WO2024159000A2

WO2024159000A2 - Blood gas exchanger for multifunctional respiratory support

Info

Publication number: WO2024159000A2
Application number: PCT/US2024/012927
Authority: WO
Inventors: Zhongjun Wu; Bartley Griffith; Jiafeng ZHANG; Ge HE
Original assignee: University Of Maryland, Baltimore
Priority date: 2023-01-25
Filing date: 2024-01-25
Publication date: 2024-08-02
Also published as: WO2024159000A3

Abstract

The device of the present invention includes an integrated multi-chamber gas exchanger that is configured for increased flexibility, scalability, and mobility for various clinical applications, such as in an extracorporeal membrane oxygenation (ECMO) circuitry, in a heartlung machine for cardiopulmonary support during cardiothoracic surgery, as a temporary respiratory assist device for patients with lung failure, and the like. The gas exchanger/oxygenator features two sweep gas flow paths and two consecutive hollow fiber membrane bundles enclosed in a housing structure with multiple blood flow and sweep gas distribution mechanisms and various combinations of blood flow paths through the two consecutive hollow fiber membrane bundles. The multi-chamber gas exchanger/oxygenator provides the improved flexibility in the choices of the geometries and blood flow patterns of the two hollow fiber membrane bundles and the eases complications in manufacturing. The multi-chamber gas exchanger/oxygenator includes an outer housing, an intermediate blood connector between the two hollow fiber membrane bundles, two gas exchange hollow fiber membrane bundles, a blood inlet, a blood outlet, a gas inlet for each hollow fiber membrane bundle, and gas outlets for the two hollow fiber membrane bundles.

Description

BLOOD GAS EXCHANGER FOR MULTIFUNCTIONAL RESPIRATORY SUPPORT

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Patent Application No. 63/441,030 titled “BLOOD GAS EXCHANGER FOR MULTIFUNCTIONAL RESPIRATORY SUPPORT,” filed by the inventors herein on January⁷ 25, 2023, the specification of which is incorporated herein by reference in its entirety⁷.

GOVERNMENT LICENSE RIGHTS

This invention was made with government support under Grant numbers HL118372 and HL141817 awarded by the National Institutes of Health. The government has certain rights in the invention.

FIELD OF THE INVENTION

This invention relates generally to blood gas exchanges devices, and more particularly to a blood gas exchanger for extracorporeal respiratory support or cardiopulmonary support.

BACKGROUND

Chronic lung disease is a leading cause of death in the United States. Annually, 400,000 deaths are attributed to pulmonary causes despite $ 154 billion in annual expenditures to address such conditions. Mortality due to chronic respiratory diseases increased 18% from 1990 to 2017. However, there is a lack of effective treatment for early acute and initially more clinically subtle disease leading to an inexorable progression to end stage lung disease (ESLD). At present, irreversible and chronic lung disease can only be treated by lung transplantation. However, the availability of donor organs limits the number of lung transplant procedures, and patients are often living a poor quality of life.

Extracorporeal membrane oxygenation (ECMO) systems have been used as a rescue treatment for patients suffering from critical respiratory /lung failure and waiting for lung transplantation. ECMO is also widely used for patients suffering cardiac or cardiopulmonary failure. Current gas exchangers/oxygenators in ECMO systems are typically made with hollow fiber membrane (HFM) devices, in which oxygen and carbon dioxide transfer through the fiber lumen between sweep gas and blood. Although multiple studies have show n that patients with ECMO support had better survival compared with mechanical ventilators, many problems are seen in current oxygenators.

Current ECMO systems are typically designed for bedside use, and the oxygenators are by default to be used with unlimited sweep gas supplies (i.e., wall oxygen in a hospital or large gas tanks). Removing carbon dioxide from the oxygenator typically requires that the ratio of sweep gas flow rate to blood flow rate is higher than 1 : 1 and the sweep gas should be nearly free of carbon dioxide. Therefore, current oxygenators typically can only be used to transfer oxygen and remove carbon dioxide simultaneously w hen a high flow' rate of oxygen is available (sustainable). As a result, current HFM oxygenators are inadequate in situations where oxygen supply is limited, such as field deployment/transport, ambulation, home settings, or the recent COVTD-19 pandemic centers where oxygen became unavailable due to increasing consumption. Oxygen sources are particularly a challenge in ambulatory applications. Patients must use bulky oxygen tanks for high sweep gas flow rates to achieve both O2 and CO2 exchange. Using oxygen as the sweep gas at high flow rate is very expensive. At a sweep gas flow rate of 1 : 1 to blood flow rate, only 5% of the oxygen is delivered to patients at a normal blood flow rate of 5.0 L/min. In the situation when much higher oxygen flow rates are required to remove carbon dioxide concurrently, the percentage of oxygen utilization can be lower. In certain applications, adequate air can be a cheap sweep gas to remove carbon dioxide.

Additionally, studies have shown that active rehabilitation during ECMO bridge to transplant in adults was associated with shorter duration of post-transplant ventilation, ICU stay, and hospital stay. The total hospital cost for ambulatory ECMO patients is 22% less than that associated with non-ambulatory patients. For patients to move and exercise, the oxygenators need to be compact and safe, with low oxygen sweep gas consumption, capable of meeting patients’ possible rising demand for oxygen deliver}' and carbon dioxide removal simultaneously during ambulation. It is possible to use two oxygenators in an ECMO system for separate oxygen delivery' and carbon dioxide removal, but such a configuration will increase the system complexity. The safety and biocompatibility can be compromised as well because large HFM surface area, extra connectors and tubing, and an increased pumping requirement to overcome higher blood flow resistance may cause increased thrombosis risks and potential for tubing disconnection. Clearly, an innovative oxygenator that can fulfill patients’ needs for simultaneous, customized oxygen transfer and carbon dioxide removal, and that is easily capable of ambulation and flexibility' for various applications, is needed.

SUMMARY OF THE INVENTION

Provided herein according to several exemplary configurations is a novel ambulatory' gas exchanger / oxygenator configured with dual chamber blood flow paths with dual sweep gas paths and other extemal/intemal structures. Gas exchangers / oxygenators configured in accordance with certain aspects of the invention may provide one or more of the following benefits: (i) increase the efficiency of gas exchange and sweep gas usage, which can improve the gas exchanger’s performance and also reduce the oxygen waste; (ii) provide significant flexibility for various clinical applications including, but not limited to. field deployment / transport, ambulation, and home setting with various choices of sweep gases for the two chambers; (iii) provide significant flexibility for manufacturing processes, in that the hollow fiber membrane bundles (HFM) can be of the same or different geometries and the HFM bundles can be potted separately; (iv) provide optimal choices of the HFM bundles, which will result in a compact gas exchanger / oxygenator and low pumping requirement (low pressure loss); and (v) integrate the gas exchanger / oxygenator with a blood pump and portable oxygen source (i.e., oxygen concentrator) for increased mobility (compared to ty pical devices). A blood gas exchanger configured in accordance with certain aspects of the invention may provide flexibility for clinical applications, meet demands of patients for mobility and ambulation, and improve patients’ quality of lives (compared to typical devices).

A gas exchanger / oxygenator configured in accordance with certain aspects of the invention may further provide increased flexibility, scalability, and functionality for various clinical applications, such as in an extracorporeal membrane oxygenation (ECMO) circuitry, in a heart-lung machine for cardiopulmonary support during cardiothoracic surgery, as the gas exchange unit of an integrated pump-oxygenator, and/or as a respiratory assist device for patients with lung failure, cardiopulmonary failure, and respiratory support failure, cardiac failure, and the like. In accordance with certain aspects of an embodiment, the gas exchanger / oxygenator includes gas exchange HFM bundles enclosed at each end of the blood gas exchanger / oxygenator in a housing structure. The structure can include separate chambers to isolate gas flow and form sequential blood flow with various blood flow distribution and gas distribution mechanisms. In certain configurations, the gas exchanger I oxygenator may include: (i) an outer housing; (ii) a blood inlet; (iii) a blood outlet; (iv) a first HFM bundle and a second HFM bundle (e.g., each bundle having potting that separates the bundles); (v) two gas inlets; (vi) at least one gas outlet or exhaust; (vii) an intermediate connector through which the blood leaves one HFM bundle and enters another HFM bundle (e.g.. leaves the first HFM bundle and enters the second HFM bundle); (viii) an exhaust gas chamber between the HFM chambers; and (ix) two gas distribution chambers. Likewise in certain configurations, the gas exchanger I oxygenator includes blood deflectors located in a middle portion of one or more of the of the HFM bundles to guide blood flow and reduce stagnation. Likewise in certain configurations, the gas exchanger / oxygenator includes an intermediate housing to form different blood flow paths inside at least one of the HFM bundles. Further in certain configurations, the gas exchanger / oxygenator includes a heat exchanger. Still further in certain configurations, the gas exchanger / oxygenator may be configured to manipulate the concentration of the sweep gas that is exposed to the patient’s blood to transfer oxygen and to remove carbon dioxide, such as sweep gases that include oxygen, blended oxygen and atmospheric air, other medical gases, and the like. Thus, the gas exchanger / oxygenator is preferably configured so that the blood is first exposed to a stripping gas in a first HFM bundle to remove carbon dioxide and exposed to an oxygenation gas in a second HFM bundle to receive oxygen.

The HFM bundles are centrally located in the outer housing and further include fibers, and potting in contact with the fibers, such as in certain configurations an upper potting and a lower potting at opposite ends of the HFM bundle. The upper potting and lower potting hold the fibers within the outer housing and separate the two HFM bundles to provide isolated gas flow paths and blood flow paths. In certain configurations, the potting may extend circumferentially around the HFM bundle. Likewise in certain configurations, the fibers are formed of gas exchange membranes.

In one embodiment, the first HFM bundle includes a blood distributor configured as a spiral volute wrapping around the inner surface of the housing. The blood distributor is coupled to the blood inlet located between the upper potting and lower potting of the first HFM bundle. The blood distributor is configured to gradually discharge blood into an annular space formed between the radially inward surface of the outer housing and the radially outward surface of the first HFM bundle and provides a uniformly pressurized annular blood volume surrounding the first HFM bundle, and such that blood flows radially through gas exchange membranes of the first HFM bundle in a uniform manner.

In certain configurations, the inward surface of the outer housing and the outward surface of the first HFM bundle are in close contact without an annular space between them. The blood distributor may be configured as a spiral volute wrapping around the inner surface of the housing near the upper potting or lower potting and discharge blood around the outer fiber bundle such that it creates a pressurized annular blood volume surrounding the outer fiber bundle, while an intermediate housing is in close contact with the inward surface of the first HFM bundle with a narrow annular gate opening located in the opposite potting side of the HFM bundle as the blood distributor. The configuration may allow blood to flow axially through gas exchange membranes of the first HFM bundle.

Further in certain configurations, the blood distributor may include a rectangular gate opening, or first vertical gate opening (e.g., a gate opening having a cross-sectional shape other than rectangular, such as elliptical or conical), at one side of the outer housing from the upper potting to the lower potting. The first vertical gate opening is typically a vertically oriented slot configured to couple the blood inlet to discharge the incoming blood to the first HFM bundle. An intermediate housing is in close contact with an inward surface of the first HFM bundle and a second vertical gate opening is located on the opposite side of the first HFM bundle relative to the first vertical gate opening on the outer housing. Thus, the blood generally flows circumferentially through gas exchange membranes of the first HFM bundle.

In certain configurations, a cylindrical space may be formed by a radially inward surface of the first HFM bundle. A blood deflector may be located at the center of the cylindrical space to help guide the blood exiting the first HFM bundle and avoid stagnation. Further in certain configurations, an intermediate housing may be configured to selectively provide circumferential or axial flow through the first HFM bundle. A flow deflector may be configured to avoid stagnation.

The gas exchanger / oxygenator further includes a second HFM bundle. The second HFM bundle may be generally concentric with the first HFM bundle and located at the other end of the outer housing (with respect to an inlet of the first HFM bundle), and thus positioned serially with respect to blood flow through the first and second HFM bundles, with the second HFM bundle likewise including fibers and potting, such as an upper potting and a lower potting. In certain configurations, the second HFM bundle may not be concentric with the first HFM bundle but still located at the other end of the outer bundle (with respect to an inlet of the first HFM bundle).

Certain configurations of the gas exchanger / oxygenator may further include an intermediate connector, typically of a circularly symmetrical geometry such as a cylinder and cone, that is configured to substantially provide a channel for blood to flow betw een the first HFM chamber to the second HFM chamber. Thus, the intermediate connector is generally located between the first HFM chamber and the second HFM chamber and may be concentric w ith at least one of the first HFM bundle or second HFM bundle. In certain configurations, the intermediate connector may provide for manual connection of the first HFM bundle to the second HFM bundle in a modular configuration when the exchange / oxygenator is to be put into use, thus allowing a physician or other operator to customize the configuration to allow blood and sweep gas flows that are optimally selected for a given clinical situation.

Certain configurations may include an exhaust gas chamber between the first and second HFM bundles, formed by the inward surface of the outer housing, potting of both first and second HFM bundles, and the intermediate connector. At least one exhaust gas outlet is configured in the exhaust gas chamber for the exhaust gases through the first and second HFM bundles to exit. In certain configurations, the exhaust gas chamber may be shared by the two HFM bundles. In other configurations, the exhaust gas chamber may be separated and each HFM bundle may have its own exhaust gas chamber adjacent to its potting. In other configurations, the oxygenator may further include a one-way valve that divides the exhaust gas chamber such that exhaust oxy genation sweep gas from the second HFM bundle only blends with the stripping gas from the first HFM bundle. This can increase the oxygen transfer while removing carbon dioxide.

Again in certain configurations, the second HFM bundle may be configured to allow blood through the intermediate connector to flow radially through the gas exchange membrane of the second HFM bundle in a uniform manner. A cylindrical space may be formed by the radially inward surface of the second HFM bundle and the annular space formed between the radially inward surface of the outer housing and the radially outward surface of the second HFM bundle provide a uniformly distributed pressure environment to allow a uniform radial flow. A blood outlet may be located at the outer housing to return the blood to a patient through a cannula. A blood deflector may be configured to avoid stagnation, such as described above.

Likewise in certain configurations, an intermediate housing may be configured to be in contact with the inward surface of the second HFM bundle with an annular gate opening located near a potting side of the second HFM bundle, and a blood collector may be configured as a spiral volute wrapping around the inner surface of the outer housing at the opposite potting side of the second HFM bundle. This configuration allows blood to flow axially through the gas exchange membranes of the second HFM bundle. A blood deflector may be configured to avoid stagnation. The blood collector may be configured as a circular volute.

Further in certain configurations, a first vertical gate opening (e.g., a rectangular vertical gate opening, although a gate opening having a cross-sectional shape other than rectangular, such as elliptical or conical, may likewise be employed) is configured at one side of the intermediate housing from the upper potting to the lower potting. Another second rectangular gate opening (e.g., a gate opening again having a rectangular cross-sectional shape or a cross-sectional shape other than rectangular, such as elliptical or conical) is configured at the opposite side of the outer housing from the upper potting to the lower potting. Thus, the blood through the intermediate connector flows circumferentially across the gas exchange membranes of the second HFM bundle.

In still further configurations, the second HFM bundle may further include fibers and an annular potting extending circumferentially around the HFM bundle. The annular potting holds the fibers within the outer housing. An inner housing plate is configured to separate the second HFM bundle from the exhaust gas chamber with the potting of the first HFM bundle, and connect with the intermediate connector to guide blood flowing transversely through the second HFM bundle. A blood outlet is located at the other end of the second HFM bundle and returns oxygenated blood to patients via a cannula. A gas inlet and gas outlet are located on each side of the outer housing for oxygenation gas to flow through the fiber membranes of the second HFM bundle. Brackets with blood deflectors may be configured to help hold the fibers and avoid stagnation.

The gas inlets are preferably configured to provide separate gas passages for gases, such as oxygen and/or air (or air blended with oxygen), to enter the fibers. The gas inlets are positioned on each end of the outer housing. In certain configurations, one of the gas inlets on the second HFM bundle is positioned at the side of the outer housing instead of the end (with respect to the gas inlet of the second HFM bundle).

The at least one gas outlet is configured to provide gas passages for gases, such as the oxygen and/or air (or air blended with oxygen) to leave the fibers. The at least one gas outlet is preferably generally located at the middle of the outer housing where the exhaust gas chamber is formed between the two HFM bundles. In one embodiment having more than one gas outlet, each gas outlet of the second HFM bundle is preferably positioned separately with respect to other gas outlets (e.g., distributed around the second HFM bundle) at the side of the outer housing away from an axial middle area of the second HFM bundle.

In certain configurations, the blood gas exchanger / oxygenator may include at least one blood sample port that is configured to allow external sampling of the blood within the blood gas exchanger. 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 affixed to the blood outlet, and a temperature port affixed to the blood outlet. Likewise in certain configurations, the blood gas exchanger / oxygenator may include a blood gas sensor configured to detect conditions of the blood.

Still further in certain configurations, a heat exchanger may be configured to adjust the blood temperature in the blood gas exchanger / oxygenator. The heat exchanger may include a cylindrical annulus of heat exchange elements around at least one of the first HFM bundle or the second HFM bundle. The cylindrical annulus is formed of a plurality of capillaries that are potted to one of the HFM bundles. In certain configurations, the heat exchanger may be positioned downstream of the second HFM bundle and potted with the second HFM bundle. The capillaries may have lumens that are opened to form a separated flow path for a heat transfer fluid (i.e. water).

For example, a blood oxygenator according to certain aspects of an embodiment can include a housing including a blood inlet and a blood outlet; a first oxygenator fiber bundle and a second oxygenator fiber bundle disposed within the housing at each end of the housing and configured so that blood flows through the two bundles in a predetermined path from the blood inlet to the blood outlet; and an intermediate connector between the two bundles directing the blood flowing from the first oxygenator fiber bundle to the second oxygenator fiber bundle; wherein the first oxygenator fiber bundle is upstream of the second oxygenator fiber bundle.

Furthermore, the first oxygenator fiber bundle and the intermediate connector can be concentric with the second oxygenator fiber bundle. Still further, the housing can include a stripping gas inlet, an oxygenation gas inlet, and at least one gas outlet. Still yet further, each oxygenator fiber bundle can include an upper potting and a lower potting. Furthermore, the exhaust gas chamber can be enclosed by the housing, the first oxygenator fiber bundle and second oxygenator fiber bundle, and the intermediate connector. Still further, the exhaust gas chamber can be coupled to the at least one gas outlet.

Furthermore, the stripping gas inlet can be in fluid communication with a gas chamber located at the end of the first oxygenator fiber bundle opposite to the middle exhaust gas chamber, and configured to direct a flow of stripping gas through the first oxygenator fiber bundle to the at least one gas outlet.

Furthermore, the oxygenation gas inlet can be in fluid communication with a gas chamber located on the end of the second oxygenator fiber bundle opposite to the middle exhaust gas chamber and configured to direct a flow of oxygenation gas through the second oxygenator fiber bundle to the at least one gas outlet. Still further, the blood inlet can feed the first oxygenator bundle and the second oxygenator bundle can feed the blood outlet.

Furthermore, the blood gas oxygenator can include a blood pump connected to the blood inlet, an oxygenation source connected to the oxygenation gas inlet, and a stripping gas source connected to the stripping gas inlet.

Furthermore, the blood gas oxygenator can include a guide structure (e.g., a blood deflector) in a center of at least one of the first oxygenator fiber bundle or the second oxygenator fiber bundle. Still further, the guide structure may be integrated with the intermediate housing adjacent to the inner surface of the first oxygenator fiber bundle or second oxygenator fiber bundle.

Furthermore, the blood gas oxygenator may include a heat exchanger element between the outw ard surface of the first oxygenator fiber bundle or second oxygenator fiber bundle and the inward surface of the housing, or inside the inward surface of the first oxygenator fiber bundle or second oxygenator fiber bundle. Still further, the heat exchanger may be in front of the first oxygenator fiber bundle or second oxygenator fiber bundle or after the first oxygenator fiber bundle or second oxygenator fiber bundle. In some embodiments, the heat exchanger element may be aligned in an axial direction with respect to the blood gas oxygenator, in which blood flows perpendicularly to the fibers in the first oxygenator fiber bundle or second oxygenator fiber bundle.

Furthermore, the first oxygenator fiber bundle and second oxygenator fiber bundle can be cylindrical.

Furthermore, the blood oxygenator can include a blood distributor coupled to the blood inlet and configured as a spiral volute wrapping around an inner surface of the housing between the upper potting and lower potting of the first oxygenator fiber bundle and gradually discharging blood into an annular space between the radially inward surface of the outer housing and the radially outward surface of the first oxygenator fiber bundle between the radially inward surface of the outer housing and the radially outward surface of the first oxygenator fiber bundle.

Furthermore, the blood oxygenator can include a blood distributor coupled to the blood inlet configured as a spiral volute wrapping around the inner surface of the housing near the upper or lower potting of the first oxygenator fiber bundle and gradually discharging blood into an annular gate opening below the upper potting or above the lower potting.

Furthermore, the blood oxygenator can include a blood distributor coupled to the blood inlet discharging blood through a vertical gate opening on the housing at one side of the outer surface of the first oxygenator fiber bundle from the upper potting to the lower potting. Still further, the blood distributor can include a central lumen in the first oxygenator fiber bundle configured to receive blood that has traveled through the first oxygenator fiber bundle, and to direct blood to the intermediate connector. Still yet further, the blood oxygenator can include an intermediate housing adj acent to the inner surface of the first oxygenator fiber bundle with an annular gate opening at an opposite end of the first oxygenator fiber bundle where blood exits the first oxygenator fiber bundle and is coupled to the intermediate connector. Still further, the intermediate housing can be adjacent to the inner surface of the first oxygenator fiber bundle with a vertical gate opening at the opposite side of the first oxygenator fiber bundle from the upper potting to the lower potting where blood exits the first oxygenator fiber bundle and is coupled to the intermediate connector.

Furthermore, the blood oxygenator can include a central lumen in the second oxygenator fiber bundle configured to receive blood that has traveled through the intermediate connector and the first oxygenator fiber bundle, and to direct blood to flow radially outward through the second oxygenator fiber bundle in a generally uniform manner.

Furthermore, blood oxygenator can include an intermediate housing adjacent to the inner surface of the second oxygenator fiber bundle with an annular gate opening near the upper or lower potting to discharge blood that has traveled through the intermediate connector into the second oxygenator fiber bundle.

Furthermore, the blood oxygenator can include an intermediate housing adjacent to the inner surface of the second oxygenator fiber bundle with a gate opening from the upper potting to the lower potting of the second oxygenator fiber bundle to discharge blood that has traveled through the intermediate connector into the second oxygenator fiber bundle. Still further, the blood oxygenator can include an annular space between the housing and the outer surface of the second oxygenator fiber bundle and a blood outlet attaching to the housing to collect the blood in the annular space that has travelled through the second oxygenator fiber bundle. Still yet further, the blood oxygenator can include a blood outlet connected to an annular gate opening adj acent to the outer surface of the second oxygenator fiber bundle and located at the opposite end of the intermediate housing annular gate opening. Further, the blood oxygenator can include a blood outlet connected to a gate opening adjacent to the outer surface of the second oxygenator fiber bundle, from the upper potting to the bottom potting of the second oxygenator fiber bundle, and located at the opposite side of the intermediate housing gate opening.

Furthermore, at least one or both of the first oxygenator fiber bundle or second oxygenator fiber bundle can include an annular potting, an inner housing plate, and a fiber bundle bracket at each end of the bundle. Still further, each of the first oxygenator fiber bundle or second oxygenator fiber bundle can include a stacked hollow fiber mat having layers of fibers in which (i) each layer of fibers is stacked on top of another layer of fibers, and (ii) layers of fibers can be oriented parallelly with respect to other layers. In some configurations, layers of fibers in adjacent layers are oriented at an angle between approximately 20 degrees and approximately 90 degrees with respect to each other. Still yet further, the blood oxygenator can have an intermediate housing configured as a conical shape with an opening in the center connecting to the intermediate connector. A conical space is formed between the inner housing plate and a fiber bundle bracket that is attached to the stacked hollow fiber mat, and the height of the conical space gradually increases radially inward. Still further, the blood oxygenator can include a blood collector attached to the housing to seal an end of the fiber bundle mat and form the conical space with a fiber bundle bracket. The height of the conical space gradually increases radially inward (e.g.. to a center where the blood outlet is located). Still further, the housing and the annular potting of the oxygenator fiber bundle can form an annular space, in which the annular space is separated into a sweep gas chamber and an exhaust gas chamber so that only one end of each fiber in the fiber mat is placed in the sweep gas chamber while the other end of each fiber in the fiber mat is placed in the exhaust gas chamber. Still yet further, the sweep gas chamber can include a gas inlet and the exhaust gas chamber can include at least one gas outlet.

Furthermore, the flow path of the blood oxygenator in the first oxygenator bundle or second oxygenator bundle is oriented to provide flow in at least one of: radially inward, radially outward, axial parallel to the fibers, circumferential, or axial perpendicular to the fibers with respect to other fibers.

Furthermore, a method for oxygenating blood can include providing a blood oxygenator having (i) a housing with a blood inlet, a blood outlet, a stripping gas inlet, an oxygenation gas inlet, and at least one gas outlet, (ii) two fiber bundles disposed within the housing and at each end of the housing, and (iii) an intermediate connector and intermediate housing(s) to direct the blood flow from the first oxygenator fiber bundle to the second oxygenator fiber bundle, and flowing blood through the blood inlet, through the first oxygenator fiber bundle, intermediate connector, and the second oxygenator fiber bundle, and exit from the blood outlet. Further, the method includes flowing a stripping gas through the stripping gas inlet and an oxygenation gas through the oxygenation gas inlet, wherein the stripping gas flows through the first bundle to the at least one gas outlet and the oxygenation gas through the second bundle to the at least one gas outlet and the first oxygenator fiber bundle is upstream of the second oxygenator fiber bundle.

In accordance with certain aspects of an embodiment of the invention, a blood gas exchanger is providing, comprising a housing having a first blood flow section and a second blood flow section, wherein the second blood flow section is positioned serially to the first blood flow section, a first hollow fiber membrane bundle in the first blood flow section, a second hollow fiber membrane bundle in the second blood flow section, an exhaust gas chamber serially positioned between the first blood flow section and the second blood flow section, and an intermediate connector serially between the first blood flow section and the second blood flood section and extending through the exhaust gas chamber, the intermediate connector defining a blood flow channel from the first fiber bundle to the second fiber bundle.

Still other aspects, features and advantages of the invention are readily apparent from the following detailed description, simply by illustrating a number of particular embodiments and implementations, including the best mode contemplated for carrying out the invention. The invention is also 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.

BRIEF DESCRIPTION OF THE DRAWINGS

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 similar elements, and in which:

FIG. 1 is a side perspective view of a blood gas exchanger in accordance with certain aspects of an embodiment of the invention. FIG. 2 is a cross-sectional view of the blood gas exchanger of FIG. 1.

FIG. 3 is a cross-sectional view of the blood gas exchanger of FIG. 1 and depicting blood flow paths.

FIG. 4 provides top cross-sectional views of the blood gas exchanger of FIG. 1 and depicting blood flow paths in a lower or first section of the blood gas exchanger (left) and in an upper or second section of the blood gas exchanger (right).

FIG. 5 shows a blood flow⁷ field cross-sectional view in the blood gas exchanger of FIG. 1, depicting a top cross-sectional view of the radial flow path at 5.0 L/min (left), and a side cross-sectional view⁷ of the radial flow path at 5.0 L/min (right) (generated from computational fluid dynamics modeling).

FIG. 6 shows gas transfer in the blood gas exchanger of FIG. 1, depicting a side cross- sectional view of oxygen saturation (SO2) distribution at 5.0 L/min) (generated from computational fluid dynamics modeling).

FIG. 7 is a side perspective view⁷ of a blood gas exchanger in accordance with further aspects of an embodiment of the invention.

FIG. 8 is a cross-sectional view of the blood gas exchanger of FIG. 7.

FIG. 9 is a cross-sectional view of the blood gas exchanger of FIG. 7 and depicting blood flow paths.

FIG. 10 is a side perspective view of a blood gas exchanger in accordance with further aspects of an embodiment of the invention.

FIG. 11 is a cross-sectional view of the blood gas exchanger of FIG. 10.

FIG. 12 is a cross-sectional view of the blood gas exchanger of FIG. 10 and depicting blood flow paths.

FIG. 13 provides top cross-sectional views of the blood gas exchanger of FIG. 10 and depicting blood flow paths in a lower or first section of the blood gas exchanger (left) and in an upper or second section of the blood gas exchanger (right).

FIG. 14(a) shows a side perspective view of an outer housing for use in a blood gas exchanger configured according to certain aspects of the invention.

FIG. 14(b) shows a side perspective view of an intermediate housing for use in a blood gas exchanger configured according to certain aspects of the invention.

FIG. 15 is a cross-sectional view of a blood gas exchanger in accordance with further aspects of an embodiment of the invention.

FIG. 16 is a cross-sectional view of the blood gas exchanger of FIG. 15 and depicting blood flow paths.

FIG. 17 provides top cross-sectional views of the blood gas exchanger of FIG. 15 and depicting blood flow paths in a lower or first section of the blood gas exchanger (left) and in an upper or second section of the blood gas exchanger (right).

FIG. 18 is a cross-sectional view of a blood gas exchanger in accordance with further aspects of an embodiment of the invention.

FIG. 19 is a cross-sectional view of the blood gas exchanger of FIG. 18 and depicting blood flow paths.

FIG. 20 provides atop cross-sectional view of the blood gas exchanger of FIG. 18 and depicting blood flow paths in an upper or second section of the blood gas exchanger.

FIG. 21 is a cross-sectional view of a blood gas exchanger in accordance with further aspects of an embodiment of the invention.

FIG. 22 is a cross-sectional view of the blood gas exchanger of FIG. 21 and depicting blood flow paths.

FIG. 23 provides a top cross-sectional view of the blood gas exchanger of FIG. 21 and depicting blood flow paths in an upper or second section of the blood gas exchanger.

FIG. 24 is a side perspective view of a blood gas exchanger in accordance with further aspects of an embodiment of the invention.

FIG. 25 is a cross-sectional view of the blood gas exchanger of FIG. 24.

FIG. 26 is a cross-sectional view of the blood gas exchanger of FIG. 24 and depicting blood flow paths.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following detailed description is provided to gain a comprehensive understanding of the methods, apparatuses and/or systems described herein. Various changes, modifications, and equivalents of the systems, apparatuses and/or methods described herein will suggest themselves to those of ordinary skill in the art.

Descriptions of well-known functions and structures are omitted to enhance clarity and conciseness. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present disclosure. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. Furthermore, the use of the terms a, an, etc. does not denote a limitation of quantity, but rather denotes the presence of at least one of the referenced items.

The use of the terms “first”, “second”, and the like does not imply any particular order, but they are included to identify individual elements. Moreover, the use of the terms first, second, etc. does not denote any order of importance, but rather the terms first, second, etc. are used to distinguish one element from another. It will be further understood that the terms “comprises” and/or “comprising”, or “includes” and/or “including” when used in this specification, specify the presence of stated features, regions, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, regions, integers, steps, operations, elements, components, and/or groups thereof.

Although some features may be described with respect to individual exemplary embodiments, aspects need not be limited thereto such that features from one or more exemplary⁷ embodiments may be combinable with other features from one or more exemplary⁷ embodiments.

In accordance with certain aspects of an embodiment, and with particular reference to the foregoing Figures, a blood gas exchanger 100 featuring multiple (e.g., separate) gas exchange pathways and fiber bundles is provided to allow various clinical applications of exchanging gases from a patient (such as oxygen and carbon dioxide) while reducing the likelihood of thrombosis, maintaining efficiency and size of the gas exchanger, compared to typical devices. The blood gas exchanger 100 is configured to increase efficiency of gas exchange including oxygen transfer and carbon dioxide removal. The blood gas exchanger 100 is also configured to achieve relatively low blood pressure drop, minimal volume and surface area of fiber bundles, biocompatibility, and flexibility⁷ in utilizing a gas source, such as oxygen and air, compared to typical devices. One exemplary configuration of the blood gas exchanger 100 includes a configurable blood flow path, such as including multiple fiber bundles and gas flow chambers to increase efficiency of gas transfer in fiber bundles. The device also increases the efficiency and flexibility by requiring less oxygen to oxygenate and scrub (e.g., for removing carbon dioxide) from the blood simultaneously, compared to typical devices.

Furthermore, the internal structures of the blood gas exchanger 100 are configured to provide a more favorable hemodynamic environment for flowing blood such that blood encounters lower flow resistance, increased turbulence, and enhanced gas-blood mixing, compared to typical devices. Therefore, the blood gas exchanger 100 is configured to reduce the likelihood of unfavorable high shear stress or stagnation zones. Exemplary configurations of the gas exchanger 100 may require fewer components and increase the maintainability and operability of the blood gas exchanger 100 by including more accessible joints and bonding areas, compared to ty pical devices.

The blood gas exchanger 100 is configured for various applications, such as shortterm support in cardiopulmonary' bypass (CPB) circuit for heart surgeries that require a bloodless field to increase visibility for the surgeon, and/or it can be used in ECMO circuit as a late-stage treatment for patients with advanced lung failure. For example, the blood gas exchanger 100 can include a first fiber bundle 120 to remove carbon dioxide from blood and a second fiber bundle 130 to add oxygen to blood, or both first fiber bundle 120 and second fiber bundle 130 to remove carbon dioxide/add oxygen. Referring to Figures 1, 2, 3, 7, 8, 9, 10, 11, 12, 15, 16, 18, 19, 21, 22, 24, 25 and 26, exemplary configurations of a blood gas exchanger 100 according to aspects of the present invention includes outer housing 110, blood distributor 1 11, first fiber bundle 120, second fiber bundle 130, intermediate housing 150, first flow deflector 113, second flow deflector 115, gas distribution chamber 116, and gas distribution chamber 1 17.

The outer housing 1 10 and intermediate housing 150 that enclose the first fiber bundle 120 and second fiber bundle 130 may have different configurations to allow various combinations of blood flow paths in the first fiber bundle 120 and second fiber bundle 130 (see Figures 1, 2, 3, 7, 8, 9, 10, 11, 12, 15, 16, 18, 19, 21, 22, 24, 25 and 26). For example, the blood flow path in either first fiber bundle 120 or second fiber bundle 130 can be at least one of radial, circumferential, axial or transverse flow paths. The first flow deflector 114 and second flow deflector 115 that are located respectively in the center of the first fiber bundle 120 and second fiber bundle 130 are configured to channel the blood flow from the first fiber bundle 120 to the second fiber bundle 130. In certain exemplary configurations, blood gas exchanger 100 may comprise a modular assembly in which a first blood flow section 112 housing first fiber bundle 120 may be connectable to a second blood flow section 114 having second fiber bundle 130 at intermediate connector 152 when the blood gas exchanger 100 is being prepared for use. In this configuration, blood gas exchanger 100 may be customized to provide the particular blood gas exchange configuration that is best adapted to meet the current clinical needs of a patient.

Referring to Figures 3, 9, 12, 16, 19 and 22, in certain configurations, sweep gas enters the blood gas exchanger 100 through a first gas inlet 118 and a second gas inlet 119 and is exhausted through gas outlet 142. Exhaust gas chamber 140 may comprise a single chamber configured to channel the sw eep gas from both first fiber bundle 120 and second fiber bundle 130 or be separated for channeling the sweep gas from each of first fiber bundle 120 and second fiber bundle 130 independently. Referring to Figure 26, sweep gas may, in certain exemplary configurations, enter the blood gas exchanger 100 through first gas inlet 118 and second gas inlet 1 19 and may exhaust through gas outlets 142 and a second gas outlet 114. Sweep gas used in exemplary embodiments of blood gas exchanger 100 may include air, pure oxygen, a mixture of oxygen and air, a mixture of oxygen and carbon dioxide, or other ventilating gases.

Different combinations of blood flow paths within the first fiber bundle 120 and second fiber bundle 130 may be achieved by configuring the intermediate housing 150 and outer housing 110. For example, blood gas exchanger 100 may employ blood flow patterns through first fiber bundle 120 and second fiber bundle 130 of radial-radial (Figure 3), axial- axial (Figure 9), circumferential-circumferential (Figure 12), axial -circumferential (Figure 16), axial-radial (Figure 19). circumferential-axial (Figure 22), and radial-transverse (Figure 26). It should be noted that other combinations of blood flow patterns, such as radial- circumferential, radial-axial, and circumferential-axial may also be achieved by reversing the intermediate housing 150 and outer housing 110 of the exemplary configurations shown in Figures 15, 18, 21, respectively. The first fiber bundle 120 and second fiber bundle 130 are preferably formed from hollow' fiber membranes (HFM) and are configured to remove carbon dioxide from the blood in the first fiber bundle 120 and add oxygen to the blood in the second fiber bundle 130, or remove carbon dioxide and add oxygen in both fiber bundles 120 and 130. The first fiber bundle 120 and second fiber bundle 130 are located within the center of the outer housing 110 and are separated by the exhaust gas chamber 140.

Referring to Figures 3, 9, 12, 16, 19 and 22, the first fiber bundle 120 is mounted to an upper potting 160 and a lower potting 162 and the second fiber bundle 130 is mounted to an upper potting 164 and a lower potting 166. The lower potting 162 of first fiber bundle 120 and the upper potting 164 of second fiber bundle 130 are configured to receive gas, such as being coupled to first gas inlet 1 18 or second gas inlet 119. The lower potting 162 of first fiber bundle 120 and upper potting 164 of second fiber bundle 130 are located within each side of the outer housing 110. Lower potting 166 of second fiber bundle 130 and upper potting 160 of first fiber bundle 120 are configured to exhaust gas, such as being coupled to gas outlet 142. Lower potting 166 of second fiber bundle 130 and upper potting 160 of first fiber bundle 120 are positioned at the middle portion within the outer housing 110.

In the exemplary configuration shown in Figures 25 and 26, the first fiber bundle 120 is mounted to the upper potting 160 and low er potting 162 while the second fiber bundle 130 is mounted peripherally by an annular potting 168, with a perforated fiber bundle bracket 169 holding the second fiber bundle 130 in place from above and below'. The upper potting 160, lower potting 162, and annular potting 168 are configured to communicate sweep gases into/from the first fiber bundle 120 and the second fiber bundle 130 for oxygen transfer and carbon dioxide removal. There are multiple choices of sweep gases that may be used in either first fiber bundle 120 or second fiber bundle 130. For example, depending on the clinical application, pure oxygen or an oxygen-rich gas can be used to remove carbon dioxide in the first fiber bundle 120 and add oxygen to blood in the second fiber bundle 130. Alternatively, air (e.g., atmospheric air) or a combination of air and oxygen may be used to remove carbon dioxide in the first fiber bundle 120. The sweep gases in first gas distribution chamber 116 and second gas distribution chamber 117 are preferably configured to have independent flow rates and/or gas concentrations (e.g., oxygen concentrations), such that each of first gas distribution chamber 116 and second gas distribution chamber 117 is separated and can be controlled independently. For example, referring to Figures 3, 9, 12, 16, 19 and 22, if the air is chosen as sweep gas injected through first gas inlet 118, its flow rate can be increased independently from another gas source to second gas inlet 119 to increase the carbon dioxide removal from blood in first fiber bundle 120.

Furthermore, and still referring to Figures 3, 9, 12, 16, 19 and 22, the design of two separate flow chambers as described herein allows for flexibly choosing various gas sources for oxygen transfer and carbon dioxide removal. For example, either pure oxygen/oxygen rich gases or air can be injected through first gas inlet 1 18 to remove carbon dioxide in the first fiber bundle 120. In certain configurations, first gas inlet 1 18 and second gas inlet 1 19 may be connected to a commercially available oxygen concentrator or gas tank that can provide continuous sweep gas into the blood gas exchanger 100.

Referring to Figures 3, 9, 12, 16, 19, and 22, there are multiple combinations of the use of first gas distribution chamber 116 and second gas distribution chamber 117 in transferring oxygen to or removing carbon dioxide from blood. For example, both first gas distribution chamber 116 and second gas distribution chamber 117 can be configured to remove carbon dioxide from blood or add oxygen to blood. Alternatively, first gas distribution chamber 116 may be configured to remove carbon dioxide while second gas distribution chamber 117 may be configured to add oxygen. First gas distribution chamber 116 and second gas distribution chamber 117 are positioned below the lower potting 162 and above the upper potting 164, respectively. As shown in the exemplar}' configuration of Figure 26, the transverse blood flow path can be configured such that second gas distribution chamber 116 is positioned outside of the annular potting 168.

Referring to Figures 3, 9, 12, 16, 19 and 22, the open lumen fibers that are embedded in the lower potting 162 and upper potting 164 are positioned to receive sweep gases from the first gas inlet 118 and second gas inlet 119, respectively. In exemplary configurations of blood gas exchanger 100, compressed air flows through gas distribution chamber 116 and enters the first fiber bundle 120 through the fibers (e.g., open lumen) coupled in the lower potting 1 2. The carbon dioxide in venous blood diffuses across outer walls of individual hollow fibers into the compressed air and is exhausted out of the blood gas exchanger 100 through gas outlet 142. Moreover, oxygen or oxygen-rich gas flows through open fiber lumens in the upper potting 164 into the second fiber bundle 130. Blood oxygenation then takes place within the second fiber bundle 130 where oxygen diffuses across individual fibers into venous blood. The oxygen or oxygen-rich gas also exits the blood gas exchanger 100 through gas outlet 142. Therefore, the blood gas exchanger 100 receives and transfers the sweep gases into different fiber bundles for independently oxygenating blood and removing carbon dioxide. Referring to the exemplary configuration of Figure 26, the carbon dioxide is removed in the first fiber bundle 120 in a similar way as in other oxygenator configurations and is exhausted out of the blood gas exchanger 100 through gas outlet 142, while for blood oxygenation in the second fiber bundle 130, the oxygen or oxygen-rich gas exits blood gas exchanger 100 through second gas outlet 144.

Referring to Figures 3. 9. 12. 16. 19. 22 and 26, the outer housing 110 and intermediate housing 150 are configured to achieve various flow paths in first fiber bundle 120 and second fiber bundle f 30. According to the exemplary configurations described herein, there are many different combinations of blood flow paths that can be achieved by choosing different outer housing f 10 configurations (Figures 3, 9, 12, 16, 19 and 22), in addition to the designs and locations of first gate 170 and/or second gate 172, which gates 170 and 172 control blood flow from first fiber bundle 120 to and into second fiber bundle 130. For example, as shown in Figure 9, second gate 172 is configured to have a slot-like shape and is positioned next to the bottom of second fiber bundle 130. When blood passes through second gate 172, it flows axially to the top portion of the second fiber bundle 130 and exits the blood gas exchanger 100 through blood outlet 180. The first gate 170 can also be configured to be positioned next to the top portion of first fiber bundle 120 (Figure 18) such that the blood entering the blood gas exchanger 100 through blood inlet 182 will flow axially first to the first gate 170. The blood distributor 111 (Figure 3, 9. 15, 18 and 25) is configured to help guide blood uniformly flowing into the blood gas exchanger 100.

Referring to Figures 2, 8, 11, 15, 18, 21 and 25, the configured internal structure of the blood gas exchanger 100 allows for a generally uniform pressure distribution in the blood flowing within the blood gas exchanger 100. The uniform pressure distribution consequently causes the blood to flow along a uniform direction through the first fiber bundle 120 and second fiber bundle 130, which has been demonstrated by a non-limiting computational fluid dynamics simulation (Figure 5). The simulation also demonstrates the substantially uniform oxygen transfer in the first fiber bundle 120 and second fiber bundle 130 (Figure 6).

In exemplary configurations, the first fiber bundle 120 and second fiber bundle 130 are cylindrical annulus composed of many microporous hollow fibers (e.g., open lumen), and each of those fibers contains multiple small pores with a diameter of less than 0.1 micron. The membrane fibers are commercially available and have an outer diameter between 250 microns and 400 microns, and a wall thickness of between approximately 30 microns and 50 microns. The porosity of the first fiber bundle 120 and second fiber bundle 130 of exemplar}' configurations ranges between 0.3 and 0.7. Alternatively, coated or skinned hollow fibers may be employed to allow oxygen and carbon dioxide diffusion through a non-porous skin layer of the outer wall of the fibers. In most cases, the fibers are commercially available in a tape configuration whereby individual fibers are arranged to a predetermined configuration (e.g., parallel straight or bias, multi-directional, woven, spaced, etc.) allowing tape wrapping to form a cylindrical or conical-like bundle configuration. Alternatively, fibers can be wrapped or wound like a spool of kite-string.

The first gas inlet 118 and the second gas inlet 119 (Figures 1, 2, 3, 7, 8, 9, 10, 11, 12, 15, 16, 16, 18, 19, 21, 22, 24, 25 and 26) are configured to provide uniform sweep gas in the first fiber bundle 120 and second fiber bundle 130. The blood inlet 182 and blood outlet 180 include respectively inflow and outflow connectors that can be sized to achieve desired blood flow rates and pressure. While other sizes may be used, the blood gas exchanger 100 typically includes 1/4” and 3/8” barbed fittings that receive standard tubing used in ECMO or CPB circuits.

Referring to Figures 14(a) and 14(b), the outer housing 110 and intermediate housing 150 can be divided into different parts for winding and potting the first fiber bundle 120 and second fiber bundle 130 in a separate manner. For example, the second intermediate housing 150(b) is used to support second fiber bundle 130 during the fiber winding process. The second outer housing 1 10(b) halves are then glued together to enclose the wound second fiber bundle 130 for potting. After the second fiber bundle 130 is potted, the first fiber bundle 120 can be potted in a similar way. Finally, the first outer housing 110(a) and second outer housing 110(b) can be coupled (e.g.. such as by a fastener or adhesive) together and the intermediate connector 152 is used to connect the intermediate housings 150(a) and 150(b) to the first fiber bundle 120 and second fiber bundle 130.

The present disclosure describes a blood gas exchanger device. The blood gas exchanger 100 is configured with the purpose of enhancing the efficiency of gas exchange including oxygen transfer and carbon dioxide removal. The blood gas exchanger 100 is also configured to achieve relatively low blood pressure drop, minimal volume and surface area of fiber bundles, good biocompatibility' and greater flexibility' in using a gas source such as oxygen and air, compared to typical devices. The double fiber bundle and gas flow chamber designs enable optimization of blood flow paths and thus increase the efficiency of gas transfer in fiber bundles. Blood gas exchangers configured in accordance with aspects of the invention may achieve the efficiency and flexibility⁷ of using less oxygen for adding oxygen to and removing carbon dioxide from the blood simultaneously.

Furthermore, the internal structures of the blood gas exchanger 100 are configured to provide a favorable hemodynamic environment for flowing blood such that blood encounters lower flow resistance, increased turbulence, and enhanced gas-blood mixing after passing through the first fiber bundle 120 and second fiber bundle 130. Therefore, the blood gas exchanger 100 is configured to reduce the likelihood of unfavorable high shear stress or stagnation zones for blood passing through the exchanger 100. Additionally, the blood gas exchanger 100 includes fewer components than ty pical gas exchanger devices and the joints and bonding area are more easily accessed, which greatly increase the maintainability and operability of the blood gas exchanger 100.

Having now fully set forth the preferred embodiments and certain modifications of the concept underlying the present invention, various other embodiments as well as certain variations and modifications of the embodiments herein shown and described will obviously occur to those skilled in the art upon becoming familiar with said underlying concept. Thus. it should be understood, therefore, that the invention may be practiced otherwise than as specifically set forth herein.

Claims

CLAIMS What is claimed is:

1. A blood gas exchanger, comprising: a housing having a first blood flow section and a second blood flow section, wherein said second blood flow section is positioned serially to said first blood flow section; a first hollow fiber membrane bundle in said first blood flow section; a second hollow fiber membrane bundle in said second blood flow section; an exhaust gas chamber serially positioned between said first blood flow section and said second blood flow section; and an intermediate connector serially between said first blood flow section and said second blood flood section and extending through said exhaust gas chamber, said intermediate connector defining a blood flow channel from said first fiber bundle to said second fiber bundle.

2. The blood gas exchanger of claim 1, further comprising a plurality of first blood flow sections and a plurality of second blood flow sections, wherein said housing is modular, and wherein each of said plurality of said first blood flow sections is connectable to each of said plurality of said second blood flow sections at said intermediate connector.

3. The blood gas exchanger of claim 1, wherein each of said first hollow fiber membrane bundle and said second hollow fiber membrane bundle is in contact with potting at an outer surface of each of said first hollow fiber membrane bundle and said second hollow fiber membrane bundle.

4. The blood gas exchanger of claim 3, wherein said potting further comprises a lower potting on a bottom face of each of said first hollow fiber membrane bundle and said second hollow fiber membrane bundle, and an upper potting on a top face of each of said first hollow fiber membrane bundle and said second hollow fiber membrane bundle.

5. The blood gas exchanger of claim 3, wherein said poting further comprises a lower poting on a botom face of said first hollow fiber membrane bundle and an upper poting on a top face of said first hollow fiber membrane bundle, and an upper poting circumferentially surrounding an outer circumferential wall of said second hollow fiber membrane bundle.

6. The blood gas exchanger of claim 1. further comprising a first gas inlet on said housing positioned to supply gas to a botom end of said first hollow fiber membrane bundle, and a second gas inlet on said housing positioned to supply gas to a top end of said second hollow fiber membrane bundle.

7. The blood gas exchanger of claim 6, further comprising a blood inlet on said first blood flow section having a vertically-aligned gate opening positioned to deliver blood to said first fiber membrane bundle through a vertical opening in said first blood flow section.

8. The blood gas exchanger of claim 7, further comprising a blood outlet on said second blood flow section having a vertically-aligned gate opening positioned to receive blood from said second fiber membrane bundle through a vertical opening in said second blood flow section.

9. The blood gas exchanger of claim 8, further comprising: a first intermediate housing centrally positioned in said first hollow fiber bundle; a second intermediate housing centrally positioned in said second hollow fiber bundle; a first vertical slot in a portion of said first intermediate housing positioned to pass blood from said first hollow fiber bundle into said blood flow channel; and a second vertical slot in a portion of said second intermediate housing positioned to pass blood from said blood flow channel into said second hollow fiber bundle; wherein said first blood flow section is configured to cause a blood flow through said first blood flow section to flow circumferentially through said first hollow fiber bundle, and wherein said second blood flow section is configured to cause a blood flow through said second blood flow section to flow circumferentially through said second hollow fiber bundle.

10. The blood gas exchanger of claim 7, further comprising a blood outlet on said second blood flow section having a spiral volute extending circumferentially around said second fiber membrane bundle.

11. The blood gas exchanger of claim 10, further comprising: a first intermediate housing centrally positioned in said first hollow fiber bundle; a first vertical slot in a portion of said first intermediate housing positioned to pass blood from said first hollow fiber bundle into said blood flow channel; and a second intermediate housing centrally positioned in said second hollow fiber bundle, said second intermediate housing having at least one connecting segment between a lower portion of said second intermediate housing and an upper portion of said second intermediate housing and defining one or more open windows between the lower portion of said second intermediate housing and the upper portion of said second intermediate housing to pass blood from said blood flow channel into said second hollow fiber bundle; wherein said first blood flow section is configured to cause a blood flow through said first blood flow section to flow circumferentially through said first hollow fiber bundle, and wherein said second blood flow section is configured to cause a blood flow through said second blood flow section to flow radially outward through said second hollow fiber bundle.

12. The blood gas exchanger of claim 6, further comprising a blood inlet on said first blood flow section having a spiral volute extending circumferentially around said first fiber membrane bundle and positioned to deliver blood to said first fiber membrane bundle.

13. The blood gas exchanger of claim 12, wherein said spiral volute is positioned to deliver blood into said first fiber membrane bundle at a bottom of said first fiber membrane bundle.

14. The blood gas exchanger of claim 13, further comprising a blood outlet on said second blood flow section having a spiral volute extending circumferentially around said second fiber membrane bundle.

15. The blood gas exchanger of claim 14, further comprising: a first intermediate housing centrally positioned in said first hollow fiber bundle; a first horizontal slot at a top of said first intermediate housing positioned to pass blood from a top of said first hollow fiber bundle into said blood flow channel: and a second intermediate housing centrally positioned in said second hollow fiber bundle, said second intermediate housing having at least one connecting segment between a lower portion of said second intermediate housing and an upper portion of said second intermediate housing and defining one or more open windows between the lower portion of said second intermediate housing and the upper portion of said second intermediate housing to pass blood from said blood flow channel into said second hollow fiber bundle; wherein said blood outlet is positioned at a mid-section of said second blood flow section: and wherein said first blood flow section is configured to cause a blood flow through said first blood flow section to flow axially and radially inward through said first hollow' fiber bundle, and wherein said second blood flow section is configured to cause a blood flow⁷ through said second blood flow' section to flow' radially outw ard through said second hollow' fiber bundle.

16. The blood gas exchanger of claim 14, further comprising: a first intermediate housing centrally positioned in said first hollow fiber bundle; a first horizontal slot at a top of said first intermediate housing positioned to pass blood from a top of said first hollow fiber bundle into said blood flow channel; a second intermediate housing centrally positioned in said second hollow fiber bundle; and a second horizontal slot at a bottom of said second intermediate housing positioned to pass blood from said blood flow channel to a bottom of said second hollow fiber bundle; wherein said blood outlet is positioned at a top of said second blood flow section; and wherein said first blood flow section is configured to cause a blood flow through said first blood flow section to flow axially and radially inward through said first hollow fiber bundle, and wherein said second blood flow section is configured to cause a blood flow through said second blood flow section to flow radially outward through said second hollow fiber bundle.

17. The blood gas exchanger of claim 13, further comprising a blood outlet on said second blood flow section having a vertically-aligned gate opening positioned to receive blood from said second fiber membrane bundle through a vertical opening in said second blood flow section.

18. The blood gas exchanger of claim 17, further comprising: a first intermediate housing centrally positioned in said first hollow fiber bundle; a first horizontal slot at a top of said first intermediate housing positioned to pass blood from a top of said first hollow fiber bundle into said blood flow channel: a second intermediate housing centrally positioned in said second hollow fiber bundle; and a second horizontal slot at a bottom of said second intermediate housing positioned to pass blood from said blood flow channel to a bottom of said second hollow fiber bundle; wherein said blood outlet is positioned at a top of said second blood flow section; and wherein said first blood flow section is configured to cause a blood flow through said first blood flow section to flow axially and radially inward through said first hollow fiber bundle, and wherein said second blood flow section is configured to cause a blood flow through said second blood flow section to flow radially outward through said second hollow fiber bundle.

19. The blood gas exchanger of claim 12, wherein said spiral volute is positioned to deliver blood into said first fiber membrane bundle at a mid-section of said first fiber membrane bundle.

20. The blood gas exchanger of claim 19, further comprising a blood outlet on said second blood flow section having a vertically-aligned gate opening positioned to receive blood from said second fiber membrane bundle through a vertical opening in said second blood flow section.

21. The blood gas exchanger of claim 20, further comprising: a first intermediate housing centrally positioned in said first hollow fiber bundle, said first intermediate housing having at least one connecting segment between a lower portion of said first intermediate housing and an upper portion of said first intermediate housing and defining one or more open windows between the lower portion of said first intermediate housing and the upper portion of said first intermediate housing to pass blood from said first hollow fiber bundle into said blood flow channel; and a second intermediate housing centrally positioned in said second hollow fiber bundle, said second intermediate housing having at least one connecting segment between a lower portion of said second intermediate housing and an upper portion of said second intermediate housing and defining one or more open windows between the lower portion of said second intermediate housing and the upper portion of said second intermediate housing to pass blood from said blood flow channel into said second hollow fiber bundle; wherein said first blood flow section is configured to cause a blood flow through said first blood flow section to flow radially inward through said first hollow fiber bundle, and wherein said second blood flow section is configured to cause a blood flow through said second blood flow section to flow radially outward through said second hollow fiber bundle.

22. The blood gas exchanger of claim 1, further comprising: a first gas inlet on said housing positioned to supply gas to a bottom end of said first hollow fiber membrane bundle; a second gas inlet on said housing positioned to supply gas to an annular space surrounding an outer circumference of said second hollow fiber membrane bundle; and a gas outlet on said housing positioned to receive exhaust gas from said annular space.

23. The blood gas exchanger of claim 22, further comprising a blood outlet on a top wall of said second blood flow section positioned to receive blood from a top side of said second fiber membrane bundle.

24. The blood gas exchanger of claim 23, further comprising a blood inlet on said first blood flow section having a spiral volute extending circumferentially around said first fiber membrane bundle and positioned to deliver blood to said first fiber membrane bundle.

25. The blood gas exchanger of claim 24, wherein said spiral volute is positioned to deliver blood into said first fiber membrane bundle at a mid-section of said first fiber membrane bundle.

26. The blood gas exchanger of claim 25, further comprising: a first intermediate housing centrally positioned in said first hollow fiber bundle, said first intermediate housing having at least one connecting segment between a lower portion of said first intermediate housing and an upper portion of said first intermediate housing and defining one or more open windows between the lower portion of said first intermediate housing and the upper portion of said first intermediate housing to pass blood from said first hollow fiber bundle into said blood flow channel; an inner housing plate forming a wall of said exhaust gas chamber, said inner housing plate having an opening positioned to receive blood from said blood flow channel; a lower perforated fiber bundle bracket positioned adjacent to a bottom planar face of said second hollow fiber bundle; and an upper perforated fiber bundle bracket positioned adjacent to atop planar face of said second hollow fiber bundle; wherein said first blood flow section is configured to cause a blood flow through said first blood flow section to flow radially inward through said first hollow fiber bundle, and wherein said second blood flow section is configured to cause a blood flow through said second blood flow section to flow vertically transverse through said second hollow fiber bundle.