Irrigation Rate Measurement Using Reservoir Weight Feedback
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Solution Overview
Problem
Existing irrigation systems during cataract surgery lack direct measurement of irrigation rate, leading to unstable fluid pressure and flow, which is critical for maintaining eye integrity during procedures like phacoemulsification.
Innovation Solution
A medical irrigation system that includes a force sensor to measure the mass change in the irrigation reservoir over time, allowing for precise calculation of irrigation rate, and a controller to adjust pump speed based on this measurement to maintain stable fluid flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a pump is used to deliver irrigation fluid during cataract surgery, then fluid delivery is enabled, but the irrigation rate is unstable and cannot be precisely controlled
Solution Approach 1:
The system employs a feedback control mechanism where a force sensor continuously measures the actual irrigation rate by detecting mass change in the reservoir, the controller processes this information, and the pump speed is adjusted in real-time to maintain the desired irrigation rate, thereby resolving the instability and measurement precision issues
Solution Approach 2:
The patent replaces direct mechanical flow measurement with a force-based measurement system. Instead of using complex mechanical flow meters, the system uses a force sensor to measure the weight of the reservoir, which indirectly and more accurately provides irrigation rate information through mass change over time
2Device complexity
If no direct measurement of irrigation rate is implemented, then the system is simpler, but fluid pressure and flow become unstable
Solution Approach 1:
The force sensor acts as an intermediary measurement device that indirectly measures irrigation rate through mass change rather than directly measuring fluid flow. This intermediary approach provides reliable pressure and flow stability information without requiring complex direct flow measurement mechanisms
3Measurement precision
If pump speed is not modulated at a given frequency, then the system operates continuously, but the signal analysis for irrigation rate becomes less accurate
Solution Approach 1:
The controller modulates the pump speed at a specific frequency (e.g., 1 Hz) to create periodic variations in the force sensor signal. This periodic modulation allows the system to distinguish the irrigation rate signal from noise through frequency-based analysis methods like lock-in amplification or Fourier transform, thereby improving measurement precision
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
Enables accurate control of irrigation rate, ensuring stable fluid pressure and flow during cataract surgery, reducing the risk of complications by maintaining optimal eye conditions.
Implementation Method 1
a force sensor configured to be coupled with the irrigation reservoir, and provide a signal responsively to a force exerted by the irrigation reservoir on the force sensor over time as irrigation fluid in the irrigation reservoir is depleted
Implementation Method 2
The controller is configured to modulate the speed of the pump responsively to a given frequency, and find the irrigation rate responsively to analyzing the signal at the given frequency
Data Source
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AI summary
In one embodiment, an irrigated medical system includes a medical tool, an irrigation line configured to fluidically connect an irrigation reservoir storing irrigation fluid to the medical tool, and provide at least some of the irrigation fluid to the medical tool, a force sensor configured to be coupled with the irrigation reservoir, and provide a signal responsively to a force exerted by the irrigation reservoir on the force sensor over time as irrigation fluid in the irrigation reservoir is depleted, and a controller configured to find an irrigation rate of the irrigation fluid flowing in the irrigation line responsively to the signal.