Pneumatic Infusion Pump Control with Pressure-Based Air Detection
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Solution Overview
Problem
Existing fluid flow control systems in medical devices face challenges such as wide flow rate and viscosity ranges, gas presence, varying patient pressures, and tubing configurations, leading to reliability issues, complexity, and air bubble detection inaccuracies, which affect patient safety and caregiver workflow.
Innovation Solution
A pneumatically coupled direct drive system with a linear actuator and closed-loop control, using a gas reservoir and flexible membrane to maintain precise fluid delivery, coupled with an air detection and elimination mechanism to prevent air bubbles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional fluid control mechanisms are used, then broad flow rate range and wide ranging fluid viscosity are supported, but reliability deteriorates and complexity increases
Solution Approach 1:
The patent introduces a compliance chamber as an intermediary element between the pump mechanism and the fluid delivery system. This compliance chamber absorbs pressure variations and decouples the pump's mechanical actions from the fluid flow, thereby improving reliability while maintaining adaptability across different flow rates and viscosities.
Solution Approach 2:
The system dynamically adjusts operating parameters such as pump cycle duration, stroke volume, and pressure thresholds based on detected fluid properties and flow rate requirements. This allows the pump to maintain reliable operation across a broad range of conditions without requiring complex mechanical adjustments.
2Measurement precision
If sophisticated fluid control systems are added, then flow accuracy is improved, but device complexity increases and maintenance costs rise
Solution Approach 1:
The patent implements a feedback mechanism using a pressure sensor that monitors the compliance chamber pressure and adjusts pump operation accordingly. This closed-loop control achieves accurate flow measurement and control while keeping the overall system relatively simple, as the feedback is used to modulate a basic peristaltic pump rather than requiring a completely complex pumping mechanism.
Solution Approach 2:
The system replaces complex mechanical flow measurement and control mechanisms with a simpler approach: a basic peristaltic pump combined with pressure sensing and computational control. The flow accuracy is achieved through software-based flow calculation from pressure data and pump kinematics rather than through complex mechanical flow meters or regulators.
3Object-affected harmful factors
If air detection mechanisms are added, then patient safety is improved, but false alarms increase and workflow is disrupted
Solution Approach 1:
The compliance chamber serves as an intermediary that allows air bubbles to be trapped and managed separately from the main fluid delivery path. The pressure sensor monitors the chamber for air presence, and the system can pause or adjust pumping to allow bubbles to rise and escape through designated vent paths, reducing false alarms while maintaining safety.
Solution Approach 2:
The system dynamically adjusts its air detection and response behavior based on operational context. Rather than using a fixed threshold that causes false alarms, the system adapts its detection criteria and response strategies based on flow rate, pump cycle phase, and pressure trends, thereby improving detection specificity while maintaining sensitivity to real air bubble hazards.
4Device complexity
If peristaltic pump mechanism is used, then simple tubing configuration is achieved, but harmful high fluid pressure is generated
Solution Approach 1:
The compliance chamber acts as a pressure buffer and decoupling element between the peristaltic pump and the patient line. It absorbs the high pressure pulses generated by the peristaltic rollers, smoothing out pressure variations before fluid enters the patient line, thereby maintaining simple tubing configuration while eliminating harmful pressure spikes.
Solution Approach 2:
The compliance chamber is positioned upstream in the fluid path to cushion and dampen pressure variations before they reach the patient line. This preemptive pressure smoothing prevents harmful high pressures from being transmitted to the patient while allowing the peristaltic pump to operate with its simple, effective roller mechanism.
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 ensures reliable, accurate fluid delivery with reduced complexity, minimizes air bubbles, and enhances patient safety by improving detection specificity and reducing false alarms, thus optimizing caregiver workflow.
Implementation Method 1
A pneumatic drive is provided that is coupled to the gas side chamber to effect known incremental positive or negative volume changes that in turn cause positive or negative pressure changes
Implementation Method 2
The pressure changes are communicated to the fluid side chamber through the flexible membrane
Implementation Method 3
A passive inlet check valve and an outlet check valve are provided that open in response to pressure changes in the fluid to create a unidirectional pumping action
Implementation Method 4
A pressure sensor in the gas reservoir senses the gas pressure therein
Data Source
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AI summary
A process for controlling an infusion of fluid from a fluid source to a liquid sink, comprising: a) exerting a negative pressure on a gas reservoir in fluid communication with a gas-side chamber separated from a fluid-side chamber by a flexible membrane to draw liquid from the fluid source into the fluid-side chamber through a one-way inlet valve until the fluid-side chamber fills with fluid; b) exerting a positive pressure on the gas reservoir in fluid communication with the gas-side chamber to deliver liquid in the fluid-side chamber to the liquid sink through a one-way outlet valve; c) monitoring pressure in the gas reservoir during the steps of exerting the negative pressure and exerting the positive pressure; and d) determining volumes of fluid in the fluid-side chamber from incremental changes in volume of the gas reservoir and the gas-side chamber and any connecting dead space by an ideal gas law relationship, wherein P1 V1 = P2 V2 , wherein P1 and P2 are pressures measured at two times before and after volume changes and V1 and V2 are volumes at the two times.