Nebulizer End-of-Dose Detection Using Drive Current Slope

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Solution Overview

Problem

Current nebulizer technologies face challenges in accurately predicting the end of dose, leading to inefficiencies and potential misuse or waste of medication, particularly in devices with over-moulded actuators that restrict liquid detection.

Innovation Solution

A nebulizer system with a controller that measures aperture plate drive current at multiple frequencies, determines minimum and maximum rate of change values, and calculates an indicator for end-of-dose using these parameters, improving prediction accuracy by utilizing a ratio and scaling factor, and optionally initiating a short scan to detect threshold changes in drive current.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If a single threshold value for drive current is used to detect end of dose, then the detection method is simple, but the accuracy of end-of-dose prediction is insufficient

Engineering Contradiction:

Improveend-of-dose detection accuracyVSAvoiddetection algorithm complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent applies parameter changes by transitioning from a single threshold parameter to multiple parameters including minimum drive current value, maximum rate of change of drive current, and their ratio. This multi-parameter approach significantly improves end-of-dose detection accuracy while maintaining manageable algorithm complexity through systematic processing of these parameters.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent replaces simple threshold-based mechanical detection with an algorithmic system that processes multiple electrical parameters. The controller executes algorithms that calculate minimum values, maximum rates of change, and ratios, substituting straightforward threshold comparison with a more sophisticated but computationally efficient electronic detection system.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Reliability

If drive current threshold is set to detect end of dose, then detection is achieved, but false predictions occur due to variability in aperture plate characteristics

Engineering Contradiction:

Improveend-of-dose prediction reliabilityVSAvoiddetection accuracy

Core Design Contradiction:

ReliabilityVSMeasurement precision

Solution Approach 1:

The patent implements feedback by continuously monitoring drive current and comparing it against dynamically calculated thresholds based on minimum values and maximum rates of change. The system uses the ratio of these parameters as a feedback mechanism to adjust detection decisions, significantly improving reliability by accounting for variations in aperture plate characteristics while maintaining high detection precision.

Inventive Principle:

Principle #23Feedback

3Ease of manufacture

If over-moulded actuators are used to enclose the nebulizer, then device integration is improved, but liquid detection capability is restricted

Engineering Contradiction:

Improvedevice integrationVSAvoidliquid presence detection

Core Design Contradiction:

Ease of manufactureVSDifficulty of detecting and measuring

Solution Approach 1:

The patent replaces mechanical liquid detection methods (which would require open access to the aperture plate) with an electrical detection system that measures drive current parameters. This substitution allows the actuator to be fully enclosed in over-moulded construction while maintaining liquid detection capability through electrical measurements of the aperture plate's drive current characteristics.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 a 75% improvement in distinguishing between wet and dry states, ensuring accurate and timely detection of end of dose, extending the nebulizer's operational life and reducing dosing time for patients, while enhancing battery efficiency in portable devices.

Implementation Method 1

measure aperture plate drive current at each of a plurality of measuring points in a scan, each measuring point having a drive frequency

Methodology Applied

Scientific EffectElectrical impedance measurement: Electrical Resistance

Data Source

PatentUS11998678B2End-of-dose detection in nebulizers

Publication Date: 2024.06.04 STAMFORD DEVICES LTD

AI summary

A digital processor of a nebulizer controller controls and monitors drive current (I) applied to an aperture plate. The drive current is detected as a series of discrete values at each of multiple measuring points, each having a particular drive frequency The processor in real time calculates a slope or rate of change of drive current with frequency and additionally determines a minimum value for drive current leading up to the peak value. The processor uses both the value of the minimum drive current during the scan and also the maximum slope value to achieve reliable prediction of end of dose, when the aperture plate becomes dry.