Implantable Infusion Pump Valve Pulse Width Control
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Solution Overview
Problem
Implantable infusion pumps experience variable infusion rates due to temperature-dependent propellant pressure fluctuations, affecting the consistent delivery of infusate to patients, as the spring rate of the elastic element separating the infusate and propellant spaces influences the pressure at which infusate is expelled through the throttle section.
Innovation Solution
The infusion pump employs a control unit to calculate and adjust the pulse width of the valve opening based on the pressure difference across the throttle section, using pulse width modulation to compensate for fluctuations and ensure a constant infusion rate, while also considering the counter-pressure from the catheter connected to the patient.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the elastic element supports the propellant pressure with its stretching, then the infusion rate increases, but the infusion rate becomes variable and inconsistent
Solution Approach 1:
The patent applies dynamics by making the valve opening time variable rather than fixed. The control unit adjusts the pulse width (opening time) of the switching valve dynamically based on feedback from the pressure sensor and calculations of the pressure difference across the throttle section. This dynamic adjustment compensates for temperature-induced pressure fluctuations in the propellant chamber, maintaining consistent infusion rate despite changes in propellant pressure.
Solution Approach 2:
The patent implements feedback control by using a pressure sensor to continuously monitor the pressure in front of the throttle section. The control unit processes this feedback information, calculates the actual pressure difference across the throttle, and adjusts the valve opening time accordingly. This closed-loop feedback system ensures that infusion rate remains stable despite variations in propellant pressure caused by temperature changes.
2Stability of the object's composition
If the valve opens continuously to maintain infusion rate, then power consumption increases, but infusion rate stability improves
Solution Approach 1:
The patent applies periodic action by operating the switching valve in pulsed intervals rather than continuously. The valve opens for calculated pulse widths based on the required infusion rate and current pressure conditions, then closes. This periodic operation significantly reduces power consumption compared to continuous valve opening, while the control unit ensures infusion rate stability by adjusting the pulse timing and duration to compensate for pressure fluctuations.
3Measurement precision
If the pulse width is increased to compensate for pressure fluctuations, then infusion rate accuracy improves, but the system complexity increases
Solution Approach 1:
The patent replaces complex mechanical pressure regulation mechanisms with an electronic control system. Instead of using mechanical springs or adjustable valves to compensate for pressure fluctuations, the system uses a control unit that calculates required pulse widths based on pressure sensor feedback and delivers precise electronic control signals to the switching valve. This substitution reduces mechanical complexity while improving infusion rate accuracy through computational control.
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 stabilizes the infusion rate by inversely proportional correction of pulse width, enabling precise titration and bolus administration, reducing power consumption and improving delivery accuracy despite pressure variations.
Implementation Method 1
an infusate chamber (22) separated from this by an elastic element (23)... the pressure at which the infusate expelled from the infusate space enters the throttle section depends on the spring rate of the elastic element
Implementation Method 2
the pressure of the propellant, which fluctuates with the temperature of the propellant... at a temperature below 37°C reached propellant nominal pressure lying propellant actual pressure
Data Source
AI summary
Implantable infusion pump with a propellant chamber, an infusate chamber separated from the latter by an elastic element, a catheter attachment piece, and a throttle path lying between infusate chamber and catheter attachment piece, a switching valve releasing the throttle path, a first pressure sensor lying upstream from the throttle path, and a computer which controls the valve on the basis of a default value calculated for a nominal propellant pressure via an external control device, characterized in that the computer is configured to correct the default value of the control device or the resulting duty ratio as a function of the pressure actually present upstream from the throttle path.