Implantable Pressure Sensor Drift Compensation
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Solution Overview
Problem
Implanted pressure sensors face challenges with long-term accuracy due to drift in mechanical and electrical components, and the accumulation of deposits, making them unsuitable for prolonged use outside clinical environments.
Innovation Solution
A pressure sensor device with a housing and chamber featuring a flexible diaphragm that exhibits marked volumetric stiffness changes, allowing for recalibration by identifying a 'knee feature' in pressure data, and using a processor to set a zero offset based on multiple calibration instances, which can be recalibrated non-invasively by occluding flexible tubes connected to the ports.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If absolute pressure sensors are used with sealed reference chambers, then the sensors can function independently without external reference pressure application, but the sensor output drifts over time due to mechanical and electrical component changes
Solution Approach 1:
The patent performs preliminary calibration by identifying the knee pressure point during manufacturing or initial setup. This pre-established reference point compensates for future drift by providing a known reference state against which subsequent measurements can be compared, addressing the drift issue while maintaining independent operation
Solution Approach 2:
The system continuously monitors pressure readings and compares them against the stored knee pressure reference. When drift is detected, the system can recalibrate by re-identifying the knee pressure point, creating a feedback loop that maintains measurement accuracy over time without requiring external reference pressure application
2Measurement precision
If relative pressure sensors are used with external reference pressure pathways, then the sensors can maintain accurate readings with proper reference pressure, but they require catheters or tubes extending from the body making them unsuitable for long term use
Solution Approach 1:
The patent extracts the reference pressure application mechanism from the external environment and replaces it with an internally generated reference state (the knee pressure point). This eliminates the need for external catheters or tubes while maintaining the ability to establish accurate pressure measurements
Solution Approach 2:
The sensor system performs its own calibration by automatically identifying the knee pressure point using its internal components and stored reference data. This self-calibration capability eliminates dependence on external reference pressure application equipment, enabling long-term independent operation
3Duration of action of stationary object
If implantable pressure sensors are designed for long term use, then they can provide continuous monitoring, but mechanical components and electrical components drift over time causing accuracy loss
Solution Approach 1:
The system establishes a reference knee pressure point during initial calibration that serves as a stable reference for long-term operation. This preliminary reference state compensates for component drift by providing a known baseline against which changes can be measured and corrected
Solution Approach 2:
The patent implements periodic recalibration by repeatedly identifying the knee pressure point at scheduled intervals. This periodic refresh of the reference state compensates for drift that accumulates over time, maintaining accuracy throughout the implant duration
4Measurement precision
If the chamber compliance changes repeatably at fixed pressure, then recalibration can be performed by identifying the knee feature, but additional detectors for determining contact would increase device complexity
Solution Approach 1:
The patent replaces mechanical contact detection systems with an analysis of pressure data characteristics. By identifying the knee pressure point through mathematical analysis of the compliance curve, the system achieves recalibration without requiring additional mechanical detectors or sensors
Solution Approach 2:
The system uses pressure data as an intermediary to detect the contact state. Instead of directly detecting mechanical contact with additional sensors, the analysis of pressure-compliance relationships reveals the knee pressure point, serving as an indirect but accurate indicator of the contact state
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 solution provides reliable long-term pressure monitoring by compensating for drift and maintaining accuracy, enabling the sensor to be used for extended periods outside clinical settings, such as in managing hydrocephalus conditions.
Implementation Method 1
the chamber having a compliance that exhibits a marked change in volumetric stiffness repeatably at a fixed pressure
Implementation Method 2
an increasing pressure in the chamber causes increasing deflection of the flexible wall portion
Data Source
AI summary
A device for use in pressure sensing has a housing enclosing a chamber and having at least one port that communicates with the chamber. A pressure sensor receives fluid pressure from the chamber. The chamber has a compliance that exhibits a marked change in volumetric stiffness repeatably at a fixed pressure.