Patent Document

CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application claims the benefit of the filing date of U.S. Provisional Patent Application No. 61/621,291, filed Apr. 6, 2012, the disclosure of which is hereby incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     Certain lung diseases, such as emphysema, reduce the ability of a person&#39;s lungs to sufficiently oxygenate blood. If parts of a patient&#39;s lungs are removed due to conditions such as lung cancer, the ability to oxygenate blood is impaired. Persons having such conditions require assistance in providing oxygenated blood to their bodies. Some patients with such conditions can survive if oxygen-enriched air is supplied to their lungs, as by use of an oxygen mask. However, other patients do not have sufficient lung capacity for survival with these measures. 
     It has been proposed to provide blood oxygenators to such patients. A blood oxygenator is a device which exposes the patient&#39;s blood to air or oxygen as the blood flows through the device. Blood oxygenators have long been used as a component of the so-called “heart-lung machine” to provide short-term support to a patient during surgical procedures such as heart surgery or transplantation. However, the systems incorporating such oxygenators require frequent and professional maintenance, and are suitable for use only in a hospital setting. These systems typically require that the patient be confined to a bed, which drastically impairs the patient&#39;s quality of life. Thus, there has been a significant need in the art for a patient support system using an oxygenator which can be used for long-term treatment, desirably outside of a hospital environment. 
     BRIEF SUMMARY OF THE INVENTION 
     One aspect of the disclosure provides a system for oxygenating blood. The system may include a blood pump having an outlet and an inlet adapted for communication with the circulatory system of a mammalian subject at an inlet location. The system may further include one or more return fittings adapted for communication with the circulatory system of the subject at one or more return locations remote from the inlet location. The system may further include a blood oxygenator having a blood inlet releasably connectable in communication with the outlet of the pump and a blood outlet releasably connectable in communication with one of said return fittings. The system may further include a bypass conduit adapted to connect the outlet of the pump in communication with one of said return fittings at least when the oxygenator is disconnected. 
     In one variation, the system further includes an oxygenator inlet disconnect fitting connected to the outlet of the blood pump and an oxygenator outlet disconnect fitting connected to one of said return fittings, the blood inlet and outlet of the oxygenator being adapted to releasably engage the disconnect fittings. 
     In another variation, the system further includes an adapter having an inlet connected to the outlet of the blood pump, a first branch connected to the oxygenator inlet disconnect fitting and a second branch connected the bypass conduit. 
     In another variation, the system further includes a valve in the adapter having a normal condition in which blood flow entering the adaptor is directed primarily to the first branch and a bypass condition in which blood flow is directed primarily to the second branch. 
     In another variation, the system further includes a valve connected in series with the bypass conduit, the valve having a normal condition in which flow through the bypass conduit is at least partially blocked and a bypass condition in which flow through the bypass conduit is substantially unblocked. 
     In another variation, when the valve is in the normal condition, flow through the bypass conduit is only partially blocked. 
     In another variation, the pump is an implantable pump configured to be implanted within a mammalian subject body. 
     In another variation, the implantable pump is biocompatible. 
     In another variation, the pump is selected from a group consisting of: an axial-flow blood pump, and centrifugal blood pump. 
     In another variation, at least one of the one or more return locations is selected from a group consisting of: a right atrium, a right ventricle, or a pulmonary artery. 
     In another variation, the inlet location is a pulmonary artery. 
     In another variation, the bypass conduit is configured to be at least partially disposed within the mammalian subject body. 
     In another variation, an internal diameter of the first branch is different than an internal diameter of the second branch. 
     In another variation, the internal diameter of the first branch is larger than the internal diameter of the second branch. 
     Another aspect of the disclosure provides a method of providing respiratory assistance to a mammalian subject. The method includes (a) directing blood from an inlet location in the circulatory system of the subject through a pump, through an oxygenator and back to the circulatory system. The method may further include (b) temporarily disconnecting the oxygenator. The method may further include (c) directing blood through the pump and through a bypass conduit back to the circulatory system. The method may further include (d) reconnecting the same oxygenator or a different oxygenator and then resuming step (a). 
     In one variation, steps (b), (c) and (d) are performed so that blood continuously flows through the pump. 
     In another variation, in step (c), the blood is directed back to the pulmonary artery of the subject. 
     In another variation, in step (a), the blood is directed back to the pulmonary artery of the subject. 
     In another variation, the method further includes the step of directing blood through the bypass conduit and back to the circulatory system during step (a). 
     In another variation, during step (a), blood passes through the oxygenator at a first rate and blood passes through the bypass conduit at a second rate less than the first rate. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a diagrammatic view of a system according to one embodiment of the invention in conjunction with the circulatory system of a patient. 
         FIGS. 2 and 3  are views similar to  FIG. 1  but depicting systems according to further embodiments of the invention. 
     
    
    
     DETAILED DESCRIPTION 
     A system  200  according to one embodiment of the invention includes a blood pump  204  having a pump inlet  204   b  and a pump outlet  204   a . The blood pump  204  desirably is a pump suitable for providing pumping action over a long period of time, such as months or years, without severe hemolysis or other severe effects on the blood. Pumps of the type used to provide long-term assistance to the heart, sometimes referred to as “ventricular assist devices” or “VADs” can be used. The pump desirably is a load-sensitive pump having a flow versus pressure characteristic such that the flow through the pump decreases progressively with the pressure head opposing the flow. Stated another way, the pump desirably is not a positive-displacement pump. Impeller pumps such as centrifugal or axial-flow impeller pumps can be used. The pump desirably is arranged so that it can be carried by the patient and powered by a portable power supply. Most desirably, the pump is implantable within the body of the patient. Implantable blood pumps are described in U.S. Pat. Nos. 7,699,586, 7,972,122, and 8,007,254, the disclosures of which are incorporated by reference herein. For example, an axial-flow impeller pump of the type supplied by HeartWare, Inc. of Miami Lakes, Fla. under the trademark MVAD can be used. 
     A pump inlet conduit  202  is connected to pump inlet  204   b . The pump and the inlet conduit are arranged so that the pump inlet  204   b  can be connected to an inlet location  122  within the circulatory system of the subject. 
     The system further includes a pump outlet conduit  206  having one end connected to the outlet  204   a  of the pump and having the other end connected to a branching adaptor  208 . Adaptor  208  has a single inlet connected to pump outlet conduit  206  and has two outlets. A first outlet of adaptor  208  is connected to an oxygenator supply conduit  210 , also referred to as a first branch. The second outlet of adaptor  208  is connected to a bypass conduit  228 , also referred to as a second branch. Adaptor  208  includes a valve  208   a  that can be actuated between a first position in which the flow of blood entering the adaptor is directed primarily to first branch  210 , and a second position in which the flow is directed primarily or entirely to or second branch  226 . 
     Oxygenator supply conduit  210  extends to an oxygenator inlet disconnect fitting  212 . Disconnect fitting  212  includes an interface arranged to releasably connect conduit  210  in communication with a mating fitting  212   a  and form a fluid-tight seal with the mating fitting when connected. The disconnect fitting may also include an internal valve (not shown) arranged to block flow through the disconnect and conduit  210  when the mating fitting is disconnected. The system further includes an oxygenator outlet disconnect fitting  220  similar to fitting  212 . Outlet disconnect fitting  220  is connected to one end of an oxygenator return conduit  222 . Fitting  220  is adapted to releasably engage a mating fitting  220   a  in a fluid-tight seal so as establish communication between fitting  220   a  and conduit  222 . Disconnect fitting  220  may also include a valve (not shown) for closing the end of conduit  222  when fitting  220   a  is disconnected. Merely by way of example, suitable disconnect fittings are commercially available from NovaLung GmbH of Baden-Württemburg, Germany. 
     An oxygenator  216  has a blood inlet  214  with a fitting  212   a  mateable with oxygenator inlet disconnect fitting  212 , and has a blood outlet  218  with a fitting  220   a  mateable with outlet disconnect fitting  220 . Oxygenator  216  is configured to remove carbon dioxide from blood passing through the oxygenator, and to supply oxygen to the blood. For example, the internal construction of oxygenator  216  may be the same as that of a QUADROX® Oxygenator System manufactured by Maquet. The oxygenator  216  may include subcomponents typically associated with an oxygenator, such as a permeable membrane and oxygen supply. The oxygenator desirably is arranged so as to be portable and allow the patient to move about while connected to the oxygenator. For example, the oxygenator may be coupled to a portable oxygen supply such as a cylinder (not shown). Desirably, the oxygenator and supply may be carried on a mobile cart or on a harness worn by the patient. 
     Oxygenator return conduit  222  has a return fitting  224  at the end of the conduit remote from disconnect  220 . The return fitting is adapted for connection to the circulatory system. For example, return fitting  224  may be an end of the conduit adapted for insertion into the vasculature of the patient. Bypass conduit  228  has a similar return fitting  229  at the end of the bypass conduit remote from adaptor  208 . 
     In the condition depicted in  FIG. 1 , the system is in place in a mammalian subject such as a human patient in need of respiratory assistance. Pump  204  is implanted within the body of the patient, with inlet conduit  202  connected to the circulatory system  100  of the subject at an inlet location  122  such as the right atrium  120  of the heart or the right ventricle  130 , so that the inlet  204   b  of pump  204  is in communication with the circulatory system at the inlet location. Return fittings  224  and  229  and the adjacent portions of conduits  222  and  230  are also implanted in the body of the subject. The return fittings communicate with the circulatory system of the subject at return locations  134  and  136 , respectively. The return locations may be remote from the inlet location. For example, the return locations may be in the pulmonary artery  132  of the subject. Adaptor  206  and disconnect fittings  212  and oxygenator  216  are disposed outside of the subject&#39;s body. In a normal condition, oxygenator  216  is connected to disconnect fittings  212  and  220 . 
     With the system in place, the subject&#39;s heart  110  continues to pump blood in the normal manner. The right atrium  120  collects oxygen-depleted blood from the systemic circulatory system of the body B. The oxygen-depleted blood flows from the right atrium  120  to the right ventricle  130 . The blood is then pumped into the lungs via the pulmonary artery  132  where the blood is oxygenated and where carbon dioxide is removed from the blood. The oxygenated blood is then returned to the left atrium  140  via the pulmonary veins  142 . The blood is pumped from the left atrium to the left ventricle  150 , and then pumped by the left ventricle and to systemic circulation. After passing through the systemic circulation, the blood becomes oxygen-depleted and returns to the right atrium  120  via the vena cava  125 , where the process begins again. 
     Pump  204  draws some of the blood from the circulatory system  100  of the subject at the inlet location  122 . For example, the flow rate of blood through the pump  204  may be approximately 2 to 5 L/min. In the normal condition, with the oxygenator in place, the blood passing out of pump  204  passes primarily through the first branch, through oxygenator supply conduit  210 , oxygenator  216  and oxygenator return conduit  222  to return fitting  224 , and re-enters the circulation at return location  134  in the pulmonary artery. Oxygenator  216  supplies oxygen to the blood passing along first branch  210  and removes some of the carbon dioxide present in the blood. The oxygenation and carbon dioxide removal provided by the oxygenator supplement the action of the subject&#39;s lungs. 
     Valve  208   a  of adaptor  208  desirably is arranged to allow a relatively small portion of the blood supplied by pump  204  to pass through the second branch, through bypass conduit  228  and back to the circulatory system at return fitting  229  and return location  136 , while the system is in the normal condition and the valve is in the first position. This flowing blood helps to keep the second branch free of thrombus. 
     The oxygenator must be replaced periodically. To change the oxygenator, the system is brought to a bypass condition by adjusting valve  208   a  of the adaptor to the second position. In this condition, the blood passing from pump  204  is directed entirely along the second branch, through the bypass conduit  228  and back to the circulatory system via return fitting  229  at return location  134 . While the system is in this bypass condition, fittings  212   a  and  220   a  of the oxygenator are disconnected from disconnect fittings  212  and  220 , and a new oxygenator is connected to the disconnect fittings. Once the new oxygenator is in place, the system is returned to the normal condition by readjusting valve  208   a  to the first position. Manipulating the valve and actuating the disconnect fittings are routine tasks which do not require a high level of skill. Desirably, these elements are arranged so that the oxygenator can be changed by the patient or by a medical technician or nurse without extensive training. 
     While the system is in the bypass condition, pump  204  continues to operate and blood continues to flow through the pump and through the bypass conduit. The pump thus assists blood circulation through the lungs. This assistance enhances the gas exchange function of the lungs, which helps the subject to survive during the time the system is in the bypass condition. The continued flow of blood through the pump in the bypass condition helps keep the pump free of thrombus. The continued flow of blood through the pump also helps to protect the pump from damage. Certain impeller-type blood pumps use hydrodynamic bearings, magnetic bearings or both to maintain the impeller suspended and out of contact with surrounding parts. While the pump is running, the impeller and surrounding parts do not suffer from mechanical wear, but starting and stopping the pump renders the bearings ineffective and causes wear. The continued flow of blood through the pump in the bypass condition allows the pump to continue running without prolonged exposure of blood in the pump to the relatively severe hydrodynamic conditions in the pump. 
     In a system according to a further embodiment of the invention, the valve in adaptor  208  may be arranged to direct the entire flow of blood through the first branch and thus through the oxygenator  216  in the normal condition. In a further variant, adaptor  208  and valve  208   a  may be implanted within the body provided that the valve can be controlled from outside of the body. For example, the valve may be disposed near the skin so that it can be manipulated through the skin. Alternatively, the valve may be provided with an electrically operated or fluid-operated actuation mechanism. 
     A system according to a further embodiment of the invention ( FIG. 2 ) is implanted with the inlet conduit  302  of pump  304  connected to an inlet location within the right ventricle  130  of the subject. This system uses only a single return fitting  329  connected at a single return location in the coronary artery. The system does not incorporate a valve in a branching adaptor as in the embodiment discussed above with respect to  FIG. 1 . In the system of  FIG. 2 , the bypass conduit  328  remains connected to pump  304  at all times. The bypass conduit incorporates a restriction providing resistance to flow, such as the reduced-diameter section  301 . Desirably, the flow resistance along the second or bypass branch, through the bypass conduit, is greater than the flow resistance along the first branch, through conduit  310  and oxygenator  316 . In the normal condition, most of the blood supplied by pump  304  passes through the first branch, and thus is oxygenated. In the bypass condition, valves  313  and  321  in disconnect fittings  312  and  320  are closed and the oxygenator  316  may be removed and replaced. While the system is in the disconnect condition, some blood continues to pass through the second branch, via bypass conduit  328 . The blood flow through pump  304  and through the second branch is less than the blood flow through the pump during the normal condition, but sufficient to avoid damage to the pump or to the blood disposed within the pump. 
     A system according to yet another embodiment of the invention ( FIG. 3 ) is similar to the systems discussed above, except that the system of  FIG. 3  has a second or bypass branch  428  which includes a second oxygenator  401  releasably connected in the second branch by valved disconnect fittings  403  and  405 . As in the systems discussed above, the oxygenator  416  of the first branch is releasably connected by valved disconnect fittings  412  and  420 . The system may be operated in the normal mode with valved fittings  403  and  405  closed, so that blood passes only through the first oxygenator  416 . In the bypass mode, valved fittings  412  and  420  are closed and fittings  403  and  405  are opened, so that the blood passes from the pump  404  through the second branch and second oxygenator. Here again, while the system is in bypass mode, the first oxygenator can be removed and replaced. Because the system provides full oxygenation in the bypass mode, the system can be run in bypass mode for a prolonged period, which may be greater or less than the time the system is run in normal mode. When the system is in normal mode, the second oxygenator  401  can be removed and replaced. In a further variant, the system may run in normal mode with blood passing through both oxygenators, and in bypass mode with blood passing through only one of the oxygenators. 
     The inlet location used to supply blood to the pump may be disposed at any portion of the circulatory system. For example, the inlet location may be disposed at a portion of the circulatory system that transports unoxygenated blood, such as the vena cava or the pulmonary artery. In one example, both the inlet location and the return location may be in the pulmonary artery. A dual-lumen catheter may provide both the inlet and the return fitting. Such a catheter desirably is arranged to prevent recycling of blood from the return location back to the inlet location. 
     In another example, the return locations  134 ,  136  may be disposed at the pulmonary vein  142 . 
     According to another embodiment of the disclosure, the oxygenator  216  may be implanted within the body B of the human subject. In this example, the entire system  200  may be implanted within the body B of the mammalian subject. 
     In another embodiment, the valve  208   a  at the adaptor ( FIG. 1 ) may be replaced by a valve or valves connected in series with the first branch  210 , in series with second branch  228 , or both. 
     Although the invention herein has been described with reference to particular embodiments, it is to be understood that these embodiments are merely illustrative of the principles and applications of the present invention. It is therefore to be understood that numerous modifications may be made to the illustrative embodiments and that other arrangements may be devised without departing from the spirit and scope of the present invention as defined by the appended claims.

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