Catheter Air Management System for Pressure Accuracy
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Solution Overview
Problem
Air-based pressure monitoring catheters face issues in low or negatively pressurized environments, where residual air can remain in the bladder, leading to over pressurization and inaccurate pressure readings, and existing air management systems either fail to prevent this or reduce the operating time between recharging events.
Innovation Solution
An air management system with three cylinders and sealing members, utilizing check valves to evacuate residual air to a negative pressure and reintroduce a predetermined volume of air from an evacuation cylinder, avoiding exposure to atmospheric pressure, thus maintaining accurate pressure readings and extending the operating time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of moving object
If air is injected into the bladder to maintain operating time, then the operating time between recharging events is extended, but the bladder may become over-pressurized leading to inaccurate readings
Solution Approach 1:
The system performs preliminary evacuation of the bladder to a predetermined negative pressure before injecting air. This preliminary action removes residual air that would otherwise remain in the bladder, ensuring that when air is injected, it does not cause over-pressurization. The predetermined negative pressure is established by the check valve configuration, which allows the system to control the evacuation process and prevent residual air from affecting subsequent pressure measurements.
Solution Approach 2:
The system changes the pressure parameter by establishing a predetermined negative pressure state before air injection. The check valve is configured to allow evacuation to a specific negative pressure threshold, and this pressure parameter is controlled during the air injection process. By managing the pressure parameter through these controlled changes, the system prevents over-pressurization while maintaining accurate pressure readings and extending operating time.
2Quantity of substance
If the proximal connector is open to atmospheric pressure for air replacement, then air diffusion through the bladder is compensated, but residual air remains in the bladder causing over pressurization
Solution Approach 1:
The system extracts residual air from the bladder by evacuating to a predetermined negative pressure using the check valve mechanism. Instead of leaving the proximal connector open to atmospheric pressure, the system actively removes residual air through controlled evacuation. This extraction of residual air prevents it from causing over-pressurization when new air is injected, thereby maintaining accurate pressure readings while still compensating for air diffusion.
Solution Approach 2:
The check valve acts as an intermediary mechanism that controls the interaction between the bladder and the external environment. It mediates the evacuation process by allowing air to be removed to a predetermined negative pressure while preventing uncontrolled atmospheric pressure entry. This intermediary control ensures that air replacement occurs in a controlled manner, removing residual air without causing over-pressurization.
3Ease of operation
If existing air management systems are used to vent and charge the air passage, then air management is simplified, but the bladder is over-pressurized when residual air is not adequately expressed
Solution Approach 1:
The system maintains ease of operation through the simple check valve mechanism while achieving precise pressure control by changing the pressure parameter to a predetermined negative pressure state before air injection. This parameter change enables the system to prevent over-pressurization without complicating the operation, as the check valve automatically manages the evacuation and air injection processes.
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 system effectively prevents over pressurization of the bladder, ensuring accurate pressure readings and maintaining the desired operating time between air recharging events by evacuating to a fixed negative pressure before injecting air, thereby avoiding the limitations of existing systems.
Implementation Method 1
evacuate the catheter air passage to a predetermined negative pressure
Implementation Method 2
introduce a predetermined volume of air from an evacuation cylinder into the catheter air passage
Implementation Method 3
the volume of the bladder attached to the catheter changes as pressure varies in accordance with Boyle's Law (P1V1=P2V2)
Data Source
AI summary
An air management system is described for removing and reintroducing a desired amount of air into an air passage of a pressure measurement catheter. More specifically, the system includes a cylindrical housing, check valves in communication with the housing and an moveable shaft with multiple sealing members along its length. As the shaft is moved within the housing, a piston member causes the residual air in the catheter air passage to be evacuated to a defined negative pressure. Further movement of the shaft causes a piston member to inject a predetermined volume of air into the catheter air passage. In this respect, periodic adjustments of the piston member returns the volume of air in a variable volume chamber to one that is unaffected by residual volume in the chamber and that provides an optimum volume of air to maximize the time the sensor can function accurately between recharging events.