Abstract:
Apparatus for reducing the fat content of blood and in particular to an apparatus for reducing the fat content of pericardial suction blood has a conduit for blood, an absorbing filter located in the conduit and an associated temperature control device for adjusting the temperature of blood before it flows through the filter.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an apparatus for reducing the fat content of blood and in particular to an apparatus for reducing the fat content of pericardial suction blood. 
     2. Description of background Art 
     Extra corporeal circuits are regularly used during surgery and in particular for open heart surgery and are controlled by a Perfusionist. Venous blood bypasses the heart in one such circuit and is reintroduced into an artery in a patient&#39;s body after it has been oxygenated. Pericardial blood is also removed from the surgical site and is combined with the venous blood, oxygenated and subsequently reintroduced into the patient&#39;s body. One of the remaining problems associated with cardiac surgery is post-operative neurological dysfunction. Cardiopulmonary bypass (CPB) operations have been linked with micro embolisms in the small arteries of the brain, known as SCADS. The embolic material found in the arteries is believed to contain liquid fat from the pericardial suction blood which is reintroduced into the patients body after collection. 
     A number of solutions have been proposed to overcome this problem. One such solution is to wash the pericardial suction blood, however this technique is relatively expensive and time consuming. Another solution is filtration, a technique that can be inefficient due to the difficulties associated with filtration of fat in liquid phase. A third solution is to avoid re-transfusion of the pericardial suction blood. This solution adds known problems associated with an increased use of allogeneic blood, such as immunological modulation. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to overcome the problems associated with the above outlined solutions associated with removal of fat from pericardial blood by providing an efficient and relatively inexpensive technique for fat removal. 
     Accordingly, there is provided an apparatus for reducing fat in blood comprising a conduit for blood, an absorbing material of a filter located in the conduit and an associated temperature control means for adjusting the temperature of the blood before it makes contact with the absorber. 
     Preferably, the absorber comprises a porous structure, a mesh structure, or a fibrous mass structure of lipophilic material of variable depth that increases the contact surface area to blood, herein referred to as filter. The term filter may also comprise a thin structure of surface coating when so is described. 
     Ideally, the absorbing filter is in contact with blood, not necessarily meaning blood passing thorough the filter from one side to the other. 
     As the solid or high viscosity fat makes contact with, or passes through, the absorbing filter it adheres to the filter thereby reducing the fat content of the blood. 
     In another aspect of the invention, the temperature control means maintains the blood at a suitable temperature for transfusion back into the patient&#39;s body. At the maintained temperature, or slightly heated, the separation of fat from the blood medium may also be facilitated as the viscosity of fat is maintained or lowered. 
     Preferably, the temperature control means is provided by a heat exchanger in contact with the conduit. 
     Ideally, the absorber is manufactured from cellulose or polyester fiber but can also be based on derivatives of polyamides, polyolefins, or polyvinyl fluoride, although not being limited to any of these materials. 
     In another aspect of the invention, there is provided an apparatus for reducing fat in blood comprising a chamber having an inlet and an outlet wherein the chamber is arranged with a first compartment for receiving blood via the inlet and a second compartment in fluid communication with the first compartment via a channel which connects the base of the first compartments with the base of the second compartment, the second compartment defining the outlet, the compartments being dimensioned and spatially arranged relative to one another whereby in use blood flowing into the second compartment from the first compartment reaches the same vertical height as blood in the first compartment preventing the last portion of the blood in the first compartment flows out of the first compartment. Advantageously, the last portion of blood which has collected adjacent the top surface of the blood in the first chamber has a high concentration of fat which always remains in the first compartment. 
     Preferably, the channels are releasably sealable by sealing means. 
     Ideally, a blood pipe passes through the inlet, the chamber and the outlet and the portion of the blood pipe within the chamber defines perforations. 
     Preferably, a separate filter is located within at least one compartment. 
     Preferably, the heat exchanger is mounted on the chamber. 
     Ideally, the heat exchanger is provided by a heat exchange chamber having and inlet and an outlet. 
     In another embodiment, the heat exchanger is provided by a piezoelectric element. 
     Preferably, the apparatus can be supported on a holder. 
     Ideally, the holder is constructed from a light coloured material. 
     Preferably, the holder includes an illuminating background which makes the layer of fat easier to see. 
     Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will now be described with reference to the accompanying drawings which show by way of example only, nine embodiments of an apparatus for removing fat from blood. In the drawings: 
         FIG. 1  is an elevation view of a chamber for separating fat from blood; 
         FIG. 2  is an elevation view of a second embodiment of chamber for separating fat from blood; 
         FIG. 3  is an elevation view of the chamber of  FIG. 2 ; 
         FIG. 4  is a partial side section view of the chamber of  FIG. 3  taken along A-A: 
         FIG. 5  is an elevation view of the chamber of  FIG. 2 ; 
         FIG. 6  is a partial side section view of the chamber of  FIG. 5  taken along A-A; 
         FIG. 7  is an elevation view of a third embodiment of chamber; 
         FIG. 8  is a side section view of the chamber of  FIG. 7  taken along A-A: 
         FIG. 9  is an elevation view of an apparatus for separating fat from blood; 
         FIG. 10  is a side section view of the apparatus of  FIG. 9  taken along A-A: 
         FIG. 11  is an elevation view of a second embodiment of apparatus; 
         FIG. 12  is a side section elevation view of the apparatus of  FIG. 11  taken along A-A; 
         FIG. 13  is an elevation view of a third embodiment of apparatus; 
         FIG. 14  is a side section elevation view of the apparatus of  FIG. 13  taken along A-A; 
         FIG. 15  is an elevation view of a fourth embodiment of apparatus; 
         FIG. 16  is a side section elevation view of the apparatus of  FIG. 15  taken along A-A; 
         FIG. 17  is an elevation view of a fifth embodiment of apparatus; 
         FIG. 18  is a side section elevation view of the apparatus of  FIG. 17  taken along A-A; 
         FIG. 19  is a schematic view of a sixth embodiment of apparatus for separating fat from blood; 
         FIG. 20  is a schematic view of a seventh embodiment of apparatus for separating fat from blood; 
         FIG. 21  is an eight embodiment of apparatus; and 
         FIG. 22  is a ninth embodiment of apparatus. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to the drawings and initially to  FIG. 1 , there is shown a chamber  2  for separating fat from blood. The chamber  2  has an inlet  5  and an outlet  6 . The chamber  2  has a substantially rectangular shape and a pipe  4  extends along one edge  7  of the chamber  2 . The chamber  2  has a slot  8  on the edge  7  exposing a portion  9  of the pipe  4 . The remaining portion  18  of the pipe  4  between the inlet  5  and the outlet  6  is enclosed within the chamber  2  and has perforations  201 . The pipe  4  may be located anywhere within the chamber  2  with opening  8  exposing a portion of the pipe  4 . A sealing clamp  10  is mounted on the exposed portion  9  of the pipe  4 . The chamber  2  is divided into two compartments  11  and  12  by a welded seam  14 . The compartments  11  and  12  are in communication via a first channel  15  due to an interruption in the seam  14  and a second channel, in this embodiment provided by the portion  9  of the pipe  4  bridging the slot  8 . A de-foamer  16  and an air escape valve  17  are located along the uppermost edge  19  of the chamber  2  when the chamber  2  is in an in use position. A volume scale  20  for each of the compartments  11  and  12  is incorporated into the plastic material of the chamber  2 . A second sealing clamp  22  is mounted on a portion  23  of the pipe  4  outside the chamber  2  after the outlet  6 . The chamber  2  and pipe  4  described in this embodiment are produced from a pliable transparent plastic material, although they are not limited to this particular material. A chamber  2  manufactured from a rigid material is also within the scope of the invention. 
     In use, pericardial suction blood from a surgery site is pumped to the inlet  5  of the pipe  4  and continues down through the pipe  4  until it reaches the clamp  10 . As blood abuts against the blocked pipe  4 , barometric pressure forces blood and air from the wound out through perforations  201  in the portion  18  of the pipe  4 . Blood collects in compartment  11  and the fat contained therein flows to the top of the blood under a normal process of separation. If the blood fills the compartment  11 , it can flow over into compartment  12  via channel  15 . The de-foamer  16  is activated in the event of foaming of blood in its vicinity. Seam  14  and an additional seam  31  promote the flow of blood towards the clamp  10  and the outlet  6  respectively when the chamber  2  is held in an in use position. When the perfusionist is satisfied that a substantial portion of the fat has collected in a layer on top of the blood in compartment  11 , the clamp  10  is opened and under normal barometric pressure, the blood flows from compartment  11  into compartment  12 . The geometry of compartments  11  and  12  and their spatial orientation relative to one another is designed so that a final volume of blood containing the layer of fat which has collected on top of the blood in compartment  11  remains in compartment  11  after the transfer of the blood to compartment  12 . This design feature of the chamber  2  reduces the need for careful visual monitoring of the transfer of blood from compartment  11  to compartment  12  by a perfusionist, improving the functionality of the chamber  2 . When substantially all of the blood from compartment  11  has transferred to compartment  12 , the clamp  10  is reapplied to the exposed portion  9  of the pipe  4 . It is not necessary, but it is possible, to stop the pump at any stage of the process. The compartment  11  refills with inflowing blood from the surgery site. The separated fat layer remains adjacent the surface of the blood. Fat contained in the blood flowing into the compartment  11  again begins to float towards the surface of the blood stored in the compartment  11 . The fat contained in the blood stored in compartment  12  also floats towards the top surface. There is no turbulence from incoming blood to disturb the process of separation in compartment  12  so further separation of fat and blood occurs efficiently. The second clamp  22  is opened after a predetermined time and blood flows from the compartment  12  into a venous reservoir (not shown) or directly back to the body of a patient. The perfusionist prevents the last portion of the blood which contains the layer of fat from leaving compartment  12  through the outlet  6 . The scale  20  on the chamber  2  is used for this purpose in conjunction with visual monitoring by the perfusionist. 
     This construction of chamber  2  provides the operator with a variety of uses for the chamber  2  when the chamber is manufactured from a pliable plastic material. On delivery, the chamber  2  is rolled around the pipe  4 . If an operator wishes to avail of the function of fat separation, the chamber  2  is uncoiled from the pipe  4  and mounted on a holder (not shown). Alternatively, the chamber  2  can be manufactured having a short pipe  4  which is connected, or cut in, to an existing pipe used for standard and commercially available machinery of heart lung technology. These pipe-to-pipe connectors are of standard design and commercially available. The inlet pipe  5  and outlet pipe  6  may have branched connectors for in and out coming pipes. The chamber  2  includes a recess (not shown) in or about edge  19  for receiving a spike for releasably securing the chamber  2  on the holder. Alternatively, the chamber  2  can be used as a standard blood pipe  4  with the chamber  2  remaining wrapped around the pipe  4  during use. The air valve  17  is in a closed position on delivery and must be opened if the fat separation function is needed. If a large volume of blood is being removed from the surgery site, it is possible to use the chamber  2  in an open system, allowing blood to flow through the system continuously provided the inlet  5  and outlet  6  are in direct communication. 
     Referring to  FIG. 2 , there is shown a chamber  2  substantially as described in  FIG. 1 . Reference numerals used to designate features of the chamber  2  of  FIG. 1  are used to designate identical features of the chamber  2  in  FIGS. 2 to 6 , which illustrate similar embodiments of the chamber  2 . In  FIG. 2 , an additional compartment  41  is shown having an integral filter  42  welded or glued to the plastic material of the compartment  41 . A second recess  43  exposes an additional portion  44  of the pipe  4  and a third clamp  45  is mounted on this portion  44 . The chamber  2  works in the same way as the chamber  2  of  FIG. 1  but including the additional step of blood in compartment  12  flowing into compartment  41  and contacting the absorbing material of the filter  42  prior to the blood flowing back to the venous reservoir or back into the patient&#39;s body. The filter  42  absorbs fat from the blood which has reached a partially solid state or fat which has an increased viscosity due to (1) cooling as a result of the blood being stored in the chamber  2  during the separation process and/or (2) cooling by a heat exchanger (not shown). This chamber  2  is also suitable for allowing through flow of blood by removing all the clamps  10 ,  22 ,  45 , if high volume bleeding occurs at the surgery site. 
     Referring now to  FIG. 3  and  FIG. 4 , there is shown a chamber  2  as described in  FIG. 2  above.  FIG. 4  shows a filter  42  welded or glued to an internal surface  51  of the chamber  2 . The de-foamer  16  is shown adjacent the top edge  52  of the chamber  2 . Referring now to  FIGS. 5 and 6 , a second embodiment of filter  61  is shown which is free to move in the compartment  12  and without blood passing through the filter  61 . Alternatively, the filter  61  can be fixed to either or both internal surfaces  62  of the chamber  2 . It is also within the scope of the invention to envisage an additional absorbing filter located freely or fixed in the compartment  11 . In use, the blood contacts the filter  61 , which is typically but not exclusively manufactured from cellulose or polyester fiber and fat particles adhere to the filter  61 . This filter  61  further increases the separation of fat and blood already occurring due to flotation of fat to the surface of the stored blood. 
       FIGS. 7 and 8  show a third embodiment of chamber  2  having specially formed attachments  71  integrated into a side  74  of the chamber  2  for inlet pipe  72  and outlet pipe  73 . A similar attachment  71  is used for the air escape valve  17 . This construction removes the need for a pipe  4  extending within the chamber  2 . A clamp  75  is mounted directly onto the chamber  2  on or about channel  13  in order to prevent blood from flowing between compartments  11  and  12 . It will of course be appreciated that filters of the type described in relation to  FIGS. 2 to 6  may be incorporated into the chamber  2  of this embodiment.  FIGS. 9 and 10  show the chamber  2  of  FIG. 1  incorporating a heat exchanger  80 . In particular,  FIG. 10  shows a heat exchanger  80  having a heat exchange chamber  81  fixed onto one side, of the chamber  2 . The heat exchange chamber  81  has an inlet  82  and an outlet  83  and provides a pathway for a flow, preferably although not exclusively a reverse-flow (relative to the direction of flow of blood), cooling or heating medium which can be pumped through the heat exchange chamber  81 . In use, the cooling medium lowers the temperature of the blood towards approximately 5°-10° C. At lowered temperatures, fat in the liquid form contained in the blood solidifies or has a higher viscosity, and is much easier to remove from the blood by contact with absorbing filters  42 ,  61  as described above. Alternatively, the blood temperature is maintained at 37° C. or increased towards approximately 40° C. in order to lower the viscosity of fat in liquid form which facilitates its separation from the blood medium. In this configuration, the medium passing through the heat exchange chamber  81  has a temperature to prevent cooling and may heat the blood above the 37° C. body temperature.  FIGS. 11 and 12  show a different construction of heat exchanger  90  which is provided by a coil  92  fixed to one side of the chamber  2 . The coil  92  has an inlet  93  and an outlet  94  which, in combination with the coil  92 , provide a pathway for the temperature-controlling medium. 
       FIG. 13  and  FIG. 14  show an alternative construction of heat exchanger  100  provided by a piezoelectric element  101  mounted on one side of the chamber  2 . In this embodiment, the piezoelectric element  101  has a number of recesses  102  on one face  103 . The recesses  102  extend from and are spaced angularly around a central point  104  which defines an opening into a bore  105 . Alternatively, the bore  105  may be located anywhere along any of the recesses  102 . The bore  105  extends through the piezoelectric element  101  and is connected to a vacuum pump (not shown). Alternatively, the bore  105  may extend and connect to the vacuum pump from other locations of the piezoelectric element  101 . The piezoelectric element  101  is placed in contact with the chamber  2  and the vacuum pump generates a vacuum resulting in the chamber  2  and piezoelectric element  101  adhering to one another. The piezoelectric element  101  induces cooling of the blood flowing through the chamber  2  via an electrical circuit. A piezoelectric element  101  can be provided on both sides of the chamber  2 . 
       FIGS. 15 and 16  show another configuration of heat exchanger  110  provided by a double-sided coil  111 . The double-sided coil  111  is connected via a port  112  allowing the cooling/heating medium to flow through the coil  111  on both sides of the chamber  2 . The cooling/heating medium flows in through inlet  114  and up along one side of the coil  111 . The medium passes through port  112  and flows down along the opposite side of the chamber  2  and out through outlet  115 . It is also possible to provide two separate coils  111 , one on each side of the chamber  2 .  FIGS. 17 and 18  illustrate another embodiment of heat exchanger  130 . In this embodiment a heat exchange chamber  131  having an inlet  132  and an outlet  133  is located within the chamber  2 . In use, the medium flows into the heat exchange chamber  131  through inlet  132  and is pumped up through the heat exchange chamber  131  contra to the flow of blood or in the same direction. 
       FIG. 19  illustrates an apparatus  1  having a heat exchanger  161  having an inlet  162  and an outlet  163  providing a flow path for a medium into, through and out of the heat exchanger  161 . Within the heat exchanger  161  is a separation chamber  164  having a blood inlet pipe  165  and a blood outlet pipe  166 . The separation chamber  164  also includes an air escape valve  167  and has an absorbing filter  168  housed within the chamber  164 . The blood outlet pipe  166  flows to a venous reservoir  169 , the venous reservoir  169  being a part of commercially available heart and lung machines used for cardiac surgery. Alternatively, the blood with reduced fat may also be allowed to drain directly into the body of the patient (not shown). In use, pericardial blood is pumped by a standard pump  153  from surgery site  151  to the separation chamber  164  via the blood inlet pipe  165 . It will of course be appreciated that blood could be aspirated by the standard pump  153  or a vacuum source (not shown) through the separation chamber  164  for which mode of action the air escape valve  167  is omitted. A portion  152  of the blood inlet pipe  165  is contained within the heat exchanger  161  and blood flowing through this portion  152  is subject to cooling prior to entering the chamber  164  by the cooling medium flowing through the heat exchanger  161 . The cooled blood has a temperature towards approximately 5°-10° C. as it enters the chamber  164 . At this temperature the fat contained within the blood has solidified, or reached a level of high viscosity, and is absorbed by the filter  168 , which preferably but not exclusively is formed from cellulose or polyester fiber. The fat-reduced blood returns to the venous reservoir  169 . In this embodiment, blood can flow continuously from the surgery site  151  through the apparatus without the need for clamps or other flow restrictors. The chamber  164  is produced from a pliable transparent plastic material, although they are not limited to this particular material. A chamber  164  manufactured from a rigid material is also within the scope of the invention. The heat exchanger  161  could have features similar to that described in any of the previous  FIGS. 9 to 18 . 
       FIG. 20  shows an apparatus  1  having a pump  173  mounted on a pipe  174  between the surgery site  172  and a heat exchanger  175 . The heat exchanger  175  is mounted on a portion of the pipe  174  leading into chamber  2 . The chamber  2  in this embodiment is similar in construction and function to the chamber  2  described in  FIG. 1 . A commercially available filter  179  for through flow of blood such as (PALL LeukoGuard RS®, PALL Medical, Portsmouth, England) is provided on a section of the pipe  174  leading away from the chamber  2 . The pipe  174  is then connected to a venous reservoir  176  or is connected directly back to the body of the patient  177 . In use, blood is pumped from the surgery site  172  by a standard pump  173  to the heat exchanger  175  via the pipe  174 . The heat exchanger  175  is used to reduce the temperature of the blood towards approximately 5°-10° C. The chamber  2  includes a number of absorbing filters (not shown) which are preferably, but not exclusively manufactured from cellulose or polyester fiber. Fat in the pericardial suction blood solidifies or reaches a level of high viscosity at reduced temperatures and is absorbed by the filters. In addition, the blood and fat can be separated further in the chamber  2  as described in the in use description of  FIG. 1 . The commercial filter  179  removes any fat remaining in the blood after it passes through the chamber  2 . The blood is then alternatively redirected to the venous reservoir  176  or back to the patient&#39;s body  177 . 
     Referring to  FIG. 21  there is shown a chamber  181  comprising compartments  184  and  185  as separate units connected by pipes  182  and  183 . It will of course be appreciated that a heat exchanger as previously discussed could also be applied to the apparatus  1  of this embodiment. The pipe  174  from the surgery site  172  branches into two separate pipes  202 ,  203  which enter a chamber  184  and  185  respectively. A clamp  187  blocks the pipe  203  entering chamber  185 . Outlet pipes  188 ,  189  extend from the base of the compartments  184  and  185  respectively and these pipes merge together to form a single pipe  190 . A second clamp  191  blocks the pipe  188  emerging from compartment  184  and a third clamp  192  blocks the pipe  190 . In use, blood flows unimpeded into compartment  184  until it reaches clamp  191 . The fat in the blood collecting in compartment  184  starts to float towards the surface of the blood. When the compartment  184  has a predetermined amount of blood contained therein, lamp  191  is opened and the blood flows through the outlet pipe  188  and up into the compartment  185 . The fat which has collected adjacent the surface of the blood remains in the compartment  184 . The clamp  191  is closed when the desired amount of blood has flown into the compartment  185 . This blood is allowed to settle again in the compartment  185  in order to allow additional fat to float to the surface of the blood. After a predetermined period, clamp  192  is released and all the blood except the blood containing the separated fat is allowed to flow out of the compartment  185 . This blood flows through filter  179  removing still further fat. It will of course be appreciated that filters can be located in both or either of the compartments  184  and  185 . In an alternative mode of operation, the two compartments  184  and  185  can be used separately. In use, blood flows unimpeded into compartment  184  until it reaches clamp  191 . When the compartment  184  has a predetermined amount of blood contained therein, clamp  187  is opened and moved to instead occlude inlet pipe  202 . Additional blood now enters the opened inlet tube  203  and container  185 . The fat in the blood collected in compartment  184  starts to float towards the surface of the blood without interference from turbulence of incoming blood. After a predetermined time the lower fraction of blood in container  184  is emptied by first occluding the outlet pipe  189 , by moving the clamp  192  to its new location  189 , and opening the outlet pipe  188  by removing clamp  191 . The top fraction of blood in container  184 , holding a concentrated amount of fat, is prevented from reaching the patient by re-occluding outlet pipe  188  using clamp  191 . The same procedure is carried out with compartment  185  after filling with further incoming blood being re-directed to again fill compartment  184 . 
     Referring to the drawings and finally to  FIG. 22  there is shown an apparatus  1  having a chamber  300  comprising compartments  301  and  302  and with an interconnecting conduit  303 . The chamber  300  is substantially as described in  FIG. 1  with reference to chamber  2  but with a spatial arrangement of compartment  301  being above compartment  302 . An inlet  304  directs blood via pipe  305  to collect in compartment  301  via perforations  306  identical to what is described for pipe  4 , compartment  11 , and perforations  201  in  FIG. 1 . The pipe  305  is here illustrated to have essentially a central location within chamber  300  but can be located along the edge of chamber  300  similar to what is described for pipe  4  of chamber  2  in  FIG. 1 . The chamber  300  has an opening  307  positioned within the space of compartment  301  created by an encircling welded seam  308  exposing a portion  309  of the pipe  305 . A first sealing clamp  310  is mounted on the exposed portion  309  of the pipe  305  to block the pipe  305  in order for blood to collect in compartment  301 . Air that collects in compartment  301  together with blood pumped from the patient&#39;s wound escapes from compartment  301  via a valve opening  311  that is positioned essentially along the top edge of compartment  301 , similar to what is described for valve  17  in  FIG. 1 . In the case of excess of blood in compartment  301 , due to accidental filling by the perfusionist, blood escapes through the named valve  311 . The valve  311  could be connected by a separate pipe to the venous reservoir (not shown). The compartment  301  is in connection with compartment  302  via the conduit  303 . The conduit  303  comprises a channel  312  at the bottom of compartment  301 , an entrapped space  313  of compartment  301  created by two welded seams  314  that connects with the welded seam  308 , perforation  315  of pipe  305 , an extension  316  of pipe  305  into compartment  302 , and perforation  317  of pipe  305 . The spatial arrangement of the details  312 ,  313 ,  315 , and  316  of conduit  303  create together a water-lock mechanism  320 . The water-lock mechanism  320  is symmetrically arranged on both sides of the pipe  305  but can also be single-sided in the case the pipe  305  is located along the edge of the chamber  300 , similar to what is described in  FIG. 1 . It is of course appreciated that the arrangement of details within the water-lock mechanism  320  is not limited to the described design. The conduit  303  has an opening  321 , similar to  307 , exposing a section  322  of the pipe  316 . A second sealing clamp  325  is mounted on the exposed section  322  of the pipe  316  to open and close the conduit  303 . Located at the top of the entrapped space  313  is a venting port  327  consisting of a pipe  328  inside compartment  301  in connection with the top of chamber  300 . The pipe  328  could connect with the valve opening  311 . It is of course appreciated that the port  327  and venting pipe  328  can have a path outside compartment  301 . The venting port  327  of conduit  303  prevents a negative barometric pressure to build up within the water-lock mechanism  320  to prevent a portion of the blood that has accumulated in compartment  301  to fill over to compartment  302  when the sealing clamp  325  is released. Fat collects at the top surface of blood in compartment  301  and remains in compartment  301  together with the top portion of blood that is prevented to flow over into compartment  302 . The flow rate by which fat-reduced blood fills over from compartment  301  to compartment  302  is controlled by the flow resistance of conduit  303 , in particular but not limited to a narrowing within channel  312 . A typical drainage time is about 30 seconds but can set to other time duration depending on use of the apparatus  1 . The compartment  302  comprises an extension  316  of pipe  305  with one or more perforations  317 , and pipe  305  emerges at the bottom of compartment  302  to form an outlet  330 . A third sealing clamp  331  is mounted on the pipe  305  at outlet  330  of compartment  302  to control drainage of blood from the chamber  300  into the venous reservoir (not shown) or back into the patient&#39;s body. This chamber  300  is also suitable for allowing through flow of blood by removing all the clamps  310 ,  325 ,  331 , if high volume bleeding occurs at the surgery site. It is well appreciated within the scope of the invention that the design of compartment  302  can be similar to what is described for compartment  301  comprising a second water-lock mechanism identical to the water-lock  320 . The second water lock prevents the last portion of blood in compartment  302 , containing a concentrated amount of fat that has accumulated at the top surface of blood, to reach the patient&#39;s body. It is also understood that additional compartments, identical to  301  and  302 , can be connected in series to form a multi-compartment fat-separation chamber. It will further be appreciated that a fat-absorbing filter of the type described in relation to  FIGS. 2 to 6  may be incorporated into the chamber  300  of this embodiment, that a heat exchanger as previously discussed could also be applied to the apparatus  1  of this embodiment, and that pipe connections  71  of  FIGS. 7 and 8  could be used within this embodiment. The chamber  300  and pipe  305  described in this embodiment are produced from a pliable transparent plastic material, although they are not limited to this particular material. A chamber  300  manufactured from a rigid material is also within the scope of the invention. 
     It will of course be appreciated that the clamps described are not limited to manual actuation and could be operated mechanically, electrically, pneumatically or hydraulically. 
     It will of course be appreciated that the invention is not limited to the detailed description of the specific embodiments, which are given by way of example only, and that various alterations and modifications may be made to the embodiments without departing from the scope of the invention as defined in the appended claims. 
     The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.