Abstract:
Apparatus and methods for providing extracorporeal blood circulation and oxygenation control include multi-stage de-airing of blood to provide automated cardiopulmonary replacement to sustain patient life during a medical procedure such as cardiopulonary bypass graft surgery, keyhole cardiopulonary bypass graft surgery, percutaneous angioplasty, percutaneous stent placement, and percutaneous etherectomy.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is related to U.S. application Ser. No. 11/284,515 filed Nov. 22, 2005 entitled Apparatus For Making Extracorporeal Blood Circulation Available, which is incorporated herein by reference in its entirety. This application is also related to European Patent Application No. EP 04 027 855.8 filed on Nov. 24, 2004 entitled Vorrichtung zur Bereitstellung eines estrakorporalen Blutkreislaufs (Device For Providing An Extracorporeal Blood Circuit), the disclosure of which is also incorporated herein by reference. 
         [0002]    This application is also related to U.S. application Ser. No. 11/554,524 filed Oct. 30, 2006 entitled Apparatus For Making Extracorporeal Blood Circulation Available, which is also incorporated herein by reference in its entirety. 
     
    
     BACKGROUND OF THE INVENTION 
       [0003]    1. Field of the Invention 
         [0004]    The present invention relates to cardiopulmonary apparatus and methods for preserving the life of a patient by providing extracorporeal blood oxygenation and circulation in which a patient&#39;s blood is introduced via a venous connection into the extracorporeal blood circuit and is pumped by a blood pump via different blood-conducting components to an arterial connection from where the blood is again pumped into the patient&#39;s blood circulation. 
         [0005]    The apparatus and methods are useful in a variety of medical procedures including Percutaneous Coronary Intervention (PCI) such as angioplasty and drug-eluting and non-drug-eluting stent placement and Coronary Artery Bypass Graft (CABG) procedures. The apparatus, methods, and systems are necessary for sustaining the life of a patient while the heart is slowed or stopped during PCI or CABG. 
         [0006]    2. Description of Related Art 
         [0007]    Time is critical during PCI and CABG procedures. Less time required to perform these procedures generally correlates with a lower risk of complications and mortality. When artificial cardiopulmonary assistance is required, the priming and bringing into operation of a heart-lung machine can be time consuming and requires medical staff specialized in perfusion. 
         [0008]    Additionally, during machine priming, a liquid is used to fill the blood-conducting components of the heart-lung machine. The priming liquid must be vented or deaerated prior to connection with the patient&#39;s vascular system and initiating heart-lung machine operation in order to eliminate air bubbles, which can cause thrombosis. When such an extracorporeal blood circuit is used, air bubbles may form inside the blood circuit and air present in the blood circuit while putting the extracorporeal blood circuit into operation can enter into the blood. An air bubble entering into the patient&#39;s blood circulation can cause a fatal air embolism in the worst case. Air bubble detectors can detect air bubbles in the extracorporeal blood circuit to trigger a visual or acoustic alarm signal so that the blood supply to the patient can be stopped. Subsequently, medical personnel on hand must act as fast as possible to eliminate the problem. 
         [0009]    The apparatus and methods of the present invention overcome the aforementioned limitations of prior art heart-lung machines by providing for a compact and portable heart-lung machine that can be primed and ready for operation in less than 10 minutes with little or no human intervention. The present heart-lung machine may be self-contained and include an internal power supply, and/or may be connected to an external power supply such as an on-board power supply of an emergency land, air, or sea transport vehicle. Furthermore, no perfusion specialist is required for set up or operation and, in some embodiments, the machine may be constructed to meet requirements for regulatory approval for transport and mobile use. The machine may for instance in particular meet requirements of the EN 1789 standard for use in humid environments, water subjection, and pass shake and crash tests involving up to 10 g forces. 
         [0010]    The present invention is made possible, in part, by a number of advancements in heart-lung machine technology including a fast-closing clamp, a fast-priming extracorporeal blood oxygenation, deaeration and circulation system, and an air bubble detection system, which are described in co-assigned U.S. application Ser. Nos. 11/284,515 filed Nov. 22, 2005; 11/366,342, now U.S. Pat. No. 7,597,546 filed Mar. 2, 2006; 11/366,914, now U.S. Pat. No. 7,367,540 filed Mar. 2, 2006; and 11/544,524 filed Oct. 30, 2006, which are incorporated by reference herein in their entirety. The apparatus and methods of the invention are also made possible, in part, by a multistage air removal system and various other components and procedures described herein. 
       BRIEF SUMMARY OF THE INVENTION 
       [0011]    In one aspect, the invention is a method for providing extracorporeal blood circulation to a patient by connecting the patient&#39;s circulatory system to a heart-lung machine that is configured for rapid filling and priming by a priming fluid as well as rapid and safe transition to an operational mode. The heart-lung machine comprises a base module and a patient module with pivot means at the base module and/or at the patient module to pivot the patient module relative to the base module about a horizontal axis from a filling position into an operating position. 
         [0012]    In a second aspect, the invention is a method for providing extracorporeal blood circulation to a patient by connecting the patient&#39;s circulatory system to a heart-lung machine that automatically (i.e. without human intervention) detects and eliminates automatically air bubbles in blood conducting components of the machine, redirects the blood flow through the blood circulating components to prevent the bubbles from entering the patient&#39;s circulatory system, removes the bubbles from the circulatory system and, once air bubbles are no longer detected, resumes normal operation. This increases safety with a portable device for the provision of an extracorporeal blood circuit such as is described in U.S. patent application Ser. Nos. 11/284,515 and 10/839,126, which are incorporated by reference herein in their entireties. 
         [0013]    In a third aspect, the invention is a method for providing extracorporeal blood circulation to a patient by connecting the patient&#39;s circulatory system to a heart-lung machine that comprises a fast acting clamp configured to close an arterial line when a bubble is detected in the blood circulating components of the heart-lung machine. 
         [0014]    In a fourth aspect, the invention is a method for providing extracorporeal blood circulation to a patient by connecting the patient&#39;s circulatory system to a heart-lung machine that comprises a hose roller pump configured to remove air from a blood reservoir in the heart-lung machine. 
         [0015]    The heart-lung machine may be handled by any trained hospital staff, and there is no need or necessity of a clinical specialist, such as a perfusionist, or cardio technician, to be present for operation of the heart-lung machine. Automated activities, including fast-priming, air bubble detection, air removal system, etc. are necessary for the heart-lung machine to be operated safely without a perfusionist or cardio technician present. 
         [0016]    The heart-lung machine is further a mobile, self-contained heart-lung machine and, in some embodiments, comprises a plurality of modules, including for example two or three modules. 
         [0017]    Advantageous embodiments of the invention are described in the description, in the drawings and in the dependent claims. Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0018]      FIG. 1  is a perspective view of a portable heart-lung machine; 
           [0019]      FIG. 2  is a perspective view of the control module of the heart-lung machine of  FIG. 1  connected to a mount of the base module; 
           [0020]      FIG. 3  is a perspective view of some blood-conducting components of the patient module in the filling position; 
           [0021]      FIG. 4  is the representation of  FIG. 3  in the operating position, but viewed from the rear; and 
           [0022]      FIG. 5  is a diagram showing the individual components of a heart-lung machine according to the invention. 
           [0023]      FIG. 6  shows a schematic representation of the individual components of a heart-lung machine according to the invention. 
           [0024]      FIG. 7  is a lateral section through a fast closing (quick action) clamp. 
           [0025]      FIG. 8  is a lateral plan view of a fast closing clamp. 
           [0026]      FIG. 9  is a plan view in the direction III indicated in  FIG. 8 . 
           [0027]      FIG. 10   a  is a detail of the sectional view of  FIG. 7 . 
           [0028]      FIG. 10   b  is a schematic of a cross-sectional view in an axial direction of view, designated by IVa in  FIG. 10   a , of a blocking bar. 
           [0029]      FIG. 11  is a schematic of a fast closing clamp not shown in  FIGS. 7-9 . 
           [0030]      FIG. 12  is a side view of a peristaltic hose pump. 
           [0031]      FIG. 13  is a mating piece of a hose pump. 
           [0032]      FIG. 14  is a support element of a hose pump. 
           [0033]      FIG. 15  is a support plate of the hose pump. 
           [0034]      FIG. 16  is a perspective view of a side of a drive plate of a hose pump. 
           [0035]      FIG. 17  is a perspective view of the drive plate of  FIG. 16  on that side which is remote from the support plate. 
           [0036]      FIG. 18  is a section through the drive plate of  FIGS. 16 and 17  along the line VII-VII. 
           [0037]      FIG. 19  is an enlarged representation of a coupling device of a hose pump. 
           [0038]      FIG. 20  is a diagram of an exemplary multi-stage air removal system. 
           [0039]      FIG. 21  is a flow chart showing method steps exemplary of the present methods. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0040]    In one embodiment, the apparatus and methods involve a heart-lung machine configured for rapid filling and priming by a priming fluid as well as rapid and safe transition to an operational mode. The heart-lung machine comprises a base module and a patient module with pivot means at the base module and/or at the patient module to pivot the patient module relative to the base module about a horizontal axis from a filling position into an operating position. 
         [0041]    The patient module can be pivoted in a guided manner relative to the base module by the pivot means, whereby the position and orientation of individual components of the extracorporeal blood circuit is modified so that air bubbles, which cannot escape while the machine is in the filling position, can be removed from the system at or after the transition to the operating position via venting lines. The filling and venting of the patient module can take place in approximately less than 10 minutes, whereas comparable apparatus in accordance with the prior art require approximately 20 minutes for this procedure. 
         [0042]    An automated, even quicker priming may be provided by apparatus and methods described in concurrently filed patent applications of the same applicant as the present application having obtained application numbers EP10194069.0, EP10194070.8, and EP10194071.6 (which correspond to U.S. Provisional Application Nos. ______, ______ and ______, filed on even date herewith), which hereby are incorporated herein by reference in their entirety for all purposes. Embodiments of these apparatus and methods when incorporated in the present invention have a number of advantages, including fully automatic priming and air removal, while the below described (90°) pivoting process for priming is not necessary. 
         [0043]    In one preferred embodiment, there is approximately 90° between the filling position and the operating position, which has the advantage that any air bubbles can reliably escape from the blood-conducting components. A blood reservoir is provided in the patient module and is arranged at an inclination of approximately 45° to the horizontal both in the filling position and in the operating position. This has the consequence that the blood reservoir again has the same orientation relative to the horizontal after a rotation of the patient module by 90° so that the same flow conditions result inside the reservoir before and after the pivoting. A centrifugal pump head having a central inlet and a tangential outlet can be arranged in the patient module such that the inlet is oriented vertically upwardly in the filling position and horizontally in the operating position. In this manner, the pump head can be filled with priming liquid from above without air bubbles remaining in the pump head during this process. It can likewise be advantageous in this process to provide the centrifugal pump head with a tangential outlet, which is arranged at the bottommost position of the centrifugal pump head in the operating position. This ensures that air is not pumped into the patient&#39;s circulatory system by the centrifugal pump when the pump is in the operating (operational) position. 
         [0044]    The heart-lung machine may comprise, an arterial filter having a venting outlet that can be arranged in the patient module such that the venting outlet is oriented horizontally in the filling position and vertically upwardly in the operating position. Consequently, air inside the arterial filter, which is still present in the filter after the filling with priming liquid, can escape upwardly via the venting outlet after a pivoting into the operating position. 
         [0045]    The pivot means provided can be provided in the most varied designs, such as a mount for the patient module pivotally supported at the base module. In this case, the patient module only has to be coupled to the mount in order to permit a guided pivot movement. It is particularly advantageous in this process for the pivot means to include a guide provided at the mount and at the patient module. In this case, the patient module can also be used to ensure the guided pivot movement. It is also possible to connect the patient module to a further module, for example to a control module, and to fasten the unit of the patient module and control module to the mount. In this case, the guide can be provided at the mount and at the control module. It is also possible, for example, to provide a pivot bearing at the base module into which the other module or other modules are inserted. 
         [0046]    The patient module is preferably in the operating position after being placed onto the base module since, in this case, a fast removal of the patient module from the base module is ensured without pivoting having to be carried out beforehand. The base module may comprise a device stand, which is provided with a pivotal hook to hang the apparatus on the frame of a patient&#39;s bed. The control module and the patient module may also be integrated into a stand alone unit that is operated without the base module. In some embodiments the hook is thus not present, which may provide for an alternative that is advantageous for some transportation situations. 
         [0047]    A method for putting the heart-lung machine into operation comprises bringing the patient module into the filling position, in which filling position the blood-conducting components are filled with a priming liquid. The patient module is subsequently pivoted relative to the base module, preferably by about 90°, into the operating position. The pump head provided in the patient module can be driven prior to the pivoting in order to pump the already filled-in priming liquid and thereby to further vent the blood-conducting components. 
         [0048]    One embodiment of the heart-lung machine shown in  FIGS. 1 to 4 , is composed of three modules: a base module B comprising a device stand  10 , a control module S and a patient module P comprising extracorporeal blood-conducting components. The patient module P is coupled via latch elements (not shown) to the control unit S to form a unit and this unit, consisting of the control module S and the patient module P is releasably latched to a mount  12  of the base module B. 
         [0049]    As  FIG. 1  shows, the device stand  10  may be made from tubular material and has a pivotal hooking means  14  at its upper side which is bent to form a hook at its upper side to permit hanging to a frame of a patient&#39;s bed. The pivotal hook  14  can be pivoted downwardly by 180° from the position shown in  FIG. 1  and can be plugged into two holding clips  16 ,  17  so that the pivotal hook  14  is not in the way of the mounting of the control module S and of the patient module P. 
         [0050]    The device stand  10  is permanently connected to a carrier element  20  of the base module B which has a plug socket  22  for a mains cable. The mount  12  is pivotally supported in the carrier element  20 . An operating part  24  is foldably fastened to the left hand side of the carrier element  20  in  FIG. 1  and has a touch screen  26  which represents an input and output means for a control device (computer) provided in the base module. The carrier element  20  and the non-folded operating part  24  form an annular jacket for the unit of mount  12 , control module S and patient module P. The operating part  24  must be unfolded open to the left from the position shown in  FIG. 1  to mount or remove the unit of control module S and patient module P. 
         [0051]      FIG. 2  shows the mount  12  of the base module B of  FIG. 1  to which the control module S is releasably connected by means of latch connections  28 ,  30 . The patient module P is not shown in  FIG. 2  for a simplified representation. A unit of control module S and patient module P must always be plugged onto or removed from the mount  12  in operation. The control module S supplements the disk-segment shaped geometry of the mount  12  and a handle  32  is located at the upper side of the control module S with which the unit of control module S and patient module P, on the one hand, but also the whole heart-lung machine, on the other hand, can be handled when the three modules are fastened to one another as shown in  FIG. 1 . 
         [0052]    To pivot the patient module P relative to the base module B about a horizontal axis from a filling/priming position into an operating position, the mount  12  of the base module B is equipped with two guide rails  34  which are parallel, provided at the outer periphery and cooperate with adjoining guide rails  36  of the control module S. The guide rails  34  and  36  form a continuous guide structure with the aid of which the unit of mount  12 , control module S and patient module P can be pivoted relative to the base module B. The guide rails  34  of the pivot mount  12  are provided with a cut-out  38  with whose aid the pivot mount  12  can be guided over two rollers (not shown) provided at the carrier element  20  so that the pivot mount  12  can be pivoted on the support element  20  of the base module B. The toothed arrangement recognizable in  FIG. 2  serves for the engagement of a damping mechanism ensuring a uniform and damped pivot movement. 
         [0053]    To assemble the pivot mount  12  with the support element  20 , the pivot mount  12  is first brought into a substantially vertical position and the cut-outs  38  are guided via the rollers (not shown) provided at the carrier element  20 , whereupon the pivot mount  12  can subsequently be pivoted into the position shown in  FIG. 1 . After the folding open of the operating part  24 , the previously assembled unit of control module S and patient module P can be latched on the pivot mount  12 . To pivot the patient module P from the now present operating position into a filling position, the now formed unit of control module S, patient module P and pivot mount  12  can be pivoted by 90° by pivoting down the handle  32  so that the control module S is in the position in which the pivot mount  12  was previously located. In this filling position, the blood-conducting components of the patient module P are in the position and orientation shown in  FIG. 3  with respect to the horizontal. 
         [0054]      FIG. 3  shows some blood-conducting components of the patient module, with the patient module P having been rotated about 90° counterclockwise, starting from  FIG. 1 . The view shown in  FIG. 3  corresponds to a view from the other side of the patient module P in comparison with  FIG. 1 . The wall  40  of the patient module P standing perpendicular in  FIG. 3  is thus disposed parallel next to the pivot mount  12 , whereas the horizontally oriented wall  42  adjoins the control module S. Furthermore, a plurality of hose connections are now shown in  FIG. 3  for a better clear view. Reference numeral  44  designates a centrifugal pump head having a central suction inlet  46  and a radial outlet  48  shown by broken lines in  FIG. 4 . 
         [0055]    An approximately parallelepiped shaped blood reservoir  50  is installed at a position of 45° in the patient module P and its outlet  52  is connected to the inlet  46  of the centrifugal pump head  44  via a hose line (not shown). Venting lines  54  are located at the upper side of the blood reservoir  50 . The inlet into the blood reservoir  50  coming from a venous connection is arranged approximately at the centre of the blood reservoir and cannot be seen in  FIGS. 3 and 4 . It can be recognized in  FIGS. 3 and 4  that an arterial filter  56  is provided in the patient module P which has a cylindrical shape, with a tangential inlet  58  and a central axial outlet  60  being provided. A venting connection  62  is provided centrally at the end face of the filter disposed opposite the outlet  60 . 
         [0056]    Further components shown of the patient module P are an oxygenator  64  and various connection elements which are provided at the wall  42  disposed adjacent to the control module S and which serve for the cooperation with terminals, sensors or plug connections, since all blood-conducting components are provided in the patient module P, whereas control components such as the pump drive, valves and other electrical control elements are arranged in the control module S.  FIG. 4  shows the representation of  FIG. 3  in the operating position, which corresponds to the representation of  FIG. 1  in which the control module S and the wall  42  of the patient module P contacting it are oriented vertically. 
         [0057]    As a comparison of  FIGS. 3 and 4  shows, there is 90° between the filling position ( FIG. 3 ) and the operating position ( FIG. 4 ), with the blood reservoir  50  provided in the patient module P being arranged in both positions at an inclination of 45° to the horizontal, since it is installed at 45° in the patient module. The centrifugal pump head  44  is arranged such that the central inlet  46  is oriented vertically upward in the filling position ( FIG. 3 ) and horizontally to the side in the operating position ( FIG. 4 ). The outlet  48  (not shown in  FIG. 3 ) of the pump head  44  is arranged at the bottommost position of the centrifugal pump head  44  in the operating position shown in  FIG. 4  so that the outlet  48  lies beneath the inlet  46 . 
         [0058]    The arterial filter  56  is also arranged within the patient module such that the venting outlet  62  is oriented horizontally in the filling position and vertically upwardly in the operating position ( FIG. 4 ). The inlet  58  is oriented vertically downwardly in the filling position and horizontally in the operating position, whereas the outlet  60  is oriented horizontally in the filling position and vertically downwardly in the operating position. 
         [0059]      FIG. 5  shows the different components of the heart-lung machine in accordance with the invention in which the patient blood coming from a venous connection V is guided via a line  70  into the blood reservoir  50  and flows from there via the outlet  52  into the inlet  46  of the centrifugal pump  44 . It is pumped from there via the outlet  48  into the oxygenator  64  and flows from there via the arterial filter  56  to the arterial connection A and from there back into the body of the patient. An internal bypass, which can be switched via a valve  72 , is designated by reference numeral  71 . Reference numeral  73  designates a valve for the inflow line PR with which priming liquid can be guided into the circuit. Reference numerals  74 ,  75 , and  76  each designate pressure sensors. Venting valves are designated by reference numerals  77 ,  78 , and  79 , with the valves  77  and  78  switching the vent paths into the upper region of the blood reservoir  50  not filled with blood and the venting valve  79  controlling the venting from the blood reservoir. Reference numeral  80  designates a bubble sensor, which controls an arterial quick action clamp  82  provided in the arterial outlet A if air bubbles are detected. Reference numeral  84  designates a flow sensor and reference numeral  86  an electrical interface. The oxygenator  64  is provided with inflow lines and outflow lines for water and oxygen to effect an enriching of the blood with oxygen and a temperature control of the blood. In some cases the blood temperature may be controlled to maintain normal body temperature, while in other cases, such as slowing the heart rate during CABG, the temperature of the blood may be reduced. 
         [0060]    To put the heart-lung machine described above into operation, starting from the representation of  FIG. 1 , the pivotal hook  14 , if present, is first pivoted downwardly by 180° and the operating part  24  is folded to the left. Subsequently, the total unit consisting of the control module S, the patient module P and the pivot mount  12  can be pivoted counterclockwise so that the filling position is reached. 
         [0061]    Priming liquid, which first (cf.  FIG. 5 ) fills the blood reservoir and from there the centrifugal pump head  44 , is supplied via the connection PR in the filling position. The air located in the hosing is largely removed from the system in this process by the priming liquid arranged above the machine on filling, with air bubbles, however, remaining in the upper region of the arterial filter  56  and in horizontal line portions. 
         [0062]    When the blood reservoir  50  is almost filled, the centrifugal pump head  44  is set into rotation comparatively slowly, whereby the priming liquid is pumped through the system and further air residues are removed from the system. After a time period of approximately 20 seconds, further components—such as the oxygenator  64 —are also filled with priming liquid so that the pump can be stopped and the unit of the control module S, patient module P and pivot mount  12  can be pivoted back into the operating position. After these pivoting back by 90°, that air can also escape which had remained in the arterial filter  56  and in horizontal line portions. A complete filling and venting of the patient module can thus be achieved within a time period in the order of magnitude of approximately 6 to 10 minutes. 
         [0063]    In one embodiment, the heart-lung machine is a mobile, self-contained heart-lung machine comprising a battery power supply configured to power the heart-lung machine and particularly well suited for use in the field and for emergency use. In another embodiment, the heart-lung machine is a mobile, self-contained heart-lung machine comprising a battery power supply and/or connectors for an external electrical power supply from a transport vehicle with the heart-lung machine configured to operate on battery power and/or the external electrical power supply of the transport vehicle. 
         [0064]    In a second embodiment, the apparatus and method of the invention involve a heart-lung machine comprising a blood reservoir, a blood pump, and a bubble detector for the detection of air bubbles between venous and arterial connections to the patient circulatory system. Blood entering at the venous connection is pumped by the blood pump through the blood reservoir and, optionally, through further blood-conducting components via the bubble detector to the arterial connection. An arterial line located downstream of the bubble detector leads to the arterial connection and can be closed by an arterial quick action clamp. If the bubble detector detects an air bubble, the arterial quick action clamp can be closed immediately so that the air bubble cannot enter into the patient&#39;s blood circulation from the arterial line. Simultaneously, the blood pump is stopped, a bypass clamp is opened, and the blood pump is re-started so that the blood is guided back into the blood reservoir through a bypass. The blood reservoir is connected to a further pump, which removes air from the top of the blood reservoir where air bubbles collect. As soon as the bubble detector no longer detects any air bubbles, the arterial quick action clamp is opened again and the bypass clamp is closed. 
         [0065]    In accordance with an advantageous embodiment of the invention, a blood oxygenator is arranged between the blood pump and the bubble detector. The oxygenator comprises a membrane that is impermeable to air bubbles, which contributes to the elimination of air in the system. An arterial filter configured to collect and hold back microparticles which have entered into the blood as well as gas bubbles can furthermore be provided in front (upstream) of the bubble detector. 
         [0066]    It is particularly advantageous for multiple blood-conducting components of the apparatus such as an oxygenator or an arterial filter to be connected to the blood reservoir via a venting line that primarily serves for flushing and venting during a priming process before the apparatus is placed into operation to pump blood. The venting line comprises of clamps that can be used to open and close each venting line during priming. The venting clamps can, however, also be opened briefly during the operation of the apparatus at regular time intervals so that air which has collected in the blood-conducting components is conveyed into the blood reservoir. The air then rises to the surface in the reservoir and can be extracted by a pump provided for this purpose. The venting line is connected to blood-conducting components in each case at the side of the components disposed upwardly during operation so that upwardly rising air bubbles migrate into the venting line. The regular venting of the blood-conducting components prevents the saturation of blood with air and reduces the risk of an air bubble moving up to the bubble detector. 
         [0067]    The pump extracting the air from the blood reservoir is preferably a roller pump, which can additionally have a clamping function. Such a pump is described in U.S. patent application Ser. No. 11/366,342 and permits the extraction of air from the blood reservoir with simple means, with it being ensured by the clamping function that no air can flow in the opposite direction, i.e. into the reservoir, even when the pump is switched off. 
         [0068]    In accordance with an advantageous embodiment of the invention, the air extracted from the blood reservoir is pumped into an air container arranged downstream of the pump extracting air from the blood reservoir. The total extracorporeal blood circuit thereby remains closed toward the outside. A simple plastic pouch can serve as the air container. 
         [0069]    Additional protection from air bubbles in the blood exiting the apparatus can be achieved by configuring the blood reservoir to comprise an inlet region separated from an outlet region by a screen unit which is a membrane permeable for blood, but impermeable for air bubbles. 
         [0070]    In accordance with a further advantageous embodiment of the invention, means are provided for the monitoring of the filling level of the blood reservoir. A first sensor is preferably provided which detects whether the filling level reaches a first threshold value. A second sensor detects whether the filling level falls below a second threshold value lying below the first threshold value. The corresponding information can be passed on to an electronic control unit of the apparatus so that the roller pump can be switched on to extract air from the blood reservoir when the filling level falls below the first threshold value. The air which collects in the blood reservoir in bypass operation after detection of an air bubble or on a regular venting of blood-conducting components is thus extracted automatically as soon as a predetermined amount of air is present in the reservoir. As further security, the blood pump can be switched off if the filling level falls below the second threshold value. In this case, an alarm signal is simultaneously output. It is possible for the filling level of the reservoir to fall below the second threshold value, for example, if the venous connection is not properly connected to the patient&#39;s blood circulation, but has become loose so that air is pulled into the blood conducting components. In such cases, the described filling level monitoring switches the blood pump off immediately. 
         [0071]    In accordance with a further advantageous embodiment of the invention, the bypass clamp is opened at regular time intervals for a short period to flush any pooled blood from the upstream side of the bypass clamp. This prevents coagulation of any pooled blood, which might then enter into the extracorporeal blood circuit after the bypass clamp is opened and, in the worst case, subsequently enter into the patient&#39;s blood circulation via the arterial connection. 
         [0072]    As a consequence of the described automated safety features present in the heart-lung machine, an intervention by trained medical staff due to an error report is only necessary in an extreme emergency. In the normal case, the apparatus in accordance with the invention can successfully prevent air bubbles from entering into the blood circulation of the patient connected to the apparatus without any human intervention. 
         [0073]    A heart-lung machine according to the present invention may be used to provide extracorporeal blood circulation and oxygenation to a patient undergoing conventional or keyhole CABG surgery. A heart-lung machine according to the present invention may also be required in some cases to provide extracorporeal blood circulation and oxygenation during percutaneous angioplasty and/or placement of one or more drug-eluting or non-drug-eluting stents and/or during rotational or laser atherectomy, particularly if complications arise during the procedure such as the heart stopping or complications requiring the sowing or stopping of the heart. In the event of a complication during any of these procedures, the ability to quickly prime the heart-lung machine and bring it into operation is of particular importance. Additionally, no perfusionist is required to prime or operate a heart-lung machine according to the present invention, which expands the conditions and locations under which extracorporeal blood circulation and oxygenation can be safely provided and procedures dependent thereon can be safely performed. 
         [0074]      FIG. 6  shows a schematic of a heart-lung apparatus according to the invention. Patient blood entering through a venous connection V is guided via a line  70  into a blood reservoir  50  and moves from there through an outlet  52  and into an inlet  46  of a centrifugal pump  44 . The inlet  46  is arranged centrally at the pump head of pump  44  and blood is pumped through a tangential outlet  48  arranged at the bottom most point of the pump head of the centrifugal pump  44  and into an oxygenator  64  to which an oxygen supply line is connected. Blood enriched with oxygen is subsequently filtered in an arterial filter  56  and finally flows, in the normal case, through an arterial line  168  and via an arterial connection A back into the patient. 
         [0075]    The blood reservoir  50  is split into an inlet region  50   in , and a separate outlet region  50   out  by a membrane  128  that is permeable for blood, but prevents air bubbles entering into the outlet region from the inlet region. 
         [0076]    A bubble detector  80  is arranged between the arterial filter  56  and the arterial connection A. As long as it does not detect any air bubbles, an arterial clamp  82  in the arterial line  168  remains open, while a bypass clamp  72  remains closed. Blood flow can be continuously monitored by flow sensor  84 , which measures blood flow in the arterial line  168 . 
         [0077]    If an air bubble is detected in the bubble detector  80 , the arterial clamp  82  is closed immediately. The reaction path between the bubble detector  80  and the arterial clamp is configured to be long enough that a detected air bubble cannot reach the clamp before the clamp is closed. The clamp  82  is preferably a fast-closing clamp, which closes in less than 300 ms, as described in co-assigned U.S. patent application Ser. No. 11/366,914. Clamp  82  is also called quick action clamp herein. The sufficiently long reaction path and the speed with which the clamp closes advantageously prevents any air bubble detected by the bubble detector  80  from reaching the arterial connection A. Simultaneously, the blood pump  44  is stopped, the bypass valve or clamp  72  is opened, and the blood pump  44  is re-started, so that the blood, together with the detected air bubble, flows via a bypass  71  back into line  70  and into the blood reservoir  50 . 
         [0078]    In the blood reservoir  50 , air bubbles rise upwardly so that blood is located at the bottom in the reservoir  50   out , and air collects at the top  50   in . Means  122  for the monitoring of the filling level of the blood reservoir are electronically coupled, for example via an electronic control unit, to a hose roller pump  170  configured for the extraction of air from the reservoir. The hose roller pump  170  may be, for example, a hose pump as disclosed in U.S. application Ser. No. 11/366,342. As soon as the monitoring means  122  of the filling level of the blood reservoir  50  reports that the filling level has fallen below a first threshold value, the hose roller pump  170  is switched on to remove air from the top of the reservoir  50   h , and pump the air into a waste container  180 . The hose roller pump  170  has a clamping function so that it acts as a clamp if it is not actively pumping to prevent a backflow of air into the blood reservoir  50 . If the filling level of the blood reservoir falls further, despite the removal of air by the hose roller pump  170 , below a second threshold value, the centrifugal pump  44  is switched off and an alarm, for example an audible and/or visible signal is output. 
         [0079]    The oxygenator  64  and the arterial filter  56  are each connected to the upper region of the blood reservoir  50   h , by a venting line  96  provided with venting valves  92 ,  94 . The venting line first serves for the flushing and venting of the heart-lung machine during a priming procedure before it is put into operation. In this procedure, a priming liquid is filled in via a priming connection PR and priming circuit (dashed line passing through valve  90 ) and the extracorporeal blood circuit is vented. The venting clamps  92  and  94  are normally closed during the operation of the heart-lung machine but are, however, opened briefly at regular time intervals, for example every 10 to 15 minutes, so that accumulated air in the oxygenator or the arterial filter is guided into the reservoir  50  for removal from the system. 
         [0080]    Pressure sensors  74 ,  75  monitor the pressure before (upstream of) and after (downstream of) the oxygenator. The measured values of the pressure sensors are forwarded to a pressure monitoring unit  127  via a connection (not shown for reasons of clarity). An abnormal increase in the pressure drop at the oxygenator  64  can be an indicator of clogging by coagulated blood, and a need for action may be indicated, for example, by triggering an audible and/or a visual signal. Additionally, the extraction pressure at which blood is extracted from the patient into the line  70  is monitored using pressure sensor  76 , which measures the pressure in the line connecting the blood reservoir  50  and the hose roller pump  170 . The measured result is likewise passed on to the pressure monitoring unit  127 . 
         [0081]    To avoid coagulation of standing or pooled blood in the bypass  71  in  FIG. 6  beneath the bypass clamp  72  while the arterial clamp  82  is open and the bypass clamp  72  is closed, the bypass clamp  72  may be opened at regular time intervals for a short time to periodically flush the bypass  71 . 
         [0082]    Arterial quick action clamp  82  shown in  FIG. 6  is preferably a fast closing clamp as shown in  FIGS. 7-11 . The sectional view of  FIG. 7  corresponds to the cross-section indicated by A in  FIG. 9 . The hose  201  contacts a wall  203 , which is formed for example by the rear wall of a housing part receiving the hose. A clamp jaw  205  is configured to be brought into a clamping position in the arrow direction by the fast closing clamp, pinching the hose  201  closed. 
         [0083]    A holding apparatus  207  comprises an inner hollow space in which the clamp jaw  205  is guided. In the embodiment shown, the clamp jaw  205  is an internal piston and the holding apparatus  207  is an external piston, with the internal piston  205  being displaceably received in the external piston  207  and the external piston  207  being displaceably received in a housing  209 . A spring  217  is supported against a seat  216  inside the external piston  207  and a seat  218  is supported at the external periphery of the internal piston  205 , said spring being under compressive tension in the open position of the internal piston shown in  FIG. 7 . 
         [0084]    The spindle  219  of a spindle drive comprises an external thread  221  in the region in which it engages into the external piston  207 , which has a corresponding mating thread at the internal periphery where the spindle  219  passes through it. The spindle  219  is rotatably held in the housing  209  in a bearing  223 . The spindle is connected to a toothed wheel  225  via the grub screw  227 . The toothed wheel  225  meshes with a toothed wheel  229  which, in turn, meshes with a toothed wheel  231  that is connected via a grub screw  233  to the axis of an electric motor  235  which is fixedly installed in a holding plate  237 . 
         [0085]    The toothed wheel  229  is rotatably supported in the holding plate  237 . The housing  209  is permanently connected to the holding plate  237 . A hollow space  215  is located in the external piston  207  and balls  213  can partly enter into it, which project radially out of the internal piston  205  in the latched state. 
         [0086]      FIG. 8  shows the fast closing clamp of  FIG. 7  in a lateral plan view. The direction of view visible in the plan view of  FIG. 9  is indicated by III in  FIG. 9 . The internal piston  205  comprises a radially outwardly extending abutment bar  239 , which is guided in an elongate hole  238  of the housing  209  ( FIG. 8 ). 
         [0087]      FIG. 10   a  shows a detail of  FIG. 7  in the region of the latch device between the external piston  207  and the internal piston  205 . The latched state is also shown in FIG.  10   a . The tip of the blocking bar  211  lies in the axial cut-out  206  of the rear part of the internal piston  205 . In this process, the tip presses balls  213  outwardly through radial openings  214  in the internal piston  205 , which partly enclose the balls  213 . The tip of the blocking bar  211  is made in ball shape and tapered toward the front so that it can easily be pushed between the balls  213 . In the embodiment shown, three of the radial openings  214  are provided with corresponding balls  213  at an angle of 120° to one another. The two other openings are therefore not visible in the sectional representation of  FIG. 10   a.    
         [0088]    The balls  213  engage into a cut-out  215  in the external piston  207 . In the state shown, the internal piston  205  cannot move out of the external piston  207  to the right since the balls  213  are fixed in the cut-out  215  of the external piston  207 . If the blocking bar  211  is pulled out of the axial cut-out  206  of the internal piston  205  to the left, the balls can move into the axial cut-out  206  and the internal piston  205  can be moved out of the external piston  207  to the right by the force of the spring  217 . The inward movement of the balls  213  is in particular facilitated by the chamfering  220  of the cut-out  215 . The right hand end of the spindle  219  can be recognized in  FIG. 10   a  with the thread  221 , which meshes in an internal thread of the external piston  207 . 
         [0089]    Whereas  FIG. 10   a  shows a section through the fast closing clamp in which a ball  213  is sectioned precisely at the center.  FIG. 7  shows a section in which no ball  213  is precisely cut. In this respect, the sectional planes of  FIG. 7  and of  FIG. 10   a  are tilted with respect to one another by 30° around an axis which is, for example, defined by the blocking bar  211 . This relationship is illustrated in  FIG. 10   b , which shows a view in the direction of the arrows IVa, which are given in  FIG. 10   a . A view in an axial direction of the tip of the blocking bar  211  and of the balls  213  is shown in a schematic representation in  FIG. 10   b . S 1  shows the sectional plane of  FIG. 7 , while S 4  shows the sectional plane of  FIG. 10   a . The direction of view of the sectional plane, which is the subject matter of  FIG. 7 , is designated by the arrows I in  FIG. 10   b . The direction of view of the sectional plane, which is the subject matter of  FIG. 10   a , is designated by the arrows IV in  FIG. 10   b . The angle β indicated amounts to 60°, whereas the tilt angle of the sectional plans α amounts to 30°. 
         [0090]      FIG. 11  shows a part of the quick action, fast closing clamp not shown in  FIGS. 7-10   a , which is a mechanism that moves the blocking bar  211  in the axial direction. The blocking bar  211  is connected via a hinge point  212  to a rocker  241 , which is rotatably supported at the point  243 . This rocker is connected via a hinge point  249  to a metallic actuation bar  247 , which projects into an electromagnet  245 . In this arrangement, the bar  247  moves to the right on a flow of current through the electromagnet  245 . The rocker rotates around the center of rotation  243  and moves the blocking bar  211  to the left in the representation of  FIG. 11 . A compression spring  248  biases the rocker  241 , the actuation bar  247 , and the blocking bar  211  in the direction of their positions of rest when the electromagnet  245  again has no current. The force of the electromagnet  245  acts against the spring force of this spring  248 . 
         [0091]    When a bubble is detected in the hose  201 , a signal is transmitted to put the electromagnet  245  under current for approximately 50 ms so that the actuation bar  247  moves into the electromagnet. The rocker  241  rotates around the center of rotation  243  and pulls the blocking bar  211  to the left. The blocking rod  211  thereby moves out of the axial hollow space  206  ( FIG. 10   a ) of the internal piston  205 . The internal piston  205  is urged in the direction of the arrow ( FIG. 7 ) by the spring force of the spring  217 . Since the blocking bar  211  no longer blocks the axial hollow space, the balls  213 —facilitated by the chamfer  220 —escape back into this hollow space  206  and the latch connection between the internal piston  205  and the external piston  207  is cancelled. The spring force of the spring  217  drives the internal piston  205  against the hose  201  and pinches it off against the rear wall  203  of the passage conducting the hose. It is, for example, sufficient to operate the electromagnet only for approximately 50 milliseconds to trigger this action. The hose is pinched off after only around 100 milliseconds. The abutment bar  239  guided in the longitudinal hole  238  in the housing  209  prevents the internal piston  205  from being able to completely exit the housing  209  on an unintentional triggering. 
         [0092]    To move the internal piston back into its open position, the electric motor  235  is switched on. The spindle  219  is driven via the toothed wheels  231 ,  229 , and  225 . The external piston  207  moves axially to the right out of the housing  209  by the spindle rotation. The internal piston  205  is in the meantime still supported against the hose  201  or the rear wall  203  of the passage. As soon as the external piston  207  and the internal piston  205  are again completely pushed onto one another, the radial openings  214  in the internal piston  205  are again in the region of the cut-out  215  inside the external piston  207 . The tip of the blocking bar  211  can again push between the balls  213  which are in turn moved radially outwardly through the openings  214  in the internal piston  205 . The blocking bar  211  is pushed into the axial cut-out  206  of the internal piston  205  by the action of the spring  248  which acts on the rocker  241  for this purpose. The balls  213  again engage into the cut-out  215  in the external piston  207  as is shown in  FIG. 10   a  and latch the external piston  207  and the internal piston  205 . 
         [0093]    If the electric motor  235  is operated in the reverse direction, the spindle  219  pulls the external piston  207  to the left in the representation of the Figures. The internal piston  205  is also moved back due to the latching of the internal piston  205  in the external piston  207  and the fast closing clamp again moves to its open position. The spring  217  again starts to tense while the external piston  207  is again pushed over the internal piston  205  and stores energy for a new triggering process. It is possible in this way to trigger a further pinching process as required on the returning of the internal piston  205  together with the external piston if e.g. a bubble is again detected in the extracorporeal circuit during the return of the internal piston  205 . 
         [0094]    The hose roller pump  170  in  FIG. 6  is preferably a peristaltic hose pump as shown in  FIGS. 12-19 . The pump, as shown in  FIG. 12 , comprises a support plate  310 , which can be installed in a fixed position, and a bore through which a drive shaft  312  is rotatably inserted. The right end of the drive shaft  312  in  FIG. 12  can be driven by a drive (not shown), for example by an electric motor, whereby a rotor  314  attached to the left end of the drive shaft  312  in  FIG. 12  likewise rotates. The rotor  314  has a plurality of rollers  316  which are distributed over its periphery and which serve in a known manner to press fluid (e.g. air or blood) through a flexible hose (not shown). 
         [0095]    A mating piece  318 , shown in a perspective view in  FIG. 13 , is screwed beneath the rotor  314  to the left side of the support plate  310  in  FIG. 12  and has two vertical blind bores  320  and  321 , on the one hand, and two V-shaped grooves  322  and  323 , on the other hand, which extend at an angle to the horizontal and extend inside one and the same vertical plane. The mating piece  318  furthermore has an approximately semi-circular opening in which the rotor can rotate freely. 
         [0096]      FIG. 12  shows that a support element  326  above the rotor  314 , which is movable in the direction of the double arrow by a predetermined distance in the direction toward the rotor  314  or by a predetermined distance away from the rotor  314 .  FIG. 12  shows the pump with the support element completely moved away from the rotor  314  by the predetermined distance. 
         [0097]    Two guide pins  328  (only one is shown in  FIG. 12 ), which are inserted into the blind bores  320  and  321  of the mating piece, guide the support element  326 . As  FIG. 14  shows, the support element  326  likewise has two blind bores  330  (only one is shown in  FIG. 14 ) so that the support element  326  is guided by the guide pins  328 .  FIG. 14  shows that the support element  326  also has two V-shaped grooves  332  and  334  which, together with the grooves  322  and  323  of the mating piece  318 , form a clamping device in which the hose can be clamped by a movement of the support element in the direction toward the rotor. A groove  336  provided at the rear side of the support element  326  serves for the insertion of a metal piece to permit a contact free position detection with the help of a sensor (not shown). A blind bore  338  is provided centrally at the rear side of the support element  326 . A pin  340  is inserted into this blind bore, as shown in  FIG. 12 , extending through an elongate hole  341  in the support plate  310  and simultaneously serving as an end abutment for the movement of the support element  326 . The pin  340  projects somewhat from the support plate  310  on the side thereof opposite to the support element  326  and the projecting end of the pin  340  is inserted into a plain bearing  342  which is movable in a spiral groove  344  ( FIG. 17 ) of a drive plate  346 . 
         [0098]    The drive plate  346  is shown in more detail in  FIGS. 16-18  and is placed freely rotatable onto the drive shaft  312  via a plain bearing  348 .  FIG. 17  shows a view of that side of the drive plate  346  which faces the support plate  310 . The spiral groove  344  extends from the outer rim of the drive plate  346  in the direction of the center, with the spiral groove extending over an angle of somewhat more than 180°. A ring groove  350  is provided at the interior of the spiral groove  344  and receives a fixed position cam guide  352 , which is made integrally with the support plate  310  ( FIG. 15 ).  FIGS. 15 and 19  show that the fixed position guide cam  352  has a rising and a falling flank of the same gradient. In this process, the guide cam  352  is curved in the peripheral direction such that it fits into the ring groove  350  of the drive plate  346 . 
         [0099]      FIG. 16  shows the side of the drive plate  346  disposed at the bottom in  FIG. 17 . A curved recess is provided at this side of the drive plate  346 , which has two guide chamfers  354  and  356  whose lowest point forms an opening  358  through which a passage into the ring groove  350  is created. This passage serves for the passing through of a drive pin  360 , which serves as a coupling member between the drive shaft  312  and the drive plate  346 . 
         [0100]      FIG. 12  shows that a drive plate  362  is rotationally fixedly connected to the drive shaft  312 , with the drive pin  360  being resiliently supported in a sleeve  364  provided at the drive plate  362  such that it is displaceably supported against the force of the spring in the axial direction of the drive shaft  312 . When the drive shaft  312  thus rotates, the drive plate  362  and also the drive pin  360  rotate together with it. In this process, the drive pin  360  presses against the drive plate  346  due to the spring and the front end of the drive pin  360  runs on the drive plate on an orbit which is indicated by a broken line in  FIG. 16 . If, in this process, the drive pin  360  moves into the region of the guide chamfers  354  and  356 , the front end of the drive pin  360  moves on these guide chamfers until it moves through the opening  358  in the drive plate. 
         [0101]    The starting position is the situation shown in  FIG. 12  in which the support element  326  has been moved away from the rotor  314  by the predetermined distance. In this position, the drive pin  360  is located in the situation shown in  FIG. 19  in which it projects through the opening  358  in the drive plate  346  and its front end lies on the fixed position cam guide  352 . If, in this process, the drive shaft  312  and thus the drive wheel  362  are moved against the arrow direction S, the drive pin  360  is moved to the right in  FIG. 19  and first runs on the fixed position cam guide  352  and subsequently on the guide chamfer  356  of the drive plate  346  which merges constantly into the left hand flank of the fixed position cam guide  352 . Subsequently, the drive pin  360  runs on the orbit shown by a broken line in  FIG. 16  until it again moves toward the guide chamber  354  and slides along on this until the situation of  FIG. 19  being the result. This means that the drive shaft can be rotated as desired against the arrow direction shown in  FIG. 19 , without the drive plate  346  moving. 
         [0102]    After a flexible hose has been inserted into the intermediate space between the support element  326  and the rotor  314 , the direction of rotation of the drive shaft  312  is reversed and now runs in the direction of the arrow S shown in  FIG. 19 . However, this means that the drive pin  360  abuts the lower end of the guide chamfer  354 , so that, on a further rotational movement, the drive plate  346  is taken along by the drive pin  360  and likewise rotates in the direction of the arrow S. In this process, the front end of the follow pin runs along the falling flank of the cam guide  352  until it revolves on the orbit shown by a broken line in  FIG. 15 . 
         [0103]    On this rotation of the drive plate  346 , the plain bearing  342  simultaneously runs in the spiral orbit  344  and thereby moves in the direction of the axis of rotation, whereby the pin  340  in the elongate bore  341  is likewise moved in the direction of the axis of rotation. Consequently, the support element  326  is moved by the predetermined distance in the direction toward the rotor  314  such that the flexible hose (not shown) is respectively clamped between the V grooves  322  and  332 , and  323  and  334 . At the same time, the hose is clamped between the support element  326  and the rotating rollers  316  of the rotor  314  so that a pump effect is achieved. 
         [0104]    After a complete revolution of the drive pin  360  on the orbit shown in a broken line in  FIG. 15 , said drive pin moves from the right side in  FIG. 19  back up to the cam guide  352  and subsequently slides upwardly on this until the front end moves onto the guide chamfer  354  of the drive plate  346  constantly adjoining the cam guide  352  at this point in time. The drive pin  360  then slides further upwardly on this guide chamfer  354  until the front end of the drive pin  360  revolves on the orbit shown in a broken line in  FIG. 16 . When the drive shaft is rotated further in the direction of the arrow S, the drive pin  360  can revolve for any desired length of time without effecting a movement of the drive plate  346 . Only when the direction of rotation is reversed again does the drive pin  360  again couple with the drive plate  346  in that it moves through the opening  358  and slides downwardly on the fixed position cam guide  352 . The front end of the drive pin  360  subsequently again revolves once on the orbit shown by a broken line in  FIG. 15  until the situation shown in  FIG. 19  is the result. 
         [0105]    One important advantage of the present apparatus and methods over existing apparatus and methods is the ability to quickly provide extracorporeal blood circulation and oxygenation without the need for a specially trained operator. Quickly and automatically priming the apparatus and then placing the apparatus into an automated operational mode required is enabled by the safety features described herein. Various combinations and configurations of Quick-action (fast closing) clamps, vent lines, filters, air removal pumps, and other components achieve a level of safety that permits the automation of the heart-lung machine and methods involving an automated heart-lung machine. 
         [0106]      FIG. 20  shows a preferred embodiment of a multi-stage air removal system providing a level of safety that permits automated extracorporeal blood circulation and oxygenation. A screen filter with a suitable pore size, such as 120 μm, separates the blood reservoir  50  into two sections ( FIG. 5 ). Air bubbles having a diameter of greater than 120 μm cannot pass through the screen from the venous blood input section of the reservoir to the output section of the reservoir. 
         [0107]    An upper level fill sensor  122   a  capable of distinguishing between gas (air) and liquid (blood) is connected to a roller pump  170  configured to remove air from the inlet portion of the blood reservoir. When the upper level sensor  122   a  detects a liquid, the roller pump  170  is inactive. When the level of blood falls below the level of the upper fill sensor  122   a , the sensor detects air and sends a signal to the roller pump  170 , causing the pump to remove air from the top of the reservoir. Removing air from the reservoir results in a relative negative pressure within the reservoir that increases the rate at which blood is drawn into the inlet of the reservoir from the venous blood source. 
         [0108]    A lower level fill sensor  122   b  capable of distinguishing air from blood is connected to a centrifugal pump  44  configured to pump blood from the reservoir  50  to an oxygenator  64 . As long as the lower level fill sensor  122   b  detects blood, blood is pumped from the reservoir  50  to the oxygenator  64 . When the lower level fill sensor  122   b  detects air, it sends a signal to the centrifugal pump  44 , causing the pump to immediately stop pumping blood from the reservoir. This prevents the centrifugal pump from emptying the reservoir and pumping air into the downstream blood conducting components of the heart-lung machine. 
         [0109]    The centrifugal pump  44  has a central inlet and a tangential outlet at the lowest point of the pump head with respect to gravity. Should air enter the inlet of the pump, the rotation of the pump causes liquid in the pump to move toward the outer wall of the pump head leading to the outlet while any air is moved toward the center of the pump head and prevented from reaching the outlet. Any air in the pump remains in the top center portion of the pump head, which successfully prevents even a small volume of air from reaching the downstream blood conducting components of the heart-lung machine. 
         [0110]    The oxygenator  64  has a separate ventilation system where air rises to and is removed from the highest point of the oxygenator  64 . A vent line (purgeline)  96   a  is connected to the top of the oxygenator and configured to carry the air away from the oxygenator. In a preferred embodiment, the oxygenator vent line  96   a  carries air from the oxygenator  64  to the blood reservoir  50  as shown in  FIG. 20 . 
         [0111]    Oxygenated blood moves from the oxygenator  64  to a vented arterial filter  56 . A vent line  96   b  (purge line) is connected to the highest point in the arterial filter  56  and removes air that is trapped by the filter. In a preferred embodiment, the arterial filter vent line  96   b  carries air from the filter  56  to the blood reservoir  50 . 
         [0112]    The air bubble sensor  80  (detector) is positioned downstream of the arterial filter  56  and communicates with a quick-action clamp  82  positioned on the arterial line leading to the arterial connection A and to a bypass clamp  72  located on a bypass line (not shown). In normal operation without air bubbles, the quick-action clamp  82  is open and the bypass clamp  72  is closed. In response to the detection of an air bubble by the bubble sensor  80 , the quick-action clamp  82  on the arterial line closes immediately. Then the bypass clamp  72  on the bypass line opens to divert blood flow away from the arterial connection A and back to the blood reservoir  50  through the bypass line. As the bypass clamp is not a quick action clamp, but an ordinary hose clamp, it opens much slower than the quick action clamp  82  closes. Therefore, when the quick-action clamp  82  is activated, the blood pump is simultaneously stopped, and the bypass clamp is “slowly” opened. After a short delay period, when the bypass clamp is open, the blood pump is re-started. This is made to ensure that the running blood pump does not generate undesired high pressures in the blood conveying system against the closed quick action clamp  82  and the closed bypass clamp  72 . Thus leakage caused by overpressure in the system is effectively avoided. Once no air bubbles are detected in the bypass flow by the air bubble sensor and a predetermined time interval has elapsed, the first and second quick-action clamps revert to their normal operating positions. 
         [0113]    A method according to the present invention comprises priming, or filling, the heart-lung machine with a priming fluid such as sterile saline. Once initiated, the priming can take place in an automated manner without human intervention. When primed and operational, the machine is fluidly coupled to the circulatory system of the patient through a vein to the venous coupling of the machine and through an artery to the arterial coupling of the machine. 
         [0114]    The heart of the patient may optionally be slowed or stopped, if necessary. The blood returned to the patient is enriched with oxygen. In some cases the blood temperature may be controlled to a body temperature below normal body temperature and above a temperature where organs may be damaged. Such a temperature range may currently be achieved by placing the patient, or only the heart, in an ice bath during surgery. Controlling the blood temperature, and perhaps cooling the blood before re-entering it into the patient via the venous vessel connection, is an elegant solution whereby the body temperature and/or the heart temperature is much better controlled. 
         [0115]    In the case of a coronary artery bypass graft a graft vessel, such as a segment of saphenous vein, an internal thoracic artery, or a radial artery is taken from the patient, a cannulae is sutured into the heart, and cardiopulmonary bypass using the heart-lung machine is initiated. The aorta is clamped and the heart is stopped and cooled to, for example, 29° C. One end of the graft vessel is sutured a coronary artery beyond a blockage to be bypassed. The heart is then restarted, the other end of the graft vessel is sutured to the aorta while the heart is beating, and the heart-lung machine is disconnected from the patient ( FIG. 21 ). 
         [0116]    The method may include the addition of drugs or other additives to the blood by way of the heart-lung machine. For example, an anticoagulant may be added to the blood to prevent clotting while the heart is stopped. 
         [0117]    In the case of percutaneous angioplasty or stent placement, a balloon is inflated inside a coronary artery to widen the passage or to expand a stent that will widen the artery and support the artery in a more open configuration to improve blood flow therethrough. The heart may be, but is usually not stopped for percutaneous angioplasty or stent placement, but the expansion of the balloon catheter inside the artery may cause the artery to rupture and necessitate emergency heart surgery. The heart-lung machine may be used in the event of such a complication or other complications that require the heart to be stopped or slowed. The heart-lung machine may be, but need not be, primed as a precaution before a possible complication. 
         [0118]    The description of the invention is merely exemplary in nature and, thus, variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Apparatus and methods comprising combinations of two or more of the various aspects and/or embodiments described herein and other variations are not to be regarded as a departure from the spirit and scope of the invention.