Patent Publication Number: US-2005118059-A1

Title: Cardiopulmonary bypass extracorporeal blood circuit apparatus and method

Description:
BACKGROUND OF THE INVENTION  
      Conventional cardiopulmonary bypass uses an extracorporeal blood circuit that is coupled between arterial and venous cannulae and includes a venous drainage line, a venous blood reservoir, a blood pump, an oxygenator, an arterial filter, and blood transporting tubing or lines, ports, and valves interconnecting these components. Prior art, extracorporeal blood circuits as schematically depicted in  FIGS. 1-3  and described in commonly assigned U.S. Pat. No. 6,302,860, draw venous blood of a patient  10  during cardiovascular surgery through the venous cannulae (not shown) coupled to venous return line  12 , oxygenates the blood, and returns the oxygenated blood to the patient  10  through an arterial line  14  coupled to an arterial cannulae (not shown). Cardiotomy blood and surgical field debris that is aspirated by a suction device  16  is pumped by cardiotomy pump  18  into a cardiotomy reservoir  20 .  
      Air can enter the extracorporeal blood circuit from a number of sources, including around the venous cannulae, through loose fittings of the lines or ports in the lines, and as a result of various unanticipated intra-operative events. It is necessary to minimize the absorption of air in the blood in the extracorporeal blood circuit and to remove any air that does accumulate in the extracorporeal blood circuit before the filtered and oxygenated blood is returned to the patient through the arterial cannulae to prevent injury to the patient. Moreover, if a centrifugal blood pump is used, a large volume of air accumulating in the venous line of the extracorporeal blood circuit can accumulate in the blood pump and either de-prime the blood pump and deprive it of its pumping capability or be pumped into the oxygenator and de-prime the oxygenator, inhibiting oxygenation of the blood.  
      In practice, it is necessary to initially fill the cannulae with the patient&#39;s blood and to prime (i.e., completely fill) the extracorporeal blood circuit with a biocompatible prime solution before the arterial line and the venous return lines are coupled to the blood filled cannulae inserted into the patient&#39;s arterial and venous systems, respectively. The volume of blood and/or prime solution liquid that is pumped into the extracorporeal blood circuit to “prime” it is referred to as the “prime volume.” Typically, the extracorporeal blood circuit is first flushed with CO2 prior to priming. The priming flushes out any extraneous CO2 gas from the extracorporeal blood circuit prior to the introduction of the blood. The larger the prime volume, the greater the amount of prime solution present in the extracorporeal blood circuit that mixes with the patient&#39;s blood. The mixing of the blood and prime solution causes hemodilution that is disadvantageous and undesirable because the relative concentration of red blood cells must be maintained during the operation in order to minimize adverse effects to the patient. It is therefore desirable to minimize the volume of prime solution that is required.  
      In one conventional extracorporeal blood circuit of the type depicted in  FIG. 1 , venous blood from venous return line  12 , as well as de-foamed and filtered cardiotomy blood from cardiotomy reservoir  20 , are discharged into a venous blood reservoir  22 . Air entrapped in the venous blood rises to the surface of the blood in venous blood reservoir  22  and is vented to atmosphere through a purge line  24 . The purge line  24  can be about 6 mm inner diameter flexible tubing, and the air space above the blood in venous blood reservoir  22  can be substantial. A venous blood pump  26  draws blood from the venous blood reservoir  22  and pumps it through an oxygenator  28 , an arterial blood filter  30 , and the arterial line  14  to return the oxygenated and filtered blood back to the patient&#39;s arterial system via the arterial cannulae coupled to the arterial line  14 .  
      A negative pressure with respect to atmosphere is imposed upon the mixed venous and cardiotomy blood in the venous blood reservoir  22  as it is drawn by the venous blood pump  26  from the venous blood reservoir  22 . The negative pressure causes the blood to be prone to entrain air bubbles. Although arterial blood filters, e.g., arterial blood filter  30 , are designed to capture and remove air bubbles, they are not designed to handle larger volumes of air that may accumulate in the extracorporeal blood circuit. The arterial blood filter  30  is basically a bubble trap that traps any air bubbles larger than about 20-40 microns and discharges the air to atmosphere through a typically about 1.5 mm ID purge line  32 . The arterial filter  30  is designed to operate at positive blood pressure provided by the venous blood pump  26 . The arterial blood filter  30  cannot prevent accumulation of air in the venous blood pump  26  and the oxygenator  28  because it is located in the extracorporeal blood circuit downstream from them.  
      As shown in  FIG. 2 , it has been proposed to substitute an assisted venous return (AVR) extracorporeal blood circuit for the conventional extracorporeal blood circuit of the type depicted in  FIG. 1 , whereby venous blood is drawn under negative pressure from the patient&#39;s body. The venous blood reservoir  22 , which accounts for a major portion of the prime volume of the extracorporeal blood circuit, is thereby eliminated. Furthermore, the arterial blood filter  30  is moved into the venous return line  12  upstream of the venous blood pump  26  to function as a venous blood filter. De-foamed and filtered cardiotomy blood from cardiotomy reservoir  20  is drained into the arterial blood filter  30 , and venous blood in venous return line  12  and the venous cannulae coupled to it is pumped through the arterial blood filter  30 . Exposure of the venous blood to air is reduced because the arterial blood filter  30  does not have an air space between its inlet and outlet (except to the extent that air accumulates above the venous blood inlet), as the venous blood reservoir  22  does. Suction is provided in the venous return line  12  through the negative pressure applied at the outlet of arterial blood filter  30  by the venous blood pump  26  to pump the filtered venous blood through the oxygenator  28  and into the arterial blood line  14  to deliver it back to patient  10 . Again, the arterial blood filter  30  is basically a bubble trap that traps any air bubbles larger than about 20-40 microns and discharges the air to atmosphere through a typically about 1.5 mm inner diameter purge line  32 .  
      The arterial blood filter  30  is relocated with respect to the cardiotomy reservoir  20  and modified to function as a venous blood filter in the extracorporeal blood circuits shown in  FIGS. 3 and 4 , referred to as an “AVR” extracorporeal blood circuit in the above-referenced &#39;860 patent. Evacuation of air from venous blood received through venous return line  12  is facilitated by increasing the size of the purge port  34  of the arterial blood filter  30  to accept a larger diameter purge line  42 , e.g. a 6 mm ID line, rather than the 1.5 mm ID line. A vacuum greater than that normally used for venous drainage is applied through purge line  42  to the purge port  34  to actively purge air from arterial blood filter  30 . The cardiotomy reservoir  20  is at ambient pressure but is conveniently purged by the same vacuum that purges air from arterial blood filter  30 . A valve  36 , e.g., a one-way check valve, is incorporated into the purge port  34  or purge line  42  to prevent air or blood purged from the cardiotomy reservoir  20  from being drawn into arterial blood filter  30  by the negative pressure in arterial blood filter  30  when the purging vacuum is not active.  
      As shown in  FIG. 4  from the above-referenced &#39;860 patent, venous blood is drawn through the upper venous blood inlet  44 , down through the filter  46  and a screen or other conventional bubble trapping device (not shown), and out the venous blood outlet  48  by the venous blood pump  26 . The purge port  34  can be located above the venous blood inlet  44 , and air that is separated out by the screen or other conventional bubble trapping device can accumulate in the space  50  above the venous blood inlet  44 . An air sensor  38  is disposed adjacent the purge port  34  that generates a sensor signal or modifies a signal parameter in the presence of air in the space  50 . The sensor signal is processed by circuitry in a controller (not shown) that applies the vacuum to the purge line  42  to draw the accumulated air out of the space  50 . The vacuum is discontinued when the sensor signal indicates that venous blood is in the space  50 . Thus, an “Active Air Removal” (AAR) system is provided to draw the accumulated air out of space  50  when, and only when, air present in the space  50  is detected by air sensor  34  to purge the air and to prevent venous blood filling space  50  from being aspirated out the purge line  42  by the purging vacuum. The purging vacuum may be produced by a pump  40 , or it may be produced by connecting the purge line  42  to the vacuum outlet conventionally provided in operating rooms.  
      Again, suction is provided in the venous return line  12  through the negative pressure applied at the outlet  48  of arterial blood filter  30  by the venous blood pump  26  to pump the filtered venous blood through the oxygenator  28  and into the arterial blood line  14  to deliver it back to patient  10 . De-foamed and filtered cardiotomy blood is also pumped by venous blood pump  26  from cardiotomy reservoir  20  through the oxygenator  28  and into the arterial blood line  14  to deliver it back to patient  10 .  
     SUMMARY OF THE INVENTION  
      While the AVR extracorporeal blood circuit illustrated in  FIGS. 3 and 4 , and particularly the use of the AAR method and system, represents a significant improvement in extracorporeal circuits, its implementation can be further refined and improved. A need remains for an AAR system and method that optimizes the air sensor and its functions and that detects and responds to error conditions and faults that can arise over the course of prolonged surgical use.  
      Moreover, the typical prior art extracorporeal blood circuit, e.g. the above-described extracorporeal blood circuits of  FIGS. 1-3 , has to be assembled in the operating room from the above-described components, primed, and monitored during the surgical procedure while the patient is on bypass. This set-up of the components can be time-consuming and cumbersome and can result in missteps that have to be corrected. Therefore, a need remains for an extracorporeal blood circuit having standardized components and that can be set up for use using standardized setup procedures minimizing the risk of error.  
      The resulting distribution of the components and lines about the operating table can take up considerable space and get in the way during the procedure. The connections that have to be made can also introduce air leaks introducing air into the extracorporeal blood circuit. A need remains for a compact extracorporeal blood circuit that is optimally positioned in relation to the patient and involves making a minimal number of connections.  
      The lengths of the interconnected lines are not optimized to minimize prime volume and attendant hemodilution and to minimize the blood contacting surface area. A large blood contacting surface area increases the incidences of embolization of blood cells and plasma traversing the extracorporeal blood circuit and complications associated with immune response, e.g., as platelet depletion, complement activation, and leukocyte activation. Therefore, a need remains for a compact extracorporeal blood circuit having minimal line lengths and minimal blood contacting surface area.  
      Furthermore, a need remains for such a compact extracorporeal blood circuit with minimal blood-air interfaces causing air to be entrained in the blood. In addition, it is desirable that the components be arranged to take advantage of the kinetic assisted, venous drainage that is provided by the centrifugal venous blood pump in an AVR extracorporeal blood circuit employing an AAR system.  
      Occasionally, it becomes necessary to “change out” one or more of the components of the extracorporeal blood circuit during the procedure. For example, it may be necessary to replace a blood pump or oxygenator. It may be necessary to prime and flush the newly constituted extracorporeal blood circuit after replacement of the malfunctioning component. The arrangement of lines and connectors may make this very difficult to accomplish. A need therefore remains for a compact extracorporeal blood circuit that can be rapidly and easily substituted for a malfunctioning extracorporeal blood circuit and that can be rapidly primed.  
      Consequently, a need remains for a extracorporeal blood circuit that is compactly arranged in the operating room, that takes advantage of kinetic assist, and is small in volume to minimize the required prime volume and to minimize the blood contacting surface area and blood-air interfaces. Moreover, a need remains for such an extracorporeal blood circuit that is simple to assemble and prime, provides for automatic monitoring of blood flow and other operating parameters, and facilitates change-out of components during the procedure.  
      One embodiment of the invention provides an extracorporeal blood circuit for use with a venous return line and an arterial line coupled to a patient. The extracorporeal blood circuit can include a venous air removal device coupled to the venous return line. The venous air removal device can perform an active air removal function. The extracorporeal blood circuit can include a sensor that determines a blood level in the venous air removal device and a purge line coupled to the venous air removal device. The extracorporeal blood circuit can include a controller connected to the sensor. The controller can cause the venous air removal device to perform the active air removal function through the purge line when the blood level is less than a threshold. The extracorporeal blood circuit can further include a pump coupled to the venous air removal device, an oxygenator coupled to the pump, and a blood filter coupled to the oxygenator and the arterial line.  
      Some embodiments of the invention can provide a disposable circuit support module for use with an extracorporeal blood circuit including a venous air return device, a pump, an oxygenator, and a blood filter. The disposable circuit support module can include a C-shaped arm and a plurality of snap fittings coupled to the C-shaped arm. Each one of the plurality of snap fittings can include a concave band rigidly coupled to the C-shaped arm and a movable U-shaped band that snaps into engagement with the concave band in order to engage one of the venous air return device, the oxygenator, and the blood filter.  
      One embodiment of the invention includes a method of priming an extracorporeal blood circuit. The method can include connecting a venous return line to an arterial line using a pre-bypass loop, preventing flow of prime solution into a venous air return device and a blood filter, and filling a pump and an oxygenator with prime solution in order to drive air bubbles upward and out of the pump and the oxygenator. The method can also include allowing prime solution to fill the venous return line and to pass into the venous return line after the pump and the oxygenator are filled with prime solution, allowing prime solution to rise upward through the venous return line into the blood filter, and coupling a vacuum source to a purge line coupled to the venous air removal device.  
      Embodiments of the invention provide a method of sensing and removing air and blood froth from an extracorporeal blood circuit including a venous air removal device, a pump, an oxygenator, and a blood filter. The method can include connecting at least one piezoelectric crystal to the venous air removal device and to an active air removal controller, sensing a level of blood in the venous air removal device, and controlling the venous air removal device based on the level of blood in the venous air removal device in order to automatically remove air and blood froth when the level of blood falls below a threshold level.  
      Other features and aspects of the invention will become apparent to those skilled in the art upon review of the following detailed description, claims and drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a schematic diagram of a first prior art extracorporeal blood circuit that uses a venous reservoir.  
       FIG. 2  is a schematic diagram of a second prior art extracorporeal blood circuit that does not use a venous reservoir.  
       FIG. 3  is a schematic diagram of a third prior art extracorporeal blood circuit that does not use a venous reservoir and employs a venous blood filter with active air removal.  
       FIG. 4  is a simplified schematic view of the prior art venous blood filter of  FIG. 3 .  
       FIG. 5  is a schematic view of an extracorporeal blood circuit according to one embodiment of invention in relation to prime solution holding bags and a sequestering bag.  
       FIG. 6  is a perspective view of the extracorporeal blood circuit of  FIG. 5  supported by a disposable circuit support module and a reusable system holder.  
       FIG. 7  is a perspective view of the disposable circuit support module of  FIG. 6 .  
       FIG. 8  is a schematic view of the extracorporeal blood circuit of  FIG. 5  supported by the disposable circuit support module of  FIGS. 6 and 7 .  
       FIGS. 9-11  are schematic views of the extracorporeal blood circuit of  FIG. 5  in relation to a sequestering bag and first and second prime solution bags and illustrating the steps of priming the disposable, integrated, extracorporeal blood circuit with prime solution.  
       FIGS. 12A and 12B  are cross-section views of one embodiment of a Venous Air Removal Device (VARD) for use in the extracorporeal blood circuit of  FIG. 5 .  
       FIG. 13  is a schematic view of sensor elements for use in the VARD of  FIGS. 12A and 12B .  
       FIG. 14  is a plan view of an Active Air Removal (AAR) controller for use with the extracorporeal blood circuit of  FIG. 5 .  
       FIG. 15  is a system block diagram of the AAR controller of  FIG. 14 .  
       FIGS. 16-19  are screen displays for automatic operating mode states for use with the AAR controller of  FIG. 14 .  
       FIGS. 19-46  are screen displays for automatic troubleshooting modes of operation for use with the AAR controller of  FIG. 14 . 
    
    
     DETAILED DESCRIPTION  
      Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limited. The use of “including,” “comprising” or “having” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. The terms “mounted,” “connected” and “coupled” are used broadly and encompass both direct and indirect mounting, connecting and coupling. Further, “connected” and “coupled” are not restricted to physical or mechanical connections or couplings, and can include electrical connections or couplings, whether direct or indirect.  
      In addition, it should be understood that embodiments of the invention include both hardware and electronic components or modules that, for purposes of discussion, may be illustrated and described as if the majority of the components were implemented solely in hardware. However, one of ordinary skill in the art, and based on a reading of this detailed description, would recognize that, in at least one embodiment, the electronic based aspects of the invention may be implemented in software. As such, it should be noted that a plurality of hardware and software based devices, as well as a plurality of different structural components may be utilized to implement the invention. Furthermore, and as described in subsequent paragraphs, the specific mechanical configurations illustrated in the drawings are intended to exemplify embodiments of the invention and that other alternative mechanical configurations are possible.  
      Some embodiments of the invention can include a method and system that incorporates a disposable, integrated, extracorporeal blood circuit with reusable components including the reusable components of a heart-lung machine. The extracorporeal blood circuit can include a Venous Air Removal Device (VARD), a centrifugal blood pump, an oxygenator, and an arterial blood filter all interconnected with fluid lines. The disposable centrifugal blood pump can be coupled with the reusable blood pump driver that can in turn be coupled to a pump driver console. Oxygen and water lines can be coupled to the disposable blood oxygenator and an oxygenator control console for controlling oxygen and water flow and water temperature. One embodiment of the VARD can include a venous filter that provides an Active Air Removal (AAR) function under the control of a reusable AAR controller. The extracorporeal blood circuit of one embodiment of the invention can include a disposable circuit support module for supporting the components and lines in a predetermined three-dimensional spatial relationship. One embodiment of the invention further comprises a reusable system holder adapted to be coupled to the reusable components of the heart lung machine to support the AAR controller and the disposable circuit support module. It will be understood that the various aspects of the invention can be practiced in alternative contexts than the context provided by the described embodiments.  
      The extracorporeal blood circuit of one embodiment of the invention can include access ports through which the operator or perfusionist may administer medications, fluids, and blood. In addition, the extracorporeal blood circuit can include multiple sites for sampling blood and for monitoring various parameters, e.g., temperature, pressure, and blood gas saturation. Clamps and valves can be disposed in the lines extending between or from the components of the extracorporeal blood circuit. The extracorporeal blood circuit can be set up and changed out more rapidly than conventional extracorporeal blood circuits, and arrangement of the supplied components can minimize the possibility of erroneous setup. The extracorporeal blood circuit can be a closed system that reduces the air-blood interface and that minimizes the blood contacting surface area. The extracorporeal blood circuit may be rapidly primed with prime solution. In some embodiments, the prime solution can be displaced retrograde with the patient&#39;s own blood at least in part to reduce hemodilution by the prime volume.  
       FIGS. 5 and 6  illustrate an extracorporeal blood circuit  100  according to one embodiment of the invention. The extracorporeal blood circuit  100  can include a VARD  130 , a centrifugal blood pump  150 , an oxygenator  160 , and an arterial blood filter  180 . The extracorporeal blood circuit  100  is illustrated in  FIG. 5  in relation to prime solution holding bags  50  and  52  that drain prime solution into the extracorporeal blood circuit  100  during priming and a sequestering bag  54  adapted to sequester excess prime solution or blood at times during the bypass procedure. The prime solution holding bags  50  and  52  can be intravenous bags including penetrable seals through which spikes can be inserted. The sequestering bag  54  can be supplied with three bag tubes  56 ,  58 , and  60  that have respective Roberts clamps  66 ,  68 , and  70  applied to selectively clamp shut or open the bag tube lumens. For example, the Roberts clamps  66 ,  68 , and  70  may be clamped shut when the sequestering bag  54  is attached to or detached from the extracorporeal blood circuit  100 .  
      The extracorporeal blood circuit  100  is illustrated in  FIG. 5  with a U-shaped, tubular, pre-bypass loop  120  that can be selectively used to connect the arterial blood line  114  with the venous return line  112  during flushing of the extracorporeal blood circuit  100  with CO 2  gas and during priming of the extracorporeal blood circuit  100  with prime solution from prime solution bags  50  and  52  as described further below with respect to  FIGS. 9-11 . The pre-bypass loop  120  can be coupled to the venous return line  112  by a quick connect connector  102  and to the arterial line  114  by a quick connect connector  104 . In one embodiment, the arterial line  114  and venous return line  112  can be formed of 0.375 inch inner diameter polyvinyl chloride tubing.  
      It will be understood by one of ordinary skill in the art that the pre-bypass loop  120  can be disconnected from the venous and arterial blood lines  112  and  114  after the extracorporeal blood circuit  100  is primed. Table lines extending to venous and arterial cannulae extending into the patient and primed with the patient&#39;s blood can then be connected to the respective venous and arterial blood lines  112  and  114  through quick connectors  102  and  104 , respectively. Any air that enters the extracorporeal blood circuit  100  during this switching process can be eliminated by the AAR system.  
      The venous return line  112  can extend from the quick connector  102  through a quick disconnect connector  122  to the inlet  132  of the VARD  130 . In one embodiment, a tri-optic measurement cell (TMC)  38  BioTrend® connector  108  having a 0.375 inch inner diameter lumen can be coupled to a utility connector  110  having a 0.375 inch inner diameter lumen and can be interposed in the venous return line  112 . The TMC  38  BioTrend® connector  108  may be used to hold a TMC cell (not shown) of the BioTrend™ Oxygen Saturation and Hematocrit System, sold by Medtronic, Inc., to measure blood oxygen saturation and blood hematocrit of venous blood passing through the venous return line  112 . The utility connector  110  can support a plurality of standard luer ports and barbed ports.  
      A venous blood sampling line  106 , which can be formed of  0 . 125  inch inner diameter polyvinyl chloride tubing, can extend between one port of the utility connector  110  to one side of a manifold  115 . The manifold  115  can include a rigid tube having a 0.125 inch inner diameter tube lumen and three stopcocks with side vent ports arrayed along the tube.  
      A venous blood pressure monitoring line  116  can be formed of 0.125 inch inner diameter polyvinyl chloride tubing, can be coupled to a stopcock  196  attached to a luer port of the utility connector  110 , and can extend to a pressure isolator  117  and stopcock  125 . The pressure isolator  117  of the venous blood pressure monitoring line  116  can include a flexible bladder and can be sized to be attached to a Medtronic® Model 6600 pressure monitor and display box. Venous blood pressure monitoring may be used to optimize kinetic drainage. For example, venous blood pressure that is too high, too low, oscillating, and/or chattering may indicate that the speed of the venous blood pump is incorrect and should be adjusted.  
      An arterial filter purge line  118 , which can be formed of 0.125 inch inner diameter polyvinyl chloride tubing and can include a check valve  119 , can extend from a further luer port of the utility connector  110  to the arterial filter purge port  186  of the arterial filter  180 . Under operating conditions, a small volume of arterial blood and any air bubbles can be drawn through the arterial filter purge line  118  and check valve  119  from the arterial filter  180  into the venous return line  112 . The check valve  119  can prevent reverse flow of venous blood into the arterial filter  180 .  
      In certain cases, it is desirable to provide passive venting of the venous blood in the venous return line  112 . A short tube stub  124  can be attached to a barbed port  124  (e.g., with a 0.250 inch inner diameter) extending from the utility connector  110  in order to serve as a vent blood return port. A Roberts clamp  194  can be fitted across the tube stub  124  to be opened or closed when the tube stub  124  is coupled to active or passive venting equipment, e.g., the Gentle Vent passive venting system sold by Medtronic, Inc.  
      A blood temperature monitoring adapter  126  can extend from the utility connector  110  and can enable insertion of a temperature probe connected with temperature monitoring equipment.  
      The VARD  130  is described further below with reference to  FIGS. 10, 12A , and  12 B. In general, air that is entrained in the venous blood drawn through a VARD inlet  132  can be separated from the venous blood within VARD  130  and can accumulate in an upper chamber of the VARD  130 . The presence of air can be detected by signals output from air sensors located about the VARD  130 , and the air can be evacuated from the chamber.  
      A venous blood outlet  136  of VARD  130  can be coupled to one branch of a “Y” style segment or line  156 , which can be formed of 0.375 inch inner diameter polyvinyl chloride. The trunk of the “Y” style segment or line  156  can be coupled to a blood pump inlet  152  of the centrifugal venous blood pump  150 . The blood pump  150  can be adapted to be positioned in use with a drive motor (not shown) that can be selectively operated to draw venous blood through the VARD  130  and pump it into the oxygenator  160 .  
      The venous blood pump  150  can be a centrifugal blood pump, e.g., a BioPump® centrifugal blood pump sold by Medtronic, Inc., that is capable of providing sufficient negative pressure (e.g., to approximately −200 mmHg) for kinetic assisted drainage of venous blood from the patient. Operation of the Bio-Pump® centrifugal blood pump can be controlled by a Bio-Console® drive console sold by Medtronic, Inc. The Bio-Console® drive console can provide electrical energy to drive a reusable pump drive that in turn drives the Bio-Pump® centrifugal blood pump. Exemplary blood pump drive systems are disclosed, for example, in U.S. Pat. Nos. 5,021,048 and 5,147,186.  
      A fluid infusion line  176 , which can be formed of 0.375 inch inner diameter polyvinyl chloride tubing, can be coupled to the other branch of the “Y” style segment or line  156  and can extend to a connection with the tube  60  of the sequestering bag  54 , which can be made through a tubing size adapter and Roberts clamp  197 . Prime solution can be selectively pumped or drained from the sequestering bag  54  during priming, and blood can be selectively pumped or drained from the sequestering bag  54  during the course of the bypass procedure.  
      The location of VARD  130  upstream of venous blood pump  150  can provide kinetic assisted venous drainage due to the negative pressure exerted on venous blood by the venous blood pump  150 . An AAR system and method can automatically detect and suction off air that collects in a high, quiescent point in the venous line of the extracorporeal blood circuit  100 . In one embodiment of the invention, the high point can be within the upper part of VARD  130  adjacent to a purge port  134 .  
      A VARD purge line  141 , which can be formed of  0 . 250  inch inner diameter polyvinyl chloride tubing, can be coupled to the purge port  134  of the VARD  130  through a stopcock  135  and can extend to a vacuum source or pump that can be coupled to the purge line distal end connector  143 . A VARD purge line segment  147 , which can be formed of silicone rubber, and a vacuum sensor line  145  can be coupled to an AAR controller  400 . The VARD purge line  141  or the vent port  134  of the VARD  130  can include a one-way check valve that can prevent air from being pulled into the VARD  130  before the purge line distal end connector  143  is attached to the vacuum source. For example, a check valve  123  can be located at the connection of the VARD purge line  141  and the VARD purge line segment  147 . In addition or alternatively, a fluid isolator/filter can be located in the vacuum sensor line  145  at a T-connector  149  to prevent any blood suctioned from the VARD  130  during operation of the AAR system from being suctioned into the vacuum sensor within the AAR controller  400  to which the vacuum sensor line  145  is connected.  
      The purging vacuum applied through distal end connector  143  may be produced by a pump or it may be produced by connecting the purge line distal end connector  143  directly or indirectly to a vacuum outlet provided in operating rooms. Although not shown in  FIG. 5 , a liquid trap can be interposed between the purge line distal end connector  143  and the vacuum source or pump to salvage the red blood cells that may be suctioned from the VARD  130  through the VARD purge line  141  and return the blood to the patient. The liquid trap can be a hard-shell venous reservoir, a cardiotomy reservoir, a chest drainage container, or a blood collection reservoir used with the autoLog™ Autotransfusion System sold by Medtronic, Inc. The blood collection reservoir used with the autoLog™ Autotransfusion System has a 40 micron filter and may be mounted onto a mast of the console of the heart-lung machine or other equipment in the operating room to function as a liquid trap. In one embodiment, the vacuum source or pump can be capable of supplying a minimum of about −200 mmHg vacuum, and can be capable of suctioning about 400 ml/mm of air from the liquid trap without the vacuum decreasing below about −180 mmHg.  
      One end of a trunk of a further “Y” style segment or line  158 , which can be formed of 0.375 inch inner diameter polyvinyl chloride tubing, can be coupled to a blood pump outlet  154 . One end of a priming line  159 , which can be formed of 0.250 inch inner diameter polyvinyl chloride tubing, can be coupled to a side branch of the “Y” style line  158  through a reducing connector. The priming line  159  can extend to branching segments or lines  151  and  153 , which can be formed of 0.250 inch inner diameter polyvinyl chloride tubing, that can terminate in spikes that can be inserted into the penetrable openings or seals of the prime solution bags  50  and  52 . Roberts clamps  161 ,  163 , and  165  can be fitted over the respective tubing segments or lines  151 ,  153 , and  159  to selectively clamp shut or open the tube lumens during gravity priming of the extracorporeal blood circuit  100 . Due to this arrangement, substantially fewer air bubbles can become entrapped in the lines  158  and  159  during priming or operation of the extracorporeal blood circuit  100 .  
      The other branch of the “Y” style tubing segment or line  158  can be coupled to an oxygenator blood inlet  170  of the oxygenator  160  that modulates the temperature of the venous blood and oxygenates the venous blood pumped from the venous blood pump  150 . The oxygenator  160  can be a blood oxygenator of the type disclosed U.S. Pat. Nos. 4,975,247, 5,312,589, 5,346,621, 5,376,334, 5,395,468, 5,462,619, and 6,117,390, for example. In one embodiment, the oxygenator  160  includes an AFFINITY® hollow fiber membrane oxygenator sold by Medtronic, Inc.  
      A blend of oxygen and air can enter the oxygenator  160  through an access port  162  and can exit the oxygenator  160  through an access port  164 . Gas exchange between the oxygen and the venous blood entering the oxygenator blood inlet  170  can then take place by diffusion through the pores in the hollow fibers of the oxygenator  160 . Thermal energy may be added or removed through a blood heat exchanger, which can be integral with the oxygenator  160 . Water can be heated or cooled by a heater/cooler of the heart-lung machine and warmed or chilled water can be delivered to the water-side of the heat exchanger. Water can enter the heat exchanger through a hose (not shown) coupled to a water inlet port  166  and can exit the heat exchanger through a water outlet port  168  and a hose (not shown).  
      The temperature modulated, oxygenated blood can be pumped out of an oxygenator blood outlet  169  and through an oxygenator outlet line  188 , which can be formed of 0.375 inch inner diameter polyvinyl chloride tubing, that can be coupled to an arterial filter inlet  182  of the arterial filter  180 . The heated or cooled, oxygenated blood can also be pumped out of a branch of the oxygenator outlet  169  and through an arterial blood sampling line  172  (which can be formed of 0.125 inch inner diameter polyvinyl chloride tubing and can include a check valve  121 ) that can extend to one input of the manifold  115  for sampling of arterial blood and for drug administration.  
      A temperature monitoring adapter  171  like adapter  126  can branch from the oxygenator blood outlet  169  to be used to monitor oxygenated blood temperature.  
      A recirculation/cardioplegia line  174 , which can be formed of 0.250 inch inner diameter polyvinyl chloride tubing, can extend from a recirculation port  173  of the oxygenator  160  to a “Y” style connector having two branches  175  and  177 . The branch  175  can be coupled to the luer port of line  58  of the sequestering bag  54 . A Roberts clamp  195  can be used to open or close the branch  175  of the “Y” style connector coupled to line  58  so that prime solution or oxygenated blood can be selectively pumped into the sequestering bag  54  during the course of priming or performance of the bypass procedure. A second branch  177  of the recirculation/cardioplegia line  174  can include a tube that can be provided with a closed end and can be left intact or cut away so that the recirculation/cardioplegia line  174  can be selectively coupled to a blood cardioplegia source or a hemoconcentrator while the Roberts clamp  195  is closed.  
      The arterial blood filter  180  may take the form disclosed in U.S. Pat. Nos. 5,651,765 and 5,782,791, for example. In one embodiment, the arterial blood filter  180  can include an AFFINITY® Arterial Filter sold by Medtronic, Inc. The oxygenated blood can be pumped under the pressure exerted by the venous blood pump  150  through the arterial filter inlet  182  through a filter and screen disposed within the arterial blood filter  180  and through an arterial filter outlet  184  into the arterial line  114 . Microemboli can be filtered from the oxygenated blood as it passes through the arterial filter  180 . Air that is entrained in the oxygenated blood can be separated from the oxygenated venous blood by the screen and can accumulate in an upper chamber of the arterial filter  180  below an arterial filter purge port  186 .  
      The arterial filter purge port  186  can be coupled to a three-way stopcock  187  in an arterial filter purge port  186  that has a branch coupled to an end of arterial filter recirculation line  118 . The three-way stopcock  187  can be in an air evacuation position normally that can connect the arterial filter recirculation line  118  with the arterial filter purge port  186 . A low volume of arterial blood and air that collects in the upper chamber of the arterial filter  180  below the arterial filter purge port  186  can be drawn by the blood pump  150  through the utility connector  110  and the venous return line  112  into the VARD  130 . The difference in pressure between the positive pressure of the oxygenated blood within the chamber of the arterial filter  180  and the negative pressure in the venous return line  112  can draw the blood and air from the chamber of the arterial filter  180  when the venous blood pump  150  is running and the three-way stopcock  187  is moved to the air evacuation position. A check valve  119  in the arterial filter recirculation line  118  can prevent reverse flow of venous blood through the recirculation line  118  when the blood pump  150  is not pumping. The three-way stopcock  187  can be manually moved to a priming position opening the arterial filter chamber to atmosphere to facilitate priming of the extracorporeal blood circuit  100 . The arterial filter  180  can be fitted into a receptacle of a circuit support module such that the operator can manually lift and tilt the arterial filter during priming or during the bypass procedure to facilitate evacuation of air observed in the arterial filter  180 .  
      The filtered, oxygenated blood can be returned to the patient as arterial blood through the arterial line  114  coupled to the arterial filter outlet  184  and through a table line fitted to the quick connector  104  and coupled to an arterial cannulae (not shown) or directly to an end of an elongated arterial cannulae extending into the patient&#39;s heart. The arterial line  114  can pass through a blood flow transducer connector  190  that can receive and support a Bio-Probe® blood flow transducer sold by Medtronic, Inc., to make arterial flow rate measurements. In normal operation, the Bio-Console® drive console can determine arterial blood flow rate from the output signal of the Bio-Probe® flow probe transducer mounted to blood flow transducer connector  190  to make flow rate measurements of blood flow in arterial line  114  or in oxygenator outlet line  188 . Oxygenated, arterial blood flow rate can generally be determined to an accuracy of ±5%.  
      In some embodiments, the above-described barbed connections and luer connections with lines or tubing do not leak at pressures ranging between +750 mmHg and −300 mmHg. In some embodiments, the barbed connections can withstand pull forces up to 10 lbs linear pull.  
      Substantially all surfaces of the extracorporeal blood circuit  100  exposed to blood can be blood compatible through the use of biocompatible materials (e.g., silicone rubber, polyvinyl chloride, polycarbonate, or plastisol materials). In one embodiment, the blood contacting surfaces of the extracorporeal blood circuit  100  can be coated with Carmeda® BioActive Surface (CBAS™) heparin coating under license from Carmeda AB and described in U.S. Pat. No. 6,559,132.  
      In one embodiment, the extracorporeal blood circuit  100  can have operable flow rates of approximately 1-6 liters per minute of blood without producing substantial gas bubbles within the venous blood pump  150  or through the fibers of the oxygenator  160 . The extracorporeal blood circuit  100  can be spatially arranged and supported in three-dimensional space by a component organizing and supporting system, which can be positioned at the height of the patient so that the venous return and arterial lines  112  and  114  can be made as short as possible to reduce prime volume.  
      The extracorporeal blood circuit  100  are spatially arranged and supported in three dimensional space, as shown in  FIG. 5 , by a circuit support module  200  (which can be disposable in some embodiments) and a system holder  300  (which can be reusable in some embodiments), as shown in  FIGS. 6-8 . Most of the above-described lines and other components interconnecting or extending from the VARD  130 , the centrifugal blood pump  150 , the oxygenator  160 , and the arterial blood filter  180  are not shown in  FIG. 6  to simplify the illustration.  
      The circuit support module  200  can be formed of a rigid plastic material having a C-shaped arm  202  extending between lower snap fittings  204  and  206  and an upper snap fitting  208 . A receptacle  210  can be adapted to fit into engagement with the reusable system holder  300 . As shown in  FIG. 6 , the centrifugal blood pump  150  may not be directly supported by the C-shaped arm  202 . The “Y” style lines  156  and  158  can couple the centrifugal blood pump  150  to the VARD  130  and the oxygenator  160 , which can be supported by the C-shaped arm  202 .  
      The snap fittings  204  and  206  can each include a fixed, concave band formed as part of the C-shaped arm  202  and a separate, U-shaped band. The snap fitting  208  can include a concave band that can be attached to or detached from the C-shaped arm  202  and a separate, U-shaped band. The separate, U-shaped bands can be snapped into engagement with the concave bands to form a generally cylindrical retainer band dimensioned to engage the sidewalls of the oxygenator  160 , the VARD  130 , and the arterial blood filter  180 .  
      During assembly, the oxygenator  160  can be positioned against the fixed, concave half-band and the U-shaped half-band can be snapped around the oxygenator  160  and into slots on either side of the fixed, concave half-band to entrap oxygenator  160  in the lower snap fitting  204 . Similarly, the VARD  130  and the arterial blood filter  180  can be supported and entrapped in the lower and upper snap fittings  206  and  208 , respectively. The upper snap fitting  208  encircling arterial blood filter  180  can be detachable at a clip  218  from the C-shaped arm  202 . The arterial blood filter  180  and the upper snap fitting  208  can be manually detached at the clip  218 , tilted, and then reattached at the clip  218 . Air bubbles trapped in the lower portion of the arterial blood filter  180  adjacent the arterial filter outlet  184  can move into the arterial filter purge port  186  to be drawn through the arterial filter purge line  118  into the VARD  130 .  
      As shown in  FIG. 8 , lateral raceways  220  and vertical raceways  222  can be provided in the C-shaped arm  202  into which laterally and vertically extending lines, respectfully can be press-fit. The VARD purge line  141  and the fluid infusion line  176  can be extended vertically from the VARD  130  and the branch of the “Y” style line  156 , respectively, through the vertical raceway  222 . The priming line  159  and the recirculation/cardioplegia line  174  can be extended laterally through the lateral raceways  220 .  
      The circuit support module  200  can maintain proper orientation and positioning of the supported components and the lines extending between or from the supported components. With the circuit support module  200  positioned closer to the patient, shorter lines can be used and can help to minimize the surface area contacted by blood. The oxygenator  160  can be supported by the circuit support module  200 , so that the blood pump outlet  154  and the oxygenator blood inlet  170  connected by “Y” style line  158  can be at about the same level below prime solution holding bags  50  and  52 , in order to facilitate gravity priming through priming line  159  and retrograde filling of the blood pump  150  and oxygenator  160  with prime solution. The circuit support module  200  can position the VARD  130  above the blood pump  150  and can position the arterial blood filter  180  above the VARD  130 , in order to facilitate retrograde priming and movement of air into the arterial filter purge port  186  to be drawn into the VARD  130  and purged.  
      The circuit support module  200  can allow access for clamping or unclamping the lines or tubing segments or for making connections to the various ports. The circuit support module  200  can allow the venous blood pump  150  to be independently manipulated, e.g., rotated, swiveled, and/or pivoted, with respect to the circuit support module  200  and the system holder  300 . The circuit support module  200  can maintain proper positioning and/or alignment of the components and lines of the extracorporeal blood circuit  100  to optimize priming in a relatively short time. In one embodiment, the circuit support module  200  can be transparent to allow sight confirmation of prime solution or blood in the lines and/or other transparent components.  
      Moreover, the extracorporeal blood circuit  100  and the circuit support module  200  can be assembled as a unit and then attached to the system holder  300  for priming and use during a bypass procedure. A replacement assembly of a extracorporeal blood circuit  100  mounted to a circuit support module  200 , as shown in  FIG. 8 , can be quickly assembled and substituted, if necessary, in a change-out during priming or the bypass procedure.  
      As shown in  FIG. 6 , the system holder  300  can include a mast  302  that can extend through a shaft collar  304  of a mast arm assembly  306 . The shaft collar  304  can be moved along the mast  302 , and the mast arm assembly  306  can be fixed at a selected position by tightening a lever  308 . The mast arm assembly  306  can include a U-shaped notch  310  that can be inserted around an upright mast (not shown) of a heart-lung machine console (not shown), and a clamp  312  can be rotated and tightened to hold the mast  302  in a vertical orientation close to the heart-lung machine console. The mast  302  can be provided with an intravenous hanger  313  from which the prime solution holding bags  50  and  52  and the sequestering bag  54  can be hung.  
      The mast  302  can extend downward from the mast arm assembly  306  and through a collar  316  of an electronics arm assembly  314  that can be moved along the mast  302  and fixed in place by tightening a lever  318 . The electronics arm assembly  314  can extend to a cross-bar  326  supporting a right support arm  320  adapted to support an AAR controller  400  and a left support arm  322  adapted to support a pressure monitor and display box (e.g., the Medtronic® Model 6600 pressure monitor and display box sold by Medtronic, Inc.). The support angle provided by the right and left support arms  320  and  322  can be adjusted by loosening a lever  324 , pivoting the right and left support arms  320  and  322  to the desired angle, and tightening the lever  324 .  
      The lower end of the mast  302  can be coupled to a laterally-extending support arm assembly  330  that can be formed with a line supporting and routing channel  332 . A laterally-extending module arm assembly  340  and a downwardly-extending external drive arm assembly  350  can be mounted to an upward extension  334  of the support arm  330  by a spring lock mechanism  342 . A tapered male receiver  344  can extend upward to be received in the downwardly-extending female receptacle  210  of the circuit support module  200  when the extracorporeal blood circuit  100  is mounted to the system holder  300 . Line receiving slots  348  can be provided in the laterally-extending module arm assembly  340  for supporting cables for temperature monitoring and a VARD cable  450 . The VARD cable  450  can include a cable connector  452  that can be attached to a VARD sensor connector  454 , as schematically illustrated in  FIG. 12B .  
      A tri-optic measurement cell (TMC) clip  346  can be fitted to the free end of the laterally-extending module arm assembly  340 . The TMC clip  346  can engage a TMC  38  BioTrend® connector  108  into which a TMC cell of a BioTrend® Oxygen Saturation and Hematocrit System can be inserted to measure venous blood oxygen saturation and venous blood hematocrit of venous blood flowing through the venous return line  112  of the extracorporeal blood circuit  100 . A cable (not shown) from the TMC cell supported by TMC clip  346  can extend to a BioTrend™ Oxygen Saturation and Hematocrit System.  
      The Bio-Probe® blood flow transducer sold by Medtronic, Inc. to make blood flow rate measurements through the arterial line can be adapted to be mounted to the laterally-extending module arm assembly  340  at a pin  354 . A cable (not shown) can extend from the Bio-Probe® blood flow transducer supported at pin  354  and can extend to a Bio-Probe® blood flow monitor sold by Medtronic, Inc.  
      An external drive motor for the blood pump  150  can be attached to the free end mount  352  of the external drive arm assembly  350  to mechanically support and drive the blood pump  150  through magnetic coupling of a motor driven magnet in the external drive motor with a magnet of the centrifugal blood pump  150 . An adapter can be attached to the free end mount for coupling a hand-cranked magnet with the magnet of the centrifugal blood pump  150  in an emergency situation.  
      The VARD  130 , the centrifugal blood pump  150 , the oxygenator  160 , and the arterial blood filter  180 , as well as the lines and other associated components shown in  FIG. 5 , can be spatially arranged and supported in three-dimensional space by the circuit support module  200  and the system holder  300 , as shown in  FIGS. 6-8 . The entire assembly can be closely positioned to the heart-lung machine console that operates the drive motor of the centrifugal blood pump  150 , that supplies oxygen to the oxygenator  130 , and that controls the temperature of the blood or cardioplegia solution traversing the oxygenator  130 . The position of the mast arm assembly  306  along the mast  302  can be adjusted to optimally extend the support arm assembly  330  toward and over the patient during the procedure. In some embodiments, the position of the electronics arm assembly  314  along the mast  302  can be adjusted and fixed in place by tightening a lever  318  to optimally position the AAR controller  400  and a Medtronic® Model 6600 pressure monitor and display box for use during the bypass procedure.  
      Various sensors, lines, and ports can be coupled to other components after the extracorporeal blood circuit  100  is positioned within the circuit support module  200  and mounted to the system holder  300 . For example, a reusable VARD sensor cable  450  shown in  FIGS. 8 and 14  can extend from the VARD connector  454  laterally through channel  332  to make a connection with an AAR controller  400 .  
      In some embodiments, flushing, priming, and general use of the extracorporeal blood circuit  100  is simplified and made more reliable and efficient. The extracorporeal blood circuit  100  can be flushed with CO 2  gas when the pre-bypass loop  120  is in place after set-up, but before priming, in order to drive out any ambient air. As shown in  FIG. 8 , the fluid infusion line  176  can be clamped by closing a Roberts clamp  197 . As shown in  FIG. 14 , the VARD purge tubing segment  147  can be fitted into a fluid in-line (FIL) sensor  404 , and the T-connector  149  can be fitted into a clip  426  to vertically orient the fluid isolator/filter. The VARD purge tubing segment  147  may not be fitted into a pinch valve  410 , so that CO 2  gas can flow through the VARD  130  and the VARD purge line  141  and tubing segment  147  to atmosphere. As shown in  FIG. 5 , the VARD stopcock  135  can be set to the open position, so that CO 2  gas can flow through the VARD  130  to atmosphere. The arterial filter purge port  186  can be opened to atmosphere by setting the stopcock  187  to the appropriate position, so that CO 2  gas can flow through the arterial filter  180  to atmosphere.  
      A CO 2  gas delivery line can include a microporous bacteria filter and can be attached to a spike (e.g., a 0.250 inch spike) at the end of one of priming line branches  151  or  153 , and the associated Roberts clamp  161  or  163  and the Roberts clamp  165  can be opened. The Roberts clamps  195  and  197  can also be opened. In some embodiments, the CO 2  gas can then be turned on to flow through tubing priming line  159  (e.g., ¼″ polyvinyl chloride) and then through the components and lines of the extracorporeal blood circuit  100  to atmosphere at a flow rate of approximately 2-3 liters per minute. Upon completion, the CO 2  gas can be turned off, and the VARD stopcock  135  can be closed. The priming line branches  151  or  153  can be disconnected from the CO 2  line, and the associated Roberts clamp  161  or  163  can be clamped again.  
      In one embodiment, the prime volume of the extracorporeal blood circuit  100  can be about 1000 ml or less including a pre-bypass filter (not shown) substituted for the pre-bypass loop  120 . In other embodiments, the prime volume of the extracorporeal blood circuit  100 , excluding a pre-bypass filter, can be about 900 ml or less. In one embodiment, the extracorporeal blood circuit  100  may be primed using a single one liter intravenous bag  50  of prime solution, e.g., a saline solution. However, in other embodiments, two prime solution bags  50  and  52  can be provided and filled with prime solution for use in initial priming or as required during the bypass procedure.  
       FIGS. 9-11  illustrate a method of priming the extracorporeal circuit  100  with the bypass circuit  120  in place. The prime solution bags  50  and  52 , filled with prime solution, and the empty sequestering bag  54  can be hung on the intravenous hanger  313  (as shown  FIG. 6 ) in preparation for priming. The Roberts clamps  66  and  70  can be left open, as shown in  FIG. 9 , before the spike ports  56  and  60  are perforated. The branch  177  of the “Y” style connector (which can be attached to the recirculation/cardioplegia line  174  used during cardioplegia) can remain plugged, and the temperature sensor ports  171  and  126  can be sealed by the sensor element. Initially, Roberts clamps  68 ,  161 ,  163 ,  165 ,  194  and  195  can be closed, and the Roberts clamp  197  can remain open.  
      The spikes (which can be ¼ inch spikes) of the lines  151  and  153  branching from the priming line  159  (which can also be a ¼ inch in diameter) can be inserted through the penetrable seals of the prime solution bags  50  and  52 , respectively. A branch  175  of the “Y” style connector (which can be attached to the recirculation/cardioplegia line  174 ) can be coupled to the bayonet access port at the free end of the bag line  58  of the sequestering bag  54 . The remaining ports and stopcocks can remain as set at the end of the flushing operation. As shown in  FIG. 9 , tubing clamps (e.g., hemostats) can be applied at about point C 1  of the branch of the “Y” style line  156  that can be coupled at its trunk to the blood pump inlet  152  and at about point C 2  in the oxygenator outlet line  188 , in order to prevent flow of prime solution into the chambers of VARD  130  and arterial blood filter  180 , respectively.  
      The Roberts clamps  161  and  165  can then be opened to gravity fill the pump  150 , the oxygenator  160 , the fluid infusion line  176 , and the oxygenator outlet line  188  with prime solution draining from prime solution bag  50 . Filling of the oxygenator outlet line  188  can be assisted by unclamping the tubing clamp at about C 2  and applying the tubing clamp again at about C 2  when prime solution reaches the arterial filter inlet  182 . The Roberts clamp  197  can be closed when the prime solution fills the fluid infusion line  176 . One of the Roberts clamps  68  and  195  can be closed, as shown in  FIG. 10 , when prime solution rises through the recirculation/cardioplegia line  174  and begins to fill the sequestering bag  54 . Thus, filling of the oxygenator  160 , the pump  150 , the fluid infusion line  176 , and the recirculation/cardioplegia line  174  can be accomplished in a retrograde fashion to drive air bubbles upward and out of the venous blood pump  150  and oxygenator  160  and the lines coupled therewith, as shown by the cross-hatching in  FIG. 9 .  
      As shown in  FIG. 10 , the spike at the end of the fluid infusion line  176  (e.g., a 0.250 inch spike) can then be inserted into a bayonet port at the free end of bag line  60  extending from sequestering bag  54 . The tubing clamp at C 1  can be released to allow the prime solution to rise upward through the VARD outlet  136 , to fill the VARD  130 , and to pass through the VARD inlet  132  into the venous return line  112 .  
      The prime solution can rise upward through the venous return line  112 , the utility connector  110 , the TMC  38  BioTrend® connector  108 , the bypass circuit  120 , the arterial line  114  passing through the blood flow transducer  190 , and through the arterial filter outlet  184  into the chamber of the arterial filter  180 . The check valve  119  can prevent prime solution from rising from the utility connector  110  through the arterial filter purge line  118  to the stopcock  187 . The housing of the arterial filter  180  can be transparent so that the retrograde rising prime solution and any air bubbles can be seen. The stopcock  187  can be closed when the prime solution starts to escape the arterial filter purge port  186 .  
      The stopcock  135  can also be opened so that prime solution begins to fill the VARD purge line  141  and can then be closed. At least an upper part of the housing of the VARD  130  can be transparent so that any air bubbles can be seen. The purge line segment  147  can be inserted into the purge line pinch valve  410  to close the purge line segment  147  as the VARD purge line  141  begins to fill with prime solution. The stopcock  135  can be opened, and the stopcocks  196  and  125  can also be opened. The stopcock  125  can then be closed when prime solution rises and fills the venous blood pressure monitoring line  116  and the pressure isolator  117 .  
      Thus, air can be driven upward and out of the chambers of the VARD  130  and the arterial filter  180  as they are filled with prime solution, as shown in the cross-hatching in  FIG. 10 . The Roberts clamps  161  and  165  can remain open. As shown in  FIG. 11 , the tubing clamp that was applied at about C 3  can be removed to allow priming fluid to drain from prime solution bag  50  through the priming line  159 , the pump  150 , and the fluid infusion line  176  into the sequestering bag  54 . The sequestering bag  54  can be filled with sufficient prime solution to enable priming of the cardioplegia circuit through the cardioplegia port  56 . It may be necessary to open Roberts clamp  163  to drain prime solution from the second prime solution bag  52  in filling sequestering bag  54 .  
      The wall vacuum source can then be coupled to the purge line distal end connector  143  to provide a regulated vacuum (e.g., approximately −215 mmHg) through the VARD purge line  141  when the pinch valve  410  is opened. The VARD sensor cable  450  can be attached to the sensor element connector on VARD  130  and the cable connector  454  on the housing  402  of the AAR controller  400 . The Roberts clamp  165  can be closed, the tubing clamp at C 2  can be released, and the venous blood pump  150  can be turned on at the minimum flow.  
      The three stopcocks of sampling manifold  115  can then be set to allow arterial blood flow and air to be drawn by the venous blood pump  150  through the arterial blood sampling line  172 , the check valve  121 , the sampling manifold  115 , the venous blood sampling line  106 , and into the utility connector  110 . Air can thereby be vented out of the arterial filter purge line  118  and the sampling manifold  115  through the utility connector  110  into the VARD  130  by the venous blood pump  150 . The air that accumulates in the VARD upper chamber can then be suctioned out through the line VARD purge line  141  under the action of the VARD controller  400 . The arterial filter  180  and a fitting  208  can be detached, inverted, and gently tapped so that the pumped prime solution can move any air in the arterial filter  180  out through the arterial filter outlet  184  and to the VARD  130 . The arterial filter  180  can then be reinstalled into the fitting  208  and inspected visually for evidence of any air bubbles that may require repeating of the inverting and tapping steps. The stopcocks of the sampling manifold  115  can then be reset to block flow.  
      At this point, the extracorporeal blood circuit  100  is primed, and the AAR controller is connected and operational. The pre-bypass loop  120  can be disconnected and table lines can be attached to the quick disconnect connectors  102  and  104 . The oxygen lines can be coupled to the access ports  162  and  164  and the water lines can be coupled to the water inlet  166  and water outlet  168  of the oxygenator  160 . The AAR controller  400  can be set up to operate the VARD  130 .  
      In one embodiment of the invention, an improved AAR system and method can be used to sense and remove air and blood froth from the VARD  130 , while removing a minimal amount of liquid blood. The AAR system can include the VARD  130  (as shown in  FIGS. 12A, 12B , and  13 ) which can be controlled by the AAR controller  400  (as shown in  FIGS. 14-16 ). In some embodiments, the AAR system can be capable of removing a continuous stream of air injected into the venous return line  112  at a rate of up to about  200  ml/mm from VARD  130 . In one embodiment, the AAR system can handle a maximum rate of air removal of about 400 ml/mm of air and blood froth. In some embodiments, the AAR system is capable of removing a 50 cc bolus of air injected into the venous return line  112  over several seconds from the VARD  130 .  
      The VARD  130  can be a modified conventional arterial blood filter having upper and lower air sensors. For example, the VARD  130  can be a modified AFFINITY® Arterial Filter sold by Medtronic, Inc. Air entrapped in the venous blood can be actively removed by a vacuum applied to the purge port  134  of the VARD  130  through the VARD purge line  141 . The VARD  130  can include a housing  142  having a hollow volume displacer  146 . The hollow volume displacer  146  can include an inverted cone that can extend down into center of the chamber  140  and can define an annular upper inlet chamber  148 . The housing  142  can incorporate components for filtering the venous blood drawn through the housing  142  by blood pump  150  and for detecting and automatically removing air and froth rising to the inlet chamber  148 . The lower cap or lower portion of the housing  142  (including the outlet port  136 ) are not shown in  FIGS. 12A and 12B .  
      The chamber  140  (which can include the inlet chamber  148 ) of VARD  130  can be filled with blood as the venous blood pump  150  draws venous blood through an upper inlet  144  coupled to venous return line  112  into an inlet chamber  148 , through an internally disposed filter element (not shown), and out of the lower VARD outlet  136 . A screen or other conventional bubble-trapping device may be inserted in chamber  140  below the inlet chamber  148  to trap air bubbles in the blood stream and cause them to stay in the inlet chamber  148 . The VARD  130  can differ from the arterial blood filter  180  in that it can incorporate a sensor array  138 . In one embodiment, the sensor array  138  can include four piezoelectric crystal sensor elements  138 A,  138 B and  138 C,  138 D, which can be arranged in orthogonally-disposed pairs  138 A,  138 B and  138 C,  138 D (as shown in  FIGS. 12A, 12B , and  13 ) in order to sense the level of blood within inlet chamber  148 .  
      In one embodiment of the invention, a first or upper pair of ultrasonic crystals  138 A and  138 B can be disposed across the vent port  134 , and a second or lower pair of ultrasonic crystals  138 A and  138 B can be disposed across the inlet chamber  148 . The crystals  138 A and  138 C can be bonded onto the exterior surface of the cavity inside the volume displacer  146 . The crystals  138 B and  138 D can be bonded on the exterior surface of the housing extending between the upper portion of the inlet chamber  148  to the vent port  134  and the housing  142 , respectively.  
      In one embodiment, the piezoelectric crystals  138 A,  138 B and  138 C,  138 D can be piezoelectric crystal rectangular sheets of a thickness selected to be resonant in the range of 1 to 3 MHz, and specifically about 2.25 MHz, and mounted as shown in  FIGS. 12A and 12B . Conductive thin film electrodes can be deposited, plated, or otherwise applied to the major surfaces of the crystals. Conductors can be welded or soldered to the electrodes. Such a piezoelectric crystal can be excited to oscillate in a thickness mode by an RF signal applied, via the conductors and electrodes, across the thickness of the crystal. The resulting mechanical motion of the transmitting crystal can be transmitted though a fluid chamber or conduit. Ultrasonic vibrations emitted by the transmitting crystal can pass through the liquid in the chamber or conduit to impinge upon the receiving crystal. The receiving crystal can vibrate in harmony with the ultrasonic vibrations and can produce an alternating current potential proportional to the relative degree of vibratory coupling of the transmitting and receiving crystals. The degree of coupling of the ultrasonic vibrations can abruptly drop when air is introduced between the transmitting and receiving crystals, and the output amplitude of the signal generated by the receiving crystal can drop proportionally.  
      In one embodiment, one crystal of each pair  138 A,  138 B and  138 C,  138 D can be used as a transmitting crystal, and the other crystal of each pair  138 A,  138 B and  138 C,  138 D can be used as the signal receiver. In some embodiments, pairs of crystals (one a transmitter and the other a receiver) are used, rather than a single crystal (as both transmitter and receiver), in order to provide a more robust sensing system. However, some embodiments of the invention can use a single crystal as both the transmitter and the receiver. The presence of liquid or air between the transmitting crystal and the receiving crystal can differentially attenuate the transmitted ultrasonic signal in a manner that can be detected from the electrical signal output by the receiving crystal in response to the ultrasonic signal.  
      In one embodiment, eight conductors can be coupled to eight electrodes of the piezoelectric crystals  138 A,  138 B and  138 C,  138 D. The eight conductors can be extended to a VARD connector  454  (as shown schematically in  FIG. 12B ), which can be mounted to the VARD housing  142 . A distal cable connector  452  of a reusable VARD cable  450  can extend to the AAR controller  400 , as shown in  FIG. 14 . The distal cable connector  452  can be coupled to the VARD connector  454 . In one embodiment, the VARD cable  450  can include  10  conductors, and the distal cable connector  452  and the VARD connector  454  can include  10  contact elements. Eight of the cable conductors can be coupled through eight of the mating connector elements with the eight conductive thin film electrodes of the sensor array  138 . Two further connector elements of the VARD connector  454  can be electrically in common, and a continuity check can be performed by VARD controller circuitry  460  through the two cable conductors joined when contacting the two connector elements. In this way, a cable or connector failure can be quickly detected and an alarm sounded by the VARD controller  400 .  
      The AAR controller  400  can excite the transmitting crystals and can process the signals generated by the receiving crystals. The AAR controller  400  can include a microprocessor or controller that can use the processed received signals to determine when the liquid level is below the upper crystals  138 A,  138 B. When the liquid level is below the upper crystals  138 A,  138 B, the AAR controller  400  can open a pinch valve  410  that normally closes a silicone rubber purge line segment  147 . When the pinch valve  410  is open, the VARD purge line  141  can apply suction through the vent port  134  to evacuate the air and froth within the upper inlet chamber  148  below the level of the upper crystals  138 A,  138 B. The vacuum applied at the vent port  134  can overcome the negative pressure imposed by the venous blood pump  150  within the chamber  148  in order to draw out the accumulated air through the vent port  134 . An audible and/or visual warning may be activated to indicate the presence of air within the inlet chamber  148 . For example, an audible and/or visual alarm may be activated if liquid, e.g., blood or saline, is not sensed for a particular time period (e.g., approximately five seconds). The warning may continue while air is being removed. When the AAR controller  400  detects liquid between the upper pair of crystals  138 A,  138 B, the AAR controller  400  can close the pinch valve  410  in order to halt the application of vacuum through the VARD purge line  141 .  
      The lower crystals  138 C,  138 D, which can be located just above the transition of the main chamber  140  with the inlet chamber  148 , can provide a backup to the upper crystals  138 A,  138 B, should the upper crystals fail. The lower crystals  138 C,  138 D can also provide a way to detect when the liquid level drops below a minimally acceptable level, even though the AAR controller  400  has opened the pinch valve  410  after detecting air between the upper crystals  138 A,  138 B. A further distinctive audible and/or visual alarm may be activated if the blood level falls below the lower crystals  138 C,  138 D. Other embodiments of the invention can include only one set of crystals or even a single crystal positioned to sense the liquid level in the chamber  140 . It should also be understood by one of ordinary skill in the art that other types of sensors can be used rather than piezoelectric crystals. Accordingly, the term “sensor(s)” as used herein and in the appended claims refers to piezoelectric crystals or other suitable types of sensors.  
      In one embodiment of the invention, the crystals  138 A,  138 B,  138 C,  138 D can be rectangular in shape and can be arranged so that the long axis of the transmitter crystal  138 A,  138 C is rotated approximately  90  degrees from the long axis of the receiver crystal  138 B,  138 D, as shown in  FIGS. 12A, 12B , and  13 . This configuration can improve transmission overlap at  139  (as shown in  FIG. 13 ) of the transmitted ultrasonic signal to the receiver crystal.  
       FIGS. 14 and 15  illustrate the AAR controller  400 . As shown schematically in  FIG. 15 , the AAR controller  400  can include AAR controller circuitry  460 . The AAR controller circuitry  460  can be powered by an AC line input to a power supply  464 , but can also be powered by a back-up battery  462  in case of general power failure or failure of the power supply  464 . The AAR controller circuitry  460  can include a microprocessor-based computer operating under control of software stored in memory (e.g., RAM) and can be programmed via a programming port  466 . In other embodiments, the AAR controller circuitry  460  can include one or more integrated circuits, programmable logic controllers, or any suitable combination of hardware and software capable of performing one or more of the functions described with respect to  FIGS. 16-46 .  
      The AAR controller  400  can include a clamp (not shown) on the rear side of a housing  402 , and the clamp can be adapted to be attached to the left support arm  322  of the system holder  300  (as shown in  FIG. 6 ). After attachment, a user interface  420  (including a display  430  and a control panel  440 ) can be positioned outward for reading the displayed text and/or warning lights and for use of controls on the control panel  440 .  
      A clip  426 , a fluid in-line (FIL) sensor  404 , and a pinch valve  410  can be disposed on the housing  402 . The FIL sensor  404  can include a lid, which can extend across a notch so that the cross section of the notch is substantially constant when the lid is closed. The lid can be opened, the VARD purge line  141  can be extended laterally across the oxygenator  160 , a first section of the VARD purge line segment  147  can be fitted into the notch of the FIL sensor  404 , and the lid can be closed. A T-connector  149  can be fitted into the clip  426  with the vacuum sensor line  145  extending vertically.  
      The pinch valve  410  can include upper and lower members  406  and  408  that can define a slot within which a second section of the VARD purge line segment  147  can be positioned. A pinch rod  430  can extend upward from within the housing  402 . The pinch rod  430  can be under spring tension and can extend transversely into the slot between the upper and lower members  406  and  408 . The pinch rod  430  can be moved downward out of the slot when a mechanical release button  412  is pressed, in order to insert the second section of the VARD purge line segment  147  into the slot. The pinch rod  430  can then compress the second section of VARD purge line segment  147  upon release of the mechanical release button  412 . The pinch rod  130  can be retracted by again depressing the mechanical release button  412  or by operation of a solenoid controlled by the AAR controller  400 .  
      In some embodiments, the tubing of the purge line segment  147  inserted into the slot can be constructed of a soft, biocompatible material having a suitable durability and resilience (e.g., silicone rubber tubing). In one embodiment, the silicone rubber tubing of the purge line segment  147  can have a 0.250 inch inner diameter and a 0.375 inch outer diameter, and the silicone rubber tubing can have sufficient resilience to restore the lumen diameter to at least  3 / 4  of its nominal lumen diameter upon retraction of the pinch rod  430 .  
      The distal end of the vacuum sensor line  145  can be attached to a vacuum sensor input  414  on the housing  402 , as shown in  FIG. 14 . An audible tone generator  416  can be mounted to the housing  402 . An AC power cord  418  can be attached to the housing  402 . The VARD sensor cable  450  (in one embodiment, including the eight conductors attached to the eight surface electrodes of the piezoelectric crystals  138 A,  138 B,  138 C and  138 D and the two continuity checking conductors) can extend between the cable connector  452  and the cable connector  422  on the housing  402 . In some embodiments, the purge line segment  147  fitted into the FIL sensor  404  and a pinch valve  410  can be at the same level as the VARD purge port  134 . The height of the AAR controller  400  can be adjusting by moving the electronics arm assembly  314  along the mast  302 .  
      The pinch rod  430  can be axially aligned with and coupled to a solenoid core that can move downward into the housing  402  when the solenoid coil is energized. A solenoid driver  470  (as shown schematically in  FIG. 15 ) can be selectively actuated by the AAR controller circuitry  460  to drive the pinch rod  430  downward, overcoming the biasing force of a spring. In one embodiment, pinch valve sensors  472  (as shown schematically in  FIG. 15 ) can be provided within the housing  402  to determine the position of the downwardly-extending pinch rod  430  or the solenoid core coupled to the pinch rod  430 . The pinch rod sensors  472  can provide output signals to indicate whether the pinch rod  430  is in an upper closed position, a lower open position, or in a fault position between the upper and lower positions. The output signals can confirm that the pinch rod  430  has moved between positions in response to the applied appropriate command, or that the pinch rod  430  is malfunctioning.  
      As shown in  FIG. 14 , a user interface  440  can include controls, such as soft keys. The soft keys can include an “ON” key and an “OFF” key that can be depressed to power up and power down, respectively, the controller circuitry and sensors. A “RESET” key can be depressed to reset the controller signal processor. A “CAUTION” light (e.g., a yellow LED) and an “ALARM” light (e.g., a red LED) can be lit when the signal processor determines certain respective caution and alarm conditions. Respective audible caution and alarm tones can be emitted by an audible tone generator  416 . A “MUTE” switch can be depressed to silence the audible tones. “STANDBY” and “AUTO” buttons can be depressed to initiate respective standby and automatic operating modes. Manual depression of a “MANUAL” soft key can open the pinch valve  410  for as long as the “MANUAL” soft key remains depressed or for a particular time period. Function keys F 1 , F 2 , and F 3  can be depressed in response to a message displayed on the display  432 .  
      When the AAR controller is operating in an automatic mode, the solenoid driver  470  can be actuated automatically when air is detected in the VARD chamber  148  and/or when other conditions are met. The solenoid driver  470  can also be actuated in response to a user-initiated command. The pinch rod  430  can be released to open the lumen of the VARD purge line segment  147  by depressing mechanical release button  412 .  
      The purging operation in the automatic mode can be dependent upon a number of conditions and sensor input signals, such as one or more of those described as follows. The output signal of the upper crystals  138 A,  138 B (or the lower crystals  138 C,  138 D) can indicate that air is present in the VARD upper chamber  148 . A vacuum threshold level can be met by the vacuum in the vacuum line segment  147 , as measured through vacuum sensor line  145  and T-connector  149  by the vacuum sensor coupled to vacuum sensor input  414 . The output signal of the FIL sensor  404 , which is proportional to the amount of fluid in the vacuum line segment  147 , should not exceed an FIL signal threshold. In general, the operating states of a number of components and sensors can be monitored, and the operating states can determine whether the automatic mode can be performed using the piezoelectric crystals  138 A,  138 B,  138 C and  138 D.  
      The output signals from the position sensors  472  can confirm whether the pinch rod  430  is in a fully-open or a fully-closed position. Positions other than a fully-open or a fully-closed position may be considered error states and an audible and/or visible alarm may be activated. The pinch valve  410  may be electrically operated, pneumatically operated, or manually operated in case of a power failure.  
      The AAR controller  400  can perform a Self Test of one or more components. In one embodiment, the following five components can undergo the Self Test:  
      Display  432 : A liquid crystal display (LCD) can be solid a particular time period (e.g., about two seconds), followed by a display of the version of the installed software.  
      Indicators: The CAUTION light and/or the ALARM light can flash momentarily.  
      Audible Indicator: A single “chirp” with a delay (e.g., about one second) between sounds can occur for several seconds.  
      Pinch Valve  410 : The pinch valve solenoid  470  can open and close the pinch valve slot to verify proper operation.  
      Battery  462 : The power level in the battery  462  (e.g., a 9 Volt batter) can be evaluated.  
      In one embodiment, upon successful completion of the Self Test, the display  432  can indicate “NO ERROR DETECTED” and the operating algorithm can automatically switch to a Standby Mode. The appropriate corrective action can be taken if an error is indicated on the display  432  upon completion of the Self Test or during the Standby Mode. Priming of the extracorporeal blood circuit  100  can then be commenced, and the AAR system can be used when the blood pump  150  is performing the priming function.  
      The AAR system can then be used in manual or automatic operating modes to detect and remove air in the VARD  130 . In one embodiment, in either the manual or automatic operating modes, the Caution message “AIR IN VARD” can appear on the display  432  when air is detected between the upper crystals  138 A,  138 B. In addition or alternatively, the CAUTION light can flash and/or a repeating, audible tone can be emitted by the tone generator  416  when air is detected and/or being removed.  
      In some embodiments, the manual mode can override the automatic mode, e.g., in order to compensate for an error or a low-battery state. For example, the pinch valve  410  can be opened (by the pinch rod  430  being retracted from the slot) by depressing the mechanical button  412 .  
      If the AAR controller circuitry  460  is powered by line power, the user can also manually evacuate the air by depressing the MANUAL key on the user interface  440 . Depressing the MANUAL key can open the pinch valve  410  and can allow the vacuum source coupled to nozzle  143  to remove air from the VARD  130  through the VARD purge line  141 . Once air has been removed from the VARD  130 , the user can release the MANUAL key to close the pinch valve  410 . When the MANUAL key is depressed and the AAR controller circuitry  460  is functioning, the display  430  can indicate “VALVE OPEN.” Depressing the MANUAL key can over-ride the automatic response to an output signal of the FIL sensor  404  detecting fluid in the tubing segment  147  and can prevent the automatic closing of the pinch valve  410 . The message “AIR IN VARD” can automatically clear from the display  432 , and the display  432  can reverts to the Standby Mode display. The CAUTION light can stop flashing and/or the audible tone can stop being emitted.  
      The automatic mode can be initiated by depressing the AUTO key on the user interface  440 . In the automatic mode, the pinch valve  410  can be automatically opened in some embodiments, as long as air is detected between the upper crystals  138 A,  138 B, as long as the output signal of the FIL sensor  404  indicates fluid is in the tubing segment  147 , and/or as long as other operating conditions are satisfied. For example, if the AAR controller  400  is running on battery back-up power, the pinch valve  410  may not open automatically when the upper crystals  138 A,  138 B detect air in the VARD  130 . The display  432  can indicate “OPEN THE VALVE.” In this case, pressing the MANUAL key will not open the pinch valve  410 . The CAUTION light can flash and repeating audible tones can sound. To open the pinch valve  410  manually, the user can depress the mechanical button  412 .  
      The automatic mode screens for the display  432  of one embodiment of the invention are shown and described with respect to  FIGS. 16-18 . A user can first ensure that the wall vacuum regulator is adjusted to −225 mmHg. The user can press the AUTO key. The AAR controller  400  can transition from the Standby Mode to the Automatic Mode, as indicated in  FIG. 16  (Automatic Mode, Normal Operation).  
      A Caution condition can occur in the Automatic Mode when the upper crystals  138 A,  138 B in the VARD  130  detect air. The AAR controller  400  can command the pinch valve  410  to open automatically to evacuate the air in the VARD  130 . As shown in  FIG. 17  (Automatic Mode, Caution State), the display  432  can read “AIR IN VARD.” The CAUTION light can flash and the repeating, audible tone can sound.  
      After the air in the VARD is removed and the upper crystals  138 A,  138 B detect fluid, the AAR controller  400  can command the pinch valve  410  to automatically close. The display  432  indication of “AIR IN VARD” can clear. The CAUTION light can stop flashing and the audible tones can stop. In the Battery Back-Up Mode, the pinch valve  410  may not open automatically when the upper crystals  138 A,  138 B detect air. Pressing the MANUAL key may not open the pinch valve  410 . However, a user can press the mechanical button  412  on top of the pinch valve  410  to evacuate any accumulated air in the VARD  130 .  
      In the AAR controller  400  is running on battery back-up and air is detected in the VARD  130 , the display  432  can read “OPEN THE VALVE,” as shown in  FIG. 18  (Automatic Mode, Caution State in Battery Back-Up). The CAUTION light can flash and repeating audible tones can sound. A user can press the mechanical button  412  on top of the pinch valve  410  to remove any accumulated air in the VARD  130 . Once air is removed, the user can release the mechanical button  412 . When the upper crystals  138 A,  138 B detect fluid, the display  432  indication of “OPEN THE VALVE” can clear. The CAUTION light can stop flashing and the audible tones can stop.  
      The troubleshooting screens for the display  432  and the responses taken are shown in  FIGS. 19-46 .  FIGS. 19-25  illustrate screens for Self Test Mode Corrective Action Procedures.  FIG. 19  illustrates the screen for a self test Cyclical Redundancy Check (CRC) failure, corresponding to the following Message, Condition, and Corrective Action information:  
      Message: CRC Failure— FIG. 19   
      Condition: The Cyclical Redundancy Check (CRC), indicating a general software failure.  
      Corrective Action: Press RESET. If failure persists, a user can call a local Technical Support representative. Use a back-up AAR controller  400 .  
       FIG. 20  illustrates the screen for a self test pinch valve stuck open failure, corresponding to the following Message, Condition, and Corrective Action information:  
      Message: Valve Stuck Open— FIG. 20   
      Condition: The Pinch valve is stuck in the OPEN position when it should be closed.  
      Corrective Action: Press RESET. If failure persists, a user can call a local Technical Support representative. Use a back up AAR controller  400 .  
       FIG. 21  illustrates the screen for a self test pinch valve stuck closed failure, corresponding to the following Message, Condition, and Corrective Action information:  
      Message: Valve Stuck Closed— FIG. 21   
      Condition: The pinch valve is stuck in the CLOSED position when it should be open.  
      Corrective Action: Press the RESET key. If failure persists, a user can call a local Technical Support representative. Use a back-up AAR controller  400 .  
       FIG. 22  illustrates the screen for a self test pinch valve general failure, corresponding to the following Message, Condition, and Corrective Action information:  
      Message: Controller Failure— FIG. 22   
      Condition: The pinch valve failed the software test.  
      Corrective Action: Press the RESET key. If failure persists, a user can call a local Technical Support representative. Use a back-up AAR controller  400 .  
       FIG. 23  illustrates the screen for a self test low battery message, corresponding to the following Message, Condition, and Corrective Action information:  
      Message: Low Battery— FIG. 23   
      Condition: Battery power is below minimum specifications.  
      Corrective Action: Replace battery per the IFU or press the F 3  key to transition to Standby Mode.  
       FIG. 24  illustrates the screen for a self test battery failure, corresponding to the following Message, Condition, and Corrective Action information:  
      Message: No Battery Back-Up— FIG. 24   
      Condition: Self Test failed to detect a functional battery back-up circuit.  
      Corrective Action: Press the F 3  key. If failure persists, a user can call a local Technical Support representative. Use a back-up AAR controller  400 .  
       FIG. 25  illustrates the screen for a self test battery back-up on state, corresponding to the following Message, Condition, and Corrective Action information:  
      Message: Battery Back-Up On— FIG. 25   
      Condition: The AAR controller  400  was started in the Battery Back-up Mode.  
      Corrective Action: Plug the AAR controller  400  into an AC outlet.  
       FIGS. 26-31  illustrate screens for Standby Mode Corrective Action Procedures. A user can initiate the appropriate corrective action if any of the Caution messages in  FIGS. 26-31  appear on the display  432  during the Standby Mode. If necessary, the user can press the RESET key.  FIG. 26  illustrates the screen for a standby mode, VARD not connected state, corresponding to the following Message, Condition, and Corrective Action information:  
      Message: VARD Not Connected— FIG. 26   
      Condition: AAR controller  400  is not detecting the cable connection between the AAR controller  400  and the VARD  130 .  
      Corrective Action: Connect the cable, or replace the cable.  
       FIG. 27  illustrates the screen for a standby mode, air in VARD state, corresponding to the following Message, Condition, and Corrective Action information:  
      Message: Air In VARD— FIG. 27   
      Condition: Air is present in the VARD  130  at the level of upper crystals  138 A,  138 B.  
      Corrective Action: Prime the VARD  130 , or press the MANUAL key on the user interface  440  to withdraw air from the VARD  130 .  
       FIG. 28  illustrates the screen for a standby mode, low suction state, corresponding to the following Message, Condition, and Corrective Action information:  
      Message: Low Suction— FIG. 28   
      Condition: There is insufficient negative pressure being detected by the AAR controller  400 .  
      Corrective Action: Connect the suction monitoring line to the pressure sensor. Connect the suction source. Increase vacuum.  
       FIG. 29  illustrates the screen for a standby mode, battery back-up state, corresponding to the following Message, Condition, and Corrective Action information:  
      Message: Battery Back-Up On— FIG. 29   
      Condition: The AAR controller  400  is being powered by the 9-volt long life alkaline battery.  
      Corrective Action: Confirm the AAR1000 is plugged into a functioning 120-volt AC receptacle, or replace the power cable, or call a local Technical Support representative and use a back-AAR controller  400 .  
       FIG. 30  illustrates the screen for a standby mode, low-battery state, corresponding to the following Message, Condition, and Corrective Action information:  
      Message: Low Battery— FIG. 30   
      Condition: Battery power is below minimum specification in Battery Back-up Mode.  
      Corrective Action: Replace the battery per the instructions.  
       FIG. 31  illustrates the screen for a standby mode, battery failure, corresponding to the following Message, Condition, and Corrective Action information:  
      Message: No Battery Back-Up— FIG. 31   
      Condition: The AAR controller  400  failed to detect a functional battery back-up circuit.  
      Corrective Action: Call a local Technical Support representative and use a back-up AAR controller  400 .  
       FIGS. 32-46  illustrate screens for Automatic Mode Corrective Action Procedures.  FIGS. 32-36  illustrate screens for a Transition Mode. The messages shown in  FIGS. 32-36  may appear on the display  432 . The AAR controller  400  may not convert (“Transition”) to the Automatic Mode until the condition in the display  432  is corrected or the F 3  key is pressed.  FIG. 32  illustrates the screen for a transition mode, VARD not connected state, corresponding to the following Message, Condition, and Corrective Action information:  
      Message: VARD Not Connected— FIG. 32   
      Condition: Software is not detecting the cable connection between the AAR1000 and the VARD.  
      Corrective Action: Connect the cable, or replace the cable, or press F 3  to return to Standby Mode.  
       FIG. 33  illustrates the screen for a transition mode, check tubing state, corresponding to the following Message, Condition, and Corrective Action information:  
      Message: Check Valve Tubing— FIG. 33   
      Condition: The AAR controller  400  is not detecting the silastic tube in the pinch valve.  
      Corrective Action: Insert silastic tube in the pinch valve, or reposition the silastic tube in the pinch valve, or press F 3  to return to standby Mode, or call a local Technical Support representative and replace with a back-up AAR controller  400 .  
       FIG. 34  illustrates the screen for a transition mode, check tubing state, corresponding to the following Message, Condition, and Corrective Action information:  
      Message: Check VARD Sensors— FIG. 34   
      Condition: The software is detecting an improper signal from the ultrasonic sensors on the VARD.  
      Corrective Action: Disconnect and reconnect the VARD sensor cable. Replace the cable, or press F 3  to return to Standby Mode, or call a local Technical Support representative and replace with a back-up AAR controller  400 .  
       FIG. 35  illustrates the screen for a transition mode, circuit failure, corresponding to the following Message, Condition, and Corrective Action information:  
      Message: Controller Failure— FIG. 35   
      Condition: The pinch valve failed the software test  
      Corrective Action: Press the RESET key. If failure persists, call a local Technical Support representative. Use a back-up AAR controller  400 .  
       FIG. 36  illustrates the screen for a transition mode, low suction state, corresponding to the following Message, Condition, and Corrective Action information:  
      Message: Low Suction— FIG. 36   
      Condition: There is insufficient negative pressure being detected by the AAR controller  400 .  
      Corrective Action: Attach the suction monitoring line to the sensor, and ensure the connections are secure, or connect the wall vacuum source, or increase the vacuum, or after correcting the problem, press F 3  to enter Automatic Mode. Initiate Cardiopulmonary Bypass. Monitor the Resting Heart™ Module and the AAR controller  400  for operational charges that may cause a Caution condition or Alarm condition to occur.  
       FIGS. 37-46  illustrate screens for Alarm Conditions. Alarm condition in the Automatic Mode can occur when the lower crystals  138 C,  138 D in the VARD  130  detect air. The AAR controller  400  can command the pinch valve  410  to open automatically to evacuate the air in the VARD  130 . The ALARM light can flash and two rapid repeating, audible tones can sound. Pressing the MUTE key can only silence the audible tones for  15  seconds. The messages shown in  FIGS. 37-46  may occur at the time of an Alarm condition and warrant the immediate intervention and corrective action on the part of the user.  
      When too much air is entering the VARD  130  ( FIG. 37 ), the user can perform the following procedure: Immediately reduce pump flow. This will improve the efficiency at which the suction source removes air for the VARD  130 . Check that the vacuum source is at −225 mmHg. Check for loose fittings or disconnects in the venous circuit proximal to the VARD  130 . Confirm with the surgeon that the venous catheter is properly positioned and the right atrial purse strings at the cannulation site are secure. As the blood level in the VARD  130  rises above the lower and upper crystals, the Alarm message will clear, the ALARM light will stop flashing, and the audible tone will stop. Resume normal blood flow once the air is totally removed from the VARD  130 .  
      The user can perform the following procedure to open the pinch valve  410  ( FIG. 38 ): In the Battery Back-up Mode, the pinch valve  410  will not open automatically when the lower crystals  138 C,  138 D detect air. Pressing the MANUAL key will not open the pinch valve  410 . Press the mechanical button  412  on the top of the pinch valve  410  to evacuate any accumulated air in the VARD  130 . Immediately reduce pump flow if necessary. This will improve the efficiency at which the suction source removes air from the VARD  130 . Press and hold the mechanical button  412  on the top of the pinch valve  410 . This will open the pinch valve  410  to evacuate air in the VARD  130 . The pinch valve  410  will stay open as long as the mechanical button  412  is being pressed. Release the mechanical button  412  when air has been sufficiently removed from the VARD  130 . Check for loose fittings or disconnects in the venous circuit proximal to the VARD  130 . Confirm with the surgeon that the venous catheter is properly positioned and the right atrial purse strings at the cannulation site are secure. Repeat pressing the mechanical button as necessary to evacuate air from the VARD  130 . As the blood level in the VARD  130  rises above the lower crystals  138 C,  138 D, the AAR controller  400  will revert to the Caution condition. Resume normal blood flow once the air is totally removed from the VARD  130 . If there has been no disruption in the hospital electrical power, check the AC power cord for a disconnection.  
      The user can perform the following procedure when the pinch valve  410  is stuck open ( FIG. 39 ): Press the F 3  key to clear the error condition. Observe the VARD  130  for the presence of air. If there is no visual evidence of air in the VARD  130 , clamp the VARD purge line  141  with a hemostat proximal to the one-way valve  123  at the inlet of the pinch valve  410 . If there is visual evidence of air in the VARD  130 , continue to allow the wall vacuum source to evacuate the air. Once the air is removed and the message persists, clamp the VARD purge line  141  with a hemostat proximal to the one-way valve  123  at the inlet to the pinch valve  410 . Closely monitor the circuit for the appearance of air in the venous line  112  and the VARD  130 . Manually open and close the hemostat on the VARD purge line  141  to evacuate air as necessary. If problem persists, call a local Technical Support representative and use a back-up AAR controller  400 .  
      The user can perform the following procedure when the pinch valve  410  fails ( FIG. 40 ): Press the F 3  key to clear the error condition. Inspect the VARD  130  for the presence of air. Visually confirm the position of the pinch valve  410 . If there is no visual evidence of air in the VARD  130  and the pinch valve  410  is open, manually clamp the VARD purge line  141  with a hemostat proximal to the one-way valve  123 . If the pinch valve  410  is closed, manually clamp the VARD purge line  141  with a hemostat proximal to the one-way valve  123 , press down on the mechanical button  412  on the top of the pinch valve  410  and remove the silastic tube from the pinch valve  410 . Closely monitor the venous line  112  and the VARD  130  for entrapment of air. Unclamp and clamp the hemostat at the VARD purge line  141  as necessary to evacuate air. Call a local Technical Support representative and use a back-up AAR controller  400 .  
      The user can perform the following procedure when the pinch valve  410  is stuck closed ( FIG. 41 ): Press the F 3  key to clear the error condition. Press the MANUAL key on the front panel to open the pinch valve  410 . If the MANUAL key fails to operate, manually clamp the VARD purge line  141  with a hemostat proximal to the one-way valve  123 , press down on the mechanical button  412  on top of the pinch valve  410 , and remove the silicone tube from the pinch valve  410 . Closely monitor the venous line  112  and the VARD  130  for air entrapment. Unclamp and clamp the hemostat at the VARD purge line  141  as necessary to evacuate air. Call a local Technical Support representative and use a back-up AAR controller  400 .  
      The user can perform the following procedure during a system failure when blood is being removed ( FIG. 42 ): Press the F 3  key to clear the error condition. Immediately clamp the VARD air removal line  141  proximal to the one-way valve  123 . If the pinch valve  410  is closed, manually clamp the VARD purge line  141  with a hemostat proximal to the one-way valve  123 , press down on the mechanical button  412  on the top of the pinch valve  410  and remove the silastic tube form the pinch valve  410 . Closely monitor the venous line  112  and the VARD  130  for air entrapment. Unclamp and clamp the VARD air removal line  141  as necessary to evacuate air. Call a local Technical Support representative and use a back-up AAR controller  400 .  
      The user can perform the following procedure during a VARD sensor failure ( FIG. 43 ): Press the F 3  key to clear the error condition. Immediately manually clamp the VARD line  141  with a hemostat proximal to the one-way valve  123 . Press the mechanical button  412  on top of the pinch valve  410  and remove the silicone tube from the pinch valve  410 . Closely monitor the venous line  112  and the VARD  130  for air entrapment. Unclamp and clamp the hemostat at the VARD purge line  141  as necessary to evacuate air.  
      The user can perform the following procedure during a low suction state ( FIG. 44 ): Confirm the wall vacuum regulator is set to −225 mmHg. Confirm the ¼ inch inner diameter suction lines between the regulator and the vacuum canister, and between the vacuum canister and the AAR controller  400  are connected, secure and functional. Confirm luer fittings and connections for the pressure line on the VARD air removal line  141  are secure. Confirm that the suction canister is not elevated. It should be on the floor. Confirm that the height of the pinch valve  410  on top of the AAR controller  400  is level with the VARD  130  height. Replace the air/separation filter on the vacuum monitoring line, if it is wetted out and no longer functional. Press RESET. If corrective action does not resolve the Alarm condition, call a local Technical Support representative and use a back-up AAR controller  400 .  
      The user can perform the following procedure when the VARD  130  is not connected ( FIG. 45 ): Check LEMO cable connections to the VARD and to the AAR controller  400 . Confirm there is no fluid in the LEMO connections. If the message does not clear, replace cable. Press RESET. If corrective action do not resolve the Alarm condition, closely monitor the VARD  130  for the appearance for air. Press the MANUAL key or mechanical button  412  as necessary to remove air from the VARD  130 . Call a local Technical Support representative and use a back-up AAR controller  400 .  FIG. 46  illustrates the screen when the battery back-up is on.  
      All patents and publications referenced herein are hereby incorporated by reference in their entireties. It will be understood that certain of the above-described structures, functions and operations of the above-described embodiments are not necessary to practice the invention and are included in the description simply for completeness of the described embodiments. It will also be understood that there may be other structures, functions and operations ancillary to the typical operation of mechanical instruments that are not disclosed and are not necessary to the practice of the invention. In addition, it will be understood that specifically described structures, functions and operations set forth in the above-referenced patents can be practiced in conjunction with the invention, but they are not essential to its practice. It is therefore to be understood, that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described without actually departing from the spirit and scope of the invention.