Dual chamber gas exchanger and method of using the same for respiratory support

Abstract

To provide a dual chamber gas exchanger that is configured for increased flexibility and scalability for many clinical applications.SOLUTION: A dual chamber oxygenator can be configured and used in various applications, such as in a heart-lung machine for cardiopulmonary support during cardiothoracic surgery, in an extracorporeal membrane oxygenation (ECMO) circuit, and in a respiratory assist device for patients with lung failure. The dual chamber gas exchanger comprises two sweep gas flow paths 121, 123 and two gas exchange membrane bundles 116, 120 enclosed in a housing structure with various blood flow distribution and gas distribution mechanisms. The gas exchanger includes an outer housing 112, an intermediate housing 118, two gas exchange fiber bundles 116, 120, a blood inlet 142, a blood outlet 144, two gas inlets 121, two gas outlets 123, two gas distribution chambers 110, 113, and an optional heat exchanger.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] This invention was made with Government support under Grant No. HL118372 awarded by the National Institutes of Health. The Government has certain rights in this invention.

[0002] This application claims the benefit of Provisional Patent Application No. 62 / 545,512, filed August 15, 2017, the entire disclosure of which is incorporated herein by reference.

[0003] FIELD OF THEINVENTION The present invention relates generally to medical devices and methods, and more particularly to devices for extracorporeal membrane oxygenation, respiratory assistance, and cardiopulmonary assistance. [Background technology]

[0004] Blood oxygenation by artificial devices began in the 1930s. Early blood oxygenators, such as thin-film blood oxygenators and bubble oxygenators, were based on exposing the blood directly to oxygen or air. Direct contact of blood with oxygen is an effective way to exchange gases, but it also damages blood proteins and formed elements. Therefore, these early blood oxygenators could only be used for a limited time, such as a few hours.

[0005] Other approaches, such as gas-permeable solid membranes, separated the blood and the sweep gas, eliminating the damage caused by direct blood-gas contact. Solid membranes were the basis of many design platforms but were hampered by manufacturing challenges and thrombogenicity. Thus, hollow fiber membranes emerged. Hollow fiber membranes enabled the design and construction of efficient, compact blood oxygenators with low prime volumes, increased ratios of blood exchange surface area to blood volume, and reduced thrombogenicity. Many current blood oxygenators contain hollow fibers of microporous material.

[0006] Many types of blood oxygenators based on hollow fiber membrane materials have been designed and developed. Hollow fiber membrane oxygenators usually have a single chamber with one fiber bundle and are characterized by the blood flow paths within the fiber bundle. For example, four types of blood flow paths are: (1) longitudinal (axial) flow through the annular bundle, (2) circumferential flow around the annular bundle, (3) flow across a bundle of substantially rectangular cross section, and (4) radial flow through the annular bundle.

[0007] Although membrane blood oxygenators based on the above principles are generally tolerated for cardiopulmonary bypass during open-heart surgery, they have several problems when used for respiratory support over extended periods of time (days to weeks). For example, typical hollow fiber membrane blood oxygenators have a relatively large blood contact surface area, large prime volume, large physical size with very limited long-term biocompatibility and durability, and limited flexibility for various clinical applications. Patients receiving respiratory support with these current blood oxygenators are often bedridden and have limited mobility due to the complexity and bulkiness of typical blood oxygenators caused by inherent blood fluid dynamics. Further complications are caused by non-uniform blood flow through the fiber membrane and laminar boundary flow zones between blood cells and the fiber membrane.

[0008] Uneven blood distribution can cause many problems for hollow fiber membrane blood oxygenators, such as hyperperfusion and hypoperfusion of blood in the flow paths. Hyperperfusion has no additional advantages compared to oxygen-saturated blood. However, hypoperfusion can be harmful to patients. Hollow fiber membrane blood oxygenators use long flow paths to increase blood contact with a larger fiber membrane surface area, ensuring that all blood cells in the hypoperfused areas are well oxygenated. However, the large gas exchange membrane surface area and large prime volume reduce biocompatibility and wearability. Uneven blood flow can also cause excessive mechanical shear stress or stagnation in the blood flow paths of the oxygenator. These are major factors in blood activation and thrombus formation, resulting in limited long-term biocompatibility and durability.

[0009] In addition to these technical issues, typical hollow fiber membrane blood oxygenators lack flexibility for different clinical applications. Often, one device is only suitable for one application, which may be insufficient for some patients. Often, these oxygenators have limited capacity to remove carbon dioxide while delivering oxygen to some patients. Furthermore, high sweep gas flow rates are required to remove carbon dioxide. Or, because the sweep gas flow rate is limited (e.g., in outpatient use), blood flow rates must be kept low. Low blood flow rates can lead to blood clot formation within the oxygenator.

[0010] In different clinical applications such as hospital, outpatient, or home environments, the requirements and availability of sweep gases vary. In particular, oxygen sources can be a challenge in ambulatory applications, where bulky oxygen tanks or large, heavy oxygen concentrators are required. Thus, typical blood oxygenators can limit the patient's mobility and flexibility.

[0011] To remove carbon dioxide from an oxygenator, a higher flow rate and a gas with little carbon dioxide content are usually required. Oxygen is the typical primary sweep gas to provide oxygen and remove carbon dioxide. For example, at a 1:1 sweep gas flow rate and blood flow rate, only 5% of the oxygen (50cc / liter) is delivered to the circulating blood. However, to increase the amount of carbon dioxide removed, the ratio of sweep gas to blood flow rate needs to be greater than 1:1. Thus, the percentage of oxygen utilization is much less than 5%, and the efficiency of oxygen delivery is very low and expensive. Even in an acute situation with 5 liters / min for 24 hours, the patient consumes 7,200 liters of oxygen, and less than 5% is delivered to the patient. Room air at a high flow rate can also be a sufficient sweep gas to remove carbon dioxide. Current oxygenators have limited adjustment capabilities, which results in a lack of precise control of oxygen delivery and carbon dioxide removal.

[0012] It can therefore be seen that there is a need for an improved oxygenator that efficiently uses sweep gas for gas exchange. Such an oxygenator can be useful for a variety of applications and patients.

[0013] 2. Background of the Invention: Related background patents include U.S. Patent Application Publication No. 2013 / 0296633; U.S. Patent No. 9,320,844; U.S. Patent No. 8,709,343; U.S. Patent No. 8,529,834; U.S. Patent No. 7,871,566; U.S. Patent No. 5,270,005; U.S. Patent No. 8,795,220; U.S. Patent No. 8,545,754; U.S. Patent No. 8,518,259; and U.S. Patent No. 6,998,093. Summary of the Invention

[0014] The device of the present invention includes a gas exchanger configured to increase flexibility and scalability for many clinical applications. The gas exchanger can be configured and used in a variety of applications, such as a heart-lung machine for heart-lung support during cardiopulmonary surgery, an extracorporeal membrane oxygenation (ECMO) circuit, and a respiratory support device for patients with pulmonary failure. In some embodiments, the dual chamber gas exchanger features two sweep gas flow paths. In other embodiments, the two gas exchange membrane bundles are surrounded by a housing structure that provides two chambers that isolate the gas flow and provide continuous blood flow with various blood flow distributions and gas distribution mechanisms. In some embodiments, the gas exchanger includes an outer housing, a middle housing, two gas exchange fiber bundles, a blood inlet, a blood outlet, two gas inlets, two gas exhausts or outlets, two gas distribution chambers, and an optional heat exchanger. In certain embodiments, the gas exchanger can be configured to transfer oxygen and remove carbon dioxide, such as by using a sweep gas that includes oxygen, mixed oxygen, and atmospheric air, other medical gases, and the like, to manipulate the concentration of the sweep gas exposed to the patient's blood.

[0015] The present invention includes a compact dual chamber gas exchanger with low priming volume, small gas exchange surface area, and ability to break boundary layer effects. The dual chamber gas exchanger removes carbon dioxide while transferring oxygen. The dual chamber gas exchanger includes an outer housing enclosing internal components and a host connector, a blood inlet, and an annular outer fiber bundle of hollow fiber membranes. The dual chamber gas exchanger is configured for a wide range of applications, including cardiopulmonary bypass, extracorporeal membrane oxygenation (ECMO), integrated pump oxygenation devices, passive respiratory support devices (e.g., right ventricle to pulmonary artery configuration or pulmonary artery to left atrium configuration), ambulatory cardiopulmonary, and respiratory support.

[0016] The outer fiber bundle is disposed centrally in the housing and further includes fibers, an upper potting, and a lower potting. The upper potting and the lower potting hold the fibers within the housing. In one embodiment, the outer fiber bundle includes a blood distributor configured as a helical spiral that wraps around the inner surface of the housing. The blood distributor is coupled to a blood inlet near the upper potting or the lower potting. The blood distributor is configured to eject blood around the outer fiber bundle and create a pressurized annular blood volume surrounding the outer fiber bundle, with blood flowing axially through the gas exchange membrane of the outer fiber bundle.

[0017] In an alternative embodiment, the blood distributor of the dual chamber gas exchanger includes a rectangular inlet or first gate opening on one side of the outer housing from one end of the potting region to the other. The rectangular gate opening is typically a vertically oriented slot configured to couple the blood inlet and release the incoming blood into the outer fiber bundle. Thus, blood generally flows circumferentially through the gas exchange membrane of the outer fiber bundle and typically exits through a second or exit gate as described below.

[0018] One embodiment of the dual chamber gas exchanger further includes an annular inner fiber bundle of hollow fiber membranes concentrically disposed within the outer fiber bundle and further including fibers, an upper potting, and a lower potting, the upper potting and the lower potting of the annular inner fiber bundle holding the fibers in place within the housing.

[0019] Other embodiments of the dual chamber gas exchanger further include an intermediate housing, typically formed as a cylindrical wall, configured to substantially separate the outer and inner fiber bundles. The intermediate housing is thus generally located between a radially inner surface of the outer fiber bundle and a radially outer surface of the inner fiber bundle. An intermediate annular space is formed between the radially inner surface of the intermediate housing and the radially outer surface of the inner fiber bundle, providing an annular flow path around the inner fiber bundle and enabling a radially inner blood flow path through the inner fiber bundle. In other embodiments, the intermediate housing may be configured to provide circumferential or axial flow through the inner fiber bundle.

[0020] The dual chamber gas exchanger further includes a narrow slot in the upper potting area to allow blood to exit the outer fiber bundle and enter an intermediate annular space that exists between the intermediate housing wall and the outer annular surface of the inner fiber bundle. In other embodiments having a circumferential flow path through the outer fiber bundle, the dual chamber gas exchanger includes a rectangular gate configured to allow blood flow from the outer fiber bundle to the intermediate annular space.

[0021] The dual chamber gas exchanger includes components for transferring fluids, including a blood inlet, a blood outlet, and at least one gas inlet. The blood outlet is configured to collect oxygenated blood from the fibers and further couples to a cannula through which the oxygenated blood is returned to the patient. The blood outlet is generally located in a central location at the top of the housing and is fluidly coupled to the inner fiber bundle, such as the top potting of the inner fiber bundle.

[0022] At least one gas inlet, such as two gas inlets in one embodiment, is configured to provide separate gas passages for gases, such as oxygen and / or air, to enter the hollow fibers. The at least one gas inlet is disposed at the bottom of the housing. In one embodiment, the at least one gas inlet forms two separate gas chambers with the lower potting of the two bundles of hollow fiber membranes.

[0023] The two gas outlets are configured to provide a gas passage for gases, such as oxygen and air, to exit the hollow fibers. The gas outlets are generally located at the top of the housing and generally form two separate gas chambers with the top potting of the two bundles of hollow fiber membranes.

[0024] In other embodiments, the blood gas exchanger includes a blood sample port or blood gas sensor configured to allow for external sampling of blood within the blood gas exchanger. For example, the blood sample port may be fluidly coupled to the blood inlet or blood outlet. The blood sample port may further include an oxygen saturation detector attached to the blood outlet, and a temperature port attached to the blood outlet.

[0025] Although each clinical scenario may have different considerations and requirements, there is a widespread desire for an efficient, long-term biocompatible, long-term durable and versatile blood exchanger. In other words, it is desirable to achieve the most efficient gas transfer using the minimum number of required fiber membranes while minimizing blood trauma and maintaining long-term durability and reliability. Also, a variety of sweep gas sources can be accommodated to provide oxygen transfer, carbon dioxide removal, or both for different clinical applications.

[0026] In a first aspect, the present invention provides a blood oxygenator including a housing with a blood inlet, a blood outlet, a stripping gas inlet, an oxygenation gas inlet, and at least one gas outlet. An oxygenator fiber bundle is disposed within the housing and configured such that blood flows through the blood flow region of the oxygenator fiber bundle in a predetermined path from the blood inlet to the blood outlet. The stripping gas inlet is configured to direct a flow of stripping gas through the stripping region of the oxygenator fiber bundle to at least one gas outlet. The oxygenation gas inlet is configured to direct a flow of oxygenation gas through the oxygenation region of the oxygenator fiber bundle to at least one gas outlet. The stripping gas region of the oxygenator fiber bundle is upstream of the oxygenation region of the oxygenator fiber bundle. The term "upstream" refers to the direction of blood flow such that the blood to be oxygenated is first exposed to the stripping gas in the stripping region and then to the oxygenation gas in the oxygenation region of the fiber bundle.

[0027] In a first set of exemplary embodiments, the blood oxygenator of the present invention may have a cylindrical fiber bundle with at least a portion of the blood flow path in a radially inward or radially outward direction. In such embodiments, a portion of the fiber bundle along the central axis is typically open to provide an outlet or inlet plenum for receiving blood from or distributing blood to the cylindrical fiber bundle, respectively. In yet other embodiments, the fiber bundle is cylindrical and at least a portion of the blood flow path follows an annular path, typically with the bundle having a blood inlet or outlet plenum along the central axis of the fiber bundle. In still other embodiments, at least a portion of the blood flow path may be unidirectional across the oxygenator fiber bundle.

[0028] In certain examples, the fiber bundle of the oxygenator is cylindrical and has an outer portion of the blood flow path following an annular path and an inner portion of the blood flow path following a radially inward path. In these examples, the blood inlet typically feeds the outer portion of the fiber bundle, and the inner portion of the fiber bundle feeds the blood outlet. More specifically, the stripping region may be at least partially located in the outer portion of the blood flow path and the oxygenation region may be at least partially located in the inner portion of the blood flow path where the blood inlet feeds the inner portion and the outer portion feeds the blood outlet. Alternatively, the stripping region may be at least partially located in the inner portion of the blood flow path and the oxygenation region may be at least partially located in the outer portion of the blood flow path.

[0029] The blood oxygenator may further comprise a cylindrical wall separating the outer and inner portions of the cylindrical fiber bundle, wherein blood flows from the blood inlet through the axial opening in the housing to the outer portion of the fiber bundle, flows annularly through the outer portion of the fiber bundle, then flows through the axial opening in the cylindrical wall to a distribution ring surrounding the inner bundle where the blood flows radially inward through the inner portion of the fiber bundle and to an axial collection area along the central axis of the inner portion of the fiber bundle.

[0030] In another embodiment, the oxygenation fiber bundle of the blood oxygenator of the present invention has a cross-sectional area, the stripping region receiving stripping gas from the stripping gas inlet has an inlet area that is 20% to 80% of said cross-sectional area, and the oxygenation region receiving oxygenation gas from the oxygenation gas inlet has an inlet area that is 80% to 20% of said cross-sectional area.

[0031] In a further embodiment, the blood oxygenator may further comprise a manifold divider that divides and directs both (1) stripping gas from the stripping gas inlet to the stripping region of the oxygenator fiber bundle, and (2) oxygenation gas from the oxygenation gas inlet to the oxygenation region of the oxygenator fiber bundle. The manifold divider may be located in a manifold that receives stripping gas from the stripping gas inlet and oxygenation gas from the oxygenation gas inlet, the manifold typically being open to the entire gas inlet side of the oxygenation fiber bundle, and the location of the manifold divider controls the inlet area of ​​the stripping region that receives stripping gas from the stripping gas inlet and the inlet area of ​​the oxygenation region that receives oxygenation gas from the oxygenation gas inlet. The manifold divider may be fixed or movable, in the latter case allowing the relative areas of the stripping and oxygenation regions of the fiber bundle to be adjusted during or between uses.

[0032] In a further embodiment, the oxygenating fiber bundle of the blood oxygenator may comprise an upper potting and a lower potting. A manifold may be disposed within the housing adjacent one of the pottings, and a blood pump may be connected to the blood inlet. An oxygenation gas source may be connected to the oxygenation gas inlet, and a stripping gas source may be connected to the stripping gas inlet.

[0033] In a second aspect, the present invention provides a method for oxygenating blood. The blood oxygenator has (1) a housing with a blood inlet, a blood outlet, a stripping gas inlet, an oxygenation gas inlet, and at least one gas outlet, and (2) an oxygenator fiber bundle disposed within the housing. Blood flows through the blood inlet, the oxygenator fiber bundle, and the blood outlet. Stripping gas flows through the stripping gas inlet and oxygenation gas flows through the oxygenation gas inlet. The stripping gas flows through a stripping region of the oxygenator fiber bundle to at least one gas outlet, and the oxygenation gas flows through an oxygenation region of the oxygenator fiber bundle to at least one gas outlet. The stripping gas region of the oxygenator fiber bundle is disposed upstream of the oxygenation region of the oxygenator fiber bundle. This configuration provides a particularly efficient CO 2 Removal and oxygen uptake are achieved, especially CO 2 The need for pure oxygen to perform both stripping and blood oxygenation can be reduced.

[0034] In certain embodiments of the method of the present invention, blood may move through the stripping region of the oxygenator fiber bundle in an annular flow path, while in other embodiments, blood moves through the oxygenation region of the oxygenator fiber bundle in a radially inner flow path. In still other embodiments, blood may move in a straight direction through the stripping and oxygenation regions of the oxygenator fiber bundle. In some cases, blood may move through the oxygenator fiber bundle with a substantially uniform blood flow distribution. In other examples, the fiber bundle may have a cross-sectional area in which the stripping region receiving stripping gas from the stripping gas inlet has an inlet area that comprises 20% to 80% of the cross-sectional area, and the oxygenation region receiving oxygenation gas from the oxygenation gas inlet has an inlet area that comprises 80% to 20% of the cross-sectional area. The method of the present invention may further include moving a manifold divider directing flow stripping gas from the stripping gas inlet to the stripping zone of the oxygenator fiber bundle, and directing oxygenation gas from the oxygenation gas inlet to the oxygenation zone of the oxygenator fiber bundle, to adjust the relative areas of the stripping zone and the oxygenation zone of the oxygenator fiber bundle. [Brief description of the drawings]

[0035] [Figure 1] FIG. 1 is a perspective view of a first embodiment of a dual chamber gas exchanger with circumferential-radial flow paths according to the principles of the present invention. [Diagram 2] FIG. 2 is a vertical cross-sectional view of the dual chamber gas exchanger of FIG. 1 with a circumferential flow channel design in the outer fiber bundle and radial flow channels in the inner fiber bundle, two gas inlets, and two gas exhausts. [Diagram 3] 3 is a vertical cross-sectional view of the dual chamber gas exchanger of FIGS. 1 and 2, showing the blood flow paths within the blood distributor and the inner and outer fiber bundles. FIG. [Figure 4] FIG. 4 is a horizontal cross-sectional view of the dual chamber gas exchanger of FIGS. 1-3, showing the circumferential blood flow path of the outer fiber bundle from the distributor through gate 1 to the outer fiber bundle and through gate 2 to the inner fiber bundle. [Diagram 5] FIG. 13 is a perspective view of a dual chamber gas exchanger with axial radial flow paths according to another embodiment of the present invention. [Figure 6] FIG. 6 is a vertical cross-sectional view of the dual-chamber gas exchanger of FIG. 5 with an axial flow path design in the outer fiber bundle and a radial flow path design in the inner fiber bundle, two gas inlets, and two gas exhausts. [Figure 7] FIG. 6 is a vertical cross-sectional view of the dual-chamber gas exchanger of FIG. 5 showing the blood flow pathways. [Figure 8A] Horizontal and partial cross-sectional views of the dual-chamber gas exchanger in Figure 5 showing the axial blood flow path of the outer fiber bundle from the helical distributor through gate 1 to the outer fiber bundle, then through gate 2 to the inner fiber bundle (Left: top cross-sectional view of the helical spiral with blood flow through gate 1; Right: perspective cross-sectional view of the axial blood flow path through gates 1 and 2 into the inner fiber bundle and exiting the dual-chamber gas exchanger). [Figure 8B]Horizontal and partial cross-sectional views of the dual-chamber gas exchanger in Figure 5 showing the axial blood flow path of the outer fiber bundle from the helical distributor through gate 1 to the outer fiber bundle, then through gate 2 to the inner fiber bundle (Left: top cross-sectional view of the helical spiral with blood flow through gate 1; Right: perspective cross-sectional view of the axial blood flow path through gates 1 and 2 into the inner fiber bundle and exiting the dual-chamber gas exchanger). [Figure 9A] Horizontal and vertical cross-sections of examples of computational fluid dynamics modeling of blood flow fields in two embodiments of a dual-chamber gas exchanger (left: cross-section of the embodiment of Figure 1 at 6 liters per minute, right: central cross-section of the embodiment of Figure 5 at 6 liters per minute). [Figure 9B] Horizontal and vertical cross-sections of examples of computational fluid dynamics modeling of blood flow fields in two embodiments of a dual-chamber gas exchanger (left: cross-section of the embodiment of Figure 1 at 6 liters per minute, right: central cross-section of the embodiment of Figure 5 at 6 liters per minute). [Figure 10A] Horizontal and vertical cross-sectional views of computational fluid dynamics modeling of the oxygen transfer process and velocity vectors in two embodiments of a dual-chamber gas exchanger (left: cross-section of the embodiment of Figure 1 at 6 liters per minute, right: central cross-section of the embodiment of Figure 5 at 6 liters per minute). [Figure 10B] Horizontal and vertical cross-sectional views of computational fluid dynamics modeling of the oxygen transfer process and velocity vectors in two embodiments of a dual-chamber gas exchanger (left: cross-section of the embodiment of Figure 1 at 6 liters per minute, right: central cross-section of the embodiment of Figure 5 at 6 liters per minute). [Figure 11] FIG. 1 is a schematic diagram of a dual chamber blood oxygenator showing the various components used in cardiopulmonary bypass surgery applications. [Figure 12] FIG. 13 is a diagram of a dual chamber gas exchanger for use as a removable integrated pump oxygenator (e.g., an integrated pump oxygenator) according to another embodiment of the present invention. [Figure 13A]1A-1D are diagrams of a dual-chamber gas exchanger for use as portable respiratory and / or cardiopulmonary support according to another embodiment of the present invention ((A) harness-like configuration; (B) wheeled configuration). [Figure 13B] 1A-1D are diagrams of a dual-chamber gas exchanger for use as portable respiratory and / or cardiopulmonary support according to another embodiment of the present invention ((A) harness-like configuration; (B) wheeled configuration). [Figure 14] FIG. 13 is a vertical cross-sectional view of a dual chamber gas exchanger having a radial flow channel design in the outer fiber bundle and circumferential flow channels in the inner fiber bundle according to another embodiment of the present invention. [Figure 15] FIG. 15 is a vertical cross-sectional view of the dual chamber gas exchanger of the embodiment of FIG. 14 with arrows indicating the direction of blood flow. [Figure 16] FIG. 15 is a horizontal cross-sectional view of the blood flow path within the helical spiral, outer and inner fiber bundles of a dual-chamber gas exchanger similar to that of FIG. 14. [Figure 17] FIG. 1 is a schematic vertical cross-sectional view of a dual-chamber gas exchanger having radial blood flow through the inner and outer annular chambers. [Figure 18] FIG. 18 is a vertical cross-sectional view of the dual chamber gas exchanger of the embodiment of FIG. 17 with arrows indicating the radial blood flow paths of the inner and outer fiber bundles. [Figure 19] 18 is a horizontal cross-sectional view of the helical spiral, outer fiber bundle, and inner fiber bundle of a dual chamber gas exchanger showing blood flow paths similar to the embodiment of FIG. 17. [Figure 20] FIG. 13 is a vertical cross-sectional view of a dual chamber gas exchanger having radial flow paths in an outer fiber bundle and axial flow paths in an inner fiber bundle according to another embodiment of the present invention. [Figure 21] A vertical cross-sectional view of the dual chamber gas exchanger of Figure 20 with arrows indicating the radial blood flow path of the outer fiber bundle, the axial blood flow path of the inner fiber bundle, two gas inlets, and two gas outlets. [Figure 22]FIG. 21 is a horizontal cross-sectional view of a helical spiral blood inlet in a dual chamber gas exchanger similar to that of FIG. 20 with arrows showing the blood flow path of the helical spiral and outer fiber bundle. [Figure 23A] 23A-23B are schematic diagrams of alternative gas flow paths in a dual chamber gas exchanger according to an alternative embodiment of the invention, in which an oxygen-rich sweep gas exhausted from one of the inner or outer fiber bundles mixes with ambient air for use as a sweep gas in the other of the inner or outer fiber bundle (FIG. 23A), and each sweep gas is used separately for the inner and outer fiber bundles (FIG. 23B). [Figure 23B] 23A-23B are schematic diagrams of alternative gas flow paths in a dual chamber gas exchanger according to an alternative embodiment of the invention, in which an oxygen-rich sweep gas exhausted from one of the inner or outer fiber bundles mixes with ambient air for use as a sweep gas in the other of the inner or outer fiber bundle (FIG. 23A), and each sweep gas is used separately for the inner and outer fiber bundles (FIG. 23B). [Figure 24] 13 illustrates blood and gas flow paths in a dual chamber gas exchanger having a square fiber bundle and two gas inlets according to another embodiment of the present invention. [Diagram 25] 13 shows the blood and gas flow paths in another embodiment of a dual chamber gas exchange having a region in the fiber bundle separated by a movable wall in a cylindrical gas inlet manifold. [Figure 26A] FIG. 13 is a vertical cross-sectional view of a dual chamber gas exchanger with an alternative partition arrangement. [Figure 26B] FIG. 26B is a horizontal cross-sectional view of a variable septum mechanism similar to FIG. 26A having a helical spiral. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0036] 1-22, the dual chamber gas exchanger 100 is configured to use two separate sweep gases (e.g., ventilation gases) such that the dual chamber gas exchanger 100 can be used in various clinical applications. For example, the dual chamber gas exchanger 100 uses separate flow paths in separate chambers of the dual gas flow chamber 124, such as the first chamber 110 and the second chamber 113, to transfer oxygen to the blood and remove carbon dioxide from the blood. The dual chamber gas exchanger 100 of this embodiment includes an outer housing 112, a blood distributor 114, an outer fiber bundle 116 of hollow membranes, a middle housing 118, an inner fiber bundle 120 of hollow membranes, an inner flow deflector 122, and a dual gas flow chamber 124. The dual chamber gas exchanger 100 can be used in various clinical scenarios. For example, it can be used in cardiopulmonary bypass during cardiothoracic surgery, extracorporeal membrane oxygenation (ECMO) for cardiopulmonary or respiratory support in hospitals, ambulatory respiratory support from an intensive care unit (see FIG. 13), at the patient's home, etc.

[0037] The outer housing 112 and the intermediate housing 118 are configured to surround the outer fiber bundle 116 and form various blood flow paths in the outer fiber bundle 116 and the inner fiber bundle 120 (see FIGS. 2, 3, 4, 6, 7, 8A, 8B, 14, 15, 16, 17, 18, 19, 20, 21, and 22). For example, each blood flow path can be at least one of an axial, circumferential, or radial flow path, etc. The inner flow deflector 122 is configured to deflect or direct blood flow from the inner fiber bundle 120 toward the blood outlet 144. The inner flow deflector 122 of this embodiment (see FIGS. 2, 3, 4, 6, 7, 8B, 14, 15, 17, 18, 20, and 21) has the general shape of a conical cylinder and is located substantially concentrically about the center of the inner fiber bundle 120.

[0038] The dual gas flow chamber 124 receives the sweep gas and distributes the sweep gas to the fiber membranes of both the inner fiber bundle 120 and the outer fiber bundle 116 (FIGS. 2, 6, 14, 15, 17, 18, 20, 21, and 23). The sweep gas in this embodiment includes air, oxygen, a mixture of oxygen and air, or other ventilation gas. The intermediate housing 118 is configured to allow blood to flow (e.g., substantially radially, axially, and / or circumferentially) through the inner fiber bundle 120 and surround the inner fiber bundle 120. The inner fiber bundle 120 and the outer fiber bundle 116 include gas exchange membrane fibers, such as hollow membrane fibers, configured to transfer oxygen to the blood and remove carbon dioxide from the blood flowing through the membrane fibers. The inner fiber bundle 120 and the outer fiber bundle 116 can be in the form of an annular fiber bundle (see Figures 2, 6, 14, 17, 20, and 23A and 23B) or a square of a plurality (e.g., thousands) of gas permeable hollow membrane fibers or membrane fibers (see Figure 24). The inner fiber bundle 120 and the outer fiber bundle 116 are generally centrally and concentrically disposed within the outer housing 112, with the middle housing 118 separating the inner fiber bundle 120 and the outer fiber bundle 116 as described above.

[0039] The hollow fiber membranes of the outer fiber bundle 116 and the inner fiber bundle 120 are coupled to an upper potting 117 and a lower potting 119 configured to fluidly communicate sweep gas to and from the hollow fiber membranes (e.g., from a gas inlet 121 into the hollow fiber membranes and / or from the hollow fiber membranes to gas outlets 123, such as gas outlet 1 and gas outlet 2). Thus, the upper potting 117 is disposed at a top within the outer housing 112 and the lower potting 119 is disposed at a bottom within the outer housing 112. Additionally, each of the inner fiber bundle 120 and the outer fiber bundle 116 are configured to be sealed to one another, including the upper potting 117 and the lower potting 119, to prevent undesirable flow paths of blood and / or sweep gas.

[0040] In one example, the sweep gas can be selected based on the clinical application, such as using oxygen or an oxygen-rich gas to substantially transfer oxygen to the blood in the outer fiber bundle 116 and substantially remove carbon dioxide in the inner fiber bundle 120. Alternatively, air (e.g., atmospheric air) or a combination of air and oxygen may be used. The sweep gas streams can be separated into flow paths (e.g., oxygen transfer and carbon dioxide removal) to control the flow rate and / or content of each sweep gas independently of the other sweep gases.

[0041] 1, 2, 5, 6, 14, 15, 17, 18, 20, 21, and 23, the dual chamber gas exchanger 100 is further configured to control how many of the hollow membrane fibers are in contact with the sweep gas. For example, one flow path can be controlled to independently supply oxygen and / or air from another flow path. Thus, the dual chamber gas exchanger 100 increases the flexibility of using various gas sources for oxygen transfer and carbon dioxide removal. For example, depending on the clinical application, both the inner fiber bundle 120 and the outer fiber bundle 116 can be used for oxygen transfer and / or carbon dioxide removal, or only the outer fiber bundle 116 can be used for oxygen transfer and the inner fiber bundle 120 can be used for carbon dioxide removal, or vice versa.

[0042] Additionally, the dual chamber gas exchanger 100 may be configured to increase the flow rate of one gas (e.g., oxygen or air). For example, sweep gas from one flow path may be recirculated and combined with gas from the other flow path in clinical applications where there is a greater clinical need for increased oxygen than for carbon dioxide removal. As a further example, a clinician may increase the sweep gas flow rate and / or surface area of ​​the oxygenator membrane (described further below) exposed to air when increased carbon dioxide removal is required.

[0043] 2, 3, 6, 7, 14, 15, 17, 18, 20, 21, and 23, the first chamber 110 of the dual chamber gas exchanger 100 can be configured to transfer a sweep gas (e.g., oxygen) to the blood or remove carbon dioxide from the blood. For example, the flow rate of the sweep gas to transfer oxygen can be between approximately 1 liter per minute and 6 liters per minute. An oxygen source then provides the sweep gas to the first chamber 110. In one embodiment, the oxygen source is a small volume, lightweight, battery-powered portable oxygen concentrator (e.g., a commercially available oxygen concentrator).

[0044] The oxygen concentrator converts air into oxygen-rich gas (e.g., oxygen concentration greater than about 90%). The oxygen concentrator can be integrated into a portable drive console configured to enclose the oxygen concentrator and other components, such as a power source (e.g., a battery), a blood pump controller, a flow sensor, blood gas sensors, etc. (FIGS. 11 and 13). For example, one embodiment can include a removable pump 126 forming an integrated pump-oxygenator (e.g., an integrated pump-oxygenator; see FIG. 12) that includes an exemplary blood pump 126 and a pump driver controlled by the blood pump controller. The blood pump 126 can be easily coupled and detached from the dual chamber gas exchanger 100 by using quick connectors, exemplary fasteners, etc. However, in other embodiments, the oxygen source can be a fixed or portable oxygen tank, atmospheric air, etc.

[0045] Referring again to Figures 2, 3, 6, 7, 14, 15, 17, 18, 20, 21, and 23, the second chamber 113 of the dual chamber gas exchanger 100 can be configured to remove carbon dioxide from the blood or transfer oxygen to the blood. For example, the flow rate of the sweep gas for removing carbon dioxide can be approximately 6 liters per minute to 18 liters per minute. In one embodiment, a small air fan compresses the air and mixes it with the sweep gas (e.g., oxygen or oxygen-rich gas) from the first chamber 110 to generate a high sweep gas flow for carbon dioxide removal. The enclosed dual gas flow chamber 124 of this embodiment is positioned below the lower potting 119 or above the upper potting 117 of the inner fiber bundle 120 and the outer fiber bundle 116.

[0046] With continued reference to Figures 2, 3, 6, 7, 14, 15, 17, 18, 20, 21, and 23, the dual gas flow chamber 124 includes a first chamber 110 and a second chamber 113 each configured to receive one of the sweep gases from two gas inlets 121 (e.g., gas inlet 1 and gas inlet 2). For example, the sweep gases in each of the first chamber 110 and the outer chamber 113 may have different compositions and / or flow rates. The gas inlets 121 distribute the sweep gas to the open lumen fibers embedded in the upper potting 117 and the lower potting 119 of the inner fiber bundle 120 and the outer fiber bundle 116, respectively. In this embodiment, oxygen or oxygen-rich gas flows through the open fiber lumens of the upper potting 119 and diffuses across the outer walls of the individual hollow fiber membranes in the first chamber 110 into the blood where blood oxygenation occurs. Additionally, carbon dioxide from the blood diffuses into the lumens of the hollow fiber membranes and is removed from the blood. The sweep gas flows through the hollow fiber membranes and exits the dual gas flow chamber 124 through the bottom potting 119. In this embodiment, the sweep gas exits the dual chamber gas exchanger 100 by venting to the atmosphere. Thus, the dual chamber gas exchanger 100 receives and diffuses the sweep gas into separate fiber membrane bundles for blood oxygenation and carbon dioxide removal.

[0047] The outer housing 112 and the intermediate housing 118 are configured to form individual or mixed blood flow paths in the inner fiber bundle 120 and the outer fiber bundle 116 (FIGS. 2, 3, 6, 7, 14, 15, 17, 18, 20, and 21). In this embodiment, various blood flow paths are possible by opening or closing one or both of the blood flow gates 128 and 130 (see FIGS. 2-4, 6-8B, 14-16, and 20-22). The blood flow gates are attached to the outer housing 112, the intermediate housing 118, and the blood distributor 114, which is coupled to the blood inlet 142. FIGS. 2-4 show the outer fiber bundle with circumferential blood flow paths (see arrows in FIGS. 3 and 4). The blood distributor 114 receives blood from the blood inlet 142 and is fluidly coupled to a first rectangular blood gate 128 (Gate 1) formed as a vertical slit or gap on one side of the outer housing 112, and a second rectangular blood gate 130 (Gate 2) disposed on the opposite side of the intermediate housing 118. In one embodiment, the blood distributor 114 discharges blood substantially uniformly through Gate 1 128 into the outer fiber bundle 116 in a substantially circumferential direction through the outer fiber bundle 116 and through Gate 2 130 into an intermediate annular space 132 (e.g., having a cylindrical or conical shape) located between the inner wall of the intermediate housing 118 and the outer surface of the inner fiber bundle 120. As a further alternative, the dual chamber gas exchanger 100 is configured to filter particulates in the blood. For example, the dual chamber gas exchanger 100 can include a filter such as a depth filter, reticulated foam, microporous filtration, filtration media, etc.

[0048] As shown in Figures 6-8, in another embodiment of the dual chamber gas exchanger 100, the outer fiber bundle 116 has an axial blood flow path. The blood distributor 114 is configured in the shape of a helical spiral with a gradually decreasing cross-sectional area (see, for example, Figures 14-16, 17-19, and 20-22). Figures 5-8 show that the blood distributor 114 generally surrounds the upper end of the outer housing 112 and is attached to a first blood gate 128 (Gate 1), which is generally a narrow slot. A second narrow slot blood gate 130 (Gate 2) is located at the end of the middle housing 118 opposite Gate 1 128. The helical spiral blood distributor 114 gradually releases blood in a circumferential direction (e.g., 360 degrees) through Gate 1 128 to the upper end of the outer fiber bundle 116. Blood flows axially, exiting the outer bundle 116 through Gate 2 130 and into the intermediate annular space 132 between the inner wall of the intermediate housing 118 and the outer surface of the inner bundle 120. The flow path through the inner bundle 120 is radial, which enhances biocompatibility, gas exchange efficiency, and has low pressure loss.

[0049] 6-8, the intermediate annular space 132 is generally formed between the inner wall of the intermediate housing 118 and the outer surface of the inner fiber bundle 120 and has a generally uniform pressure distribution (e.g., before blood enters the inner fiber bundle 120). The blood has a generally uniform pressure distribution that causes the blood to flow in a substantially uniform radially inward direction through the fiber membrane of the inner fiber bundle 120 (see FIGS. 3, 4, 7, 8, 18, and 19). Computational fluid dynamics analysis demonstrates substantially uniform flow and substantially uniform oxygen transfer in the inner fiber bundle 120 and the outer fiber bundle 116 (FIGS. 9 and 10).

[0050] Thus, the inner fiber bundle 120 and the outer fiber bundle 116 can be configured for various blood flow paths (e.g., circumferential, axial, and / or radial) depending on the clinical application. For example, one embodiment of the dual chamber gas exchanger 100 includes an inner fiber bundle 120 having a radial flow path and an outer fiber bundle 116 having a circumferential flow path (see FIGS. 2-4). As a further example, another embodiment of the dual chamber gas exchanger 100 includes an inner fiber bundle 120 having a radial flow path and an outer fiber bundle 116 having an axial flow path (see FIGS. 6-8). As a further example, another embodiment of the dual chamber gas exchanger 100 includes an inner fiber bundle 120 having a circumferential flow path and an outer fiber bundle 116 having a radial flow path (see FIGS. 14-16). As a further example, another embodiment of the dual chamber gas exchanger 100 includes an inner fiber bundle 120 having a circumferential flow path and an outer fiber bundle 116 having a radial flow path (see FIGS. 17-19). As a further example, another embodiment of the dual chamber gas exchanger 100 includes an inner fiber bundle 120 having an axial flow path and an outer fiber bundle 116 having a radial flow path (see FIGS. 20-22). Other combinations and configurations of flow paths are possible within the dual chamber gas exchanger 100.

[0051] 2, 3, 6, 7, 14, 15, 17, 18, 20, and 21, the inner fiber bundle 120 and the outer fiber bundle 116 of this embodiment are cylindrical rings including many hollow membrane fibers or microporous hollow fibers having pore sizes, for example, generally less than 0.1 microns in diameter. The hollow membrane fibers of this embodiment are commercially available and have outer diameters of about 250 microns to 400 microns and wall thicknesses of about 30 microns to 50 microns, although hollow fiber membranes having other outer diameters and wall thicknesses are feasible in the dual chamber gas exchanger 100. In other embodiments, the hollow membrane fibers are configured to be anti-thrombogenic, for example, having an anti-thrombogenic coating (e.g., heparin or a functional equivalent). Alternatively, the hollow membrane fibers may be microporous membranes for filtering blood components, such as for hemodialysis.

[0052] The porosity (or void volume) of each inner fiber bundle 120 and outer fiber bundle 116 is generally determined by the desired pressure drop across the inner fiber bundle 120 and outer fiber bundle 116. In this embodiment, the porosity is in the range of about 0.4 to 0.7. Alternatively, coated or bare hollow fibers may be used to allow diffusion of oxygen and carbon dioxide through a non-porous skin layer on the outer wall of the membrane fiber. Hollow membrane fibers are typically commercially available in a tape configuration, whereby individual hollow membrane fibers are arranged in a predetermined configuration (i.e., parallel straight or bias, multi-directional, woven, spaced, etc.) that can be tape-wrapped to form a cylindrical or conical bundle configuration. Alternatively, the hollow fiber membranes can be wrapped or wound (e.g., like a string spool). The hollow membrane fibers are attached to the lower potting 119 and upper potting 117, respectively (see Figures 2, 3, 6, 7, 14, 15, 17, 18, 20, and 21). For example, in this embodiment, the ends of the inner fiber bundle 120 and the outer fiber bundle 116 are trimmed to open the inner lumen of the membrane fiber and cast using a polymer (e.g., urethane, epoxy, etc.). Sweep gas is distributed through the lumen between the upper potting 117 and the lower potting 119.

[0053] In one embodiment, the dual chamber gas exchanger 100 includes a heat exchanger configured to control blood temperature. The heat exchanger can include a cylindrical ring of heat exchange elements around at least one of the inner fiber bundle 120 or the outer fiber bundle 116. The cylindrical ring is formed of a plurality of capillary tubes potted on one of the inner fiber bundle 120 or the outer fiber bundle 116. The heat exchanger capillaries can be formed from biocompatible metals, polymers, and the like. The capillaries have lumens that are open to form separate flow paths. The heat exchanger further includes a sweep gas chamber and a heat transfer medium chamber configured to control the heat of the sweep gas and the heat transfer medium, respectively. In one embodiment, the sweep gas chamber and the heat transfer medium chamber are disposed on top of the outer housing 112 above the top potting. However, in other embodiments, the sweep gas chamber and the heat transfer medium chamber are disposed below the outer housing 112 above the bottom potting 119. The temperature of the blood is controlled by varying the flow rate and temperature of the heat transfer medium flowing through the heat exchanger capillaries and hollow membrane fibers.

[0054] In other embodiments, rather than configuring hollow fiber membranes as heat exchangers, multiple hollow tubes are configured for heat transfer, in which a temperature controlled fluid, such as water, is used to affect temperature changes in the blood.

[0055] The gas inlet 121 (FIGS. 1-3 and 5-7) is configured to operate at low pressure while providing a uniform sweep gas to the outer fiber bundle 116 and / or inner fiber bundle 120. The gas inlet 121 includes inflow and outflow connectors sized to achieve the desired blood flow rate and pressure. For example, the dual chamber gas exchanger 100 can include typical ¼ inch or ⅜ inch barb fittings that accept standard machine-assisted extracorporeal circulation tubing.

[0056] One embodiment of the dual chamber gas exchanger includes an arterial sample port 136 and a venous sample port 138 (FIGS. 1 and 2) configured to allow an operator to collect blood samples from the dual chamber gas exchanger 100 (e.g., using a syringe, traditional stopcock, plug-type sample port, etc.). The arterial sample port 136 and the venous sample port 138 are further configured to allow blood to be sampled before blood enters the inner fiber bundle 120 and / or the outer fiber bundle 116 and after blood flow exits the inner fiber bundle 120 and / or the outer fiber bundle 116 to control various parameters (e.g., blood flow, gas transfer and pH for control of oxygen concentration).

[0057] In one embodiment, the dual chamber gas exchanger 100 may be configured to remove air bubbles from the blood. One embodiment may include an exterior vent port 140 (FIGS. 1, 3, 5-8, 12-15, and 17) located near a portion of the dual chamber gas exchanger 100 where air bubbles typically accumulate. For example, the exterior vent port 140 may be located on the exterior wall of the outer housing 112 near the upper potting 117 (FIG. 2). Additionally, other embodiments of the dual chamber gas exchanger 100 may include an interior vent port located near the top of the middle housing 118, such as the top potting 117 of the inner fiber bundle 120, to remove air bubbles. Air bubbles typically result from trapped air not properly removed during priming, broken hollow membrane fibers, or excessive negative pressure applied to the blood that pushes gas into solution.

[0058] As shown in Figures 23A and 23B, an oxygenator according to the principles of the present invention may be constructed with an oxygen-rich gas passing through one portion of the gas-exchanging fiber bundle and air or other oxygen-depleted stripping gas passing through another portion of the fiber bundle. If desired, such an oxygenator may have a gas flow path through which the oxygen-rich sweep gas exhausted from one of the inner or outer fiber bundles mixes with atmospheric air for use as a sweep gas for the other of the inner or outer fiber bundle.

[0059] As shown in FIG. 23A, the exchanger 200 with fiber bundle 210 is configured to recycle the oxygen-rich exhaust sweep gas from the inner fiber bundle 220 in the outer fiber bundle 216. Oxygen from an external source, such as a tank or an oxygen concentrator, is diffused into the inner fiber bundle 220 through the lower part or plenum 224 of the dual gas chamber. The oxygen-rich gas passes through the inner fiber bundle 220 and is partially depleted of oxygen as it passes through the upper plenum 228, where it mixes with the ambient air entering through the inlet 230. The mixed gas flow then passes through the outer fiber bundle 216 to remove or "strip" carbon dioxide from the blood that enters the fiber bundle 210 horizontally in any of the aforementioned flow paths. Although not oxygen-rich, the mixed gas provides an initial stage of oxygenation in addition to removing carbon dioxide. Oxygenation is completed in the inner fiber bundle 220, where the oxygen is exposed to a gas with a higher oxygen concentration. The sweep gas is vented to the atmosphere from the bottom of the dual gas chamber 232. Thus, because atmospheric air is generally abundant and easy to use in the dual chamber gas exchanger 200, the mixed atmospheric air and oxygen sweep gas can provide increased gas flow rates and oxygen utilization efficiencies.

[0060] 23B, an alternative embodiment of the dual chamber gas exchanger 250 embodiment can be configured to pass the oxygen-rich sweep gas 252 only through the inner fiber bundle 260 and pass only ambient air 254 only through the outer fiber bundle 262. The plenum and isolation barrier arrangements are made accordingly.

[0061] In FIG. 24, oxygenator 300 has a rectangular shape with separate gas inlets 323 and 324 at the top, and has a rectangular fiber bundle 302 disposed between top potting 317 and bottom potting 319. In contrast to the previous embodiment, fiber bundle 302 has no barriers creating isolated airflow regions therein. The flow of gas through fiber bundle 302 is controlled by a movable septum 304 disposed in gas inlet region 306 above top potting 317. Gas inlets 323 and 324 release gas on either side of septum 304 and may be connected to different gas sources such as air and oxygen, respectively. Moving septum 304 thus adjusts the fiber region to which each gas is exposed. For example, blood flowing in the direction of the horizontal arrow in FIG. 24 is first exposed to gas entering through inlet 323, which may be air or other low-oxygen stripping gas. After carbon dioxide has been at least partially removed, the blood may be exposed to oxygen-rich gas supplied through inlet 324 for complete oxygenation. Of course, blood flows vertically in the direction of the vertical arrow. In some embodiments, the septum 304 may be fixed. Adjustability of the fiber region is lost, but the efficiency of removing carbon dioxide from the blood using air or other low-oxygen gas and achieving final oxygenation with pure or other high-oxygen gas is retained.

[0062] In a further embodiment, as shown in FIG. 25, the oxygenator 400 has a cylindrical shape with separate gas inlets 423 and 424 at the top, with an annular fiber bundle 402 disposed between the top potting and the bottom potting (not shown). A circular septum 404 with an adjustable diameter is disposed in a gas inlet area 406 above the top potting. The gas inlets 423 and 424 are arranged to be located on the outside and inside of the septum 406, and may be connected to different gas sources, such as air and oxygen, respectively. Adjusting the diameter of the septum 404 adjusts the fiber area exposed to each gas. For example, blood flowing in the direction of the horizontal arrow in FIG. 24 is first exposed to gas entering through inlet 423, which may be air or other low-oxygen stripping gas. After the carbon dioxide is at least partially removed, the blood may be exposed to an oxygen-rich gas delivered through inlet 424 for complete oxygenation. Of course, the blood is flowing vertically in the direction of the vertical arrow. In some embodiments, the septum 404 may be fixed. Although the adjustability of the fiber region is lost, the efficiency of removing carbon dioxide from the blood using air or other low oxygen gas and achieving final oxygenation with pure or other high oxygen gas is retained.

[0063] 26A and 26B, a dual chamber gas exchanger 500 (similar to the dual chamber gas exchanger 100 described above) is further configured to vary the sweep gas exchange volume independent of the sweep gas concentration (e.g., without changing the sweep gas flow rate and / or concentration). The dual chamber gas exchanger 500 includes a septum mechanism 510, which in one embodiment is an adjustable opening such as an iris mechanism configured to vary the portion of the surface area of ​​the dual chamber gas exchanger membrane 512 that is in contact with the blood for oxygen transfer, and also, as described above, to vary the portion of the surface area of ​​the dual chamber gas exchange membrane 512 that is in contact with the blood for carbon dioxide removal.

[0064] The septum mechanism 510 varies the portion of the sweep gas for gas exchange by varying the access or fluid communication of the sweep gas to separate paths through different regions within the fiber bundle that lack a physical chamber wall (e.g., mid-housing). Varying access by controlling and adjusting the region of the gas flow path where the sweep gas is exposed to the patient's bloodstream (e.g., the portion of the hollow fiber membrane exposed to the inlet gas stream) allows the clinician to more precisely and efficiently match the patient's requirements (e.g., metabolic needs).

[0065] In the illustrated embodiment, the septum mechanism 510 is a mechanical mechanism such as an iris-type or shutter-type mechanism configured to vary the opening area to control the flowing gas (FIG. 26B). In other embodiments, the opening area may have a circular or hexagonal shape such that the opening area varies by changing the diameter or width. The septum mechanism 510 is fluidly coupled to at least one of the upper potting 514, the lower potting 516. A helical volute may distribute the gas to the fiber bundle (FIG. 26B), or a vortex inlet (provided in the previous embodiment) may be used (FIG. 26A). The septum mechanism 510 may be a valve or multiple valves, such as an array or series of valves that control fluid access to the various flow paths as described above. The opening area of ​​the septum mechanism 510 is controlled by a controller, such as the blood pump controller described above. Thus, the septum mechanism 510 enables the dual chamber gas exchanger 500 to control the mixture and amount of sweep gas to the portion of the dual chamber gas exchanger membrane 512 that is exposed to and in fluid contact with the patient's blood to transfer oxygen and remove carbon dioxide.

[0066] The present invention is a dual chamber gas exchange device. The dual chamber gas exchanger increases the efficiency of gas exchange, such as oxygen and carbon dioxide, and has relatively low pressure loss, good biocompatibility, and unique flexibility, but requires minimal volume and blood contact surface. The dual chamber gas exchanger provides optimal blood flow path options and increases the efficiency of gas transfer in the inner and outer fiber bundles. The dual chamber gas exchanger also reduces the amount of oxygen required for oxygen transfer to the blood and carbon dioxide removal from the blood simultaneously. The reduced oxygen requirements and reduced size and weight of the dual chamber gas exchanger further expand the range of uses. For example, the dual chamber gas exchanger can be operated with a small portable oxygen concentrator with low power consumption to provide the necessary sweep gas for oxygen transfer and carbon dioxide removal, such as in ambulatory use.

[0067] Moreover, the dual chamber gas exchanger is further configured to enhance gas exchange using an active mixing mechanism. The active mixing mechanism uses the inner fiber bundle and the outer fiber bundle to reduce boundary layer effects in blood flow and improve gas exchange efficiency. The middle housing and the inner fiber bundle form a cylindrical or conical space configured to enhance blood-membrane interaction by allowing high momentum blood flow in the space between the outer surface of the membrane and the inner housing wall such that the blood encounters lower flow resistance, increased turbulence, and increased mixing after passing through the outer fiber bundle and before entering the inner fiber bundle. Thus, the dual chamber gas exchanger mixes blood without introducing unnecessary high shear rates or stagnation zones, as in typical blood oxygenation devices. Furthermore, the dual chamber gas exchanger includes fewer components than a typical blood oxygenation device. The dual chamber gas exchanger is configured to improve maintainability and operability compared to a typical blood oxygenation device by increasing access to joints and coupling areas.

[0068] While the above is a complete description of the preferred embodiments of the present invention, various alternatives, modifications, and equivalents may be used. Accordingly, the above description should not be taken as limiting the scope of the invention, which is defined by the appended claims.

Claims

1. 1. A blood oxygenator comprising: a housing having a blood inlet, a blood outlet, a stripping gas inlet, an oxygenation gas inlet, and at least one gas outlet; an oxygenator fiber bundle disposed within the housing and configured such that blood flows through a blood flow region of the oxygenator fiber bundle in a predetermined path from the blood inlet to the blood outlet; the stripping gas inlet is configured to direct a flow of stripping gas through a stripping region of the oxygenator fiber bundle to the at least one gas outlet, and the oxygenation gas inlet is configured to direct a flow of oxygenation gas through an oxygenation region of the oxygenator fiber bundle to the at least one gas outlet; A blood oxygenator wherein a stripping gas region of the oxygenator fiber bundle is upstream of an oxygenation region of the oxygenator fiber bundle.

2. 10. The blood oxygenator of claim 1, wherein the fiber bundle is cylindrical and at least a portion of the blood flow passage is radially inward or radially outward.

3. 10. The blood oxygenator of claim 1, wherein the fiber bundle is cylindrical and at least a portion of the blood flow path follows a circular path.

4. The blood oxygenator of claim 1 , wherein at least a portion of the blood flow paths are unidirectional across the oxygenator fiber bundle.

5. 2. The blood oxygenator of claim 1, wherein the fiber bundle is cylindrical and an outer portion of the blood flow path follows an annular path and an inner portion follows a radially inner path.

6. 6. The blood oxygenator of claim 5, wherein the blood inlet feeds the outer portion and the inner portion feeds the blood outlet.

7. 7. The blood oxygenator of claim 6, wherein the stripping region is at least partially disposed in the outer portion of the blood flow path and the oxygenation region is at least partially disposed in the inner portion of the blood flow path.

8. 6. The blood oxygenator of claim 5, wherein the blood inlet feeds the inner portion and the outer portion feeds the blood outlet.

9. 9. The blood oxygenator of claim 8, wherein the stripping region is at least partially disposed in the interior portion of the blood flow path and the oxygenation region is at least partially disposed in the exterior portion of the blood flow path.

10. 6. The blood oxygenator of claim 5, further comprising a cylindrical wall separating an outer portion and an inner portion of a cylindrical fiber bundle, wherein blood flows from the blood inlet through an axial opening in the housing to the outer portion of the fiber bundle, flows annularly through the outer portion of the fiber bundle through the axial opening in the cylindrical wall, and enters a distribution ring surrounding the inner bundle, from which blood flows radially inward through the inner portion of the fiber bundle to an axial collection area along a central axis of the inner portion of the fiber bundle.

11. 2. The blood oxygenator of claim 1, wherein the oxygenating fiber bundle has a cross-sectional area, the stripping region receiving stripping gas from the stripping gas inlet has an inlet area that comprises 20%-80% of the cross-sectional area, and the oxygenating region receiving oxygenation gas from the oxygenation gas inlet has an inlet area that comprises 80%-20% of the cross-sectional area.

12. 12. The blood oxygenator of claim 11, further comprising a manifold splitter that directs stripping gas from the stripping gas inlet to the stripping region of the oxygenated fiber bundle and directs oxygenation gas from the oxygenation gas inlet to the oxygenation region of the oxygenated fiber bundle.

13. 13. The blood oxygenator of claim 12, wherein the manifold divider is disposed in a manifold that receives stripping gas from the stripping gas inlet and oxygenation gas from the oxygenation gas inlet, the manifold being open to the entire gas inlet side of the oxygenation fiber bundle, and the placement of the manifold divider controls the inlet area of ​​the stripping region that receives stripping gas from the stripping gas inlet and the inlet area of ​​the oxygenation region that receives oxygenation gas from the oxygenation gas inlet.

14. 14. The blood oxygenator of claim 13, wherein the manifold divider is movable.

15. 15. The blood oxygenator of claim 14, wherein the manifold divider is fixed.

16. 10. The blood oxygenator of claim 1, wherein the oxygenation fiber bundle further comprises an upper potting and a lower potting, and the manifold is disposed within the housing adjacent one of the pottings.

17. 2. The blood oxygenator of claim 1, further comprising a blood pump connected to the blood inlet, an oxygenating gas source connected to the oxygenating gas inlet, and a stripping gas source connected to the stripping gas inlet.

18. 1. A method for oxygenating blood, comprising: The method includes the steps of: (1) providing a blood oxygenator having a housing with a blood inlet, a blood outlet, a stripping gas inlet, an oxygenation gas inlet, and at least one gas outlet; and (2) an oxygenator fiber bundle disposed within the housing; flowing blood through the blood inlet, through the oxygenator fiber bundle, and to the blood outlet; flowing a stripping gas through the stripping gas inlet and an oxygenated gas through the oxygenated gas inlet, wherein the stripping gas flows through a stripping region of the oxygenator fiber bundle to the at least one gas outlet and the oxygenated gas flows through an oxygenation region of the oxygenator fiber bundle to the at least one gas outlet; A method wherein a stripping gas region of the oxygenator fiber bundle is upstream of an oxygenation region of the oxygenator fiber bundle.

19. 20. The method of claim 18, wherein the blood travels in an annular flow path through the stripping region of the oxygenator fiber bundle.

20. 20. The method of claim 19, wherein the blood travels in a radially inward flow path through the oxygenation region of the oxygenator fiber bundle.

21. 20. The method of claim 19, wherein the blood moves in a straight line direction through the stripping region and the oxygenation region of the oxygenator fiber bundle.

22. 20. The method of claim 18, wherein the blood moves through the oxygenator fiber bundle with a substantially uniform blood flow distribution.

23. 20. The method of claim 18, wherein the fiber bundle has a cross-sectional area, the stripping zone receiving stripping gas from the stripping gas inlet has an inlet area that comprises 20% to 80% of the cross-sectional area, and the oxygenation zone receiving oxygenation gas from the oxygenation gas inlet has an inlet area that comprises 80% to 20% of the cross-sectional area.

24. 24. The method of claim 23, further comprising moving a manifold divider that directs stripping gas from the stripping gas inlet to the stripping zone of the oxygenated fiber bundle and directs oxygenated gas from the oxygenated gas inlet to the oxygenation zone of the oxygenated fiber bundle to adjust the relative areas of the stripping zone and the oxygenation zone of the oxygenated fiber bundle.

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