Impedance-Based Needle Disconnection Detection in Dialysis Circuits
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Solution Overview
Problem
Current patient access disconnection detection systems in medical treatments, such as dialysis, face challenges in quickly and accurately detecting needle dislodgment to minimize blood loss, while avoiding false triggers and being cost-effective for existing machines.
Innovation Solution
The system employs an electrical circuit with contacts in the fluid circuit to inject a signal and measure impedance changes, using techniques like creating a virtual open circuit to prevent current flow through the blood pump and placing contacts close to the patient to enhance sensitivity and specificity of needle dislodgment detection, and includes a wireless communication between a detector and protector module to clamp tubing and shut down the blood pump.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If visual monitoring is used to detect needle dislodgment, then the system is simple and low cost, but detection sensitivity and response time are insufficient
Solution Approach 1:
The patent replaces visual monitoring (mechanical observation) with an electrical impedance detection system. Electrical contacts are placed in fluid communication with the blood circuit to continuously monitor impedance changes that occur when a needle dislodges, providing automatic detection without requiring visual inspection by medical staff.
Solution Approach 2:
The patent introduces an electrical impedance measurement system as an intermediary between the needle and the detection mechanism. The electrical contacts serve as intermediaries that detect changes in electrical impedance caused by needle dislodgment, translating a mechanical event into an electrical signal for detection.
2Reliability
If electrical impedance detection is implemented, then detection sensitivity and response time improve, but system complexity and cost increase
Solution Approach 1:
The patent makes the blood pump serve multiple functions: it not only pumps blood through the dialysis circuit but also acts as part of the detection system. The electrical contacts are positioned to utilize the existing blood pump infrastructure, allowing the pump to participate in both its primary function and the impedance detection function.
Solution Approach 2:
The patent combines the impedance detection function with the existing blood pump and tubing system. By placing electrical contacts within the fluid circuit and utilizing the blood pump's electrical characteristics, the system merges detection capabilities with existing components rather than adding completely separate systems.
3Measurement precision
If electrical contacts are placed in the fluid circuit, then detection precision improves, but risk of false triggers from current flow through blood pump increases
Solution Approach 1:
The patent extracts the harmful current flow path from the detection circuit by removing the blood pump from the electrical measurement loop. The electrical contacts are positioned to measure impedance through the blood and needle without requiring current to flow through the blood pump, thereby eliminating the source of false triggers while maintaining detection precision.
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 approach enables immediate, sensitive, and specific detection of needle dislodgment, minimizing blood loss and reducing costs by integrating with existing machines, and effectively operating in home hemodialysis settings.
Implementation Method 1
an electrical circuit with a number of electrical contacts in fluid contact and electrical communication with the fluid circuit allowing a direct conductivity measurement to be used
Data Source
Figure 1A
Figure 1B
Figure 1C
AI summary
An access disconnection system is described. The system comprises: an extracorporeal circuit; arterial and venous contacts (163b, 163a) provided in the extracorporeal circuit; arterial and venous patient access apparatuses; a signal source (160) communicating with at least one of the arterial and venous contacts and configured to generate a signal within fluid flowing through the extracorporeal circuit; and a sensing apparatus (168) configured to sense a first portion of the signal indicative of a first impedance produced by fluid flowing through the extracorporeal circuit. At least one of the arterial and venous contacts is placed close enough to a respective arterial and venous patient access apparatus such that a second portion of the signal indicative of a second impedance produced by fluid flowing through a parallel ground loop can be ignored.