Buffer Cartridge System for pH Stabilization
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Solution Overview
Problem
Conventional methods for storing and delivering sodium bicarbonate buffering solutions in glass vials with pierceable rubber caps lead to pH instability and carbon dioxide loss due to reduced pressure and agitation during solution transfer, which can alter the pH of the solution undesirably.
Innovation Solution
A buffer cartridge system with a transfer needle and exhaust needle is used to transfer a predetermined volume of buffer solution into an anesthetic cartridge while expelling an equal volume of anesthetic, maintaining pressure to inhibit carbon dioxide vaporization and stabilize the pH, using a compression member like a spring to apply sufficient pressure to maintain the buffer solution's stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the buffer solution is drawn up into a syringe from a glass vial, then the solution can be delivered to the patient, but the reduced pressure and agitation during transfer cause CO2 to leave the solution and create bubbles, altering the pH
Solution Approach 1:
The system divides the buffer storage into two separate cartridges: a buffer cartridge containing the sodium bicarbonate solution and an anesthetic cartridge containing the anesthetic. This segmentation allows each cartridge to be optimized for its specific function - the buffer cartridge maintains stable pH through pressurization while the anesthetic cartridge delivers the medication, resolving the contradiction between deliverability and composition stability.
Solution Approach 2:
A transfer needle acts as an intermediary device to move the buffer solution from the buffer cartridge to the anesthetic cartridge without requiring direct syringe intervention. This intermediary mechanism maintains pressure throughout the transfer process, preventing CO2 escape and pH alteration while enabling solution delivery.
2Ease of operation
If a glass vial with pierceable rubber cap is used to store buffer solution, then the practitioner can withdraw the solution with a syringe, but significant headspace is required which creates vacuum during drawing and allows CO2 loss
Solution Approach 1:
The invention extracts the headspace from the buffer storage system by filling the buffer cartridge completely with buffer solution, eliminating the gas-filled region. This prevents CO2 loss while maintaining withdrawability through the needle penetration mechanism, resolving the contradiction between operational ease and substance retention.
Solution Approach 2:
The system changes the pressure parameter within the buffer cartridge by applying sufficient pressure to inhibit CO2 vaporization. This parameter change allows the buffer to be stored without headspace while preventing CO2 loss, enabling both easy withdrawal and substance retention.
3Ease of operation
If conventional cartridges are used to hold anesthetic, then the anesthetic can be delivered through a needle, but there is no provision for maintaining volatile CO2 in solution or for displacing anesthetic as buffer is introduced
Solution Approach 1:
The system segments the delivery mechanism into two specialized cartridges: one for buffer and one for anesthetic. The anesthetic cartridge is modified to include an exhaust needle that allows displaced anesthetic to escape during buffer introduction, maintaining volume equilibrium and preventing overpressurization while preserving anesthetic deliverability.
Solution Approach 2:
The transfer needle serves as an intermediary that introduces buffer into the anesthetic cartridge while the exhaust needle simultaneously removes displaced anesthetic. This dual-needle intermediary system maintains composition stability during mixing while preserving the ability to deliver the final anesthetic solution.
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 method effectively maintains the stability of the buffer solution's pH and minimizes carbon dioxide loss, ensuring predictable and stable chemical composition for optimal anesthetic effectiveness and reduced injection pain.
Implementation Method 1
applying sufficient pressure to the buffer solution to inhibit vaporization of a volatile species, such as vaporization and loss of carbon dioxide from bicarbonate buffers
Implementation Method 2
bicarbonate ions are in equilibrium as represented by the following expression: 2HCO3- ↔ CO2↑+CO32-+H2O
Data Source
AI summary
A device for delivering buffer solution into a buffer cartridge comprises a needle assembly and a pusher. The septa of a buffer cartridge and an anesthetic cartridge are advanced onto a transfer needle, and the pusher advances a plunger into the buffer cartridge to deliver buffer through the transfer needle into the anesthetic cartridge. A separate exhaust needle allows excess anesthetic from the anesthetic cartridge to be exhausted. A compression member is usually provided to maintain a force against the plunger on the buffer cartridge to pressurize and stabilize the contents during sterilization and/or storage.