Blood warmer

A cartridge for reception into a receiver assembly for changing the temperature of an infusible liquid from a first temperature to a second predetermined temperature, said receiver assembly including a thermoelectric heat pump means for transferring heat to and absorbing heat from said cartridge, said heat pump being deflectable from a first position to a second position, said cartridge having an upper end and a lower end and comprising:

• a first wall formed of material having relatively good heat transfer properties;
• a second wall joined to said first wall and defining therewith a liquid passageway, said second wall being formed of material having relatively poor heat transfer properties;
• a liquid inlet communicating with said passageway adjacent said lower end and extending from said second wall away from said first wall;
• a liquid outlet communicating with said passageway adjacent said upper end;
• and
• deflection means for urging said heat pump means toward said second position in response to incipient insertion of said cartridge into said receiver assembly.

A disposable liquid cartridge for use with an apparatus for changing infusible liquids from a first temperature to a second temperature, said apparatus including a thermoelectric heat pump means for transferring heat to and absorbing heat from said cartridge, said cartridge forming a wide, thin, enclosed volume defining a flow path for an infusible liquid flowing therethrough, said cartridge comprising:

• a liquid inlet communicating with said enclosed volume and disposed toward the bottom of said cartridge;
• a liquid outlet communicating with said enclosed volume and disposed toward the top of said cartridge;
• a thin first cartridge plate;
• a second cartridge plate joined to said first plate to define said volume;
• and
• means for purging air bubbles from said liquid as said cartridge is filled with liquid.

An apparatus for varying the temperature of a transfusable liquid from the first temperature to a selected second desired temperature said apparatus comprising:

• a cartridge forming an enclosed volume for confining said liquid, said cartridge having a liquid inlet and liquid outlet, said cartridge having at least one wall formed of a material having good heat transfer properties;
• at least one thermoelectric heat pumping means for transferring heat to and absorbing heat from said cartridge, said heat pumping means being disposed in intimate thermal contact with at least one of said walls formed of a material having good heat transfer properties for changing the temperature of the transfusable liquid exiting the cartridge;
• temperature sensing means for determining the temperature of the liquid near said outlet;
• and
• thermal control means for regulating said thermoelectric heat pumping means in response to the liquid outlet temperature and maintaining the transfusable liquid at said second temperature.

A method for warming an infusible liquid from a first variable temperature to a second temperature comprising:

• providing a liquid cartridge having a liquid inlet and liquid outlet contiguous with a wide thin enclosed volume of relatively short liquid path length for confining an infusible liquid flowing therethrough, said cartridge having at least one thin high surface area wall made from a material with good thermal transfer properties;
• providing an infusible liquid flowing into a liquid cartridge inlet;
• providing heat to the liquid in the enclosed volume from at least one high surface area wall made of a material with good thermal transfer properties;
• providing heat to at least one high surface area wall at a rate proportional to the amount of heat absorbed by said liquid at said wall from at least one thermoelectric heat pumping means for transferring heat to and absorbing heat from said cartridge;
• sensing the temperature of the liquid near said liquid outlet;
• activating said thermoelectric heat pumping means when the sensed temperature is a predetermined temperature less than the second temperature;
• deactivating said thermoelectric heat pumping means when the sensed temperature is equal to the desired temperature, said deactivation of said thermoelectric heat pumping means causing substantially instantaneous thermal equilibrium between the cold and hot sides of said thermoelectric heat pumping means and drawing a small amount of heat from the liquid cartridge;
• providing a conduit attached to the liquid outlet for receiving the warmed blood, whereby the temperature of the blood at the liquid outlet is maintained at substantially the desired temperature.