US 4,707,587 AGranted

Blood warming method and apparatus using gaseous heat exchange medium

OwnerGordon M. Greenblattinventor

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Abstract

A blood warming device circulates air as a heating medium through a heater element and heat exchangers to transfer heat from the air to chilled blood being forced through the channels in a disposable warming jacket. A temperature sensor is disposed near an outlet of the blood warming jacket. An electronic control circuit operates on the signals produced by the temperature sensor to produce a cutoff signal that immediately stops the flow of heated air through the heat exchanger if the sensed blood temperature exceeds a predetermined level. The low heat capacity of the air is sufficiently low that no overheating of blood in the blood warming jacket occurs even if the blood flow is interrupted so that blood remains stationary in the blood warming jacket. The disposable warming jacket inclues a plurality of parallel blood paths, resulting in a high flow rate of heated blood. Blood output from one section of a warming jacket can be input to the inlet of another section to further raise the temperature thereof.

Claims32

Dependent claims

A method of warming chilled fluid forced out of a pressure infusion device, the method comprising the steps of:

(a) inserting a flexible disposable fluid warming jacket into a fluid warming device, the fluid warming jacket having an inlet and an outlet and a plurality of thin elongated fluid conducting paths leading from the inlet to the outlet, the fluid warming device having a narrow, deep elongated recess for receiving the fluid arming jacket, the recess being bounded by a pair of thermally conductive opposed major walls, each thermally conductive wall having a heat exchanger in thermal contact therewith;
(b) guiding air from an outlet of an electric blower through an electric heating element to heat the air to a predetermined temperature;
(c) guiding the heated air from the heating element through the heat exchangers to heat the major walls;
(d) forcing chilled fluid from the pressure infusion device into the inlet of the fluid warming jacket, thereby causing the chilled fluid to be forced into the plurality of fluid conducting paths of the fluid warming jacket and causing the fluid warming paths to expand, thereby causing the fluid warming jacket to tightly contact the heated major walls of the recess, whereby fluid moving through the fluid conducting paths is heated;
(e) guiding air from a downstream portion of the heat exhangers to an inlet of the electric blower to thereby recycle and reheat that air;
(f) sensing the temperature of the fluid near the outlet of the fluid warming jacket;
and
(g) immediately controlling the temperature of the heating element in response to the sensed fluid temperature to rapidly correct any overtemperature condition in the fluid,
whereby the low heat capacity of the guided, heated air is so low that corrections in the temperature of the heating element lead to immediate corresponding corrections in the temperature of the air and prevent temperature overshoot of the fluid as the fluid absorbs heat from the air during the temperature correction so that the temperature of the guided air can be be increased to allow increased flow of the fluid without danger of overheating portions of the fluid.

6 more elements

A fluid warming device for warming chilled fluid forced out of a pressure infusion device, the fluid warming device comprising in combination:

(a) a flexible disposable fluid warming jacket having an inlet and an outlet and a plurality of thin elongated fluid conducting paths leading from the inlet to the outlet;
(b) a narrow, deep elongated recess for recess for receiving the fluid warming jacket, the recess being bounded by a pair of thermally conductive opposed major walls;
(c) heat exchanging means for transferring heat to the major walls;
(d) an electric blower;
(e) an electric heating element;
(f) means for guiding air from an outlet of the electric blower through the heating element and for guiding the heated air through the heat exchanging means;
(g) means for guiding chilled fluid from the pressure infusion device into the inlet of the fluid warming jacket, thereby causing the chilled fluid to be forced into the plurality of fluid conducting paths of the fluid warming jacket and causing the fluid warming paths to expand, thereby causing the fluid warming jacket to tightly contact the heated major walls of the recess, whereby fluid moving through the fluid conducting paths is heated;
(h) means for sensing the temperature of fluid near the outlet of the fluid warming jacket;
and
(i) means for immediately controlling the temperature of the heating element in response to the sensed fluid temperature to rapidly correct any overtemperature condition in the blood,
whereby the low heat capacity of the guided, heated air is so low that corrections in the temperature of the heating element lead too immediate corresponding corrections in the temperature of the air and prevent temperature overshoot of the fluid as the fluid absorbs heat from the air during the temperature correction so that the temperature of the guided air can be increased to allow increased flow of the fluid without danger of overheating portions of the fluid.

8 more elements

Dependencies are inferred from the claim text.