Membrane Heat Exchanger for CRRT Blood Temperature Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Continuous renal replacement therapy (CRRT) experiences significant heat loss from extracorporeally circulated blood due to diffusion or convection to surrounding fluids, leading to patient hypothermia, especially during low blood flow rates, and existing solutions struggle to efficiently heat treatment fluids without direct contact or excessive temperature increase.
Innovation Solution
A heat exchanger with multiple fluid circuits and membranes is used to recover heat from effluent fluid and transfer it to treatment fluids, maintaining blood temperature by alternatingly heating multiple secondary fluids with a primary fluid, thereby reducing heat loss from the extracorporeal circuit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If treatment fluids are stored sterile in flexible bags or rigid containers, then fluid sterility and integrity are maintained, but heating the treatment fluid becomes challenging without direct contact devices
Solution Approach 1:
The patent introduces a heat exchanger as an intermediary device that enables indirect heating of treatment fluids through thermal conduction via the blood circuit components. The blood warmer acts as a mediator between the heat source and the treatment fluid, allowing heating without direct contact between the heating element and the sterile fluid, thus maintaining sterility while achieving the desired temperature increase.
2Temperature
If treatment fluid temperature is increased to compensate for heat loss, then blood temperature can be maintained, but the temperature may exceed the safe limit of 41°C
Solution Approach 1:
The patent employs parameter changes by dynamically adjusting the heating parameters based on blood flow rate and temperature measurements. The system monitors blood temperature and flow rate, then modulates the heating power accordingly to maintain blood temperature within the safe range (37-41°C) without exceeding the maximum safe temperature limit, thus preventing thermal damage while compensating for heat loss.
3Loss of energy
If heat is recovered from effluent fluid to heat treatment fluids, then heat loss from blood is reduced, but the temperature of treatment fluids must be carefully controlled
Solution Approach 1:
The patent implements feedback control by continuously monitoring the temperature of both the effluent fluid and the treatment fluid, as well as the blood flow rate. The system uses this feedback information to dynamically adjust the heating process in the heat exchanger, ensuring that heat is recovered efficiently from the effluent while preventing the treatment fluid from exceeding the safe temperature limit of 41°C, thus balancing energy recovery with temperature control.
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 heat exchanger effectively recovers heat from effluent fluid and transfers it to treatment fluids, maintaining blood temperature across varying blood flow rates, reducing heat loss and preventing patient hypothermia while ensuring treatment fluid temperatures do not exceed 41°C.
Implementation Method 1
exchanging heat between a primary fluid and at least a first secondary fluid
Implementation Method 2
a stack of fluid plates and a membrane arranged between each of the fluid plates such that one interspace is formed between one side of a fluid plate and one side of a membrane
Data Source
Figure 1
Figure 2a
Figure 2b
AI summary
The present invention relates to a method for exchanging heat between an effluent fluid (4) and a treatment fluid (5, 7, 9) and a heat exchanger (11) for heat exchange as well as an arrangement and a kit comprising a heat exchanger. The heat exchanger comprises a first and a second fluid circuit (19, 20) extending through the heat exchanger. The heat exchanger further comprises a stack of fluid plates (12, 13, 40) and a membrane (16) arranged between each of the fluid plates (12, 13, 40) where one interspace is formed between each fluid plate and membrane. The first and the second fluid circuit (19, 20) is each constituted by a passage extending through the fluid plates and membranes and along the fluid plates and membranes in at least two interspaces (17, 18). According to the method for heat exchanging an effluent fluid (4) is passed through the first fluid circuit (19) and a treatment fluid (5, 7, 9) is passed through the second fluid circuit (20) such that the effluent fluid (4) is passed along one side of a membrane (16) and simultaneously the treatment fluid (5, 7, 9) is passed along the other side of the membrane (16). Heat is thus exchanged between the effluent fluid (4) and the treatment fluid (5, 7, 9) over the membrane (16).