Electric heating – Inductive heating – With heat exchange
Patent
1998-11-05
2000-09-12
Walberg, Teresa
Electric heating
Inductive heating
With heat exchange
219628, H05B 610
Patent
active
061181110
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a fluid heater. More particularly, although not exclusively, the present invention relates to an inductive fluid heater which is particularly suitable for heating blood, plasma or other medical fluids.
BACKGROUND TO THE INVENTION
While the present discussion is directed towards apparatus for heating blood or plasma, it is to be understood that the present invention may find application in other areas involving a range of geometries, capacities and subject liquids.
Blood and blood products are generally refrigerated for the purposes of storage at approximately 1-6 degrees celcius. Consequently, infusion of such fluids at below body temperature may result in shock, hypothermia or cardiac dysfunction. Additionally, such conditions can be aggravated by the infusion of physiologically cold fluids. Accordingly, it is known, indeed required, in the art to heat such fluids prior to infusion into a patient.
The minimum acceptable infusion temperature will depend on the condition of the patient, the duration of the infusion, the volume of liquid to be administered to the patient, and the patient's blood volume prior to infusion. However, generally the infusion temperature must be at least at or near the patient's body temperature.
In addition to the temperature criteria discussed above, it is known that the combination of insufficiently heated blood with high infusion rates can result in destabilisation of the patient's thermoregulatory system. Alternatively, excessive warming may damage the red blood cells.
Accordingly, it is vital that the infusion temperature be closely monitored and controlled in response to a particular patients physiological condition and the other factors mentioned above.
To the present time it is known to warm blood, plasma or other medical fluids, using water bath warming, circulating fluid and dry heat devices. Water bath blood warmers incorporate a warm water reservoir set to maintain a constant temperature of between approximately 36 and 40 deg C, a bag, or coil of tubing is immersed in the water bath. The blood or plasma is then warmed by passing it through the bag or coil prior to infusion. A variation on this is the counter flow circulating fluid device, where two concentric tubes form a heat exchanger, the blood or plasma to be heated is passed through the inner tube, while the heated fluid from the reservoir (usually water) is pumped in the opposite direction through the outer tube. Dry heat warmers warm the blood by passing it through tubing or a bag which is located between heating plates or by passing it through a disposable cuff style bag which is wrapped around a cylindrical heating element.
Many blood warming systems known in the art are significantly limited in that high infusion rates cannot be sustained in combination with sufficient blood heating. A further difficulty with prior art blood warming devices, particularly heated water bath units, is that the blood may become contaminated by contact with the heated liquid. It is of prime importance that the blood flowing through the blood warmer be contained within a sterile environment. Reported cases of blood contamination in the context of water bath blood heaters, indicates that this type of blood warmer is particularly susceptible to such contamination effects. While repeated and thorough cleaning of the water bath may avoid contamination, such processes can be time consuming and necessitate the dismantling of the blood warming device.
Another significant limitation of prior art blood warmers is that they generally, because of their construction, do not lend themselves to mobility and ease of use. Particularly in the context of field operation or warfare environments, where conventional blood heaters may be difficult to operate properly.
As noted above, the need for potentially high flow rates coupled with the requirement that the blood temperature be elevated and regulated precisely, means that conventional blood warming systems exhibit significant limitations in functi
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Fright William Richard
McCallum Bruce Clinton
Nixon Mark Arthur
Price Nigel Brent
BBMR Limited
Pwu Jeffrey
Walberg Teresa
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