Abstract:
A two-chambered centrifugal blood pump for pumping biological fluids such as blood. One chamber is for pumping blood through the natural lungs, and a second chamber is for pumping blood through the remainder of the body. Each chamber has it&#39;s own inlet and outlet ports for attachment of tubing and cannulae. A small, adjustable clamp may alternatively be provided if minor adjustments of pressure to both the pulmonary and systemic circuits is required.

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S)  
         [0001]    None.  
         BACKGROUND OF THE INVENTION  
         [0002]    The present invention relates to centrifugal blood pumps.  
           [0003]    Delicate surgical procedures require that the site of surgery remain motionless. This requirement made early heart surgery difficult to impossible as interruption of the heart&#39;s pumping action for the required length of surgical time would invariably be fatal.  
           [0004]    Traditional heart surgery is carried out with the aid of devices generally referred to as a “heart/lung machine”. With the heart/lung machine in operation, the patient&#39;s heart can be stopped while the surgeon performs the delicate surgery required to repair the ailing heart. The two fundamental parts of the heart/lung machine are a blood pump that takes the place of the arrested heart, and an oxygenator that replaces the patient&#39;s lungs during the surgical procedure. The heart/lung machine also includes filters, blood reservoirs, and plastic tubing as required to connect several parts of the bypass circuit.  
           [0005]    Although the mortality and morbidity of heart/lung bypass surgery have been greatly reduced, hospital stays of two weeks and a gradual recovery of over six months are the norm. Many of the bad side-effects of heart/lung surgery are thought to be the result of blood contact with the various parts of the heart/lung machine.  
           [0006]    Quite recently, a new technique for heart surgery has been developed. The technique is generally referred to as “surgery on the beating heart”. In this process, a stabilizing device is used to hold steady the portion of the heart that is being addressed by the surgeon. The heart/lung machine is not required, because the heart and lungs function normally throughout the procedure. Advantages claimed for this method include reduced hospital stay, reduced hospital cost, and fewer side-effects such as mental deficit. All of these advantages are claimed due to the reduced blood trauma by elimination of blood contact with the devices making up the heart/lung machine.  
           [0007]    Beating-heart surgery is not without some problems both for the surgeon and the patient. First, the most commonly used stabilizing device consists in part of a series of small suction cups that attach to the portion of the heart being stabilized. The relatively high vacuum required to grasp the heart typically results in blood blisters on the heart muscle at the site of the suction cups. Second, since the heart is pumping, the surgeon must contend with blood spurting from the coronary artery during graft attachment. Third, there is no data concerning the durability of the coronary artery graft done with this procedure. Lastly, the cost of disposable devices is comparable to that required for conventional open-heart surgery.  
           [0008]    The single component of the heart/lung machine that is most suspect for blood trauma is the oxygenator. This is typically a device with hundreds of hollow plastic fibers. The blood passes over the outside surface of the fibers and oxygen passes through the fibers to imitate the function of the natural lungs. Unlike the natural lungs, however, the hollow fibers are made out of a plastic material and must have a large surface area in order to oxygenate the blood and remove carbon dioxide from it. Elimination of the oxygenator would also eliminate tubing, reservoirs, and filters resulting in a significant reduction of foreign blood-contact surfaces.  
           [0009]    The mammalian heart performs two pumping functions. The first function is to pump blood through the lungs, and the second is to pump blood to the remainder of the body. The elimination of the oxygenator can be accomplished through the use of two mechanical blood pumps to duplicate the function of the natural heart. This method has been tried experimentally but has not gained favor because of several problems. First, the use of two blood pumps requires that they be synchronized. This is technically difficult with roller-type pumps, which are the most commonly used type in open-heart surgery. Second, cannulae must be placed in both the systemic and pulmonary circuits, which increases surgical time. Third, the extra cannulae crowd the operating area and compromise ready access to the heart. Fourth, although conventional centrifugal blood pumps readily self-synchronize, their size adds to the crowding of the operating field.  
         BRIEF SUMMARY OF THE INVENTION  
         [0010]    With the present invention, the reduction of blood trauma is achieved by eliminating the oxygenator. The present device is a two-chambered centrifugal blood pump. The first chamber has a first inlet and a first outlet and the second chamber has a second inlet and a second outlet. A shaft extends through and between the first and second chambers and defines a rotational axis. First and second impellers are also positioned within the first and second pumping chambers, respectively. In the preferred embodiment, one chamber pumps deoxygenated blood to the natural lungs, and the other chamber pumps oxygenated blood to the remainder of the body. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]    [0011]FIG. 1 is a cross-sectional view of the preferred embodiment of the invention.  
         [0012]    [0012]FIG. 2 a  is a cross-sectional view of the duplex pump including a shaft seal.  
         [0013]    [0013]FIG. 2 b  is a cross-sectional view of the duplex pump including a shaft bearing.  
     
    
     DETAILED DESCRIPTION  
       [0014]    [0014]FIG. 1 shows the preferred embodiment of the present invention. Duplex pump  10  includes housing  12 , first pumping chamber  14 , second pumping chamber  16 , shaft  18 , opening  20 , back bearing  22 , front bearing  24 , first impeller  26 , second impeller  28  with magnets  30 , axis of rotation  32 , first inlet  34 , first outlet  36 , second inlet  38 , second outlet  40 , first and second pulmonary flow lines  42  and  44 , first and second systemic flow lines  46  and  48 , clamps  50 ,  52 ,  54 , and  56 , drive motor  58  with magnets  60 , web  62 , pulmonary unit  64 , and systemic unit  66 .  
         [0015]    Housing  12  forms first chamber  14  and second chamber  16 , with first chamber  14  positioned on top of second chamber  16 . Shaft  18  extends from second chamber  16  through opening  20  to first chamber  14  and is supported by back bearing  22  and front bearing  24 . First impeller  26  is positioned within first chamber  14  and connected to shaft  18 . Second impeller  28  with magnets  30  is positioned within second chamber  16  and connected to shaft  18 . Shaft  18  with impellers  26  and  28  rotate about axis of rotation  32 . First inlet  34  and first outlet  36  extend from first chamber  14 , and second inlet  38  and second outlet  40  extend from second chamber  16 . Flow lines  42 ,  44 ,  46 , and  48  are coupled to first inlet  34 , first outlet  36 , second inlet  38 , and second outlet  40 , respectively. Clamps  50 ,  52 ,  54 , and  56  are adjustably attached to flow lines  42 ,  44 ,  46 , and  48 , respectively. Drive motor  58  contains magnets  60 , which are magnetically coupled to magnets  30  in impeller  28 . Web  62  aids in support of first chamber  14  over second chamber  16 . Collectively, first chamber  14 , shaft  18 , impeller  26 , first inlet  34 , first outlet  36 , and flow lines  42  and  44  form pulmonary unit  64 . Accordingly, second chamber  16 , shaft  18 , impeller  28 , second inlet  38 , second outlet  40 , and flow lines  46  and  48  form systemic unit  66 .  
         [0016]    To power duplex pump  10 , drive motor  58  rotates magnets  60  around axis of rotation  32 . Magnets  60  are magnetically coupled to magnets  30  in second impeller  28 . Thus, second impeller  28 , shaft  18 , and first impeller  26  synchronously rotate around axis of rotation  32 . First impeller  26  and second impeller  28  are preferably a bladed-type impeller, but any other type of impeller or device which provides the proper fluid motion can be used.  
         [0017]    In operation, liquid is pumped through a load having two circuits, or preferably, blood is pumped through the pulmonary and systemic circuits of a patient. Flow line  42  connects to a source of systemic venous blood such as the right atrium or vena cava, and flow line  44  connects to a pulmonary artery of the patient. Flow line  46  connects to a source of oxygenated blood such as the left atrium or left ventricle, and flow line  48  connects to a systemic artery of the patient, such as the aorta. Deoxygenated blood from the right atrium or vena cava enters first chamber  14  through first inlet  34 . The blood contacts first impeller  26 , and is propelled to and through first outlet  36  and to a pulmonary artery. Thus, pulmonary unit  64  performs the function of carrying deoxygenated blood from the patient&#39;s systemic circuit to the patient&#39;s lung or lungs to become oxygenated.  
         [0018]    Simultaneously, oxygenated blood from the left atrium or left ventricle enters second chamber  16  through second inlet  38 . The blood contacts second impeller  28 , and is propelled to and through second outlet  40  and to the aorta. Systemic unit  66 , thus, performs the function of dispersing oxygenated blood from the patient&#39;s pulmonary circuit to the patient&#39;s systemic circuit.  
         [0019]    Alternatively, clamps  50 ,  52 ,  54 , and  56  may be attached to flow lines  42 ,  44 ,  46 , and  48 , respectively. Clamps  50 ,  52 ,  54 , and  56  may be adjusted, as needed, to make minor adjustments in pressure to either of the circuits.  
         [0020]    In the preferred embodiment, opening  20  remains open which allows some leakage between first chamber  14  and second chamber  16 . In this embodiment, the blood remains in motion and is less likely to form clots. However, a seal may fitted within opening  20  to prevent any leakage. Two variations of sealing off first chamber  14  and second chamber  16  are presented in FIGS. 2 a  and  2   b.    
         [0021]    [0021]FIG. 2 a  shows duplex pump  10  with shaft  18  supported by back bearing  22  and front bearing  24 . Shaft seal  68  is fitted circumferentially around shaft  18  within opening  20 . Shaft seal  68  may be an o-ring or the like.  
         [0022]    [0022]FIG. 2 b  shows duplex pump  10  with shaft  18 , which is supported by back bearing  22  and shaft bearing  70 . Shaft bearing  70  is fitted into opening  20  and circumferentially around shaft  18 . In this embodiment, front bearing  24  is not necessary because shaft  18  is supported by shaft bearing  70 .  
         [0023]    There are several advantages of using the present invention for heart/lung bypass. First, many of the benefits of beating-heart surgery is attained but with the surgical advantages of conventional heart/lung bypass surgery. Second, systemic unit  66  is much smaller than conventional centrifugal blood pumps, because there is no need to overcome the pressure resistance of the traditional heart/lung machine. Pulmonary unit  64  is even smaller because of the lower resistance of the pulmonary circuit. The small size of units  64  and  66  allow pump  10  to be placed close to the operating field, which reduces the length of tubing normally required by a heart/lung machine. Third, the reduced pressure requirement also permits using smaller diameter tubing and cannulae, which further reduces clutter at the operating field. Fourth, no special equipment or controls are required to equalize the flow between the pulmonary and systemic circuits, because centrifugal pumps are inherently self-balancing. Fifth, eliminating an oxygenator, and eliminating or reducing other disposable products used in conventional open-heart surgery reduces the cost of the procedure.  
         [0024]    Although the present invention has been described with reference to preferred embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention.