Patent Publication Number: US-2022211925-A1

Title: Oxygenator with wound filter membrane and flow diffuser

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of International Application No. PCT/US2020/055201, filed Oct. 12, 2020, which claims the benefit of and priority to U.S. Provisional Patent Application Ser. No. 62/915,175, filed on Oct. 15, 2019, the disclosures of which are incorporated herein by reference. 
    
    
     BACKGROUND OF THE DISCLOSURE 
     Field of the Disclosure 
     The present disclosure is generally related to an apparatus that allows for the exchange of gases in a liquid sample. More specifically, the disclosure relates to a blood oxygenator having a wound filter membrane and a flow diffuser to allow external oxygen to be incorporated into a blood sample while carbon dioxide is removed from the blood sample. 
     Description of Related Art 
     Blood oxygenators are commonly used to accomplish the gas exchange functions normally performed by the lungs. Conventional blood oxygenators contain a gas exchange medium, such as a filter membrane made from hollow fibers, across which blood is flowed. The filter membrane is connected to an oxygen supply such that oxygen is diffused from the filter membrane into the blood and carbon dioxide is removed from the blood into the filter membrane. 
     Conventional oxygenators are commonly used in medical situations when a patient&#39;s lungs are temporarily disabled and/or incapable of performing their normal function. In some medical situations, blood oxygenators are used as a temporary gas exchange member to substitute or supplement the lung function during, for example, open heart surgery. During such procedures, vital functions of the circulatory system are assumed by an extracorporeal bypass circuit where a pump sends the patient&#39;s blood through a blood oxygenator to deliver oxygen to the patient. In other medical situations, a patient may have an indwelling catheter connected to a pump to deliver blood to a blood oxygenator. In these applications, the oxygenator can be used for an indefinite term. 
     Membrane blood oxygenators transfer oxygen into the blood as it flows over a bundle of hollow fiber membranes. The liquid side boundary layer is the limiting factor in transferring oxygen. Increasing the mixing of blood around the hollow fiber membranes decreases the liquid side boundary layer thickness and increases the exchange of oxygen. A solution for existing blood oxygenators is to increase the amount of fiber membrane surface area or to increase the mixing of blood around the fibers through impellers or rotation of the fibers. However, increasing the amount of fiber surface area increases the foreign surface to blood contact area, which can lead to adverse events such as thrombosis or platelet activation. Additionally, implementing active mixing technologies adds complication to the manufacturing and design of the oxygenator. 
     There is a need in the art for a blood oxygenator that is suitable for use for an indefinite term to provide gas exchange function without imposing a significant load onto the patient&#39;s heart. It would be further desirable to have a blood oxygenator having an increased gas exchange efficiency and a smaller size compared to conventional blood oxygenators. 
     SUMMARY OF THE DISCLOSURE 
     In some examples or aspects of the present disclosure, an improved blood oxygenator is provided for use for an indefinite term to provide gas exchange function without imposing a significant load onto the patient&#39;s heart. The improved blood oxygenator has an increased gas exchange efficiency and a small size. 
     In some examples or aspects of the present disclosure, a blood oxygenator may have a housing with a first end opposite a second end and a sidewall extending between the first end and the second end along a longitudinal axis. The housing may define an interior chamber having a fluid inlet and a fluid outlet. The blood oxygenator may have a gas exchange medium positioned within the interior chamber. The gas exchange medium may have a plurality of hollow fibers rolled into a spiral shape. The blood oxygenator may have a flow diverter positioned within the interior chamber and configured for guiding fluid flow through the gas exchange medium. 
     In other examples or aspects of the present disclosure, the flow diverter may have a fixed end connected to a central portion of the housing and a free end extending from the first end along the longitudinal axis. The flow diverter may have a spiral shape between the fixed end and the free end. A diameter of the flow diverter may increase or decrease between the fixed end and the free end. The flow diverter may extend along 25% to 100% of a longitudinal length of the gas exchange medium. 
     In other examples or aspects of the present disclosure, the flow diverter may have one or more annular sleeves extending longitudinally through the gas exchange medium. The one or more sleeves may be offset longitudinally relative to each other to define a tortuous fluid path therebetween. The one or more sleeves may be arranged concentrically relative to the longitudinal axis. The flow diverter may be a baffle positioned between a first section of the gas exchange medium and a second section of the gas exchange medium. The baffle may be configured to permit at least a portion of the fluid flow to pass through the baffle in a radial direction. The flow diverter may be a screen having a plurality of openings, pores, or slots. A size of the openings, pores, or slots may increase or decrease between the first end and the second end of the housing. The one or more sleeves, baffle, or screen may include a combination of regions with openings, pores, and/or slots. 
     In other examples or aspects of the present disclosure, the flow diverter may include at least one first ring and at least one second ring arranged in an alternating manner Each first ring may be a solid plate and each second ring may be an annular plate. 
     In other examples or aspects of the present disclosure, the flow diverter may be an inflatable balloon positioned in a central portion of the interior chamber. The inflatable balloon may be in fluid communication with a pump via a fluid line, and wherein the pump is configured for selectively inflating or deflating the inflatable balloon via the fluid line. 
     Various other aspects of the present disclosure are recited in one or more of the following clauses: 
     Clause 1: A blood oxygenator comprising: a housing having a first end opposite a second end with a sidewall extending between the first end and the second end along a longitudinal axis, the housing defining an interior chamber having a fluid inlet and a fluid outlet; a gas exchange medium positioned within the interior chamber, the gas exchange medium having a plurality of hollow fibers rolled into a spiral shape; and a flow diverter positioned within the interior chamber and configured for guiding fluid flow through the gas exchange medium. 
     Clause 2. The blood oxygenator of clause 1, wherein the flow diverter has a fixed end connected to a central portion of the housing and a free end extending from the first end along the longitudinal axis, and wherein the flow diverter has a spiral shape between the fixed end and the free end. 
     Clause 3. The blood oxygenator of clause 2, wherein a diameter of the flow diverter increases or decreases between the fixed end and the free end. 
     Clause 4. The blood oxygenator of any of clauses 1-3, wherein the flow diverter extends along 25% to 100% of a longitudinal length of the gas exchange medium. 
     Clause 5. The blood oxygenator of any of clauses 1-4, wherein the flow diverter has one or more annular sleeves extending longitudinally through the gas exchange medium. 
     Clause 6. The blood oxygenator of clause 5, wherein the one or more sleeves are offset longitudinally relative to each other to define a tortuous fluid path therebetween. 
     Clause 7. The blood oxygenator of clause 5 or 6, wherein the one or more sleeves are arranged concentrically relative to the longitudinal axis. 
     Clause 8. The blood oxygenator of clause 1, wherein the flow diverter is a baffle positioned between a first section of the gas exchange medium and a second section of the gas exchange medium and wherein the baffle is configured to permit at least a portion of the fluid flow to pass through the baffle in a radial direction. 
     Clause 9. The blood oxygenator of clause 1, wherein the flow diverter is a screen having a plurality of openings, pores, or slots. 
     Clause 10. The blood oxygenator of clause 9, wherein a size of the openings, pores, or slots increases or decreases between the first end and the second end of the housing. 
     Clause 11. The blood oxygenator of any one of clauses 5-10, wherein the one or more sleeves, baffle, or screen may include a combination of regions with openings, pores, and/or slots. 
     Clause 12. The blood oxygenator of clause 1, wherein the flow diverter includes at least one first ring and at least one second ring arranged in an alternating manner. 
     Clause 13. The blood oxygenator of clause 12, wherein each first ring is a solid plate and each second ring is an annular plate. 
     Clause 14. The blood oxygenator of clause 1, wherein the flow diverter is an inflatable balloon positioned in a central portion of the interior chamber. 
     Clause 15. The blood oxygenator of clause 14, wherein the inflatable balloon is in fluid communication with a pump via a fluid line, and wherein the pump is configured for selectively inflating or deflating the inflatable balloon via the fluid line. 
     Further details and advantages of the various examples or aspects described in detail herein will become clear upon reviewing the following detailed description of the various examples in conjunction with the accompanying drawing figures. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a cross-sectional view of a blood oxygenator in accordance with one example or aspect of the present disclosure; 
         FIG. 2A  is a cross-sectional view of a blood oxygenator in accordance with another example or aspect of the present disclosure; 
         FIG. 2B  is a cross-sectional view of a blood oxygenator in accordance with another example or aspect of the present disclosure; 
         FIG. 3  is a cross-sectional view of a blood oxygenator in accordance with another example or aspect of the present disclosure; 
         FIG. 4  is a cross-sectional view of a blood oxygenator in accordance with another example or aspect of the present disclosure; 
         FIG. 5  is a side view of an insert for use with the blood oxygenator of  FIG. 3  or  FIG. 4 ; and 
         FIG. 6  is a cross-sectional view of a blood oxygenator in accordance with another example or aspect of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The illustrations generally show preferred and non-limiting examples or aspects of the apparatus and methods of the present disclosure. While the description presents various aspects of the apparatus, it should not be interpreted in any way as limiting the disclosure. Furthermore, modifications, concepts, and applications of the disclosure&#39;s aspects are to be interpreted by those skilled in the art as being encompassed, but not limited to, the illustrations and descriptions herein. 
     The following description is provided to enable those skilled in the art to make and use the described examples contemplated for carrying out the disclosure. Various modifications, equivalents, variations, and alternatives, however, will remain readily apparent to those skilled in the art. Any and all such modifications, variations, equivalents, and alternatives are intended to fall within the spirit and scope of the present disclosure. 
     For purposes of the description hereinafter, the terms “upper”, “lower”, “right”, “left”, “vertical”, “horizontal”, “top”, “bottom”, “lateral”, “longitudinal”, and derivatives thereof shall relate to the disclosure as it is oriented in the drawing figures. 
     As used herein, the terms “parallel” or “substantially parallel” mean a relative angle as between two objects (if extended to theoretical intersection), such as elongated objects and including reference lines, that is from 0° to 5°, or from 0° to 3°, or from 0° to 2°, or from 0° to 1°, or from 0° to 0.5°, or from 0° to 0.25°, or from 0° to 0.1°, inclusive of the recited values. 
     As used herein, the term “perpendicular” or “substantially perpendicular” mean a relative angle as between two objects (if extended to theoretical intersection), such as elongated objects and including reference lines, that is from 85° to 90°, or from 87° to 90°, or from 88° to 90°, or from 89° to 90°, or from 89.5° to 90°, or from 89.75° to 90°, or from 89.9° to 90°, inclusive of the recited values. 
     It is to be understood, however, that the disclosure may assume alternative variations and step sequences, except where expressly specified to the contrary. It is also to be understood that the specific devices and processes illustrated in the attached drawings, and described in the following specification, are simply exemplary aspects of the disclosure. Hence, specific dimensions and other physical characteristics related to the examples disclosed herein are not to be considered as limiting. 
     It should be understood that any numerical range recited herein is intended to include all sub-ranges subsumed therein. For example, a range of “1 to 10” is intended to include all sub-ranges between (and including) the recited minimum value of 1 and the recited maximum value of 10, that is, having a minimum value equal to or greater than 1 and a maximum value of equal to or less than 10. 
     In this application, the use of the singular includes the plural and plural encompasses singular, unless specifically stated otherwise. In addition, in this application, the use of “or” means “and/or” unless specifically stated otherwise, even though “and/or” may be explicitly used in certain instances. Further, in this application, the use of “a” or “an” means “at least one” unless specifically stated otherwise. 
     Referring to  FIG. 1 , a blood oxygenator  10  is shown in accordance with one example or aspect of the present disclosure. The blood oxygenator  10  may be suitable for use in an extracorporeal membrane oxygenation (ECMO) system. The blood oxygenator  10  has a housing  12  having a liquid inlet  14 , a liquid outlet  16 , a gas inlet  18 , and a gas outlet (not shown). The housing  12  has a first end  20  opposite a second end  22  along a longitudinal axis  24 . A sidewall  26  extends between the first end  20  and the second end  22  and encloses an interior chamber  28  that provides the space in which gas exchange functions are performed. A gas exchange medium  30  is positioned within the interior chamber  28 . 
     With continued reference to  FIG. 1 , the housing  12  may have a circular or oval cross-sectional shape and may be made from a rigid material, such as a biocompatible plastic. The plastic may be transparent, translucent, or opaque. 
     With continued reference to  FIG. 1 , the liquid inlet  14 , the liquid outlet  16 , the gas inlet  18 , and the gas outlet are in fluid communication with the interior chamber  28 . In some examples or aspects, the liquid outlet  16 , the gas inlet  18 , and the gas outlet may have features that facilitate connection to another device, such as tubing or the like. Such features can include barbs, clamps, and/or any other suitable connection feature. 
     With continued reference to  FIG. 1 , the gas exchange medium  30  is disposed within the interior chamber  28  and is configured for diffusing a gas flowing therethrough into the liquid flowing around the gas exchange medium  30 . In some examples or aspects, the gas exchange medium  30  has a plurality of individual hollow fibers, such as those discussed in U.S. Pat. No. 6,682,698. The fibers are configured to carry a gas, such as oxygen, in such a manner that allows the gas to be taken up by a liquid, such as blood, flowing around the fibers, and to absorb any other gas given off by the liquid, such as carbon dioxide. The gas exchange medium  30  provides the required surface area for the gas exchange to occur. In some examples or aspects, the gas exchange medium  30  may be a woven fiber mat that is rolled into a spiral shape about the longitudinal axis  24 . In this manner, the gas exchange medium  30  may have an outer diameter than is configured to fit within an inner diameter of the housing  12  and an inner diameter inside of which a flow diverter is received, as discussed herein. Alternatively, the gas exchange medium  30  can be any other gas exchange medium known in the art. A potting material (not shown) may be used to seal the inlet and outlet sides of the hollow fibers of the gas exchange medium  30  in order to prevent direct mixing of the gas flowing through the fibers with the liquid flowing around the fibers. 
     During operation, blood enters the oxygenator  10  through the liquid inlet  14  along an axial path extending along the longitudinal axis  24  from the first end  20  toward the second end  22 . The blood must be radially diverted so that it can pass through the gas exchange medium  30 . Various devices for radially diverting the flow of blood within the interior chamber  28  and promoting mixing flow of the blood between the fibers of the gas exchange medium  30  are disclosed herein with reference to  FIGS. 1-6 . 
     With continued reference to  FIG. 1 , a flow diverter  32   a  is shown in accordance with one example or aspect of the present disclosure. The flow diverter  32   a  is positioned within the interior chamber  28  at a central portion of the housing  12  and in a central opening within the gas exchange medium  30 . The flow diverter  32   a  is configured to divert the blood flowing along an axial path in a radial direction toward the gas exchange medium  30 . The flow diverter  32   a  has a first, fixed end  34  fixedly connected to the second end  22  of the housing  12 , and a second, free end  36  opposite the first end  34 . The second, free end  36  is directed toward the liquid inlet  14  such that liquid entering the interior chamber  28  through the liquid inlet  14  is directed toward the flow diverter  32   a . The flow diverter  32   a  desirably extends along 25% to 100% of the length of the gas exchange medium  30 . In some instances, the flow diverter  32   a  extends along 50% or more, or 60% or more, or 75% or more of the length of the gas exchange medium  30 . 
     With continued reference to  FIG. 1 , the flow diverter  32   a  has a spiral shape having 0.5 to 10 twists per inch in a direction about the longitudinal axis  24  between the first end  34  and the second end  36 . In some instances, the flow diverter  32   a  has a spiral shape having 0.5 to 5 twists per inch, 5 to 10 twists per inch, 2 to 8 twist per inch, or 3 to 10 twists per inch in a direction about the longitudinal axis  24 . In some examples or aspects, a diameter of the flow diverter  32   a  may be uniform along its length. In other examples or aspects, the diameter of the flow diverter  32   a  may increase or decrease in a direction from the first end  34  toward the second end  36 . The flow diverter  32   a  may have a diameter that is 90-95% of the inner diameter of the gas exchange medium  30 . In some instances, the flow diverter  32   a  may have a diameter that is 80% or more, 85% or more, or 90% or more of the inner diameter of the gas exchange medium  30 . The spiral shape of the flow diverter  32   a  imparts a spiral flow to the blood flowing in through the liquid inlet  14 . This results in an even radial distribution of flow across the gas exchange medium  30 . Additionally, gas exchange is improved due to a more tortuous fluid path compared to oxygenators without the flow diverter  32   a.    
     With reference to  FIG. 2A , a blood oxygenator  10  having a flow diverter  32   b  is shown in accordance with another example or aspect of the present disclosure. The flow diverter  32   b  has one or more annular sleeves  38  positioned within the interior chamber  28 . In some examples or aspects, the one or more sleeves  38  may be positioned within the gas exchange medium  30 . The one or more sleeves  38  are arranged concentrically relative to the longitudinal axis  24 , with a first sleeve  38   a  positioned closest to the longitudinal axis  24  and the remaining sleeves  38   b - 38   c  positioned radially outward relative to the first sleeve  38   a . The sleeves  38   a - 38   c  are axially offset from one another such that a tortuous path  39  is defined between the sleeves  38   a - 38   c  and through the gas exchange medium  30 . For example, the sleeves  38   a - 38   c  may be arranged such that the end of one or more of the sleeves  38   a - 38   c  closest to the first end  20  is closer to the first end  20  than one or more of the other sleeves  38   a - 38   c  and/or the end of one or more of the sleeves  38   a - 38   c  closest to the second end  22  is closer to the second end  22  than one or more of the other sleeves  38   a - 38   c . In this manner, blood flowing around the fibers of the gas exchange medium  30  must take the tortuous path  39  around the sleeves  38   a - 38   c  when flowing from the liquid inlet  14  to the liquid outlet  16 . 
     With continued reference to  FIG. 2A , the sleeves  38   a - 38   c  of the flow diverter  32   b  may extend along 50% to 90% of the length of the gas exchange medium  30 . In some instances, the sleeves  38   a - 38   c  extend along 50% or more, or 60% or more, or 75% or more of the length of the gas exchange medium  30 . In some examples or aspects, at least one of the sleeves  38   a - 38   c  may be made from a solid material such that the sleeve is configured to block fluid flow in a radial direction and promote fluid flow in an axial direction along the longitudinal axis  24 . In other examples, at least one of the sleeves  38   a - 38   c  may permit at least a portion of the fluid flow to pass through the sleeve in a radial direction. For example, the at least one of the sleeves  38   a - 38   c  may be made from a porous material, or have one or more slots or openings, as discussed herein. The sleeves  38   a - 38   c  are configured to promote even radial distribution of fluid flow and lower the pressure drop across the gas exchange medium  30 . The cross-sectional area of the oxygenator  10  having the flow diverter  32   b  is reduced in the regions where the sleeves  38   a - 38   c  are present, thereby increasing the velocity of the blood flowing through the tortuous path  39 , which in turn increases the gas exchange rate. 
     With reference to  FIG. 2B , a blood oxygenator  10  having a flow diverter  32   b ′ is shown in accordance with another example or aspect of the present disclosure. The flow diverter  32   b ′ has at least one first ring  33  and at least one second ring  35 . The at least one first ring  33  and the at least one second ring  35  may be arranged in an alternating manner wherein no two first rings  33  or second rings  35  are placed adjacent to each other. Thus, a first ring  33  may be positioned longitudinally between two second rings  35  and/or a second ring  35  may be positioned longitudinal between two first rings  33 . Each first ring  33  may be a solid plate that is positioned within an inner diameter of the gas exchange medium  30 . Each second ring  35  may be an annular plate that is positioned outside an outer diameter of the gas exchange medium. Thus, the inner diameter of the second rings  35  may be greater than the outer diameter of the first rings  33 . The first and second rings  33 ,  35  are spaced apart from each other in a direction along the longitudinal axis  24  such that blood must follow a tortuous path  39  as it moves from the liquid inlet  14  to the liquid outlet  16 . 
     With reference to  FIG. 3 , a blood oxygenator  10  having a flow diverter  32   c  is shown in accordance with another example or aspect of the present disclosure. The flow diverter  32   c  is configured as a baffle  40  positioned between a pair of gas exchange mediums  30   a ,  30   b . In some examples or aspects, a plurality of baffles  40  may be provided to separate a plurality of gas exchange mediums. Each gas exchange medium  30   a ,  30   b  may be a woven fiber mat that is rolled into a spiral shape about the longitudinal axis  24 . The gas exchange mediums  30   a ,  30   b  are arranged concentrically relative to the longitudinal axis  24 , with a first gas exchange medium  30   a  positioned closest to the longitudinal axis  24  and the second gas exchange medium  30   b  positioned radially outward relative to the first gas exchange medium  30   a.    
     With continued reference to  FIG. 3 , the baffle  40  is positioned between the gas exchange mediums  30   a ,  30   b . In some examples or aspects, the baffle  40  extends along the entire longitudinal length of the of the gas exchange mediums  30   a ,  30   b . In other examples or aspects, the baffle  40  extends along a portion of the longitudinal length of the gas exchange mediums  30   a ,  30   b , as shown in  FIG. 3 . In some instances, the baffle  40  extends along 50% or more, or 60% or more, or 75% or more of the length of the gas exchange mediums  30   a ,  30   b . The baffle  40  is configured to permit at least a portion of the fluid flow to pass through the baffle  40  in a radial direction. For example, the baffle  40  may be made from a porous material, or have one or more slots or openings, as discussed herein. 
     With reference to  FIG. 4 , a blood oxygenator  10  having a flow diverter  32   d  is shown in accordance with another example or aspect of the present disclosure. The flow diverter  32   d  is configured as a screen  42  having a tubular shape and is positioned at a radially inward position of the gas exchange medium  30 . The flow diverter  32   d  may extend along 25% to 100% of the length of the gas exchange medium  30 . In some instances, the flow diverter  32   d  may extend along 50% or more, or 60% or more, or 75% or more of the length of the gas exchange medium  30 . The flow diverter  32   d  is configured to permit at least a portion of the fluid flow to pass therethrough in a radial direction. For example, the flow diverter  32   d  may be made from a porous material, or have one or more slots or openings, as discussed herein. In some examples or aspects, the size or flow area of the openings through which fluid may flow through the flow diverter  32   d  may vary in a direction along the longitudinal axis  24 . For example, the size of the openings, pores, or slots may vary (e.g., increase or decrease) between the first end  20  and the second end  22  of the housing  12 . 
     With reference to  FIG. 5 , a flow diverter  32   e  is shown in accordance with another example or aspect of the present disclosure. The flow diverter  32   e  may be used as one of the annular sleeves  38  shown in  FIG. 2A , the baffle  40  shown in  FIG. 3 , or the screen  42  shown in  FIG. 4 . The flow diverter  32   e  has an annular shape having a first end  44 , a second end  46 , and sidewall  48  defining a central opening  50  between the first end  44  and the second end  46  along a central axis  52 . In some examples or aspects, the flow diverter  32   e  has a plurality of openings  54  extending through the sidewall  48 . Each of the plurality of openings  54  is configured to permit fluid to flow therethrough. The openings  54  may have a substantially circular shape with a uniform or a non-uniform diameter in a direction along the longitudinal axis  24 . In some examples or aspects, the size of the openings  54  may increase from the first end  44  to the second end  46 . 
     In further examples or aspects, the flow diverter  32   e  may be made from a mesh  56  defining a plurality of pores  58  configured to permit fluid to flow therethrough. The pores  58  may have a substantially quadrilateral shape. In some examples or aspects, the size of the pores  58  may increase from the first end  44  to the second end  46 . 
     In further examples or aspects, the flow diverter  32   e  may have a plurality of slots  60  configured to permit fluid to flow therethrough. The slots  60  may have an elongated shape. In some examples or aspects, the size (i.e., width) of the slots  60  may increase from the first end  44  to the second end  46 . 
     In further examples or aspects, the flow diverter  32   e  may include a combination of regions with openings  54 , mesh  56  with pores  58 , and/or slots  60 . 
     With reference to  FIG. 6 , the blood oxygenator  10  is shown in accordance with another example or aspect. The blood oxygenator  10  has a flow diverter  32   f  in the form of an inflatable balloon  64  positioned within the interior chamber  28 . In some examples or aspects, the balloon  64  is positioned in a central portion of the interior chamber  28  and in a central hollow portion of the gas exchange medium  30 . The balloon  64  is connected to a fluid source  66  that is configured for selectively inflating or deflating the balloon  64 . In some examples or aspects, the fluid source  66  may be a fluid pump  68  that is in fluid communication with the balloon  64  via a fluid line  70 . In various examples or aspects, the balloon  64  may be inflated and deflated via hydraulic, pneumatic, mechanical, electrical, or electromechanical devices, including any combinations thereof. A controller  69  may be operatively connected to the fluid pump  68  for controlling the flow of fluid to and from the balloon  64 . Using the pump  68 , pressurized fluid is delivered to the balloon  64  via the fluid line  70  to inflate the balloon  64  in a direction of arrows A. Conversely, by depressurizing the pump  68  or reversing its operating direction, the balloon  64  can be deflated in a direction of arrows B. 
     Inflation of the balloon  64  is configured to force the fluid within the interior chamber  28  to flow radially outward through the fibers of the gas exchange medium  30 . In some examples or aspects, the balloon  64  may be expanded such that an outer diameter of the balloon  64  is the same as the inner diameter of the gas exchange medium  30  to force any fluid present in the space between the balloon  64  and the gas exchange medium  30  into the space between individual fibers of the gas exchange medium  30 . Deflation of the balloon  64  allows additional fluid to enter the interior chamber  28  so that the fluid can be forced radially outward with the subsequent inflation of the balloon  64 . 
     The controller  69  controls operation of the pump  68  to selectively inflate and deflate the balloon  64 . In some examples or aspects, the controller  69  can be configured to operate the pump  68  in a pulsatile manner to selectively inflate and deflate the balloon  64  according to a pre-defined pressure profile. In other examples or aspects, the controller  69  can be configured to operate the pump  68  to selectively inflate and deflate the balloon  64  based on input from at least one sensor that measures a physiological characteristic of a patient. For example, the controller  69  can operate the pump  68  to inflate and deflate the balloon  64  based on input received from a heart rate sensor. Thus, inflation/deflation of the balloon  64  may be coordinated with the patient&#39;s heart rate. 
     The present disclosure also provides a method of operating a blood oxygenator. The method includes introducing blood into the interior chamber  28  through the liquid inlet  14  along an axial path in a direction of the longitudinal axis  24 . The blood is radially diverted toward the outer portion of the interior chamber such that the blood passes around the fibers of the gas exchange medium  30 . As the blood flows around the fibers of the gas exchange medium  30 , gas exchange takes place between the blood and the gas flowing through the fibers of the gas exchange medium  30 . In order to facilitate the gas exchange, the method further includes introducing a gas, such as oxygen or air, into the gas inlet  18  such that the gas passes through the gas exchange medium  30  and exits through the gas outlet. Oxygenated blood is directed through the liquid outlet  16 . Radial diverting of the blood may be facilitated using one or more of the diverter, the baffle, the separator screen, or the inflatable balloon described herein. 
     While examples or aspects of an improved blood oxygenator are provided in the foregoing description, those skilled in the art may make modifications and alterations to these examples or aspects without departing from the scope and spirit of the disclosure. Accordingly, the foregoing description is intended to be illustrative rather than restrictive. The disclosure described hereinabove is defined by the appended claims, and all changes to the disclosure that fall within the meaning and the range of equivalency of the claims are to be embraced within their scope.