Ambulatory Infusion Device Pressure-Based Volume Correction
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Solution Overview
Problem
Conventional ambulatory infusion devices face challenges in accurately monitoring and correcting delivery inaccuracies, as they can only evaluate delivery accuracy at refill times, which are infrequent, and existing methods for monitoring and compensating for deviations are inefficient.
Innovation Solution
An infusion device equipped with a pressure sensor and flow restrictor, which determines actual volume delivered by sensing pressure upstream of the flow restrictor and adjusts the number of actuations in the delivery profile to correct volumetric inaccuracies, allowing for real-time compensation without a flow sensor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If delivery accuracy is evaluated only at refill times in conventional implantable infusion devices, then device complexity is reduced, but delivery accuracy monitoring and correction capability deteriorates
Solution Approach 1:
The patent introduces a pressure sensor as an intermediary component that indirectly measures delivered volume by detecting pressure changes in the reservoir. This mediator enables continuous monitoring without requiring direct flow measurement, thus improving delivery accuracy monitoring while avoiding the complexity of flow sensors or direct volume measurement systems.
Solution Approach 2:
The patent replaces mechanical flow sensing or direct volume measurement systems with a pressure-based sensing system. By using pressure changes to infer volume delivered, the system achieves continuous monitoring capability without the complexity of mechanical flow meters or direct volumetric measurement mechanisms.
2Measurement precision
If continuous delivery monitoring and automatic compensation is implemented, then delivery accuracy is improved, but device complexity increases
Solution Approach 1:
The patent implements a feedback mechanism where the pressure sensor continuously monitors the volume delivered, compares it against the intended delivery profile, and automatically adjusts future pump actuations to compensate for deviations. This closed-loop feedback system improves delivery accuracy while keeping the control logic relatively simple by only adjusting the number of pump actuations.
Solution Approach 2:
The infusion device performs self-correction by automatically detecting delivery inaccuracies and adjusting its own operation without external intervention. The controller autonomously modifies the delivery profile based on pressure sensor data, enabling the device to self-correct volumetric errors and maintain accuracy without requiring external monitoring or manual adjustment.
3Measurement precision
If pressure sensor with compliant diaphragm is used to sense volume delivered, then measurement capability is improved, but device complexity increases
Solution Approach 1:
The patent employs a compliant diaphragm made from elastomeric material that flexes in response to pressure changes within the reservoir. This flexible film serves as the sensing element, translating pressure variations into measurable deformations that correlate with volume delivered. The use of simple elastomeric materials and flexible membrane structures avoids complex sensor assemblies while maintaining measurement capability.
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 enables more efficient correction of delivery inaccuracies by adding or subtracting actuations, improving accuracy and responsiveness compared to conventional methods, ensuring precise delivery of medication over time.
Implementation Method 1
determine based on pressure sensed only upstream of the flow restrictor whether an actual volume delivered during a fluid transfer device actuation is the predetermined volume
Implementation Method 2
a pressure sensor, including a compliant diaphragm with a compliance value, associated with the fluid path
Implementation Method 3
a flow restrictor between the pressure sensor and the outlet port
Data Source
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AI summary
A method of operating an infusion device (100) that includes the steps of actuating a fluid transfer device (200), which is configured to deliver a predetermined volume during each actuation, in accordance with a delivery profile that includes a plurality of fluid transfer device actuations, determining, based on sensed pressure, whether an actual volume delivered during a fluid transfer device actuation is the predetermined volume, and adjusting the number of actuations in the delivery profile in response to the actual volume delivered differing from the predetermined volume.