Therapeutic Fluid Volume Estimation Using Pressure Differential
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Solution Overview
Problem
Current implantable fluid delivery devices face challenges in accurately monitoring the volume of therapeutic fluid in their reservoirs due to human error in initial fill volume estimation and theoretical dispense rate calculations, which can lead to underdosing or overdosing of patients, and are complicated by temperature-dependent variations that require additional sensors, increasing cost and complexity.
Innovation Solution
The use of a pressure differential between the therapeutic fluid reservoir and a propellant gas chamber to estimate the volume of therapeutic fluid, canceling out temperature effects and providing a proportional measurement unaffected by temperature changes, thus simplifying the monitoring process and reducing costs and complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If temperature sensors are added to compensate for temperature-dependent variations in fluid volume measurement, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent extracts the temperature dependency from the measurement system by using a differential pressure measurement approach. Instead of measuring absolute pressure (which is temperature-dependent) and compensating with temperature sensors, the system measures only the differential pressure between two chambers, which cancels out temperature effects. This removes the need for temperature sensors while maintaining measurement accuracy.
Solution Approach 2:
The patent changes the measurement parameter from absolute pressure to differential pressure. By measuring the pressure difference between the fluid reservoir chamber and the propellant gas chamber rather than absolute pressure, the system eliminates temperature dependency in the measurement, as temperature effects are common to both chambers and thus cancel out in the differential measurement.
2Reliability
If multiple sensors are used to account for temperature variations, then reliability is improved, but manufacturing cost increases
Solution Approach 1:
The patent extracts the temperature sensitivity from the measurement system by using differential pressure measurement. This eliminates the need for additional temperature sensors, reducing manufacturing costs while maintaining reliable and accurate fluid delivery through the temperature-compensated measurement approach.
3Device complexity
If initial fill volume estimation and theoretical dispense rate calculations are used, then device complexity is reduced, but measurement precision deteriorates due to human error
Solution Approach 1:
The patent implements a self-service measurement system where the device automatically monitors its own fluid volume using differential pressure sensors. The system continuously measures the pressure difference between chambers and calculates actual fluid volume and dispense rates without requiring manual estimation or external intervention, thereby improving accuracy while maintaining simplicity.
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 method allows for accurate and reliable estimation of the therapeutic fluid volume in implantable devices, ensuring consistent and accurate delivery of medications, reducing the risk of underdosing or overdosing, and eliminating the need for additional temperature sensors, thereby enhancing the operational efficiency and safety of the devices.
Implementation Method 1
measuring a pressure within a therapeutic fluid reservoir of an implantable fluid delivery device
Implementation Method 2
measuring a pressure within a chamber of the fluid delivery device at least partially surrounding the reservoir
Implementation Method 3
estimating a volume of a therapeutic fluid within the reservoir based on a pressure differential between the measured pressure within the reservoir and the measured pressure within the propellant gas chamber
Data Source
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AI summary
A number of parameters related to the operation of a fluid delivery device are determined based on pressures within the device sensed using multiple pressure sensors. In one example, the volume of therapeutic fluid within a reservoir of a fluid delivery device is estimated based on a measured pressure differential. In another example, the rate at which a therapeutic fluid is added to or removed from the reservoir is estimated based on the measured pressure differential.