Peritoneal Dialysis Volume Measurement Using Ideal Gas Pressure Sensing
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Solution Overview
Problem
Existing automated peritoneal dialysis systems require complex and costly disposable sets, consuming significant space and time for daily setup, and lack precise volumetric accuracy and pressure control.
Innovation Solution
An automated peritoneal dialysis machine using a bellows pump with a reusable and disposable portion, combined with pressure sensors and the ideal gas law for volumetric accuracy, measures incremental fluid volumes through flexible chambers and domes to ensure precise fluid delivery and disposal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional automated peritoneal dialysis systems use complex disposable sets, then reliability is improved, but device complexity and cost increase significantly
Solution Approach 1:
The disposable set is segmented into distinct functional modules: a bellows pump for fluid delivery, flexible chambers for volume measurement, and a dome with pressure sensor for pressure control. Each module performs a specific function independently, simplifying the overall system while maintaining reliability through modular design
Solution Approach 2:
The system uses pneumatic pressure measurement through the dome and pressure sensor to control fluid delivery. The bellows pump utilizes mechanical expansion and contraction driven by pressure differentials to deliver precise fluid volumes, replacing complex electronic pumping mechanisms with simpler pneumatic-hydraulic principles
2Reliability
If traditional systems use large disposable sets, then all necessary components are included, but space consumption and setup time increase
Solution Approach 1:
The flexible measurement chambers are nested within the rigid dome structure. The bellows pump is integrated into the disposable set housing, with fluid pathways routed through compact channels. This nesting arrangement minimizes the overall footprint of the disposable set while including all necessary components
Solution Approach 2:
Flexible chambers made of thin film materials are used for volume measurement instead of rigid containers. These flexible membranes can be collapsed when empty and expanded during use, dramatically reducing storage space requirements while maintaining measurement accuracy during operation
3Measurement precision
If volumetric accuracy is improved through complex measurement systems, then fluid delivery precision increases, but device complexity and cost increase
Solution Approach 1:
Complex electronic volumetric measurement systems are replaced with a simple mechanical displacement method. The bellows pump's known geometry and stroke volume provide inherent volumetric accuracy, eliminating the need for complex flow meters or electronic sensors while maintaining precise fluid delivery
Solution Approach 2:
The system uses its own operational parameters (pressure sensor readings and bellows pump stroke information) to determine fluid volume delivered. The measurement is derived from the system's normal operation rather than requiring separate measurement instruments, simplifying the overall system while maintaining accuracy
4Measurement precision
If pressure control precision is improved, then fluid delivery accuracy increases, but setup time and operational complexity increase
Solution Approach 1:
The pressure sensor provides real-time feedback on the pressure within the dome during fluid delivery. The control system uses this feedback to automatically adjust the bellows pump operation to maintain the desired pressure, achieving precise pressure control without requiring manual calibration or complex setup procedures
Solution Approach 2:
The pressure control system is self-regulating through the feedback mechanism, automatically maintaining the setpoint pressure during operation. This eliminates the need for manual pressure adjustments or complex setup procedures, reducing both setup time and operational complexity while maintaining 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
The system achieves precise pressure control and volumetric accuracy, reduces setup time and cost, and operates with a simple, compact disposable set, enhancing the efficiency and usability of home dialysis treatments.
Implementation Method 1
the first and second pressure readings are used with the ideal gas law to determine an amount of air in the dome
Implementation Method 2
The expandable chamber is expanded into the dome, displacing air within the dome
Data Source
AI summary
A peritoneal dialysis system includes a control unit is programmed to cause (i) a pressure sensor to take a first pressure reading of a reference chamber with a pneumatic valve closed, (ii) a pump actuator to pump fresh dialysis fluid through a fresh dialysis fluid pathway into a patient line expandable chamber, expanding the expandable chamber into a dome, (iii) the pneumatic valve to open, allowing the reference chamber to communicate pneumatically with any air in the dome, (iv) the pressure sensor to take a second pressure reading with the pneumatic valve open, (v) the first and second pressure readings to be used with the ideal gas law to determine an amount of air in the dome, and (vi) the amount of air in the dome and a known volume of the dome to be used to determine an amount of fresh dialysis fluid delivered into the expandable chamber.