referring now to fig1 , 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 fig1 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 . fig2 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 . fig3 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 fig4 . 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 . fig5 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 . fig6 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 . fig7 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 . fig8 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 . fig9 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 fig1 . 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 fig1 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 fig1 , 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 fig1 , 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 . fig1 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 . fig1 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 fig1 . 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 . fig1 - 18 illustrate the use of a gate - type valve for the flow control valve of the present invention . as shown in fig1 , 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 fig1 , a manual version utilizes a handle 107 coupled with shaft 105 for controlling gate 104 . fig1 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 fig1 , 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 .
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 .