Impedance-Based Access Disconnect Detection for Extracorporeal Therapy
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Solution Overview
Problem
Current methods for detecting venous needle dislodgement during extracorporeal blood treatments are inadequate, particularly in situations where ambient light is absent or patients are covered, leading to potential life-threatening blood accumulation.
Innovation Solution
A system that uses electrical properties to detect access disconnection by measuring impedance changes between arterial and venous lines, employing a controller and electrodes to inject a constant electric current and sense voltage changes, with a computer program adjusting alert criteria based on readings to quickly identify needle dislodgement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If photosensor-based detection is used, then needle dislodgement can be detected, but detection fails in low-light conditions or when patients are covered
Solution Approach 1:
The patent replaces optical detection (photosensor-based) with electrical impedance detection. Instead of using light to detect needle position, the system uses electrical properties of blood to detect access disconnection, eliminating dependence on ambient light conditions and making the detection reliable in both clinical and home settings.
2Device complexity
If fixed alert criteria are used, then detection is simple, but false alarms occur due to blood property changes during treatment
Solution Approach 1:
The patent implements dynamic alert criteria that automatically adjust during treatment based on measured blood properties. The system continuously monitors electrical impedance and adapts the disconnect detection threshold to account for changes in blood conductivity, hematocrit, and temperature, preventing false alarms while maintaining sensitivity to actual disconnections.
Solution Approach 2:
The system uses feedback from continuous impedance measurements to adjust alert criteria in real-time. By monitoring blood electrical properties throughout the treatment and comparing against baseline values, the system dynamically recalibrates the disconnect detection threshold, ensuring accurate detection despite physiological changes.
3Reliability
If venous needle dislodgement detection is implemented, then patient safety is improved, but blood may accumulate near patient before detection
Solution Approach 1:
The patent performs preliminary baseline measurements of blood electrical impedance before treatment begins and during initial phases. By establishing reference values early in the treatment when blood properties are most stable, the system creates a head start in detecting deviations that indicate needle dislodgement, reducing the time lag before alarm activation.
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 provides immediate and sensitive detection of needle dislodgement, minimizing blood loss and ensuring patient safety by automatically shutting off the blood pump and alerting caregivers, even in low-light conditions or home settings.
Implementation Method 1
measuring impedance changes between arterial and venous lines, employing a controller and electrodes to inject a constant electric current and sense voltage changes
Data Source
AI summary
An extracorporeal therapy machine removes blood from a patient in order to treat the blood and then return the blood to the patient. If the removal needle or the return needle is dislodged and blood is not returned, the patient may suffer a great blood loss. A new technique for detecting dislodgement uses the normal, initial values of a plurality of parameters of the patient and the therapy machine to set criteria or limits for an alarm, and then adjusts those criteria based on the later values of those parameters as they change during one therapy or over several therapies experienced by the patient.