Two-Loop Patient Heat Exchange With Cold-Plate Cassette Cooling
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Solution Overview
Problem
Current patient temperature control systems for neuro ICU patients, such as those suffering from subarachnoid hemorrhage or stroke, face inefficiencies in heat exchange due to the complexity of existing systems, particularly in the design of fluid circuits and heat transfer mechanisms.
Innovation Solution
A heat exchange system with a working fluid circuit and a refrigerant circuit, where the refrigerant circuit includes a compressor and cold plates with a serpentine passageway, and a working fluid cassette is disposed between the cold plates to facilitate efficient heat exchange between the refrigerant and the working fluid, reducing the conductive path length and backpressure, thus enhancing heat transfer efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a complex fluid circuit design is used in patient temperature control systems, then heat exchange capability can be maintained, but system complexity and inefficiency increase
Solution Approach 1:
The system divides the heat exchange function into two separate loops: a refrigerant loop (with compressor and condenser) and a working fluid loop (with pump and heat exchange catheter). This segmentation allows each loop to be optimized independently, reducing overall system complexity while improving heat exchange efficiency through dedicated functional pathways.
Solution Approach 2:
The patent extracts the heat exchange function from a single complex circuit and separates it into distinct refrigerant and working fluid circuits. The working fluid circuit is extracted to directly contact the patient (via catheter or pad) while the refrigerant circuit remains isolated, eliminating unnecessary complexity in the patient-contact pathway while maintaining effective heat transfer.
2Temperature
If multiple fluid circuits are used for heat exchange, then heat transfer capability is enhanced, but system complexity and cost increase
Solution Approach 1:
The patent introduces a working fluid (such as saline) as an intermediary between the refrigerant system and the patient. The working fluid absorbs heat from the patient's blood in the heat exchange catheter and transfers it to the refrigerant in the external heat exchanger. This intermediary approach enables effective heat transfer with only two circuits, avoiding the need for more complex multi-circuit arrangements.
Solution Approach 2:
The patent extracts the patient-contact function to a separate working fluid circuit, allowing the refrigerant circuit to be simplified. The working fluid circuit handles all patient interaction while the refrigerant circuit provides purely thermal management, reducing the number of circuits needed compared to integrated designs.
3Speed
If intravascular catheter method is used for temperature control, then rapid temperature change is achieved, but risk of complications increases
Solution Approach 1:
The working fluid acts as a mediator between the refrigerant system and the patient's bloodstream. In the intravascular approach, the working fluid directly contacts the blood through the catheter, enabling rapid heat transfer while the refrigerant remains isolated in the external circuit, minimizing direct exposure risks.
Solution Approach 2:
The patent extracts the potentially harmful refrigerant from the patient-contact pathway and confines it to the external circuit. Only the biocompatible working fluid contacts the patient's blood, separating the rapid heat transfer function (intravascular catheter) from the harmful agent (refrigerant), thus achieving fast temperature control with reduced complications.
4Object-affected harmful factors
If external heat exchange pad method is used for temperature control, then safety is improved, but heat transfer efficiency decreases
Solution Approach 1:
The working fluid serves as an efficient heat transfer intermediary between the external pad and the patient's body. The refrigerant cools the working fluid in the external heat exchanger, and the cooled working fluid then transfers heat through the heat exchange pad to the patient, achieving both safety and efficiency through this mediated heat transfer pathway.
Solution Approach 2:
The patent ensures continuous heat transfer through the external pad by maintaining steady circulation of the working fluid through the heat exchange catheter and external heat exchanger. The pump continuously circulates the working fluid, eliminating interruptions and maintaining efficient heat transfer throughout the treatment period, thus achieving both safety and sustained effectiveness.
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 achieves improved heat transfer efficiency by minimizing the conductive path length and reducing backpressure, leading to a more effective and cost-efficient patient temperature control, suitable for both intravascular and external applications.
Implementation Method 1
a refrigerant circuit configured for circulating refrigerant between a compressor and sides of cold plates between which a working fluid cassette is disposable
Implementation Method 2
a refrigerant circuit configured for circulating refrigerant between a compressor and sides of cold plates
Implementation Method 3
At least one cold plate may be formed with a serpentine passageway through which the refrigerant flows
Data Source
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AI summary
A heat exchange system for exchanging heat with working fluid from an intravascular heat exchange catheter (12) or an external heat exchange pad (18) includes a working fluid that circulates between the catheter (12) or pad (18) and a fluid cassette (50), and a refrigerant that flows against the outer sides of cold plates (30, 32) between which the cassette (50) is disposed.