Abstract:
An oxygenator combines, in a single structure, a heat exchanger, a gas exchanger and an arterial filter. Such an oxygenator permits fewer fluid connections and thus may simplify an extracorporeal blood circuit, including a heart-lung machine and a blood reservoir, in which it is used. In some cases, the oxygenator may be configured to include multiple purge ports for purging bubbles both before and after filtering the blood.

Description:
TECHNICAL FIELD 
     The disclosure pertains generally to arterial filters used in blood perfusion systems. 
     BACKGROUND 
     Blood perfusion entails encouraging blood through the vessels of the body. For such purposes, blood perfusion systems typically entail the use of one or more pumps in an extracorporeal circuit that is interconnected with the vascular system of a patient. Cardiopulmonary bypass surgery typically requires a perfusion system that provides for the temporary cessation of the heart to create a still operating field by replacing the function of the heart and lungs. Such isolation allows for the surgical correction of vascular stenosis, valvular disorders, and congenital heart defects. In perfusion systems used for cardiopulmonary bypass surgery, an extracorporeal blood circuit is established that includes at least one pump and an oxygenation device to replace the functions of the heart and lungs. 
     More specifically, in cardiopulmonary bypass procedures oxygen-poor blood, i.e., venous blood, is gravity-drained or vacuum suctioned from a large vein entering the heart or other veins in the body (e.g., femoral) and is transferred through a venous line in the extracorporeal circuit. The venous blood is pumped to an oxygenator that provides for oxygen transfer to the blood. Oxygen may be introduced into the blood by transfer across a membrane or, less frequently, by bubbling oxygen through the blood. Concurrently, carbon dioxide is removed across the membrane. The oxygenated blood is filtered and then returned through an arterial line to the aorta, femoral, or other artery. 
     Often, an arterial filter is added to the extracorporeal circuit, after the oxygenator, as last barrier before the patient, so as to block any solid or gaseous emboli and prevent any such emboli from entering into the aorta of the patient. Recently, arterial filters integrated in the oxygenator have been developed, allowing the reduction of the priming volume of the circuit and decreasing the global haemodilution of the patient. 
     SUMMARY 
     According to an embodiment of the present invention, a blood processing apparatus includes an apparatus housing having a blood inlet and a blood outlet. The blood inlet may extend into an interior of the apparatus housing. A heat exchanger is in fluid communication with the blood inlet and is disposed about the blood inlet. A gas exchanger is disposed about the heat exchanger such that an inner surface of the gas exchanger is positioned to receive blood exiting an outer surface of the heat exchanger, an annular space being defined between an outer surface of the gas exchanger and an interior surface of the apparatus housing such that blood exiting the outer surface of the gas exchanger can collect in the annular space. An annular filter housing is arranged concentrically about the apparatus housing. A filter is arranged within the annular filter housing, forming a first annular chamber between the cylindrical filter and the apparatus housing and a second annular chamber between the cylindrical filter and the annular filter housing. An elongate opening is formed within the annular filter housing such that blood collecting in the annular space can pass into the first annular chamber. A first purge port is in communication with the first annular chamber and a second purge port is in communication with the second annular chamber. 
     According to another embodiment of the present invention, an integrated blood processing apparatus includes a housing having a blood inlet and a blood outlet, the blood inlet extending into an interior of the housing. A heat exchanger is disposed about the blood inlet and is in fluid communication with the blood inlet. An oxygenator is disposed about the heat exchanger and is in fluid communication with the heat exchanger. A filter housing defining an interior volume is secured to the housing. A filter is disposed within the filter housing, dividing the interior volume into a first chamber that is in fluid communication with the oxygenator and a second chamber that is in fluid communication with the blood outlet. A first purge port is in fluid communication with the first chamber and a second purge port is in fluid communication with the second chamber. 
     According to another embodiment of the present invention, an oxygenator includes an oxygenator housing having a blood inlet and a blood outlet. The oxygenator housing defines an oxygenator volume. An annular filter housing defining an interior filter volume is disposed about the oxygenator housing. A filter is disposed within the annular filter housing, dividing the interior filter volume into a first chamber that is in fluid communication with the oxygenator volume and a second chamber that is fluid communication with the blood outlet. A first purge port is disposed within a wall forming the annular filter housing and is in fluid communication with the first chamber. A second purge port is disposed within the wall forming the annular filter housing and is in fluid communication with the second chamber. 
     While multiple embodiments are disclosed, still other embodiments of the present invention will become apparent to those skilled in the art from the following detailed description, which shows and describes illustrative embodiments of the invention. Accordingly, the drawings and detailed description are to be regarded as illustrative in nature and not restrictive. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic illustration of a blood processing apparatus including an integrated arterial filter in accordance with an embodiment of the invention. 
         FIG. 2  is a cross-sectional illustration of the blood processing apparatus of  FIG. 1 . 
         FIG. 3  is an illustrative view of a filter deployed within the blood processing apparatus of  FIG. 1 . 
         FIG. 4  is an illustrative view of another filter deployed within the blood processing apparatus of  FIG. 1 . 
         FIG. 5  is a schematic illustration of a blood processing apparatus including an integrated arterial filter in accordance with an embodiment of the invention. 
         FIG. 6  is a schematic cross-sectional illustration of the blood processing apparatus of  FIG. 5 . 
         FIG. 7  is an illustrative view of a filter deployed within the blood processing apparatus of  FIG. 5 . 
         FIG. 8  is a schematic illustration of a blood processing apparatus including an integrated arterial filter in accordance with an embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION 
     The disclosure pertains to a blood processing apparatus that combines, in a single structure, a heat exchanger, a gas exchanger or oxygenator and an arterial filter. In some embodiments, the term oxygenator may be used to refer to a structure that combines a heat exchanger, a gas exchanger and an arterial filter in a unitary device. In some embodiments, an oxygenator may be used in an extracorporeal blood circuit. An extracorporeal blood circuit, such as may be used in a bypass procedure, may include several different elements such as a heart-lung machine, a blood reservoir, as well as an oxygenator. 
     In some embodiments, by combining the arterial filter with the oxygenator, the tubing set used to create the extracorporeal blood circuit may be reduced in complexity or number of parts and thus may simplify the extracorporeal blood circuit. In some embodiments, this will reduce the priming volume of the extracorporeal blood circuit. 
       FIG. 1  is a schematic illustration of a blood processing apparatus or oxygenator  10 . While the internal components are not visible in this illustration, the oxygenator  10  may include one or more of a heat exchanger, a gas exchanger and an arterial filter. According to some embodiments, each of the heat exchanger, gas exchanger and arterial filter are integrated into a single structure that forms an oxygenator housing. The oxygenator  10  includes a device compartment or housing  12  and an arterial filter compartment or housing  14 . In some embodiments, the arterial filter housing  14  may be integrally molded or otherwise structurally integrated with the device housing  12 . In some cases, the arterial filter housing  14  may be separately formed and then secured or otherwise coupled to the device housing  12 . According to various embodiments the heat exchanger, the gas exchanger, and the arterial filter housing  14  may have a cross-section shaped generally as a circle or as a parallelogram (e.g., a square or rectangle). Each of the heat exchanger, the gas exchanger and the arterial filter housing  14  may have generally the same sectional shape or each may have a different sectional shape. 
     In some embodiments, a blood inlet  16  extends through the arterial filter housing  14  and into the device housing  12 . A blood outlet  18  exits the arterial filter housing  14 . As noted, in some embodiments the oxygenator  10  includes a gas exchanger and thus may include a gas inlet  20  and a gas outlet  22 . In some embodiments, the oxygenator  10  includes a heat exchanger and thus may include a heating fluid inlet  24  and a heating fluid outlet  26 . As will be explained in greater detail with respect to  FIG. 2 , the oxygenator  10  includes a first purge port  28  and a second purge port  30 . It is to be understood that the positions of the inlets, outlets and purge ports are merely illustrative, as other arrangements and configurations are contemplated. The purge ports may include a valve or a threaded cap. The purge ports operate to permit gases (e.g., air bubbles) that exit the blood to be vented or aspirated and removed from the oxygenator. 
       FIG. 2  is a cross-sectional view of the oxygenator  10 , illustrating internal components and an example of how blood can flow through the oxygenator  10 . The oxygenator  10  includes a heat exchanger  32  and a gas exchanger  34 . In some embodiments, the heat exchanger  32  includes a number of hollow fibers through which a heating fluid such as water can flow. The blood may flow around and past the hollow fibers and thus be suitably heated. In some embodiments, the hollow fibers may be polymeric. In some cases, metallic fibers may be used within the heat exchanger  32 . According to other embodiments, the heat exchanger  32  includes a metal bellows or other structure comprising a substantial surface area (e.g., fins) for facilitating heat transfer with the blood. 
     In some embodiments the gas exchanger  34  may include a number of hollow fibers through which a gas such as oxygen may flow. The blood may flow around and past the hollow fibers. Due to concentration gradients, oxygen may diffuse through the hollow fibers into the blood while carbon dioxide may diffuse into the hollow fibers and out of the blood. 
     The oxygenator  10 , according to some embodiments, includes an annular space  36  into which blood may flow as the blood exits the gas exchanger  34 . As illustrated, the annular space  36  may extend into the arterial filter housing  14 . According to exemplary embodiments, the annular space  16  may be generally circular or generally rectangular. The arterial filter housing  14  includes a filter  38 . In some embodiments, the filter  38  includes an annular frame  40  and a net or mesh  42  spanning the annular frame  40 . In some embodiments, the filter  38  may be considered as dividing a volume within the arterial filter housing  14  into a first chamber  44  and a second chamber  46 . In various embodiments, the annular frame  40  and the net or mesh  42  are disposed concentrically with respect to the filter housing  14 . In other embodiments the annular frame  40  and the mesh  42  are disposed about the housing  14  in a non-concentric manner. According to exemplary embodiments, the internal (i.e., priming) volume of the arterial filter housing  14  is between about 80 and about 110 mL. According to other embodiments, the priming volume is between about 90 and about 100 mL. 
     An opening  48  that may extend circumferentially up to about 360 degrees provides fluid communication between the annular space  36  and the first chamber  44 . While blood is in the first chamber  44 , any air bubbles that are present within the blood may be vented through the first purge port  28 . Blood may pass through the filter  38  and into the second chamber  46 . Any bubbles remaining in the blood, or caused by passage through the filter  38 , may be vented through the second purge port  30 . Blood may then exit the oxygenator  10  through the blood outlet  18 . The presence of the first purge port  28  in the first chamber  44  and the second purge port  30  in the second chamber  46 , according to various embodiments, will improve the priming speed due to the fact that bubbles present in the blood have both a first and a second opportunity to exit through a purge port. Moreover, in these embodiments, the efficacy of the bubble or gas removal is improved, again due to the fact that bubbles present in the blood have both a first and a second opportunity to exit through a purge port. 
     In some embodiments, the blood flow may be altered somewhat. For example, in some cases, the opening  48  may be positioned to provide fluid communication between the annular space  36  and the second chamber  46  while the blood outlet  18  is positioned in fluid communication with the first chamber  44 . In some embodiments, the annular space  36  may empty directly into the second chamber  46 , and may not extend into the first chamber  44 . 
       FIG. 3  is a view of the filter  38 , illustrating the frame  40  and the net or mesh  42 .  FIG. 4  shows an embodiment of the filter  38  including a blocking plate  100 . In some embodiments, the blocking plate  100  may be sized, shaped and positioned near the blood outlet  18  to limit preferential blood flow on the lower portion of the oxygenator  10 . According to various embodiments, the filter  38  may have a cross-sectional shape that is circular, rectangular, or any other shape. 
     In some embodiments, the net or mesh  42  may have a mesh size that is the range of about 20 to about 200 microns. In some cases, the net or mesh  42  may have a mesh size of about 120 microns. In some instances, the net or mesh  42  may have a mesh size of from about 38-40 microns, and may be formed of a polymeric material such as polyester or polypropylene. In some cases, the net  42  may be coated with a biocompatible material. The blocking plate  100  may be formed of any suitable material. In some embodiments, the blocking plate  100  may be integrally formed with the frame  40 . According to various exemplary embodiments, the net or mesh  42  has a surface area of between about 70 and about 90 square centimeters. According to other exemplary embodiments, the net or mesh  42  has a surface are of between about 75 and about 80 square centimeters. 
       FIG. 5  is a schematic illustration of a blood processing apparatus or oxygenator  110 . While the internal components are not visible in this illustration, the oxygenator  110  may include one or more of a heat exchanger, a gas exchanger and an arterial filter. The oxygenator  110  includes a device housing  112  and an arterial filter housing  114 . In some embodiments, the arterial filter housing  114  may be integrally molded or otherwise formed with the device housing  112 . In some cases, the arterial filter housing  114  may be separately formed and then secured to the device housing  112 . 
     In some embodiments, a blood inlet  116  extends through the arterial filter housing  114  and into the device housing  112 . A blood outlet  118  exits the arterial filter housing  114 . As noted, in some embodiments the oxygenator  110  includes a gas exchanger and thus may include a gas inlet  120  and a gas outlet  122 . In some embodiments, the oxygenator  110  includes a heat exchanger and thus may include a heating fluid inlet  124  and a heating fluid outlet  126 . As will be explained in greater detail with respect to  FIG. 6 , the oxygenator  110  includes a first purge port  128  and a second purge port  130 . It is to be understood that the positions of the inlets, outlets and purge ports are merely illustrative, as other arrangements and configurations are contemplated. 
       FIG. 6  is a cross-sectional view of the oxygenator  110 , illustrating internal components and an example of how blood can flow through the oxygenator  110 . The oxygenator  110  includes a heat exchanger  132  and a gas exchanger  134 . In some embodiments, the heat exchanger  132  includes a number of hollow polymeric or metallic fibers through which a heating fluid such as water can flow. The blood may flow around and past the hollow fibers and thus be suitably heated. In some embodiments the gas exchanger  134  may include a number of hollow fibers through which a gas such as oxygen may flow. The blood may flow around and past the hollow fibers. Due to concentration gradients, oxygen may diffuse through the hollow fibers into the blood while carbon dioxide may diffuse into the hollow fibers and out of the blood. 
     As shown in  FIG. 6 , the gas exchanger is configured such that blood flows radially across the gas exchanger  134 . In these embodiments, the oxygenator  110  includes an annular space  136  into which blood may flow as the blood exits the gas exchanger  134 . According to various embodiments, the annular space  136  may be either open or it may be partially or completely filled with hollow fibers. As illustrated, the arterial filter housing  114  may extend over a portion of the annular space  136 . According to other embodiments, the gas exchanger  134 , the heat exchanger  132 , or both may be configured such that blood is directed in a longitudinal flow path. In various exemplary embodiments where the gas exchanger  134  is configured such that blood flows in a longitudinal path, the annular space  136  is omitted. In these embodiments, the blood flows out of the gas exchanger  134  near an end and flows directly into the arterial filter housing  114 . In some embodiments, the opening between the gas exchanger  134  and the arterial filter housing  114  is blocked or occluded at the radial location corresponding to the blood outlet  18  of the arterial filter housing  14 , to minimize or prevent direct flow from the gas exchanger  134  into the blood outlet  18 . 
     A filter  138  may be disposed within the arterial filter housing  114 . In some instances, as illustrated, the filter  138  divides the space within the annular filter housing  114  into a first chamber  144  and a second chamber  146 . An opening  148  that may extend circumferentially up to about 360 degrees provides fluid communication between the annular space  136  and the first chamber  144 . While blood is in the first chamber  144 , any air bubbles that are present within the blood may be vented through the first purge port  128 . Blood may pass through the filter  138  and into the second chamber  146 . Any bubbles remaining in the blood, or caused by passage through the filter  138 , may be vented through the second purge port  138 . Blood may then exit the oxygenator  110  through the blood outlet  118 . 
       FIG. 7  is a view of the filter  138 . In some embodiments, the filter  138  is a cylindrical filter that includes one or more reinforcements  140  and a cylindrical net or mesh  142 . In some embodiments, the one or more reinforcements  140  may be molded into the cylindrical net or mesh  142 . In some cases, the one or more reinforcements  140  may be adhesively secured to the cylindrical net or mesh  142 . In some embodiments, the one or more reinforcements  140  may extend cylindrically about the filter  138 . In some instances, the one or more reinforcements  140  may run across the filter  138 . 
     In some embodiments, the net or mesh  142  may have a mesh size that is the range of about 20 to about 200 microns. In some cases, the net or mesh  142  may have a mesh size of about 120 microns. In some instances, the net or mesh  142  may have a mesh size of about 40 microns, and may be formed of a polymeric material such as polyester or polypropylene. In some cases, the net  142  may be coated with a biocompatible material. 
     In some embodiments, the net or mesh  142  may include a blocking region or plate  200  that is sized, shaped and positioned near the blood outlet  118  to limit preferential blood flow on the lower portion of the oxygenator  110 . The blocking plate  200  may be formed of any suitable material. In some embodiments, the blocking plate  200  may be molded or otherwise formed within the net or mesh  142 . 
       FIG. 8  is a schematic illustration of a blood processing apparatus or oxygenator  310 . While the internal components are not visible in this illustration, the oxygenator  310  may include one or more of a heat exchanger, a gas exchanger and an arterial filter. The oxygenator includes a device housing  312  and an arterial filter housing  314 . In the illustrated embodiment, the arterial filter housing  314  is integrated into an end or side face of the device housing  312  and is configured such that blood exiting the device housing  312  enters the arterial filter housing  314 . The device housing  312  includes a blood inlet  316  while the arterial filter housing  314  includes a blood outlet  318 . 
     In some embodiments, as illustrated, the arterial filter housing  314  includes a net filter  320 , a first purge port  322  and a second purge port  324 . The first purge port  322  may be in fluid communication with an interior of the arterial filter housing  314  at a position upstream of the net filter  320  while the second purge port  324  may be in fluid communication with an interior of the arterial filter housing  314  at a position downstream of the net filter  320 . As described in more detail above, this configuration allows an improvement and priming speed and efficacy, while also reducing the overall priming volume. 
     Various modifications and additions can be made to the exemplary embodiments discussed without departing from the scope of the present invention. For example, while the embodiments described above refer to particular features, the scope of this invention also includes embodiments having different combinations of features and embodiments that do not include all of the above described features.