Abstract:
The present invention is directed to a fluid warming container (a.k.a., cassette) having an integrated heating element attached to the container, not the warming device as conventionally done. The heating element provides thermal energy to the fluid contained in the container. The fluid contained in the container is designed to be injected and/or delivered, eventually and normally immediately, into a patient.

Description:
FIELD OF THE INVENTION 
     The present invention relates to an apparatus for warming blood and other fluids to a desired temperature prior to introduction of the fluid into a patient. 
     BACKGROUND OF THE INVENTION 
     Gaymar Industries, Inc., the assignee of this application, is the assignee of U.S. Pat. No. 5,875,282 (hereinafter referred to as “the &#39;282 patent”). The &#39;282 patent is directed to an apparatus for warming blood and other fluids to a desired temperature prior to introduction into a patient. The blood and other fluids flow through a pathway contained by a bag. That pathway provides high flow performance and normally provides uniform, gradual and energy efficient blood warming. The bag has a pair of guide rails and a warming device has a pair of corresponding apertures that work in conjunction to ensure the bag is properly inserted into the warming device. 
     The warming device contains at least one, and normally a pair of opposed, identical heater elements, a receptive slot down the middle in a horizontal plane with the possibility of two guide slots, one on each side of the receptive-slot. The optional guide rails align the bag so it can be spaced and located precisely between the two heater elements. The pair of guide rails, integrated into the sides of the bag, is parallel to one another providing sufficient rigidity for easy insertion of the bag, and being sized to allow easy insertion in only the correct orientation. The blood warmer preferably incorporates a microprocessor for precise control of the electric current provided to the heater. Fluid temperature can be measured by contact of a RTD sensor with a thin dielectric surface layer in contact with the bag and located proximal to the fluid outlet and within the heater elements. By monitoring the temperature of the fluid at the outlet of the bag, the temperature controller can compute and provide a visual display of the fluid temperature. In one embodiment, the sensed output temperature is an input parameter to the controller of the heater elements. The device efficiently warms the fluid to about 37.5° C. for anticipated input to a human and, is simultaneously designed to prevent the fluid from exceeding 42° C. 
     The apparatus disclosed in the &#39;282 patent is a very good fluid warming device but the applicants continue to try to improve it. One improvement is directed to making sure the heating elements are in constant contact with the cassette to ensure the fluid in the fluid path is uniformly heated to the desired temperature. Applicants are unaware of fluid warming apparatuses for fluids designed to enter a patient that are materially distinct from the apparatus disclosed in the &#39;282 patent, except for the following invention. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to a fluid warming container (a.k.a., cassette) having an integrated heating element attached to the container, not the warming device as conventionally done. The heating element provides thermal energy to the fluid contained in the container. The fluid contained in the container is designed to be injected and/or delivered, eventually and normally immediately, into a patient. 
     These and other objects are solved by the present invention. The invention will be understood more fully, while still further objects and advantages will become apparent, in connection with the following detailed description of a preferred embodiment thereof, illustrated in the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a top plan view of a fluid bag of the present invention; 
         FIG. 2  is cross-sectional view of a fluid bag in a warmer device of the present invention; 
         FIGS. 3   a–e  are top plan views or cross-sectional views of various embodiments of the fluid bag of the present invention; 
         FIG. 4  is an alternative embodiment of  FIG. 2 ; 
         FIGS. 5   a  and  b ;  6   a  and  b ; and  7   a  and  b  illustrate embodiments in which to apply a force to the fluid contained in the fluid bag; 
         FIG. 8  is an alternative embodiment of  FIG. 1 . 
         FIG. 9  is an alternative embodiment of  FIG. 1 . 
         FIG. 10  is an alternative embodiment of  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention is directed to a heating cassette  10  and alternatively, the heating cassette  10  with fluid compression capabilities. The cassette  10 , as shown in  FIG. 1 , is at least one sheet of fluid impermeable material  12  having a fluid inlet  14 , a fluid path  16 , and a fluid outlet  18 . The cassette  10  is designed to be inserted into a slot  20  of the warmer device  22 , as illustrated in  FIG. 2 . 
     In one embodiment, the warmer device  22  is identical or similar to the warmer device disclosed in the &#39;282 patent, except for the heater elements and the position of the temperature sensor. Accordingly, we hereby incorporate by reference the entire disclosure of the &#39;282 patent in this application, minus the positions of the heater element and the temperature sensor. 
     A main difference between the warmer device  22  of the present invention and the warmer device of the &#39;282 patent lies in the position of a heater element  30 . In the &#39;282 patent, the heater elements were the upper and/or lower boundary of the slot. The heater element was positioned to contact the exterior surface of the cassette and transfer the heat generated by the heater element to the fluid in the fluid path of the cassette. 
     The present invention has the heater element  30  as an integrated component of the cassette  10 . The heater element  30 , in one embodiment, is any conductive material that generates resistance when an electrical current passes through it, and therefore generates heat that is transferred to the fluid in the fluid path  16 . Moreover, the conductive material  30  must be capable of being integrated into, within and/or onto the cassette  10  by various methods, including and not limited to printing, embossing, heat sealing, adhesion, polymerizing, or lithographing. These methods are known to those of ordinary skill in the art, and have been used extensively in the field of flexible conductive circuits. Gaymar is unaware of using such technology for warming fluids designed to enter a patient. 
     The fluid impermeable material  12  must allow thermal energy to transfer into the fluid path for the first embodiment wherein the conductive element is within and/or on the material  12 . Alternatively, the material  12  must allow an electrical current to pass through at least a portion of the fluid impermeable material  12  if the conductive element  30  is in the interior of the material  12 . An example of, and not limited to such, the fluid impermeable material is thin (like four thousandth of an inch (0.004″) thick) polyethylene. The fluid impermeable, thermal energy transfer material  12  may be a single sheet folded over  23  and sealed, by various known methods (heat welding, adhesive, sonic welding), at predetermined portions  24  along the edges and within the interior section to form the fluid path  16  as shown in  FIG. 1 . Alternatively, the material  12  may comprise at least a first sheet  12   a  and a second sheet  12   b , as shown in  FIG. 2 , that are sealed, by various known methods, at predetermined portions along the edges and within the interior section to form the fluid path  16 . In any case, the material  12  is integrated with a conductive material  30 . 
     The heating element  30  can overlie the entire exterior surface  17  of the cassette  10  as shown in  FIGS. 3   a  and  e , the entire exterior surface  17  of one side of the cassette as shown in  FIG. 3   b , the entire exterior surface  17  of the fluid path  16  on one or both sides of the cassette  10  as illustrated in  FIGS. 3   c  and  3   a  and  b , predetermined portions of exterior surface  17  of the fluid path  16  on one or both sides of the cassette as illustrated in  FIGS. 1 and 3   a  and  b , or combinations thereof. 
     The heating element  30  can be incorporated into the fluid impermeable material. Such conductive fluid impermeable materials are known to those of ordinary skill in the art. Examples of such conductive films can be found at, and not limited from such location, Bennett and Bennett in Springfield, Ohio. For example, a conductive polyethylene bag can be made from a single layer of carbon-loaded polyethylene. The conductivity does not depend on humidity. It is non-abrading, does not contaminate components or fluids it comes in contact with and is groundable. 
     The heating element  30  can also be enclosed between the exterior surface  17  of the fluid path  16  and a third sheet  12   c . The third sheet  12   c  is designed to provide further protection to the heating element  30 , as illustrated in  FIG. 3   d . The third sheet  12   c  can be sealed to the single sheet  12 , the first sheet  12   a , the second sheet  12   b  or combinations thereof, at the edges, at predetermined portion of the edges, and/or at the interior surfaces, or combinations thereof. In this alternative embodiment, the heater element  30  could be a heat transfer fluid, like a Therminol fluid. 
     In yet another embodiment, the heating element can be on the interior surface  170  of the fluid path  16 . In such embodiment the heating element  30  is printed on the surface  170 . Alternatively, the heating element could also be within and/or on the impermeable material to assist in the transfer of the energy source, in most cases electricity and/or use of inductive heat, to the heating element. 
     To allow the present invention to properly operate with a conductive heating element  30 , the warming device  22  has at least one electrical contact  32 , or direct wired, designed to transmit an electrical current to the integrated heater element  30 . The electrical contact  32  can be a spring or other device, actuating or not, that contacts the heater element  30  when the heating cassette  10  is positioned within the slot  20 . In one embodiment, the electrical contact  32  is not designed to materially block and/or materially restrict the flow of the fluid within the fluid path  16 . The electrical contact  32  is merely designed to merely contact the heater element  30 , as shown in  FIG. 1 , to allow electricity to travel from the warming device  22  to the heater element  30  integrated with the heating cassette  10 . 
     The electrical contact  32  can be positioned anywhere in relation to the heater element  30 . There can even be multiple electrical contacts  32 . The electrical contacts  32  can be positioned to contact (i) the top surface  50  of the cassette  10  if the heater element  30  is below the top surface  80  of slot  20  as shown in  FIG. 1 , (ii) the bottom surface  52  of the cassette  10  if the heater element  30  is over the bottom surface  82  of the slot  20  as illustrated in  FIG. 4 , (iii) the side surface  54  of the cassette  10  as illustrated in  FIGS. 3 and 4  if the heater element  30  contacts or is adjacent to the corresponding side surface  84  of the slot  20 ; or combinations thereof. 
     When operating, the warming device  10  interconnects to an electrical source  40 . The electrical source  40  delivers an electrical current to the warming device  10 , which in turn delivers the current to the electrical contact and then to the heater element  30 . 
     How is the temperature controlled in the warming device? The warming device uses a plurality of devices to control the temperature. For example, it uses a sensor  90  as a resistance temperature detector (RTD). The sensor  90  can be positioned anywhere on or over the exterior  17  of the fluid path  16 , the tubing into or out of the cassette, and/or the heater element  30 . The sensor  90  can be thermally insulated from the heating element  30  by insulation using suitable materials or by physical location distal to the heater element, for example and not limited to three layers  92  of Teflon.R™. The sensor  90  is can be positioned on a second spring or a second actuating/non-actuating device  31  (see  FIG. 4 ) that can contact the desired portion of the cassette  10 , and/or tubing. The sensor  90  is normally attached to the second device  31  by a layer of high temperature adhesive  86 . The normal, but not to be limited to such dimensions, total distance from sensor  90  to the fluid in the cassette is ten thousandths of an inch (0.010″). Suitable sensors are well known and available in the art. (For example, a suitable sensor is manufactured by Minco Products Inc., of Minneapolis, Minn.) 
     In  FIG. 1 , the applicants illustrate a conventional fluid path used in fluid cassettes. The design illustrated in  FIG. 1  is known as a counter-flow fluid path. That fluid path has been determined to provide a desired thermal exchange between the fluid and the heater elements; and the fluid exiting the cassette and the fluid entering the cassette  10 . By no means is the present fluid path design limited to this counter-flow design. In particular, the fluid path can be serpentine, or even, though not normally desired, a straight path or random path, but these paths can be used. 
     In any case, the counter-flow fluid path can be described as follows: The cold flow of fluid enters the cassette  10  at inlet port  14 . Once the fluid is within the fluid path  16 , a preferred fluid path entails having the fluid traverse down path  152 . In relation to the fluid entering the inlet  14 , the fluid turns left 90° to proceed down path  160 . Path  160  and the inlet  14 /outlet  18  are on the opposite sides of the cassette  10 . From path  160 , the fluid turns another left 90° to enter path  154 . Path  154  directs the fluid to the front of the cassette (side of the inlet and outlet  14 ,  18 ). Near the front of the cassette, the fluid again turns left. This time the turn is 180° into path  156 . Path  156  directs the fluid toward path  160 . Prior to reaching path  160 , the fluid turns 180° to the right into path  158 . From path  158 , the fluid is directed toward the outlet  18 . 
     From outlet  18 , the fluid can be directed toward a second warmer unit, or alternatively to a patient. 
     Fluid path  158  is normally the warmest fluid path portion and is located in the middle of the coldest path portion  152  and a colder path portion  156 , causing a thermal counter balance of energy. The sensor  90  is normally located near outlet  18  where fluid exits the heat exchanger  16  to ensure the fluid&#39;s temperature is at or near the desired predetermined temperature prior to entering the patient. The automatic temperature controller stabilizes at a preset temperature limit causing a thermal counter balance with the energy reservoir. 
     The described sensor in its specific location is one of many keys to the thermal control system. The sensor can be a simple on/off switch to an algorithmic controlled sensor. One example, which is in the middle of those two examples is a thermal feedback system used is a proportional, integral, derivative (PID) temperature controller. This is a control mode with three functions. The “proportional action” dampens the system response. “Integral” corrects for droop. “Derivative” seeks to prevent overshoot and undershoot. The sensor input sampling rate is, for example and not limited to,  10  samples/second of the fluid&#39;s temperature exiting the cassette  10 . A thermal counterbalance of fluid exists from the cassette  10  compared to a predetermined set temperature which is the feedback signal to a PID temperature controller, which is set forth in the &#39;282 patent. The temperature controller will adjust and replenish any energy lost to the cassette  10  through the heater element  30 . 
     The primary PID temperature controller maintains an output temperature of approximately 35° to 40° C. in the fluid over the flow range of 10 to 300 ml/min for 10° C. fluid input. For 20° C. or above, the fluid input may be warmed to a flow rate of 500 ml/min. If the primary controller senses a fluid temperature above 43° C. an audible alarm will also sound and cut off power to the energy reservoir. The unit will await a fluid temperature drop below 43° C., or any other desired temperature desired by the user, before turning off the audible alarm. 
     When the primary controller senses a fluid temperature below 34° C. an audible alarm will also sound and automatically adjust power to the energy reservoir, awaiting fluid temperature rise above 34° C. before turning off the audible alarm. 
     The temperature controller is recognized to be regularly available in the art. The PID primary temperature controller  100  is, for example, a series 935 auto tuning controller manufactured by Watlow Control of Winona, Minn. 
     If the cassette temperature reaches a predetermined temperature, an audible alarm will sound and power will cut off to the heating element  30  and PID controller. The audible alarm can be programmed to be terminated, for example, by removing the power cord from the wall socket. A safety cut-out switch is well known and available in the art. 
     As shown in the circuit diagram in  FIG. 5  of the &#39;282 patent, if there is a catastrophic failure, and the temperature of the energy reservoir rises to 45° C., a safety cutout bimetallic switch which is embedded in the warming device  22  cuts off all power to cassette  10 . No audible alarm is heard and the temperature display goes blank. Suitable bimetallic switches are well known and available in the art. 
     The device can also operate by battery power to make the device truly portable. 
     Thus, to allow maximum user flexibility, especially important in emergency hospital care, a blood/fluid warming system is designed and provided in which the cassette  10  is easily inserted into slot  20  of warmer device  22 . For proper operation, the cassette  10  should be inserted into the slot  20  so the first device  32  contacts the heating material  30  and the second device  31  contacts the cassette  10 . 
     To assist the cassette be properly inserted into the slot  20 , the cassette can have aligning guide rails  48   a, b  (as shown in  FIG. 3   c ) that correspond with mating slots  220   a, b , respectively, of device  22  as illustrated in  FIG. 4 . The cassette  10  is continued to be inserted into the slot  20  until the cassette can no longer be inserted therein. The stoppage of the cassette can be caused by a visual indicator  222  that projects from the opening  224  on the opposite side of the inlet/outlet  14 ,  18  side of the slot  20 . Alternatively, the cassette  10  could have tubing  99  (as shown in  FIG. 2 ) that forms a portion of the inlet  14  and outlet  18 . The tubing  99  can stop the cassette  10  from being under-inserted and/or over-inserted into the slot  20 . 
     As indicated above, the heating element  30  is any material that creates the desired thermal energy to control the temperature of the fluid in the cassette and/or tubing when an electrical current is passed through the heating element and is capable of being integrated with the cassette  10  and tubing  99 . The conductive material can also be an electromagnetic material. When an electrical current is passed through the material the electro-magnetic material acts as a magnetic material. The electromagnetic material receives the electrical current and generates the desired thermal energy and simultaneously is attracted to a corresponding magnetic or a second electromagnetic material (collectively referred to as the “other material”) on the opposite side of the cassette  10 . This embodiment is illustrated in comparison analysis of no current— FIGS. 5   a  and  6   a —to current applied— FIGS. 5   b  and  6   b . By opposite side of the cassette, we mean the other material  130  is either integrated with the cassette  10  opposite the conductive material  30  as illustrated in  FIGS. 5   a  and  b , or is a side or a portion of the surface that defines the slot as illustrated in  FIGS. 6   a  and  b . If the other material  130  is an electromagnetic material as illustrated in  FIGS. 5   a  and  b , the other material  130  receives an electrical current in the same way that the conductive material  30  receives its current. 
     When the conductive material  30  is pressed toward the other material  130 , the conductive material  30  pushes the fluid toward the outlet by decreasing the size of the fluid path (compare A to B in  FIGS. 5   a  and  b , and  6   a  and  b ). 
     Alternatively, the various devices  31 ,  32  can be interconnected to a third device  33 . The third device  33  is an actuator that applies a force (as illustrated in comparison  FIGS. 7   a  and  b —a downward force) to the devices  31 ,  32 . When that force is applied, the devices  31 ,  32  push into the fluid path  16  (see analysis of A and B height differentials of the fluid path) to apply a forward force (seen by arrows) to exterior surface  17  of the cassette  10  to direct the fluid in the fluid path  16  toward the outlet  16 . Alternatively, the third device  33  can directly apply the forward force to the exterior surface  17  of the cassette  10  to direct the fluid in the fluid path  16  toward the outlet  16 . The timing of when the forward force is applied is controlled by the controlling device. 
     In a further alternative embodiment, the cassette has a fourth fluid impermeable material  12   d , as illustrated in  FIG. 8 . This fourth material  12   d  is on the opposite side of the cassette  10  which has the heater element  30  thereon, or alternatively on the same side, which means the fourth material  12   d  can be the third material or be positioned over the third material. The fourth material  12   d  can be sealed to the remaining cassette material ( 12 ;  12   a,b ;  12   a,b,c ) in the same manner in which the third material is sealed to the other materials. Preferably, the fourth material  12   d  is positioned to conform to the fluid path  16  and therefore has an inlet and an outlet that corresponds to the inlet  14  and outlet  18  of the fluid path. That way a second fluid can be injected into a compression path positioned between the fourth material  12   d  and the remaining cassette material ( 12 ;  12   a,b ;  12   a,b,c ). 
     The second fluid can be a gas or a liquid. Preferably, the second gas is either water or air. In any case, the second fluid is occasionally pumped through the compression path to direct the fluid in the fluid path toward the outlet. The second fluid can have any temperature. Preferably, the temperature of the second fluid corresponds with the temperature of the heater elements. Controlling the temperature of the second fluid and directing the second fluid into the compression path can be accomplished with conventional devices known to those of ordinary skill in the art. 
     The present warming device  22  can be positioned horizontally, vertically or any direction there between. The warming device  22  can be positioned anywhere that is needed because it can have various adaptations to attach it to the desired device and/or in any location. 
     Turning to  FIG. 9 , the heating element  30 , as indicated previously above, can be wrapped in a cage-like manner (like chicken wire) or wire weave frame on the interior surface of the material (a.k.a., fluid path) for the tubing, within the tubing material, outside the delivery tube  99 ,  199 , or combinations thereof (the latter is the catheter tube). This design ensures that the heated fluid from the cassette  10  retains its desired temperature into the patient. The heating element  30  in the tubes can be interconnected to the same energy source as the heating elements for the cassette, or alternatively to a second energy source which could be independent or dependent on the first energy source. 
     In addition to those alternative designs, the heating element can be shaped like streamers  400  as illustrated in  FIG. 10  for the cassette  10  and/or the tubes  99 ,  199 . This streamer design can be on the exterior surface of the material, within the material itself, on the interior surface (a.k.a., fluid path) of the material, or combinations thereof. This streamer design can increase the surface area of the heating element, and possibly eliminate the need for a gap for the cassette in the warming device. The electrical contact device  402  of the streamers can be an electrical/magnetic device positioned on and/or over the streamers. The electrical/magnetic device allows the cassette and/or tubes to contact the electrical source without the gap thereon. This electrical/magnetic device can be incorporated in the other embodiments of the present invention as well. 
     Having described the invention with regard to certain specific embodiments thereof, it is to be understood that this description is not meant as a limitation since further modifications may now suggest themselves to those skilled in the art, and it is intended to cover such modifications as fall within the scope of the appended claims.