconnections, eliminating the need for extra sensors and improving detection accuracy by monitoring pressure pulses and cardiac signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If pressure monitoring is used to detect disconnection in venous return line, then the detection method is simple, but the detection reliability is low due to insignificant pressure changes
Solution Approach 1:
The patent introduces an intermediary mechanism (compliance chamber or collapsible tubing) between the venous return line and the patient that amplifies the pressure changes caused by needle disconnection. This intermediary element transforms the otherwise insignificant pressure drop into a detectable pressure wave or volume change, allowing reliable detection while maintaining system simplicity.
Solution Approach 2:
The patent changes the physical parameter being monitored from direct pressure in the return line to pressure changes in a compliance chamber or volume changes in collapsible tubing. This parameter transformation amplifies the signal from needle disconnection, making it detectable despite the low inherent pressure changes in the venous return system.
2Reliability
If moisture sensors are added to detect needle pull out, then detection accuracy improves, but device complexity increases
Solution Approach 1:
The patent extracts the detection function from separate external sensors (moisture sensors, electrical sensors) and integrates it into the existing pressure monitoring system through the compliance chamber mechanism. The disconnection detection capability is built into the blood circuit system itself, eliminating the need for additional sensing apparatus.
Solution Approach 2:
The compliance chamber serves multiple functions: it acts as a pressure equalization element during normal operation, provides a volume reservoir, and simultaneously serves as the sensing mechanism for disconnection detection. This multi-functionality eliminates the need for separate detection apparatus while maintaining detection accuracy.
3Measurement precision
If electrical conductivity sensors are used for moisture detection, then detection sensitivity improves, but false positives increase due to noisy electrical backgrounds
Solution Approach 1:
The patent replaces electrical sensing methods (electrical conductivity sensors) with a mechanical sensing approach using pressure changes in the compliance chamber. This substitution eliminates interference from noisy electrical backgrounds while maintaining high sensitivity for detecting needle disconnection events.
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 effectively detects disconnections in the venous return line, reducing the risk of fatal blood loss by triggering alarms or shutting down pumps, and continuously monitoring for deviations in signal correlation to ensure accurate detection without additional apparatus.
Implementation Method 1
a pressure transducer to generate a pulse signal
Implementation Method 2
cross-correlates it with a cardiac reference signal to detect disconnections
Data Source
AI summary
The present invention is directed to a dialysis system with a disconnection monitor for determining if a blood line connection to a patient has been disconnected. It includes a blood circuit in fluid communication with a patient and a dialysis circuit, a pressure transducer for generating a signal indicative of a pulse signal in the blood circuit, a cardiac reference signal generator for generating a signal indicative of the patient's pulse and a disconnection monitor. The disconnection monitor includes a pressure transducer data receiver for receiving the signal indicative of the pulse signal in the blood circuit, a cardiac reference signal receiver for receiving the signal indicative of the patient's pulse, and a processor for cross-correlating the signal indicative of the pulse signal in the blood circuit and the signal indicative of the patient's pulse to generate data indicative of a disconnection of the blood line connection to the patient.