Abstract:
A perfusion system for treating blood during a surgical procedure uses a flow control valve with first and second inlets and first and second outlets. A first intermediate line couples the first outlet to an air removal system. A second intermediate line couples blood from the air removal system to the second inlet. An arterial line carries treated blood from the second outlet back to the patient. The flow control valve has an open position and a recirculate position, wherein the first inlet is coupled to the first outlet when the flow control valve is in either the open position or the recirculate position. The second inlet is coupled to the second outlet and blocked from the first outlet in the open position. The second inlet is coupled to the first outlet and blocked from the second outlet in the recirculate position.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to co-pending U.S. provisional application Ser. No. 60/761,526, filed Jan. 24, 2006. 
    
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH 
     Not Applicable. 
     BACKGROUND OF THE INVENTION 
     The present invention relates to a blood perfusion system used during surgery such as cardiovascular surgery wherein air emboli present in the perfusion circuit is efficiently removed by an air removal device before returning the embolus-free blood back to circulation in the patient. 
     During cardiac bypass surgery, the heart is stopped in order to allow repair of defects, such as the replacement of defective heart valves, or the placement of bypass grafts. The patient&#39;s blood is redirected through an extracorporeal perfusion circuit typically including various items such as a venous cannula, PVC tubing, a reservoir, a pump, an oxygenator, an arterial filter, and an arterial cannula. During extraction of blood from the patient and/or at various stages of flow within the perfusion circuit, air emboli may form within the circulating blood. If these emboli are not removed from the circulating blood and are instead introduced back to the patient&#39;s bloodstream, there may be serious complications. 
     Air or other gaseous emboli can be removed (i.e., filtered) from blood that is flowing in a perfusion circuit by passing it through an air removal system. A screen or mesh filter can be employed for this purpose. Other examples of air removal devices that can be used include those shown in co-pending U.S. application Ser. No. 11/118,726, filed Apr. 29, 2005, entitled “Air Removal Device with Float Valve for Blood Perfusion System”, co-pending U.S. application Ser. No. 11/136,047, filed May 24, 2005, entitled “Vortex-Flow Air Removal in a Blood Perfusion System”, co-pending U.S. application Ser. No. 11/245,751, filed Oct. 7, 2005, entitled “Float-Driven Lever Arm for Blood Perfusion Air Removal Device”, and co-pending U.S. application Ser. No. 11/245,752, filed Oct. 7, 2005, entitled “Blood Perfusion Air Removal Device with Arcuate Manifold”, all of which are incorporated herein by reference in their entirety. 
     Some currently available perfusion systems monitor the fluid level in the perfusion circuit reservoir using a level sensor in order to infer that air emboli are present when the level in the reservoir is too low. It is known to display or sound an alert signal when the level in the reservoir drops below a predetermined threshold limit (or when emboli are otherwise detected, such as with an ultrasonic sensor). In response to the alarm, the circulation is manually stopped by a health care professional (such as a perfusionist) as quickly as manually possible. Special steps must then be taken to remove the air emboli before restoring the circulation back to the patient. 
     The perfusionist has many tasks to perform in the operating room during cardiac surgery and the corresponding distractions can lengthen the response time for stopping circulation when an alarm is triggered. Therefore, there is a need in the art for a means of automatically stopping the emboli before it reaches the patient without having to wait for action from the perfusionist. 
     Besides the need to quickly divert any emboli from reaching the patient, it is very important to clear the emboli from the blood in the perfusion circuit so that circulation to the patient can be restored as soon as possible. Once circulation is stopped in the perfusion circuit, it is time consuming for the perfusionist to isolate the quantity of blood containing the emboli and remove the emboli. Therefore, there is also a need in the art for a means of quickly purging emboli in order to safely restore blood circulation to the patient. 
     SUMMARY OF THE INVENTION 
     The present invention protects the patient from emboli in blood by automatically diverting emboli-containing blood away from the patient and then quickly removing the emboli by recirculating the blood through an air removal device. When the excess air has been removed from the blood, then circulation to the patient can be manually or automatically restored. 
     In one aspect of the invention, a perfusion system is provided for treating blood of a patient during a surgical procedure. A venous line carries blood removed from the patient. A flow control valve has first and second inlets and first and second outlets, wherein the venous line is coupled to the first inlet. An air removal system is provided for removing emboli from the blood flowing in the perfusion system. A first intermediate line couples the first outlet of the flow control valve to the air removal system. A second intermediate line couples blood having passed through the air removal system to the second inlet of the flow control valve. An arterial line couples to the second outlet of the flow control valve for carrying treated blood back to the patient. The flow control valve is selectably placed in an open position or a recirculate position, wherein the first inlet is coupled to the first outlet when the flow control valve is in either the open position or the recirculate position. The second inlet is coupled to the second outlet and blocked from the first outlet when the flow control valve is in the open position. The second inlet is coupled to the first outlet and blocked from the second outlet when the flow control valve is in the recirculate position. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic view of a perfusion system according to one embodiment of the present invention. 
         FIG. 2  is a diagram showing blood flow during a normal operating mode of the perfusion system. 
         FIG. 3  is a diagram showing blood flow during a recirculating mode of the perfusion system. 
         FIG. 4  is a flowchart showing a preferred method for controlling the flow control valve of  FIG. 1 . 
         FIG. 5  is an exploded view of a plug valve used in one embodiment of the present invention. 
         FIG. 6  is a cross-sectional view of the plug valve in its open position. 
         FIG. 7  is a cross-sectional view of the plug valve in its recirculate position. 
         FIG. 8  is an isometric view of the plug valve showing the extension of the valve stem. 
         FIG. 9  is an exploded view of a piston valve used in another embodiment of the invention. 
         FIG. 10  is a cross-sectional view of the piston valve of  FIG. 9 . 
         FIG. 11  is an exploded view of an alternate embodiment of a plug valve having magnetic coupling. 
         FIG. 12  is a perspective view of the plug valve of  FIG. 11  with the top cover removed. 
         FIG. 13  is a perspective view of the bottom of the plug valve of  FIG. 11  with the bottom cover removed. 
         FIG. 14  is a perspective view of the plug valve and a combined automatic/manual actuator. 
         FIG. 15  is an exploded view of a gate valve used in another embodiment of the invention adapted for automatic actuation. 
         FIG. 16  is an exploded view of a gate valve used in another embodiment of the invention adapted for manual actuation. 
         FIG. 17  is a perspective view of the gate valve of  FIG. 16  with the top cover removed. 
         FIG. 18  is a top, perspective view of the gate valve of  FIG. 16 . 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Referring now to  FIG. 1 , a perfusion system supporting a patient  10  includes a venous cannula  11  supplying the patient&#39;s blood to a venous line  12  is connected to an inlet of a flow control valve  13 . An intermediate line  14  passes the blood flow to an air removal system  15  and then to a blood pump  16 . Another intermediate line  17  provides blood flow from pump  16  to a second inlet of flow control valve  13 . 
     In a normal operating mode, blood from pump  16  is passed from valve  13  through an oxygenator  18  to an arterial line  19  and to an arterial cannula  20  for return to the patient. Thus, flow control valve  13  is shown in an open position such that substantially all emboli are removed from the flowing blood by air removal system  15  and the blood is passed through oxygenator  18  back to the patient. 
     In order to detect and react to emboli that may be entrained in the blood, a controller  21  is used to detect the presence of excessive air emboli and to prevent emboli-containing blood from reaching the patient. Thus, controller  21  is connected to a gas sensor  22  and/or a level detector  23 . Gas sensor  22  may comprise an ultrasonic detector disposed in contact with intermediate line  17  for measuring an overall volume of emboli present in predetermined volumes of blood, as is known in the art. Level sensor  23  is contained on or within air removal system  15 . Air removal system  15  utilizes a reservoir of blood upon which it acts to remove gas bubbles. A condition wherein the volume of blood present in the reservoir is less than a predetermined volume of blood results in a reduction of the ability to remove emboli from the blood. In response to either type of sensor indicating that excessive emboli are present, controller  21  actuates a mechanical actuator  24  on flow control valve  13  to move it from the open position shown in  FIG. 1  to a recirculation position which redirects blood from intermediate line  17  back to air removal system  15 . Simultaneously, controller  21  supplies an alert signal to an annunciator  25  such as a loudspeaker or a visual display. Sensor  22  and  23  may be used alone or together depending upon the specific air removal system being used, for example. 
       FIG. 2  represents the normal operation mode with flow control valve  13  in the open position. Blood from the patient is drawn through valve  13  and air separator  15  by pump  16 . The blood flows past sensor  22 , through the second set of ports on valve  15 , to oxygenator  18 , and finally back to the patient.  FIG. 3  shows the perfusion system in a recirculate mode with blood from the patient being drawn through valve  13  and through air separator  15  by pump  16 . Blood pumped by pump  16  past sensor  22  containing excessive emboli is coupled by valve  13  back to the flow going to air separator  15 . Importantly, both the recirculated blood from pump  16  and newly extracted blood from the patient are supplied by flow control valve  13  to air separator  15  simultaneously. Thus, if the introduction of emboli is related to a low level of blood in air separator  15 , additional volumes of blood from the patient can be added while the existing blood flow having the emboli continues to recirculate through air separator  15  until safe, emboli-free blood is detected by sensor  22  and the system can then be restored to the normal operating mode with the valve moving from the recirculate position to the open position. 
     A preferred method for operating the perfusion system is shown in  FIG. 4 . In step  30 , the perfusion system is initialized in the normal mode with the flow control valve in the open position (e.g., after system priming as is known in the art). A check is made in step  31  to determine whether excess air emboli are detected. If they are, then a check is made in step  32  to determine whether the valve is already in the recirculate position. If it is, then a return is made to step  31  for continuously checking the presence of excess air emboli. If the valve is not already in the recirculate position, then the valve is moved to the recirculate position in step  33  and a return is made to step  31 . 
     In step  31 , if excess air emboli are not detected then a check is performed step  34  to determine whether the flow control valve is already in the open position. If it is, then a return is made to step  31 . Otherwise, the flow control valve is moved to the open position in step  35  and then a return is made to step  31 . 
     In the preferred embodiment, the flow control valve for diverting emboli-containing blood starts out in the normal or open position when operation of the perfusion system is initiated. When emboli or any excess air is detected by a sensor in the blood flow path, the controller or computer moves the flow control valve to the recirculate position so that suspect blood is sent back to the air removal system. Once the air embolism event passes, the flow control valve is returned to the open position thereby permitting blood to be sent to the oxygenator and then the patient. Preferably, the control of the valve is performed electronically by the controller. However, the perfusionist may choose to bypass the controller and activate the valve manually. In particular, the perfusionist may wish to restore the normal circulation mode only after they can verify that the problem leading to the presence of emboli has been corrected. Various types of flow control valve constructions will now be described which can be adapted to both automatic and manual control. 
       FIG. 5  shows a rotating plug valve  40  including a main body  41  having a cylindrical chamber  42  for receiving a disk-shaped valve element  43 . A first inlet is formed by a nozzle  44  joined to a passageway  45  that extends through body  41  to a nozzle  46  for providing the first outlet port. A second inlet port comprises nozzle  47  mounted in communication with a passage  48  leading to chamber  42 . A second outlet port comprises a nozzle  50  joined to a passage  51  likewise leading to chamber  42 . Passage  45  also communicates with chamber  42 . Valve element  43  is received in chamber  42  and has an internal passage  52  for selectively coupling the second inlet nozzle  47  with either second outlet nozzle  50  or first outlet nozzle  46  when element  43  is rotated within cylindrical chamber  42 . 
     Valve element  43  has a control stem  53  extending out through a mating aperture in main body  41  to an actuator  54  which is mounted to the side of main body  41  by a plurality of screws  55 . Actuator  54  preferably includes an electrically controlled motor (such as a DC stepper motor) for selectably controlling the rotational position of valve element  43  in response to control signals from the controller. Valve stem  53  and actuator  54  are sealed in order to retain blood within plug valve  40 . Likewise, valve element  43  is sealed within cylindrical chamber  42  by a bottom cover  56  mounted to main body  41  using a plurality of screws  57 . Main body  41 , the nozzles, and cover  56  are preferably comprised of a clear, biocompatible plastic so that blood within the valve can be seen during perfusion. 
       FIG. 6  illustrates a cross sectional view with valve element  43  rotated to the open position with blood flow proceeding from the first inlet to the first outlet and from the second inlet to the second outlet.  FIG. 7  is a cross sectional view with valve element  43  rotated to the recirculate position wherein blood flows from the first inlet to the first outlet and from the second inlet to the first outlet so that emboli-containing blood returns to the air removal system. Simultaneously, fresh blood from the patient can enter the system while the outlet to the oxygenator is isolated so that no flow occurs to the patient. 
       FIG. 8  shows the actuator side of plug valve  40  with control stem  53  extending through actuator  54 . If manual control is desired, a handle can be attached to control stem  53  and the handle and/or valve body labeled to indicate the proper movement of the handle to obtain the open and recirculate positions, respectively. 
       FIG. 9  shows an exploded view of an alternative embodiment for the control valve wherein a piston-type valve is employed. A main valve body  60  has longitudinal bores  61  and  62  extending therethrough. A movable valve element  63  is received in bore  61 . A nozzle  64  is attached to body  61  at one end of bore  62  to form a first inlet as shown in  FIG. 10 . A nozzle  65  is connected with the other end of bore  62  to provide a first outlet which is coaxial with first inlet nozzle  64 . A nozzle  66  is connected to valve body  60  at one end of bore  61  via a connection ring  67  to form a second inlet. A nozzle  68  is connected to an aperture  69  in main body  60  to provide a second outlet. A passageway  70  is provided between bores  61  and  62 . It may be formed by drilling through main body  60  and then plugging the exterior hole as shown at  71 . 
     Valve element  63  has an internal passageway  72  that connects one end of valve element  63  to an intermediate exit hole  73  and to a flow recess  74  around the circumference of the valve element. Thus, depending upon the longitudinal position of valve element  63 , flow from second inlet  66  is recirculated to first outlet  65  through hole  70  as shown in  FIG. 10  or is directed through second outlet  68  when passage  73  and recess  74  are extended to a position aligned with second outlet  68 . In order to control the position of valve element  63 , a control end  75  is coupled to an actuator  76 . Actuator  76  may include a magnetic solenoid, for example. 
     As shown in  FIG. 11 , an alternate embodiment employing a plug-type valve includes an outer housing wall  81  for receiving a valve element  82 . Sealed bottom and top covers  83  and  84  retain valve element  82  in housing  81 . A nozzle  85  provides a first inlet port through housing  81  and a nozzle  86  provides a first outlet port through top cover  84 . A nozzle  87  provides a second inlet port through housing  81  and a nozzle  88  provides a second outlet port through housing  81 . 
     As shown in  FIG. 12 , valve element  82  includes a channel  90  and a channel  91  for interconnecting the various ports to provide the open and recirculate positions of the valve.  FIG. 12  is shown with cover  84  removed so that channels  90  and  91  can be seen. Valve element  82  is in the recirculate position wherein channel  90  is aligned with second outlet nozzle  88  at one end and is blocked at its opposite end and wherein channel  91  interconnects first inlet nozzle  85  with first outlet nozzle  86  and second inlet nozzle  87 . By rotating element  82  clockwise by 90°, the first inlet and outlet ports are interconnected and the second inlet and outlet ports are interconnected, thereby configuring the valve in the open position. 
       FIG. 13  shows that a bottom surface of valve element  82  includes a plurality of disk shaped recesses  92  for receiving disk-shaped magnets  93  for providing a magnetic coupling to valve element  82 . Pins  94  and  95  extend from housing  81  in order to receive the bottom cover and to facilitate mounting of the valve to an actuator  96  as shown in  FIG. 14 . A motor  97  is controlled by the controller and drives a magnet disk  98  configured to have magnetic poles for magnetically linking with the magnetic disks  93  on the valve element so that rotation of the valve element matches the rotation of motor  97 . A handle  99  is coupled to disk  98  via motor  97  for manually adjusting the position of the valve element. 
       FIGS. 15-18  illustrate the use of a gate-type valve for the flow control valve of the present invention. As shown in  FIG. 15 , a valve body  100  has parallel flow channels  101  and  102  separated by an opening  103 . A rotatable gate  104  is received in opening  103  and may be oriented parallel to the flow channels in order to separate the flow channels and provide the open position of the valve wherein the inlet ports are connected just to their respective output ports. A shaft  105  is connected to gate  104  and has a control wheel  106  adapted to be coupled with an actuator in order to provide an automatically controlled version of the valve. As shown in  FIG. 16 , a manual version utilizes a handle  107  coupled with shaft  105  for controlling gate  104 .  FIG. 17  shows handle  107  and gate  104  in a recirculate position so that both inlet ports are coupled to the first outlet port and the second outlet port is isolated. As shown in  FIG. 18 , handle  107  may include a pointer  111  for aligning with labeling on a cover  112  to show when the valve is in the open or recirculate position.