Abstract:
A self-contained portable unit for heating physiological fluids is disclosed. A heat exchanger is disposable to ensure sterility, and the hot exchanger is attached to a heating system by inserting it between opposed fluid connection elements. One of the fluid connection elements is movable to permit the heat exchanger to be installed and removed easily by inserting one end of the heat exchanger in one of the fluid connection units and moving the other fluid connection unit into contact with an opposite end of the heat exchanges. The heating fluid is heated by an electric heating element and is circulated by an electric pump.

Description:
This application is a continuation of application No.  08 / 758 , 853  filed Dec.  2 ,  1996 , since abandoned, which is a continuation of application No.  08 / 571 , 706  filed Dec.  6 ,  1995 , since abandoned, which is a continuation of application No.  08 / 145 , 099  filed Nov.  3 ,  1993 , since abandoned, which is a continuation of application No.  07 / 979 , 434  filed Nov.  20 ,  1992 , since abandoned, which is a continuation of application No.  07 / 558 , 177  filed Jul.  26 ,  1990 , since abandoned, which is a reissue of application No.  06 / 866 , 910  filed May  27 ,  1986 , U.S. Pat. No.  4 , 759 , 749 . 
    
    
     FIELD OF THE INVENTION 
     This invention relates to the art of devices used with physiological fluids. In particular, the invention is an apparatus for heating a physiological fluid before introduction into a patient. 
     BACKGROUND ART 
     In many medical procedures, it is necessary that fluids to be administered to a patient be heated. For example, whole blood and packed cells are stored in refrigerators at a temperature of approximately 4° C. These fluids often are required to be administered to a patient within a short period of time, which necessitates warming them to a temperature approximately equal to that of the patient, i.e. 37° C. 
     Great care must be exercised when heating fluids such as whole blood or packed cells to avoid damaging the cells. For example, it is generally accepted that whole blood and packed cells should not be exposed to a temperature above 44° C. This places a severe restriction on the techniques used to heat quickly fluids which have been stored in a refrigerator and which must be administered to a patient within a short period of time. 
     U.S. Pat. Nos. 3,614,385 (Horstmann), 3,629,552 (Edging), 4,476,867 (Parks), and 4,532,414 (Shah et al.) teach systems for heating blood prior to being administered to a patient. The Horstmann, Edging, and Parks devices use various heat exchangers whereby blood flows through a tube which communicates with a warming fluid in a heat exchanger. It is quite difficult to maintain sterility of the heating apparatus in these systems after the first use because of the complexity of the heat exchangers. The Shah et al. device is simply a heated plate having a groove therein for receiving a tube leading from the bag containing the fluid to be administered. 
     U.S. Pat. No. 2,910,981 (Wilson et at.) shows a device for conducting blood transfusions. A heat exchanger is in fluid communication with a heating element, and the blood to be ministered passes through the heat ex. changer before being administered to the patient. The heat exchanger comprises a central tube surrounded by an outer tube, and the heating fluid passes through the space between the inner and outer tubes. The heat ex. changer is threadedly connected to valves at opposite ends. No structure is described for supporting the various elements described in the patent. 
     SUMMARY OF THE INVENTION 
     The invention is a self-contained, free standing system which permits controlled, but rapid heating of cellular fluids as they are being administered to a patient. The heating of the cellular fluids is controlled to prevent damage to the fluids from various causes including overheating. 
     The system comprises two major parts. A first part includes a heating element, a support pole, and a wheeled base. A second part comprises a heat exchanger and, optionally, a filter. The heat exchanger and filter are disposable and are removably attached to the support pole. The heat exchanger is disposable to facilitate each patient&#39;s use of a new, sterile heat exchanger. 
     The heat exchanger is easily installed on the pole, which includes a fixed mounting block and a movable mounting block. Opposite ends of the heat exchanger comprise nipples which are received in O-ring containing recesses in the mounting blocks. Thus, installation and removal of the disposable heat exchanger are quite easy. 
     The system may also include a filter which would be attached to an outlet of the heat exchanger. Sensors on the pole detect when the heat exchanger or the filter is in a correct place to control operation of the heating system. The heating system comprises a tank and a heating element in the outlet line of the tank. A pump circulates a heating fluid from the tank and heating element through the disposable heat exchanger. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an exploded view of the apparatus in accordance with the invention. 
         FIG. 2  is a longitudinal cross-section of the support pole. 
         FIG. 3  is a longitudinal cross-section of the heat exchanger. 
         FIG. 4  is an enlarged cross-section of an upper end of the support pole. 
         FIG. 5  is an exploded perspective of a movable mounting block and the upper end of the support pole. 
         FIG. 6  is a side view of the upper end of the support pole shown in FIG.  4 . 
         FIG. 7  is a perspective view of the heating element with the cover removed and the storage tank shown in phantom lines. 
         FIG. 8  is a schematic view showing the preferred fluid circuit. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  is an exploded view of a preferred embodiment of the invention. A base  2 , which preferably has wheels for ease of mobility, supports a pole  4  and a heating unit  6 . Pole  4  removably receives a disposable unit  8  which includes a heat exchanger  10  and a filter  12 . Tube  14  is in fluid communication with one end of heat exchanger  10  and connects it to a pair of bags spikes  16 . The bag spikes are known in the art and are used to puncture and allow the dispensing of a body fluid from a storage bag. Tube  18  connects a lower end of heat exchanger  10  to an upper end of filter  12  and tube  20  connects a lower end of filter  12  to cannula  22  to allow fluids to be introduced into a patient. As will be more fully described below, the entire unit  8  is manufactured of an inexpensive material and is disposable to ensure sterility. 
       FIG. 2  is a longitudinal cross-section of pole  4  with heat exchanger  10  partially mounted thereon. Pole  4  includes a housing  24  which is attached to base  2  ( FIG. 1 ) to extend substantially vertically. Housing  24  is preferably a hollow square tube, and hoses  26  and  28  extend along a hollow portion of housing  24 . Preferably, hoses  26  and  28  exit housing  24  via opening  30 . In addition, electric conductor  32  extends along the hollow portion of housing  24  and exits by way of a second opening  34 . 
     Heat exchanger  10  is removably received by first detachable fluid connector  36  and second detachable fluid connector  38 . The structure of fluid connectors  36  and  38  will be more fully described with respect to  FIGS. 4 and 5 . Detachable fluid connector  36  is mounted for vertical movement with respect to housing  24  to allow heat exchanger  10  to be easily attached to pole  4  and detached. Accordion element  40  is placed in hose  28  to permit fluid connector  36  to move vertically. Sensor  42  detects when fluid connector  36  is in its lowermost position (as shown in FIG.  4 ), sensor  44  detects when heat exchanger  10  is in an operable position, and sensor  46  detects when filter  12  is in operable position. 
     Filter  12  is supported on pole  4  by U-shaped bracket  48 . The distance between the legs of the bracket is slightly less than the diameter of the filter so that it “snaps” into place. Similarly, a U-shaped bracket  49  is located between connectors  36  and  38 . Bracket  49  holds heat exchanger  10  aligned with connector  36  during insertion of the heat exchanger. 
       FIG. 3  is a longitudinal cross-section of heat exchanger  10 . An inner tube  50  has ends  52  and  54  which are adapted to be received in respective fluid connectors  36  and  38 . A central portion  56  of tube  50  is helically shaped to provide a helical groove on the exterior of tube  50 . Tube  50  is preferably made of aluminum, and the helical surface is produced by twisting the tube. 
     An outer tube  58  fits over the inner tube  50  in a central portion thereof The space between the helical central portion  56  and the outer tube  58  forms a helical path extending between opposite ends of outer tube  58 . 
     An inlet connector  60  is secured to one end of outer tube  58  and includes connection  62  which receives tube  14  (see FIG.  2 ). End  52  of inner tube  50  extends beyond the upper edge of inlet connector  60  to provide a nipple for engagement with fluid connectors  36  as will be more fully described with respect to FIG.  4 . 
     Outlet connector  64  is secured to a second end of outer tube  58 , provides connection  66  for attachment to tube  18 , and allows end  54  to project to form a nipple for being received in fluid connector  38 . 
       FIG. 4  is an enlarged cross section of an upper end of pole  4 . Housing  24  has a slot  68  in one side thereof for receiving a projection  70  from fluid connector  36 . Projection  70  has outwardly extending ears  72  (see  FIG. 5 ) to secure the fluid connector to the pole and yet to allow it to move in the direction indicated by the arrow in FIG.  4 . 
     Elbow  74  is threadedly connected to projection  70  to connect hose  28  with inner passage  76 . Recess  78  connects with passage  76  and receives nipple end  52  of heat exchanger  10 . O-ring seal  80  is received in an enlarged portion of recess  78  to provide a fluid-tight seal. It will be appreciated that fluid passing through hose  28  is thus connected to inner tube  50  of heat exchanger  10 . 
       FIG. 5  is an exploded view of the fluid connector  36  and the upper portion of housing  24 . 
     Fluid connector  38  is similar to fluid connector  36 , except that connector  38  is secured to housing  24 . 
     It will be appreciated that heat exchanger  10  may be easily attached to pole  4  by inserting end  54  into fluid connector  38  and by lowering fluid connector  36  onto end $2  52 . When this is accomplished, heat exchanger  10  will be supported mainly by fluid connectors  36  and  38 . 
       FIG. 6  is a side view of the top portion of pole  4  with a bracket  82  shown in cross-section. Bracket  82  has a hole therethrough for supporting a rod  84  which in turn supports bags containing fluids to be administered to a patient. A threaded stem  86  engages rod  84  to allow rod  84  to be adjusted in height. 
       FIG. 7  is a perspective view of heating unit  6 , with a cover removed.  FIG. 8  is a schematic flow diagram of the unit shown in FIG.  7  and these two Figures will be discussed together. 
     A base  88  supports electrical components  90 , a pump motor  92 , and a heater  94 . A tank  96  sits on top of heater  94 , and filter  98  is located between an outlet of the tank and an inlet of the heater. A fill port  100  is connected to the top of tank  96  to allow circulating fluid to be introduced into the system. Inlet  102  also connects to the top of tank  96  and receives circulating fluid from either hose  26  or  28 , and outlet  104  supplies heated fluid to hose  28  or  26 . 
     The warming fluid is driven through the heat exchanger circuit by pump  106  which is connected to the pump motor by magnetic clutch  108 . 
     With particular reference to  FIG. 8 , tank  96  includes an air vent and overflow tube  110 , and a float switch  112 . The float switch is in turn connected to a control circuit  114  to permit operation of the device only when sufficient fluid is present. Heater  94  comprises a tubular channel having an electric heating rod  116  therein, and the heating rod is connected to a temperature control circuit  118  which is in turn also connected to control circuit  114 . As fluid flows from tank  96  through filter  98  and through heater  94 , it is warmed, and the temperature is measured by temperature probe  120 , _ which is located in the outlet of heater  94 . Temperature control probe  120  is connected to temperature control circuit  118  to control energization of heating rod  116 . A second temperature control probe  122  is also located in the outlet of heater  94  and is connected to control circuit  114  to ensure that the temperature does not exceed a predetermined level. If the temperature of the warming fluid is too high, the blood cells could be destroyed, and it is thus important either to automatically shut down the heating system or to activate an alarm such as that shown at  124 . 
     Power is provided through power cord  126 , and the voltage is adjusted by an isolation transformer  128 . A switch  130  activates the entire electrical system, and the operation of the system, including the fluid temperature is displayed on panel  132 . 
     In operation of the apparatus is accordance with the invention, the unit is rolled to a location adjacent to a patient, and a sterile unit  8  is installed between fluid connectors  36  and  38 . Cannula  22  is attached to the patient, and bag spikes  16  are inserted into appropriate bags containing the desired fluid to be administered to the patient. Switch  130  is be warmed by the heat exchanger. If filter  12  has been placed in the circuit, the warmed body fluid then passes through the filter and into the patient. If filter  12  is not being used, tube  18  is connected directly to the cannula  22  for direct admission of the warm body fluid to the patient. 
     It will be appreciated that a unique self-contained unit has been described which provides sterility by use of an easily-installed disposable heat exchanger circuit. Modifications within the scope of the appended claims will be apparent to those who are skilled in the art.