Artificial lung system and method of using the same

Abstract

To provide mechanical oxygenation of ambulatory patients using an artificial lung system.SOLUTION: An oxygen supply unit for use with a blood oxygenator includes an oxygen concentrator and a carbon dioxide absorber. In the on-line mode of operation, oxygen-rich gas from the oxygen concentrator is supplied to the blood oxygenator along with a reduced flow of recycled gas from the concentrator. In an off-line mode of operation in which the oxygen supply unit is powered only by the battery, a large flow of recycled gas from the blood oxygenator is passed through the carbon dioxide scrubber and combined with a reduced amount of oxygen-rich gas from the oxygen concentrator. The oxygen supply unit may be used in combination with a blood pump and an oxygenator to provide ambulatory blood oxygenation to a patient with impaired lung function.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This application claims the benefit of U.S. Provisional Patent Application No. 62 / 081,747, filed November 19, 2014, which application is incorporated herein by reference.

[0002] This invention was made with government support under Grant No. HL118372 awarded by the National Institutes of Health. The government has certain rights in the invention.

[0003] FIELD OF THE INVENTION The present invention relates generally to systems and methods for oxygenating blood, and more particularly to systems and methods for oxygenating blood in ambulatory patients. [Background technology]

[0004] Lung failure can occur acutely or chronically. Lung disease is the third leading cause of death in the United States, accounting for one in six deaths. Chronic obstructive pulmonary disease (COPD) is one of the most common lung diseases and the fourth leading cause of death in the United States. Adult respiratory distress syndrome (ARDS) afflicts 190,000 patients annually, with an average survival rate of 30 to 50% (Rubenfeld et al. N Engl J Med 2005;353:1685-93). If lung failure occurs, mechanical ventilation or extracorporeal membrane oxygenation (ECMO) must be performed to oxygenate the blood and maintain the body's oxygen needs. Mechanical ventilation is effective for short-term support; however, the prolonged cyclical volumetric airway pressures often used may damage the lungs.

[0005] ECMO systems are an attractive alternative to mechanical ventilators because they closely mimic physiological gas exchange, and extended ECMO support is possible through multiple device exchanges. In practice, however, these systems are limited by their operational complexity, discomfort, and reduced patient mobility. Patients often become bedridden and suffer from muscle wasting as a result.

[0006] Recently, ambulatory ECMO support has been implemented in many facilities using available pumps and oxygenators, allowing patients to ambulate and go out. They can also eat and exercise. Despite the benefits offered by modern ECMO systems, they are still quite large. Their extended use is also limited due to the operating lifespan of the oxygenator. In light of the limitations described above, there is a need in the art for systems and methods for mechanically providing oxygenation for ambulatory patients using portable oxygenator systems that are adapted for extended use.

[0007] Patents and published applications related to the subject matter of the present invention include U.S. Patent Publication No. 2013296633 (Patent Document 1), U.S. Patent Publication No. 2011040241 (Patent Document 2), U.S. Patent No. 7,682,327 (Patent Document 3), U.S. Patent No. 6,935,344 (Patent Document 4), U.S. Patent No. 6,503,450 (Patent Document 5), U.S. Patent No. 5,308,320 (Patent Document 6), U.S. Patent No. 4,548,597 (Patent Document 7), U.S. Patent No. 4,610,656 (Patent Document 8), and U.S. Patent No. 3,927,981 (Patent Document 9). [Prior art documents] [Patent documents]

[0008] [Patent Document 1] U.S. Patent Publication No. 2013296633 [Patent Document 2] U.S. Patent Publication No. 2011040241 [Patent Document 3] U.S. Patent 7,682,327 [Patent Document 4] U.S. Patent 6,935,344 [Patent Document 5] US Patent 6503450 [Patent Document 6] US Patent 5,308,320 [Patent Document 7] U.S. Patent 4,548,597 [Patent Document 8] U.S. Patent 4,610,656 [Patent Document 9] U.S. Patent 3,927,981 Summary of the Invention [Problem to be solved by the invention]

[0009] The technology provides mechanical oxygenation for ambulatory patients using an artificial lung system, which offers one or more advantages over previously available oxygen delivery systems. While the system of the present invention is particularly suited as a portable system, it may also be used as a fixed or partially fixed system. [Means for solving the problem]

[0010] In a first form of embodiment, the blood oxygenator includes a pump-oxygenator unit that provides a power source and a source of oxygen, and a multi-lumen cannula that connects to a supply pack, the pump-oxygenator unit configured to be disposable and removable from the rest of the device.

[0011] In one embodiment of the invention, the pump-oxygenator unit is configured to oxygenate blood for 30 or more days continuously without needing to be replaced.

[0012] In another aspect of the invention, blood is removed from and returned to a patient using a two-lumen catheter, which includes a first lumen for removing deoxygenated blood and a second lumen for returning oxygenated blood to the patient's circulatory system. The catheter may further include a self-sealing mechanism to allow a cannula to be inserted directly into the right ventricle of the heart.

[0013] In yet another aspect of the invention, the supply pack is a portable unit that includes wheels to allow the patient to pull the unit.

[0014] In another variation, the supply pack has one or more straps that allow the patient to wear the pack as a backpack or satchel.

[0015] In another variation, the oxygen source may be an oxygen generator, an oxygen tank, or a combination of both.

[0016] In a second form of embodiment, a method of providing mechanical ventilation to an ambulatory patient is provided, comprising removing deoxygenated blood from the patient's circulatory system, passing the blood through a body-mounted pump and blood oxygenator, and returning freshly oxygenated blood to the patient's circulatory system, the pump being connected to a pump motor and controller housed separately in a portable pack, and the blood oxygenator being supplied with oxygen from a separately housed portable source. Optionally, the method includes use of a portable pack to house the pump motor, controller, and oxygen source. Also, as described hereinafter, the pump and / or blood oxygenator may be carried on a belt worn around the patient's waist.

[0017] In another aspect, the present invention provides a compact, lightweight oxygen delivery unit for a lung assist oxygenator, capable of delivering oxygen flow rates typically in the range of 0.5 to 3 liters per minute using a pressure swing oxygen concentrator combined with a disposable carbon dioxide absorber unit. The oxygen delivery unit operates using battery power (offline operation) or AC or plugged-in current (online operation). The use of a carbon dioxide absorber extends battery life because the absorber does not require power to recycle oxygen, as opposed to the oxygen concentrator producing it. Not using the carbon dioxide absorber while the system is powered from an external source is, however, preferable because the power supply is not limited, the carbon dioxide absorber life can be extended (absorption medium is not consumed), allowing for the use of a smaller absorber and / or reducing the frequency of absorber replacement. In this manner, the size and weight of the oxygen delivery unit can be minimized, and battery operation time can be maximized.

[0018] During offline or battery operation, oxygen-rich gas from the oxygen supply unit enters the blood oxygenator, exchanging oxygen for carbon dioxide and producing exhaust gas with increased carbon dioxide content. The amount of carbon dioxide, however, is not significant. Rather than removing this exhaust gas, which still contains high levels of oxygen in the environment, the gas can be scrubbed to remove carbon dioxide, typically after removing water vapor, and then returned to the oxygen supply unit. The scrubbed gas is then recycled to the blood oxygenator, with the addition of a small flow of concentrated oxygen from the oxygen concentrator unit sufficient to replace the amount of oxygen transferred during the previous pass through the blood oxygenator. In this way, a flow of highly oxygen-rich gas, on the order of 5 to 10 liters per minute, can be provided to the blood oxygenator using only 0.5 to 1 liter of oxygen per minute from the oxygen concentrator to reduce power consumption and extend battery life.

[0019] When the patient can plug in the oxygen delivery unit (online operation), power consumption is no longer a concern, oxygen concentrator output is increased, and flow through the carbon dioxide absorber is diverted. Absorbent media consumption is therefore avoided during on-line operation, reducing absorber size and / or extending absorber service life, minimizing replacement frequency. The size of the oxygen delivery unit is further minimized by using a relatively low-output oxygen concentrator (0.5 to 3 liters per minute) in combination with a disposable carbon dioxide absorber canister, making the present two-mode oxygen delivery unit cheaper, smaller, and lighter in overall size and weight than comparable battery-only systems, where the carbon dioxide absorber must be sized for consistent operation.

[0020] In accordance with certain methods of the present invention, a stream of oxygen-rich gas useful for a blood oxygenator is produced by selectively operating an oxygen concentrator from battery power or from an external power source, typically line power from the grid or a local generator. Oxygen from the oxygen concentrator will be supplied to the blood oxygenator unfiltered when the oxygen concentrator is operated from an external power source. In contrast, oxygen from the oxygen concentrator is combined with a carbon dioxide-depleted oxygen gas stream when the oxygen concentrator is operated from a battery, and the combined gas stream is supplied to the blood oxygenator. In this manner, battery life can be extended while simultaneously extending the life and / or reducing the size of a carbon dioxide absorption device utilized.

[0021] In some embodiments, the carbon dioxide-depleted gas stream is created by removing carbon dioxide from a carbon dioxide-enriched gas stream received from a blood oxygenator. Typically, the oxygen concentrator provides a flow in the range of about 0.5 liters per minute (LPM) to 1 LPM for combination with the carbon dioxide-depleted gas stream. Typically, the carbon dioxide-depleted gas flow is in the range of 4.5 LPM to 9 LPM.

[0022] In embodiments in which oxygen from an oxygen concentrator is supplied to the blood oxygenator without removing impurities, oxygen is supplied at a flow rate ranging from 2 LPM to 6 LPM. In such cases, the oxygen from the oxygen concentrator may also be combined with a carbon dioxide-enriched gas stream from the blood oxygenator. In these cases, since a high oxygen flow rate is provided by the oxygen concentrator, it is not necessary to remove impurities from the carbon dioxide-enriched gas stream, as in offline operation. The carbon dioxide-enriched gas stream will typically be combined with the oxygen from the oxygen concentrator at a rate of 3 LPM to 6 LPM.

[0023] According to certain devices of the present invention, an oxygen delivery unit for use with a blood oxygenator includes an oxygen concentrator, a carbon dioxide absorber, a power controller, and valved braided tubing. The oxygen concentrator is configured to produce a concentrated oxygen stream from air and typically comprises a pressure swing oxygen concentrator driven by an internal electric compressor. The carbon dioxide absorber is configured to receive a recycled carbon dioxide-enriched gas stream from the blood oxygenator and remove or scrub carbon dioxide from the stream, typically removing substantially all of the carbon dioxide. The recycled carbon dioxide-enriched gas stream from the blood oxygenator is likely to be inherently oxygen-rich at well over 90% oxygen, so that if carbon dioxide is removed, it is suitable for combining a sufficient amount of oxygen from the oxygen concentrator to replace that removed during the previous passage of the gas stream through the blood oxygenator and then returning it to the blood oxygenator. The power controller is configured to selectively provide power from a battery source or an external power supply, typically an AC wall outlet available in most locations. The valved braid tubing is configured to deliver oxygen-rich gas from the oxygen concentrator to the blood oxygenator without removing impurities when the power controller provides power to the oxygen delivery unit from an external power supply. The valved braid tubing is further configured to combine recycled carbon dioxide-depleted gas from the carbon dioxide absorber with the oxygen-rich gas from the oxygen concentrator when the power controller provides power from a battery. Such two-mode operation has the power efficiency advantages and reduced absorbent media consumption described above in connection with the methods of the present invention.

[0024] The oxygen delivery unit of the present invention will typically be enclosed in a shell or housing, and the shell or housing will typically include wheels configured to allow the housing to be pulled or pushed by a user. Alternatively, the housing may be configured to be worn as a backpack (optionally by an individual other than the patient), attached to a wheelchair, attached to a car, airplane or other vehicle, or the like. Still further alternatively, the housing may be configured for fixed placement.

[0025] The carbon dioxide absorber may be a conventional canister absorber having a commercially available absorption medium such as soda lime; suitable media are commercially available under the trademarks Litholyme®, Sodasorb®, Medisorb®, Sodasorb® LF, and Amsorb®.

[0026] The valved reticulated tubing of the oxygen supply unit of the present invention will typically further include a dehumidifier to remove moisture from the carbon dioxide-enriched gas stream before passing that gas stream through the carbon dioxide absorber. Useful dehumidifiers include commercially available Nafion® gas dryers. The valved reticulated tubing usually also includes a pump that passes the carbon dioxide-enriched gas stream through the carbon dioxide absorber and combines the gas stream with a relatively high-pressure oxygen gas stream from the concentrator. Another feature of the valved reticulated tubing includes a bypass line that allows oxygen-rich gas to flow through the carbon dioxide absorber during online operation. Yet another feature includes a disconnect that allows the carbon dioxide absorber canister to be removed and replaced from the oxygen supply unit with minimal difficulty.

[0027] The oxygen supply unit of the present invention may be combined with a blood-pumping oxygenator configured to be worn by a patient, as described above. The blood pump-oxygenator unit typically includes a blood oxygenator having a semipermeable membrane matrix that allows oxygen-carbon dioxide exchange when blood and oxygen-enriched air flow through the oxygenator. These systems typically also include an umbilical cord or cable connecting the oxygen supply unit to the blood pump-oxygenator. The umbilical cord will include tubing for supplying oxygen-enriched gas from the oxygen supply unit to the blood-pumping oxygenator, as well as for returning carbon dioxide-enriched gas from the blood pump-oxygenator to the oxygen supply unit. The umbilical cable still further includes electrical wires for supplying power and / or control signals from the oxygen supply unit to the blood pump-oxygenator.

[0028] Further aspects, features, and advantages of the present invention will become readily apparent from the detailed description which follows, by illustrating numerous specific embodiments and implementations, including merely the best mode contemplated for carrying out the invention. The present invention is capable of other and different embodiments, and its several details can be modified in various obvious respects, all without departing from the spirit and scope of the invention. Accordingly, the drawings and description are to be regarded as illustrative in nature, and not as restrictive.

[0029] All publications, patents, and patent applications mentioned in this specification are herein incorporated by reference to the same extent as if each individual publication, patent, or patent application was specifically and individually indicated to be incorporated by reference. [Brief explanation of the drawings]

[0030] [Figure 1] 1 illustrates one embodiment of an ambulatory blood pump-oxygenator system including a combined oxygen supply unit and pump-oxygenator. [Figure 2] 1 depicts one embodiment of tubing that removes deoxygenated blood from the circulatory system and introduces oxygenated blood; [Figure 3] 1 depicts one embodiment of a pump-oxygenator unit. [Figure 4A] 10 depicts another embodiment of the ambulatory oxygen supply unit of the present invention that includes an oxygen concentrator instead of an oxygen tank. [Figure 4B] 1 depicts a pump-oxygenator unit secured to a patient's waist belt showing a supply pipeline suitable for connection to an ambulatory oxygen supply unit. [Figure 5A] 5 illustrates the operation of the oxygen supply unit of FIG. 4, including an optional carbon dioxide absorber and battery, plug-in operation. [Figure 5B] 5 illustrates the operation of the oxygen supply unit of FIG. 4, including an optional carbon dioxide absorber and battery, plug-in operation. DETAILED DESCRIPTION OF THE INVENTION

[0031] The novel features of the invention are set forth with particularity in the appended claims. A better understanding of the features and advantages of the present invention will be obtained by reference to the following detailed description that sets forth illustrative embodiments, in which the principles of the invention are utilized. The present invention is illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawings, in which like reference numerals refer to like elements.

[0032] A method and system are described for chronic mechanical oxygenation of ambulatory patients. In the following description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the present invention. However, it will be apparent to those skilled in the art that the present invention may be practiced without these specific details. In other instances, well-known structures and devices are shown in block diagram form in order to avoid unnecessarily obscuring the present invention.

[0033] The system of the present invention provides a long-term solution for individuals in need of blood oxygenation, allowing them to no longer be bedridden. The system includes a pump-oxygenator unit that communicates with the patient's circulatory system through multiple tubing cannulas. The pump-oxygenator unit is capable of oxygenating blood for extended periods of time. A portable supply pack provides the necessary power and oxygen source for the system.

[0034] Referring now to the figures, FIG. 1 depicts one embodiment of a portable blood oxygenator system 100. System 100 comprises a multi-tube cannula 120, a blood oxygenator 310, a blood pump 320, and a portable supply pack 130. One example embodiment of multi-tube cannula 120 is further depicted in FIG. 2. In this example, cannula 120 comprises an elongate body 210 having a drain cannula and a return cannula. Both the drain cannula and the return cannula have inner lumens extending the length of the elongate body. Drain cannula 220 has a proximal end 222 and a distal end 224. Return cannula 230 also has a proximal end 232 and a distal end 234. The proximal ends of the drain and return cannulas are configured to connect to a pump and blood oxygenator combination 310 / 320. The connections between the cannula ends and the pump-oxygenator unit are detachable. The outlet cannula 220 is configured to receive deoxygenated blood from the right ventricle of the heart and return it to the pump-oxygenator. The return cannula is configured to return oxygenated blood from the pump-oxygenator unit to the pulmonary artery. The cannula 120 further comprises a self-sealing mechanism 240 near its distal end to prevent blood from leaking out of the cannulated heart. In some embodiments, the self-sealing mechanism 240 is detachable from the elongate body.

[0035] FIG. 3 illustrates one embodiment of a pump-oxygenator unit. The unit includes a blood oxygenator 310 and a blood pump 320. The blood oxygenator can be any blood oxygenator known in the art. However, in some embodiments, a blood oxygenator that provides consistent blood flow and oxygen diffusion is preferred. In the illustrated embodiment, the blood pump 320 includes an inlet 322 configured to receive unoxygenated blood from the outlet cannula 220. Unoxygenated blood exits the blood pump and enters the blood oxygenator through the blood oxygenator inlet 312. Oxygen received from an oxygen source at the gas inlet 314 is diffused into the blood as it passes through the blood oxygenator. Once oxygenated, the blood passes through a vent 316 that connects to the return cannula 230. Exhaust gas is released through a vent 318. The blood pump connects to an electric motor mounted in a supply pack, described below. This connection is removable in some embodiments.

[0036] Supply pack 130 houses power source 132, motor 136, and one or more oxygen sources 138. The supply pack is configured to be a portable system that can be readily moved and carried by the user. In some embodiments, the housing of the supply pack includes wheels and a handle so that the user can pull the unit. However, the supply pack may also be housed in a wearable case such as a backpack, satchel, or waist pouch. Power source 132 is configured for long-term, portable use. Any type of battery, including both rechargeable and non-rechargeable options, can be used to power the system.

[0037] Oxygen may be supplied to the patient by an oxygen generator 134 or an oxygen source 138. In some embodiments, the supply pack includes an oxygen generator as well as an oxygen source that may be used as a backup. The oxygen source 138 is typically a compressed gas tank that includes a regulator at the vent to control the volume and rate of oxygen released into the system. A series of oxygen tanks may be used in some embodiments. The number and size of oxygen sources or tanks housed in the supply pack will depend on the needs of the user. An electric motor 136 is powered by a power source 132 and operates the pump-oxygen unit 110. A controller connects to the pump 320 through a cable extending from the supply pack to the pump. The controller causes the motor's speed to vary to maintain the oxygen required by the user.

[0038] The blood oxygenator needs to be changed periodically due to thrombosis occurring in the membrane that allows gas transfer. In some embodiments, the pump-oxygenator unit is separate from the motor, allowing replacement of the pump-oxygenator unit without having to replace the more costly motor. The pump-oxygenator unit is capable of 30 days or more of continuous use. When replacing the pump-oxygenator unit, the cannula is removed from inlet 322 and vent 316. The motor is also removed from the pump, and the oxygen source is removed at 314. In other embodiments, the blood oxygenator is the only element of the system that must be replaced periodically.

[0039] Another embodiment of the present invention provides a method for providing permanent mechanical oxygenation to an indigent ambulatory patient. The method includes (a) directing deoxygenated blood from the patient's circulatory system through an inlet in a pump and blood oxygenator, and (b) returning oxygenated blood to the patient's circulatory system, the pump and blood oxygenator being part of a portable system with a portable power source and oxygen source housed in a pack. In one variation of the method, the blood oxygenator is capable of continuously oxygenating blood for 30 days or more.

[0040] Referring now to FIG. 4A, another embodiment of an oxygen supply unit constructed in accordance with the principles of the present invention typically includes a frame 402 mounted on wheels 404 for ease of movement and relocation. A shell or housing 406 is provided to house several system components, typically including an oxygen concentrator 408, a battery 410, a carbon dioxide absorber 412, a recirculation pump 414, a dehumidifier 416, and a control unit 418. The oxygen concentrator may be a commercial unit selected to provide a concentrated oxygen flow at a desired flow range of 1 LPM to 3.5 LPM. Typically, the oxygen concentrator will use a pressure swing principle to separate air into a highly oxygen-enriched stream and a highly nitrogen-enriched stream. The highly oxygen-enriched stream will be used, and the nitrogen stream will be released back to the atmosphere. The battery may be any conventional rechargeable battery, typically a lithium-ion battery or the like. The carbon dioxide absorber will typically include a canister filled with soda lime or other absorbent medium, as previously described herein. A recirculation pump will be used to supply carbon dioxide-enriched gas from the blood oxygenator to the absorber, as described in more detail below. The dehumidifier is typically a coil, such as a Nafion® gas dryer, that condenses moisture from the carbon dioxide-enriched stream recycled from the blood oxygenator. In some embodiments, dryer 416 is located above the oxygen concentrator 408, as shown in solid lines. In some embodiments, dryer 416a is located below the oxygen concentrator, as shown in dashed lines, thus directly exposing the dryer tubing to the hot gases produced by the concentrator. This latter location is advantageous in avoiding the need to mount the dryer above the concentrator and allows for a more compact location. The control unit typically provides an operator interface and also contains the operating electrical and logic circuitry that manages the valve system and power distribution system, as described in more detail below with respect to Figures 5A and 5B.An umbilical cord 420 provides for convenient attachment to a blood-pumping blood oxygenator (or pump-oxygenator unit) 440 (FIG. 4B) worn by the patient. The umbilical cord includes an oxygen-enriched gas line 422, a carbon dioxide-enriched gas line 424, and one or more power and control lines 426. Additionally, a pluggable power line 428 may be provided for use when the unit can be plugged into an AC or other external power source.

[0041] 4B, pump-oxygenator unit 440 may be worn by patient P, for example, on a belt around the patient's waist. Pump-oxygenator unit 440 may include a blood oxygenator 442 and a blood pump 444. Pump 444 receives venous blood from the patient and pumps the venous blood into blood oxygenator 442. Oxygenated blood from blood oxygenator 442 is returned to the arterial side of the patient's vasculature. For example, cannula 450 may be used to pump blood to and from the patient as described in co-pending application PCT / US2015 / 060127, filed November 13, 2015, for "Self-Sealing Cannula," all of which is incorporated by reference herein.

[0042] Referring now to FIG. 5A, the arrangement of the components of the oxygen supply unit 400 will be described in further detail. The oxygen concentrator 408 is mounted within the housing 406 and is connected to the surrounding environment to receive an inflow of air. Power is supplied to the oxygen concentrator 408 from a power control unit 418, which may receive power from a battery 410 or from a power line 428. As shown in FIG. 5A, power comes from the battery 410 when the power line 428 is not connected. The power control unit may be configured to automatically detect the power source based on whether the power line 428 is connected to an AC current source or not. When the oxygen supply unit 400 is not connected to an AC power source, carbon dioxide-enriched gas entering through the line 424 is pumped by the recirculation pump 414 through the dehumidifier 416, through the second valve 502 and quick-disconnect fitting 504, and to the carbon dioxide absorber 412. A vent T-fitting 503 is optionally provided to vent excess carbon dioxide-enriched gas from the system to the surrounding environment. The volume of vented carbon dioxide-enriched gas will be equal to the net inflow volume from the oxygen concentrator 408. Other excess gas venting mechanisms may also be used. Often, there will be liquid, including condensed water vapor and a small amount of plasma, in the carbon dioxide gas line 424 exiting the blood oxygenator unit 442. A separator (not shown) will typically be provided as part of the oxygen supply unit 400 or, alternatively, in the supply line 424 to remove these liquids.

[0043] Carbon dioxide-enriched gas from pump 414 passes through T-junction 506 to combine with oxygen from oxygen concentrator 408. As previously described, 4.5 to 6 LPM of carbon dioxide-enriched gas will typically pass through the carbon dioxide absorber, plus about 1 LPM of oxygen-rich gas from oxygen concentrator 408. The relative amounts delivered can be controlled through pump 414. The purified oxygen-rich gas from carbon dioxide absorber 412 exits through quick disconnect 508 and further control valve 510, allowing the gas to pass into oxygen-rich gas line 422, which returns the gas to the blood oxygenator 442. Gas flow will continue in this pattern as long as blood delivery unit 400 remains disconnected from AC power. In this efficient mode of operation, battery life typically lasts at least several hours, and may last for four, five, six, or even longer.

[0044] Once the patient arrives at a location where AC or other external power is available, the user plugs the power cord into an AC outlet, as shown in FIG. 5B. As soon as line current is available, operation of the oxygen delivery unit 400 is altered to conserve carbon dioxide absorption medium, extend absorber life, and / or reduce absorber size. Specifically, oxygen from the oxygen concentrator will now bypass the carbon dioxide absorber through bypass line 520, previously separated by valves 500 and 510. Valves 500 and 510 are now reconfigured to allow oxygen-rich gas to pass through bypass line 520. Similarly, valves 502 and 510 are positioned to block flow through the carbon dioxide absorber. While in this configuration, the carbon dioxide absorber 412 may be removed and replaced using quick disconnects 504 and 508. During online operation, the volume of oxygen-enriched gas from the oxygen concentrator may be increased, typically in the range of 2.5 to 3.5 LPM. Carbon dioxide-enriched gas entering through line 424, however, will continue to be recycled and mixed with the oxygen-enriched gas, albeit at a lower flow rate, typically in the range of 3 to 6 LPM. Mixing occurs at valve 500, and the relative flow volumes are again controlled using pump 414. The combined oxygen-enriched gas stream and carbon dioxide-enriched gas stream flow through bypass line 520 and valve 510, where they can enter oxygen-enriched gas line 422 and return to the blood oxygenator 442.

[0045] While preferred embodiments of the present invention have been described and illustrated herein, it will be apparent to those skilled in the art that such embodiments are provided by way of example only. Numerous variations, changes, and substitutions will now occur to those skilled in the art without departing from the invention. Various modifications to the embodiments of the invention described herein may be employed in practicing the invention. The following claims define the scope of the invention, and it is intended that methods and structures within the scope of these claims and their equivalents be covered thereby.

Claims

1. 1. A method for providing an oxygen-rich gas for blood oxygenation, comprising: Selectively operate the oxygen concentrator with battery power or external power; supplying oxygen to a blood oxygenator without removing impurities from the oxygen concentrator when the oxygen concentrator is operated from an external power source; A method of combining oxygen from said oxygen concentrator with a carbon dioxide-depleted oxygen gas stream and delivering said combined gas stream to a blood oxygenator when said oxygen concentrator is battery operated.

2. 10. The method of claim 1, further comprising removing carbon dioxide from the carbon dioxide-enriched gas stream received from the blood oxygenator to produce said carbon dioxide-depleted gas stream.

3. 3. The method of claim 2, wherein the oxygen concentrator provides a flow in the range of 0.5 liters per minute to 1 liter per minute for combination with the carbon dioxide-depleted gas flow.

4. 4. The method of claim 3, wherein the flow of carbon dioxide-depleted gas is between 4.5 liters per minute and 9 liters per minute.

5. 10. The method of claim 1, wherein oxygen from the oxygen concentrator is delivered at a rate of 2 liters per minute to 6 liters per minute without removing impurities.

6. 6. The method of claim 5, further comprising combining said oxygen from said oxygen concentrator with a stream of carbon dioxide-enriched gas from said blood oxygenator.

7. 7. The method of claim 6, wherein the carbon dioxide-enriched gas stream flows at a rate of from 3 liters per minute to 6 liters per minute.

8. 1. An oxygen supply unit for a blood oxygenator that receives an oxygen-rich gas flow and generates a carbon dioxide-enriched gas flow, comprising: an oxygen concentrator that produces a stream of oxygen-rich gas from the air; a carbon dioxide absorption device for removing carbon dioxide from the carbon dioxide-enriched gas stream; a power control device that selectively supplies power from a battery or an external power supply; 1. An oxygen delivery unit comprising: (1) a valved mesh tubing configured to deliver oxygen-rich gas from the oxygen concentrator to the blood oxygenator without removing impurities when the power control device is powered from the external power supply; and (2) a valved mesh tubing configured to combine oxygen-rich gas from the oxygen concentrator with carbon dioxide-depleted gas from the carbon dioxide absorber when the power control device is powered from the battery.

9. The oxygen supply unit according to claim 8, wherein the oxygen concentrator, the carbon dioxide gas absorption device, the power control device, and the valved mesh tube are disposed within a housing.

10. 10. The oxygen delivery unit of claim 9, wherein the housing comprises wheels configured to allow the housing to be pulled or pushed by a user.

11. 10. The oxygen supply unit of claim 8, wherein the oxygen concentrator comprises a pressure swing oxygen concentrator having an electrically driven internal compressor.

12. 9. The oxygen supply unit of claim 8, wherein the carbon dioxide absorber includes a canister having an absorbent medium.

13. 13. The oxygen supply unit of claim 12, wherein the absorbent media comprises soda lime, Litholyme®, Sodasorb®, Medisorb®, Sodasorb® LF, and Amsorb®.

14. 9. The oxygen delivery unit of claim 8, wherein the valved braided tubing includes a dehumidifier that removes moisture from the carbon dioxide-enriched gas stream before the stream passes through the carbon dioxide absorber.

15. 15. The oxygen delivery unit of claim 14, wherein the valved braided tubing further comprises a pump for passing the carbon dioxide-enriched gas stream.

16. 16. The oxygen supply unit of claim 15, wherein the valved braided tubing further comprises a bypass line through which the oxygen-rich gas can flow through the carbon dioxide absorber.

17. 10. An apparatus comprising the oxygen supply unit of claim 8 and a pump blood oxygenator unit adapted to be worn by a patient.

18. 18. The apparatus of claim 17, further comprising an umbilical cable including an oxygen-enriched flow tube, a carbon dioxide-enriched flow tube, and electrical wires connecting the oxygenator unit pump that pumps blood to the power controller of the oxygen supply unit.

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