Patent Publication Number: US-11660426-B2

Title: Devices and methods for treating edema

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims benefit of U.S. Provisional Application No. 62/810,653, filed Feb. 26, 2019, which is incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     The disclosure relates to devices and methods for the treatment of edema. 
     BACKGROUND 
     Congestive heart failure occurs when the heart is unable to pump sufficiently to maintain blood flow to meet the body&#39;s needs. A person suffering heart failure may experience shortness of breath, exhaustion, and swollen limbs. Heart failure is a common and potentially fatal condition. In 2015 it affected about 40 million people globally and around 2% of adults overall. As many as 10% of people over the age of 65 are susceptible to heart failure. 
     In heart failure, the pressures in the heart ventricles and atria are excessively elevated. As a result, the heart works harder to eject blood, leading to a buildup of blood pressure, which may result in edema forming within interstitial compartments of the body. Edema refers to the abnormal accumulation of fluid in tissues of the body and results when elevated blood pressure prevents lymphatic fluid from draining from the interstitium. The additional work of the heart, with time, weakens and remodels the heart thus further reducing the ability of the heart to function properly. The fluid accumulation leads to dyspnea and acute decompensated heart failure (ADHF) hospitalization. Those conditions may result in severe health consequences including death. 
     SUMMARY 
     The invention provides devices and methods for treatment of edema that use an indwelling catheter with an impeller to lower pressure at an outlet of a lymphatic duct and a balloon on the impeller to guide and to restrict blood flow. The balloon restricts return flow from the jugular and guides that flow into the impeller cage. By funneling the flow into the impeller cage, a rate of flow down the vessel may be increased, resulting in a lateral pressure decrease effecting the lymphatic outlet. Because the lymphatic outlet is subject to a pressure decrease, fluids in the lymphatic system drain to the outlet and into the circulatory system. These effects can be optimized by having the balloon disposed on or around the impeller cage and, in some embodiments, the balloon may be connected directly the impeller cage, surrounding the cage, and forming a torus that funnels fluid flow into the impeller cage. A shape of a balloon in a deployed state directs and facilitates blood flow into an inlet of an impeller. By using the impeller in conjunction with the balloon on the catheter, the ability of the device to lower pressure at the lymphatic outlet is optimized. 
     The geometry of the combined impeller cage and toroidal balloon employ flow dynamics to drain the lymphatic system. The impeller cage in combination with the balloon creates a local constriction (or choke) in the cross-sectional area of flow through the vessel (e.g., the innominate vein). This flow constriction results in a Venturi effect, in which fluid pressure is reduced as applicable to the outlet of the lymphatic duct. Due to the pressure decrease experienced by the lymphatic outlet, lymph drains from the lymphatic system to the circulatory system. Thus devices and methods of the disclosure use a balloon mounted to an impeller to exploit the laws of fluid mechanics to drain lymph. Since operating an impeller in an innominate vein near a lymphatic outlet with a balloon connected to the impeller cage is effective to reduce pressure at the lymphatic outlet and drain lymph, devices and methods of the invention are useful to relieve the symptoms of edema. Accordingly, the invention provides methods and devices that use a balloon mounted to an impeller cage to treat edema and congestive heart failure. 
     In certain aspects, the disclosure provides a device for treating edema. The device includes a catheter having a proximal portion and a distal portion, an impeller housing attached to the distal portion of the catheter with an impeller disposed therein, and an expandable member (e.g., a balloon) aligned over an outside of the impeller housing. An exterior surface of the expandable member may be physically coupled to an exterior surface of the impeller housing. Preferably, the exterior surface of the expandable member is physically coupled directly to the exterior surface of the impeller housing, i.e., without any membrane, sheath, or device between the exterior surface of the expandable member and the exterior surface of the impeller housing. The expandable member may surround the impeller housing. 
     Where the expandable member is a balloon, the balloon may inflatable and may surround the impeller housing. In some embodiments, the impeller housing comprises a metal and a portion of the expandable member is fixed to a surface of the metal by an adhesive. At least a portion of the surface of the metal may be impregnated with a polymer to promote bonding to the adhesive. Embodiments of the device may include a motor housing connected to the proximal portion of the catheter with a motor disposed within the motor housing. A drive cable may extend through the catheter from the motor to the impeller with an inflation lumen extending along the catheter to the expandable member. Related embodiments provide a method of using the device for treating edema. The method includes inserting the distal portion of the catheter into an innominate vein of a patient, operating the impeller, and expanding the expandable member to thereby decrease pressure at a lymphatic duct. 
     Aspects of the invention provide an edema treatment device that includes a catheter with a proximal portion and a distal portion, the distal portion dimensioned for insertion into a lumen of a patient and comprising a pump, and an expandable member connected to the pump. When expanded, the expandable member comprises a toroidal shape, in which a proximal surface of the toroidal shape directs fluid into the pump. Preferably an inner radius of the toroidal shape is substantially the same as a radius of the proximal end of the pump. The expandable member may include an inflatable balloon mounted on the pump. In some embodiments, the pump comprises an impeller housing with an impeller therein, with the balloon mounted around at least a portion of a proximal end of the impeller housing. In certain embodiments, the impeller housing has a distal portion and a proximal portion, in which an external diameter of the proximal portion is smaller than an external diameter of the distal portion, such that the expandable member, when not expanded, is disposed around the proximal portion of the impeller housing. The impeller may have one or more blades on a shaft, with a radius measured from an axis of the impeller to an outer edge of the blades decreasing from a distal to a proximal portion of the impeller. The outer edge of each blade may include a dogleg defining a step-down in radius located adjacent a transition between the distal portion and the proximal portion of the impeller housing. In preferred embodiments, the distal portion of the impeller housing has outlets and the impeller shaft flares outwards near a distal end of the impeller such that when the impeller is rotated, the impeller pumps blood through the impeller housing and out of the one or more outlets. 
     The pump may include an impeller disposed within an impeller housing and the expandable member may include an inflatable balloon connected to an exterior surface of the impeller housing. In certain embodiments, when the balloon is inflated, it defines a torus. When the balloon is inflated, a surface of the torus may be attached to a surface of the impeller housing. Preferably, when the expandable member is not expanded, the distal portion of the catheter may be passed through a 12 Fr introducer sheath. 
     Aspects of the disclosure provide a device and associated method that use a restrictor for compensation to pressure changes resulting from flow induced by a pump. In the restrictor for flow compensation aspects, the invention provides a method for treating edema. The method includes operating a pump to increase flow through an innominate vein of a patient and—subsequent to the operating step—deploying a restrictor upstream of the pump to thereby restrict flow from a jugular vein to the innominate vein in order to balance pressure downstream of the pump. The method may include operating the pump and then restricting the flow once the increased flow through the innominate vein affects pressure in the jugular vein. The method may further include sensing, with a pressure sensor, an increase in pressure in the jugular vein that results from the increased flow and restricting the flow in response to sensing the increased pressure in the jugular vein. Restriction of the flow may be adjusted according to the sensed pressure. Preferably, the method includes placing a device comprising the pump within vasculature of a patient prior to the operating step. The device comprises a catheter dimensioned to be at least partially implanted within the vasculature and the pump comprises an impeller assembly disposed at a distal portion of the catheter. In some embodiments, a proximal portion of the catheter is connected to a motor housing and the device includes a pressure sensor and a deployable restrictor attached to the catheter proximal to the pump. Preferably, the restrictor includes an inflatable balloon and restricting the flow includes inflating the restrictor. The sensing may be performed using a computer system communicatively connected to the pressure sensor. The inflation of the restrictor may be periodically or continually adjusted according to the sensed pressure. 
     Other aspects of the invention provide a method for treating edema. The method includes operating a pump to increase flow through an innominate vein of a patient, sensing a pressure change in a jugular vein of the patient that results from the increased flow, and adjusting a restrictor to restrict flow from the jugular vein to the innominate vein based on the sensed pressure. The method may further include inserting a catheter into the innominate vein, wherein the catheter comprises the pump, a pressure sensor, and the restrictor. Preferably, the restrictor includes an inflatable balloon and adjusting the restrictor includes at least partially inflating the balloon. The sensing may be performed using a pressure sensor. The method may include periodically or continually adjusting inflation of the restrictor according to the sensed pressure. Preferably, the method includes adjusting the inflation in order to balance pressure downstream of the pump. Optionally the pump comprises an impeller assembly disposed at a distal portion of the catheter. A proximal portion of the catheter may be connected to a motor housing having a motor therein operably coupled to the impeller assembly. In some embodiments, the catheter is coupled to a computer system operable to read the pressure or control the inflation. 
     Aspects of the invention provide a purge-free system, device, and method for treatment of edema. For example, aspects provide a purge-free device that includes a catheter with a proximal portion and a distal portion, an impeller connected to the distal portion of the catheter, a motor connected to the proximal portion of the catheter, a drive cable extending through the catheter from the motor to the impeller, and an impermeable sleeve extending through the catheter over the drive cable. The sleeve features a distal seal at the impeller and a proximal seal at the motor such that fluid external to the sleeve is prevented from entering the sleeve and contacting the drive cable. The sleeve and at least the distal seal exclude fluid from the drive cable. Either seal (or both) may include one or more O-rings. The device may include a first lumen and a second lumen, both extending through the catheter, in which the first and second lumen have respective first and second proximal ends accessible outside of the motor housing. Preferably the first lumen and the second lumen are symmetrically disposed about the drive cable to impart balance to the device. The catheter preferably does not include a purge system or a purge fluid. In some embodiments, the impeller sits in an impeller housing and the device also has at least one expandable member connected to the distal portion of the catheter. The expandable member may be connected to the impeller housing, and the device may also include a second expandable member disposed along the catheter. Preferably, the first expandable member comprises a toroidal balloon connected directly to a surface of the impeller housing. The device may also include at least one pressure sensor disposed along the catheter proximal to the impeller. 
     In some embodiments, the proximal seal comprises a fitting between the impermeable sleeve and a portion of the impeller, such that the fitting excludes fluids and allows the impeller and drive cable to rotate within the device. 
     A related aspect provides a method using the purge-free device. The purge-free device may be used in a method of treating edema. The method includes inserting into an innominate vein of a patient a distal portion of a catheter and driving an impeller connected to the distal portion of the catheter by means of motor at a proximal portion of the catheter. The motor is connected to the impeller by a drive cable extending through the catheter. Driving the impeller decreases pressure at a lymphatic duct. An impermeable sleeve extends through the catheter over the drive cable such that body fluid external to the impermeable sleeve is prevented from entering the impermeable sleeve and contacting the drive cable. The method may further comprise inflating a restrictor disposed along the distal portion of the catheter to restrict flow from a jugular vein into the innominate vein, wherein the inflating uses an inflation lumen extending through the catheter outside of the impermeable sleeve. The decreased pressure at a lymphatic duct promotes drainage from a lymphatic system into a circulatory system. 
     Preferably, the impermeable sleeve has a proximal seal at a housing of the motor and a distal seal at the impeller. The proximal seal prevents the blood and bodily fluid from escaping the patient through the motor housing or the proximal portion of the catheter. The distal seal may include a fitting between the impermeable sleeve and a portion of the impeller, in which the fitting excludes fluids and allows the impeller and drive cable to rotate within the device. The impermeable sleeve may be made of a polymer such as Teflon. 
     The method may include inflating at least one balloon disposed along the catheter by means of an inflation lumen having a proximal end accessible outside of the motor housing while the distal portion of the catheter is inserted into the innominate vein. Blood and bodily fluid is preferably excluded from the drive cable without the use of a purge fluid or purge system. 
     Other aspects of the disclosure related to methods and devices that use and deliver an anticoagulant to promote effective operation of a device of treatment of edema. For example, aspects of the disclosure provide a device that includes an intravascular pump with built-in delivery mechanism for an anticoagulant (i.e., to deliver the anticoagulant to moving parts of the pump). Thus the invention provides an edema treatment device that includes a catheter, an impeller assembly mounted at a distal portion of the catheter, and a medicament lumen extending through the catheter and terminating substantially at an inlet of the impeller assembly such that a medicament released from the medicament lumen flows through the inlet and impeller assembly. Preferably, the catheter and impeller assembly are dimensioned for insertion through a jugular vein of a patient. The device may further include a reservoir in fluid communication with the medicament lumen. The impeller assembly may comprise an impeller housing with an impeller rotatably disposed therein. The device may include a motor connected to a proximal end of the catheter and operably connected to the impeller via a drive cable extending through the catheter. Preferably, the port is located at the impeller housing, proximal to the impeller. 
     In some embodiments, the catheter comprises a tube with a drive cable extending therethrough, with a cap connected around a terminal portion of the tube. The impeller housing is mounted to the cap by a plurality of struts to define inlets into the impeller housing. The cap seals a terminus of the flexible tube to a shaft of the impeller, and the port may be located in the cap. The impeller housing may have one or more outlets around a distal portion of the impeller, such that operation of the impeller within a blood vessel drives blood into the impeller assembly via the inlets and out of the impeller assembly via the outlets. 
     The device may include an anticoagulant (e.g., tirofiban, heparin, warfarin, rivaroxaban, dabigatran, apixaban, edoxaban, enoxaparin, or fondaparinux) in the reservoir. When the device is inserted into a blood vessel of a patient and the impeller is operated, the anticoagulant is released from the port in the impeller cage and the released anticoagulant mixes with blood and washes over the rotating impeller. 
     Related aspects of the invention provide a method for treating edema. The method includes operating a pump to increase flow through an innominate vein of a patient and releasing an anticoagulant at or adjacent an inlet of the pump. The pump may include an impeller in a cage at a distal portion of a catheter and the anticoagulant may be released from a port in or adjacent a proximal portion of the cage. Optionally, a proximal end of the catheter terminates at a housing comprising a motor, with the motor operably coupled to the impeller by a drive cable extending through the catheter. The catheter may include a medicament lumen extending therethrough and terminating at the port. The method may include the steps of providing the anticoagulant in a reservoir in fluid communication with the medicament lumen; inserting the catheter into vasculature of the patient to position the impeller in the innominate vein; operating the motor to drive the impeller; and washing the anticoagulant over the impeller by releasing the anticoagulant from the port. Preferably, operating the pump decreases pressure at a lymphatic duct, thereby draining lymph from a lymphatic system of the patient. 
     In certain embodiments, the pump includes an impeller on a distal portion of a catheter and the anticoagulant is released from a port at a proximal portion of the impeller. 
     By the release of the anticoagulant, clotting or thrombosis is prevented from interfering with operation of the impeller. Optionally, the method may include restricting flow from a jugular vein to the innominate vein to thereby promote flow from a subclavian vein to the innominate vein. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    shows a device for treatment of edema. 
         FIG.  2    gives a detail view of the impeller assembly. 
         FIG.  3    shows the expandable member in a deployed state. 
         FIG.  4    shows a motor housing connected to the catheter. 
         FIG.  5    shows steps of a method of using the device for treating edema. 
         FIG.  6    is a detail view of the impeller assembly with the expandable member in a deployed state. 
         FIG.  7    diagrams a method for treating edema that uses a restrictor to balance pressure and compensate for downstream flow. 
         FIG.  8    shows the restrictor and a pressure sensor for the balance and compensation method. 
         FIG.  9    shows a device inserted into vasculature of a patient. 
         FIG.  10    diagrams a related method for treating edema using a restrictor for balance/compensation. 
         FIG.  11    is a detail view of features that provide for a purge-free system. 
         FIG.  12    diagrams a method of treating edema using a purge-free device. 
         FIG.  13    illustrates a portion of an intravascular device for treatment of edema that releases an anticoagulant at an intravascular pump. 
         FIG.  14    is a cross-sectional view through an impeller assembly. 
         FIG.  15    shows results of a computerized flow model. 
         FIG.  16    is a partial cutaway view of an impeller assembly. 
         FIG.  17    is a side view of an impeller assembly. 
         FIG.  18    shows an exemplary inlet region of an impeller assembly. 
         FIG.  19    shows an inlet region with an internal inflation lumen. 
         FIG.  20    is a detailed view of a proximal inlet. 
         FIG.  21    shows a side view of an impeller assembly with rectangular proximal inlets. 
         FIG.  22    shows an impeller assembly with arcuate proximal struts. 
         FIG.  23    shows a side view of a proximal portion of an impeller assembly. 
         FIG.  24    illustrates an impeller assembly. 
         FIG.  25    shows an elongated impeller assembly. 
         FIG.  26    shows a cross-sectional view of an impeller assembly. 
         FIG.  27    is a cross-sectional view of an impeller assembly inside a vein. 
         FIGS.  28 A-F  illustrates attachment and folding of an expandable member. 
         FIG.  29    shows an impeller assembly with an expandable member having an elongated surface for interfacing with a wall of a blood vessel. 
         FIG.  30    shows an impeller assembly with a two-part expandable member. 
         FIG.  31    is a partial cross-sectional view of a distal portion of a catheter. 
         FIG.  32    is a partial cross-section of a self-expanding impeller assembly. 
         FIG.  33    shows a partial cross-section of an impeller assembly. 
         FIG.  34    shows an inlet of an impeller assembly. 
         FIG.  35    is an exemplary catheter system. 
         FIG.  36    shows a catheter with an expandable member slidably mounted along a shaft of the catheter. 
         FIG.  37    shows a fluid channel across an expandable member that allows a controlled amount of blood flow. 
         FIG.  38    shows a catheter with an alternative bypass channel. 
         FIG.  39    shows a patient interface with a sheath in situation. 
         FIG.  40    shows a patient interface with a sheath held in situation by an adhering membrane. 
         FIG.  41    shows a flow control sheath. 
         FIG.  42    shows a proximal portion of a catheter system. 
         FIG.  43    illustrates a locking mechanism for fixing a catheter shaft to a hub of a sheath during therapy. 
         FIG.  44    shows the locking mechanism engaged with the catheter shaft. 
         FIG.  45    shows a schematic of a push lock mechanism. 
         FIG.  46    shows an alternative locking mechanism. 
         FIG.  47    is a partial cutaway of a jugular vein showing a flow control sheath inserted therein. 
         FIG.  48    shows an indwelling catheter system. 
         FIG.  49    is a cross-section taken along line A-A of  FIG.  48   . 
         FIG.  50    is an indwelling catheter. 
         FIG.  51    is an expanded view of dotted circle B of  FIG.  50    according to an embodiment of the invention. 
         FIG.  52    is an expanded view of dotted circle B of  FIG.  50    according to another embodiment of the invention. 
         FIG.  53    is an expanded view of dotted circle B of  FIG.  50    according to a different embodiment of the invention. 
         FIG.  54    illustrates a distal flush of an indwelling catheter. 
         FIG.  55    illustrates distal flush of an indwelling catheter according to a different embodiment. 
         FIG.  56    shows an indwelling catheter with a purge system. 
         FIG.  57    shows a cross-section of the central lumen taken along line A-A of  FIG.  56    according to one embodiment of the invention. 
         FIG.  58    shows a cross-section of the central lumen taken along line A-A of  FIG.  56    according to a different embodiment of the invention. 
         FIG.  59    shows a cross-section of the central lumen taken along line A-A of  FIG.  56    according to another embodiment of the invention. 
         FIG.  60    shows an optimized guide surface of a cage inlet. 
         FIG.  61    shows a suboptimal guide surface. 
         FIG.  62    shows a cage inlet. 
         FIG.  63    shows a suboptimal inlet configuration. 
     
    
    
     DETAILED DESCRIPTION 
     The disclosure relates to devices and methods for treating edema or congestive heart failure. Devices of the disclosure include catheters dimensioned for insertion through a jugular vein, in which the catheters use or include various features each alone or in combination as described herein. Embodiments of the devices include treatment devices in which a flow restrictor such as a balloon is mounted to a cage or housing of an intravascular pump or impeller. In some of those embodiments, a shape of a balloon in a deployed state directs and facilitates blood flow into an inlet of an impeller. In certain embodiments, devices of the disclosure include an impeller that has a smaller diameter proximal end as compared to a distal end to compensate in size for positioning of a balloon on an impeller cage. Aspects of the invention relate to a purge-free system, or purge-free intravascular treatment catheters that do not use a purge fluid to protect an impeller from thrombosis or clotting. In certain embodiments, devices and methods of the disclosure use the release of an anticoagulant such as heparin at an inlet of an impeller cage. Other embodiments of the disclosure relate to devices and methods that use a restrictor such as a balloon to balance pressure and to compensate for downstream flow when an impeller is operated to drain a lymphatic duct. Features and embodiments of the disclosure include edema treatment devices that include an arrangement of lumens that is symmetrical about a drive shaft to impart balance to the drive shaft. In some embodiments, those lumens have a proximal terminus outside of a motor housing and extend down to a distal portion of a catheter. Device of the disclosure may include an atraumatic tip with a thread therein to allow for a smooth material transition. Embodiments of the disclosure may include a guidewire running through an impeller cage. Those embodiments are described and shown in greater detail herein and may be present in any suitable combination in a device of the disclosure. 
       FIG.  1    shows a device  101  for treatment of edema. The device  101  includes a catheter  105  comprising a proximal portion  109  and a distal portion  115 . An impeller housing  203  is attached to the distal portion  115  of the catheter  105  with an impeller disposed therein. An expandable member  301  may be aligned over an outside of the impeller housing  203 . The expandable member  301  is depicted in a collapsed configuration, and thus appears as little more than a smooth continuation of the impeller housing  203 . 
     The device  101  may include a restrictor  801  and at least one pressure sensor  805 . In the depicted embodiment, the restrictor  801  is proximal to the expandable member  301 . Preferably, each of the restrictor  801  and the expandable member  301  is independently selectively deployable to restrict, impede, guide, or direct fluid flow around the relevant portion of the device  101 . In preferred embodiments, each of the restrictor  801  and the expandable member  301  sits in fluid communication with a dedicated inflation lumen that runs along a length of the catheter  105 . 
     One feature of the device  101  is the impeller  205 , which is preferably provided within an impeller assembly  201  that provides the impeller housing  203  and other mechanical features such as ports and openings useful to pump blood and fluid within blood vessels of a patient. 
       FIG.  2    gives a detail view of the impeller assembly  201 . The impeller assembly  201  includes an impeller housing  203  with an impeller  205  rotatably disposed therein. An expandable  301  member is aligned over an outside of the impeller housing  203 . The expandable member is represented in  FIG.  2    using dashed lines (ghosted lines to aid in seeing other features of the device  101 ). The dashed lines represent the location and disposition of the expandable member  301  in its collapsed or un-deployed state. The impeller housing  203  is attached to the distal portion  115  of the catheter  105  with an impeller disposed therein. An expandable  301  member is aligned over an outside of the impeller housing  203 . The expandable member is represented in  FIG.  2    using dashed lines (ghosted lines to aid in seeing other features of the device  101 ). The dashed lines represent the location and disposition of the expandable member  301  in its collapsed or un-deployed state. 
     As shown, the impeller comprises  205  has blades  206  on a shaft  207 . A radius measured from an axis of the impeller  205  to an outer edge of the blades  206  decreases from a distal to a proximal portion of the impeller. This can be seen in that an outer edge of each blade  206  includes a dogleg  209  defining a step-down in radius located adjacent a transition between the distal portion and the proximal portion of the impeller housing  203 . 
     When the distal portion  115  of the device  101  is inserted into vasculature of a patient and a motor in the motor in the motor housing  401  is operated, the impeller  205  rotates and drives fluid (i.e., blood) through the impeller housing  203 . To that end, a proximal end of the impeller housing  203  includes one or more inlets  255  and a distal portion of the impeller housing  203  comprises one or more outlets  227 . The impeller shaft  207  flares outwards near a distal end of the impeller  205  such that when the impeller  205  is rotated, the impeller pumps blood through the impeller housing  203  and out of the one or more outlets  227 . 
       FIG.  14    is a cross-sectional view through the impeller assembly  201  on the distal portion  115  of the device  101 . The impeller assembly  201  includes an impeller housing  203  with an impeller  205  rotatably disposed therein. 
     The impeller assembly  201  is connected to the distal portion  115  of the catheter. The impeller assembly has the impeller  205  operably disposed within the assembly. The cutaway view of the impeller assembly  201  shows a proximal portion of the impeller assembly is configured to facilitate flow into an inlet of the impeller assembly without recirculation. 
     When the impeller  205  operates within a blood vessel, blood flows through a housing  203  of the impeller assembly  201  without recirculation. 
     As illustrated by the cross-sectional view, in the depicted embodiment, the impeller assembly  201  comprises a cap  249  secured to the distal portion  115  and one or more struts  1405  extending from the cap  249  to the housing  203 . Any one or more of the struts  1405  may include a lumen  415 . The housing  203  has a diameter greater than a diameter of the cap  249 . It can be seen that structurally, a proximal base of the housing  203 , the cap  249 , and the one or more struts  105  define one or more inlets into the impeller housing  201 . 
     In the depicted embodiment, the strut  1405  has an inflation lumen  415  extending therethrough for inflating a balloon mounted on the impeller assembly. The strut  1405  is substantially parallel to an axis of the impeller  205  and protrudes radially inward from at least a portion of an inner surface of the impeller housing  203 . When structured as such, each strut  1405  defines a vane within the impeller assembly  201  that channels fluid flow when the impeller  205  operates to thereby prevent the recirculation or vortices. 
     As shown, the strut  1405  has a fluidic lumen  415  extending therethrough. The fluidic lumen  415  is non-concentric with at least a portion of the body of the strut  1405  due to material of the strut  1405  forming the vane within the impeller assembly  201 . With reference to, e.g.,  FIG.  3   , it can be seen that the device  101  may include a plurality, e.g., at least three, of the struts. Together, the struts define vanes within the impeller assembly that channels fluid flow when the impeller operates to thereby prevent the recirculation or vortices. 
     The impeller housing  201  includes one or more outlets  258  around a distal portion of the impeller  205 . Operation of the impeller  205  within a blood vessel drives blood into the impeller assembly  201  via the inlets  255  and out of the impeller assembly  201  via the outlets  258  such that the blood exhibits smooth laminar flow without the recirculation or vortices. 
       FIG.  15    shows how blood flows through the impeller assembly  201  via the inlets  255  and out of the impeller assembly  201  via the outlets  258  such that the blood exhibits smooth laminar flow without the recirculation or vortices. The image depicts results of a computerized flow model. The flow model shows that flow through an impeller assembly with a structure of the invention is smooth and does not exhibit recirculation. 
     Because the model test results show smooth and efficient flow, a device of the invention pumps blood more efficiently than other devices that lack structures as shown herein. 
     The computer model test results show that flow is smooth and that there are no vortices or recirculation within the flow. 
     Because devices of the invention are more efficient than other devices and pump blood without vortices or recirculation, devices of the invention are beneficial for treating patients with edema. Thus, using a device of the disclosure, a clinician may perform a method for treating edema. The method includes inserting into an innominate vein of a patient a distal portion  115  of a catheter. The catheter has an impeller assembly  201  on the distal portion  115 . The method includes driving an impeller  205  disposed within the impeller assembly  201  to thereby decrease pressure at a lymphatic duct. A proximal portion of the impeller assembly  201  is configured to facilitate flow into an inlet of the impeller assembly without recirculation as clearly shown in the depicted computer flow model. The catheter may have any of the other features disclosed herein (e.g., a cap secured to the distal portion with one or more struts extending from the cap to support a housing of the impeller assembly in which the housing has a diameter greater than a diameter of the cap, and in which a proximal base of the housing, the cap, and the one or more struts define the inlet). 
     As shown by the image of results from the computer flow model, the struts define vanes within the impeller assembly that channel fluid flow when the impeller operates to thereby prevent the recirculation or vortices. The flow lines appearing in the computer flow model clear avoid any loops that would appear if the flow had recirculation or vortices. Because flow through the impeller assembly  201  has no recirculation or vortices, the image from the computer flow model shows only flow lines that do not have loops, circles, spirals, etc. 
     The impeller housing includes one or more outlets around a distal portion of the impeller. When the impeller is operated within a blood vessel, the impeller drives blood into the impeller assembly via the inlets and out of the impeller assembly via the outlets such that the blood exhibits smooth laminar flow without the recirculation or vortices. 
     Devices and methods of the disclosure may include other features. 
     A device  101  of the disclosure may further include a medicament lumen  251  extending through the catheter  105  and terminating substantially at an inlet  255  of the impeller assembly  201 . In some embodiments, the impeller assembly  201  also includes an atraumatic tip  231  with a threaded fitment  237  therein to allow for a smooth transition of material properties between the rigid impeller cage  203  (e.g., a metal) and the softer material of the atraumatic tip  239 . The tip  239  preferably includes a suitable soft material such as a polymer. The material may include, for example, polyether block amides such as those sold under the trademark PEBAX by Arkema Inc. (King of Prussia, PA). Although polyether block amides are mentioned in detail, the polymer can comprise any number of other polymers such as polytetrafluoroethylene (PTFE), fluorinated ethylene propylene (FEP), polyurethane, polypropylene (PP), polyvinylchloride (PVC), polyether-ester, polyester, polyamide, elastomeric polyamides, block polyamide/ethers, silicones, polyethylene, Marlex high-density polyethylene, linear low density polyethylene, polyetheretherketone (PEEK), polyimide (PI), or polyetherimide (PEI). The threaded fitment  237  may include a threaded post (e.g., of metal or a plastic such as a polycarbonate) threadingly fitted to both the impeller housing  203  and the atraumatic tip  231 . By including a long post for the fitment  237  (e.g., longer than its own maximal diameter, preferably at least about 2 or 3× longer), the tip  231  can deform but is prevented from assuming or exhibiting any kinks or discontinuities. Further, as shown, the tip  231  may include a guidewire lumen  239 . 
     The expandable member  301  on the impeller assembly  201  is depicted in the collapsed configuration with dashed lines. The impeller assembly  201  operates as a pump and includes the impeller  205  disposed within the impeller housing  203 . In preferred embodiments, the expandable member  301  comprises an inflatable balloon connected to an exterior surface of the impeller housing  203 . 
       FIG.  3    shows the expandable member  301  in a deployed state. In the depicted embodiment, the expandable member  301  is provided as a balloon. As shown, when the balloon is inflated, it defines a torus. An exterior surface of the expandable member  301  is physically coupled to an exterior surface of the impeller housing  203  (e.g., the balloon may be cemented to the housing  203  with an adhesive). 
     Preferably, the exterior surface of the expandable member  301  is physically coupled directly to the exterior surface of the impeller housing  203  without any membrane, sheath, or device  101  between the exterior surface of the expandable member  301  and the exterior surface of the impeller housing  203 . The expandable member  301  may partially or fully surround the impeller housing  203 . The expandable member  301  may be provided as an inflatable balloon that surrounds the impeller housing  203 . 
     Devices of the disclosure may include feature to facilitate bonding of the balloon to the impeller housing  203 . For example, the impeller housing may include metal (e.g., stainless steel, steel, aluminum, titanium, a nickel-titanium alloy, etc.) and a portion of the expandable member  301  may be fixed to a surface of the metal by an adhesive. To facilitate bonding, at least a portion of the surface of the metal may be impregnated with a polymer. In some embodiments, the metal surface at least at the exterior, proximal portion of the impeller cage  203  is impregnated with polyurethane to a depth of at least 3 μm. 
     Using the expandable member  301  mounted to the impeller cage  203 , the device  101  is configured for placement in a body vessel. The impeller housing comprises an axis that may be placed substantially parallel to an axis of the vessel. Preferably, the expandable member  301  is impervious to flow across the expandable member. The expandable member  301  is configured in use to appose the wall of a blood vessel and in so doing direct fluid flow to an inlet of the impeller housing  203 . 
     In use, the expandable member  301  anchors or holds the impeller assembly  201  in a fixed position relative to the axis of the vessel. In that anchored state, the expandable member  301  conforms to the vessel wall at a region of apposition and the region of apposition comprises a substantially cylindrically segment of the vessel wall. The central axis of the expandable member and the central axis of the impeller housing are preferably substantially the same. 
     The expandable member is configured, in use, to allow the axis of the impeller housing to articulate relative to the axis of the balloon. The articulation of the impeller relative to the balloon preferably comprises two degrees of freedom. 
     In some embodiments, the expandable member  301  comprises a balloon and the membrane of the balloon comprises an omega shape in cross-section. 
     The impeller housing  203  may include a tubular member and a wall of the tubular member may include a hole extending through the wall of the tubular member to at least partially define an inflation port for the balloon. Preferably, the inflation port is connected via the catheter to an inflation system exterior of the patient. The connection may include a shaped metal tube or tubing that couples to, and forms a seal with (i.e., “sealingly coupled to”) the inflation port. In certain embodiments, the coupling of the expandable member to the impeller housing comprises at least one circumferential seal around the outside diameter of the housing. More preferably, the coupling of the expandable member to the impeller housing comprises a first circumferential seal around the outside diameter of the housing and a second circumferential seal around the outside diameter, with the second circumferential seal spaced apart axially from the first circumferential seal. In some embodiments, the circumferential seal has an axial length and a part of the seal surrounds an inflation port that extends across the walls of the impeller housing and the expandable member. The impeller housing may include an inflation port positioned between the first circumferential seal and the second circumferential seal. 
     Referencing back to  FIG.  2    and  FIG.  3   , preferably, the balloon has a collapsed state ( FIG.  2   ) for delivery and retrieval and an expanded state ( FIG.  3   ). In some embodiments, in the collapsed state at least a portion of the balloon material can slide relative to an axis of the impeller housing (i.e., is axially slidable relative to the impeller housing). For example, at least a portion of the balloon material may be configured to slide proximally during delivery and to slide distally during retrieval. It may be provided that the balloon comprises a toroidal shape with a first neck and a second neck coupled to the impeller housing. Preferably, a distance between the first neck and the second neck is smaller than the circumference of the toroidal shaped balloon. 
     A coupling between the expandable member  301  and the impeller housing  203  may include an interfacial layer. For example, the interfacial layer may include an interpenetrating layer. In certain embodiments, the impeller housing comprises interstices and the interpenetrating layer comprises an interpenetration of material of the membrane into the interstices of the impeller housing. The interpenetrating layer may include a tie layer, which may include an acrylate material. 
     In some embodiments, the expandable member  301  is configured to apply a radial outward force to the vessel wall. The device may be configured such that said application of said outward radial force substantially fixes at least a portion of the impeller housing  203  to a central axis of the vessel. The impeller housing comprises an inner lumen extending from a proximal section of the impeller housing to a distal section of, or outlets of, the housing, the inner lumen configured to house the impeller  205 . The impeller housing comprises a first diameter adjacent the proximal section and a second diameter adjacent the distal section. In certain embodiments, a diameter of the inner lumen of the impeller housing varies between said proximal section and said distal section. Similarly, a radial dimension of the impeller blades  206  may vary between said proximal section and said distal section. The diameter of the variation of impeller housing inner lumen diameter may define a tapered, a step, a plurality of steps, a plurality of tapers, a dog bone, a parabola or a combination of these. The impeller blades are configured to be in fluidic engagement with the inner lumen of the impeller housing. Preferably, the impeller blades  206  are configured to be in clearance with the inner lumen of the impeller housing. The impeller assembly  201  has at least one inlet opening and at least one outlet opening. The at least one inlet opening and the at least one outlet opening may be separated by a distance of between 1-40 millimeters. Preferably, the at least one inlet opening and the at least one outlet opening are approximately 5 millimeters apart and may position a proximal end of the impeller  205  approximately 0.5 millimeters from a distal edge of the inlet. This configuration is preferable because it helps minimize recirculation at a transition from inlet to impeller  205 . In some embodiments, discussed herein, for example, in  FIG.  25   , the distance between the inlet and outlet may be extended to the approx. 25-30 millimeters. This configuration provides a more laminar flow into the impeller  205 . In other embodiments, the at least one inlet opening and the at least one outlet opening may be approximately 3 millimeters apart to bring the impeller  205  nearer or just inside the inlet. The at least one inlet opening comprises a proximal end and a distal end. A proximal part of the torus extends proximally of the distal end of the proximal inlet opening to define an entry funnel into the inlet opening. The distal portion  115  of the catheter  101  is configured for insertion into a vessel of a patient and the proximal portion  109  of the catheter is configured to extend exterior of the patient. 
     The proximal portion  109  of the catheter  101  may terminate at the motor housing  401 . 
       FIG.  4    shows a motor housing  401  connected to the proximal portion  109  of the catheter  105 . A motor  405  is disposed within the motor housing  401 . A drive cable  411  extends through the catheter  105  from the motor  405  to the impeller. In preferred embodiments, an inflation lumen  415  extends along the catheter  105  to the expandable member  301 . The drive cable  411  preferably extends through a sleeve within the catheter  101 , such as an impermeable sleeve  121 . In purge-free embodiments, the impermeable sleeve  121  may include a seal at one or both ends to exclude fluids from the drive cable  411 . The impermeable sleeve  121  meets the motor housing  401  at the proximal seal  433 . 
     In certain embodiments, the motor  405  includes a rotor operable to rotate at high speed and the catheter  101  includes a drive cable  411  to transmit said rotational speed through the catheter  101  to the impeller  205 . The drive cable  411  may be able to transmit a rotational speed of greater than 5,000 rpms to the impeller  205  (e.g., &gt;10,000 rpm, &gt;15,000 rpm, or &gt;20,000 rpm). Most preferably, the catheter is configured for heatless operation while transmitting high rotational speeds to the impeller. 
     The impermeable sleeve  121  may include a material such as polytetrafluoroethylene (PTFE). For example, the impermeable sleeve  121  may be provided by thick-walled PTFE tubing. The thick-walled PTFE tubing may have a wall thickness of greater than 75 micrometers, preferably &gt;100 microns, &gt;125 microns, or greater than 150 microns. Optionally, the drive shaft has a second moment of area with a value. The drive cable  411  may include a cylindrical super-elastic member over at least a portion of the length of the drive shaft. The clearance between the drive shaft may be less than a certain number of micrometers. In some embodiments, the impermeable sleeve  121  comprises hydrophobic material. The impermeable sleeve  121  may include a material with a Hildebrand solubility parameter (δ) of less than 16 MPa{circumflex over ( )}(0.5). The impermeable sleeve  121  may include a material with a Hildebrand solubility parameter of less than 14 MPa{circumflex over ( )}(0.5). For example, δ of nylon is about 15.7 Mpa{circumflex over ( )}0.5; δ of polytetrafluoroethylene (PTFE) is about 6.2 MPa{circumflex over ( )}0.5. The impermeable sleeve  121  may include a PTFE material, and the drive cable  411  may include a nitinol rod and a gap between the rod and the sleeve may be less than a few microns. Preferably, a concentricity of the rod is greater than 95%. The drive cable may have a first diameter and a second diameter, with the first diameter being slightly larger than the second diameter. The impermeable sleeve may include a polymer material with a dynamic coefficient of friction of less than 0.08, or less than 0.07, 0.06, or 0.05. 
     Devices of the disclosure are useful for treating edema or congestive heart failure. Using a device of the disclosure, one may operate a pump to promote flow in an innominate vein, resulting in a decrease in pressure at an output of a lymphatic duct, which drains lymph from the lymphatic system. To compensate for what would otherwise be changes in pressure in the circulatory system that would result from operating the pump, the disclosure provides methods to compensate for a pressure change. 
       FIG.  5    shows steps of a method  501  of using the device  101  for treating edema. The method  501  includes inserting  510  the distal portion  115  of the catheter  105  into an innominate vein  939  of a patient, operating  515  the impeller, and expanding  517  the expandable member  301  to thereby decrease pressure at a lymphatic duct  907 . 
     The method  501  may include the use of a device  101  that includes a catheter  105  with a proximal portion  109  and a distal portion  115 , the distal portion  115  dimensioned for insertion into a lumen of a patient. The device  101  includes a pump (e.g., an impeller assembly  201 ) and an expandable member  301  connected to the pump. When expanded, the expandable member  301  comprises a toroidal shape, in which a proximal surface of the toroidal shape directs fluid into the impeller housing  203 . Preferably, an inner radius of the toroidal shape is substantially the same as a radius of the proximal end of the impeller housing  203 . In some embodiments, the expandable member  301  comprises an inflatable balloon mounted on the pump. The pump comprises an impeller housing  203  with an impeller therein, with the balloon mounted around at least a portion of a proximal end of the impeller housing  203 . The impeller housing  203  may include a distal portion and a proximal portion, with an external diameter of the proximal portion being smaller than an external diameter of the distal portion. The expandable member  301 , when not expanded, is disposed around the proximal portion of the impeller housing  203 . When the balloon is inflated, a surface of the torus is attached to a surface of the impeller housing  203 . When the expandable member  301  is not expanded, the distal portion  115  of the catheter  105  may be passed through a 12 Fr introducer sheath. 
       FIG.  6    is a detail view of the impeller assembly  201  with the expandable member  301  in a deployed state. The impeller  205  sits substantially within and/or just downstream of the deployed restrictor. An inflation lumen  415  extends through the distal portion  115  of the catheter and terminates at port  601  into the expandable member  301 . Visual inspection of a surface of the expandable member  301  on a proximal side and an inner surface of the impeller housing  203  reveals that those surfaces form a smooth continuous surface that funnels fluid, under an impelling power of the impeller, through the impeller housing  203 . This drives blood through blood vessels and modulates fluid pressure in the vicinity. When operated substantially within an innominate vein, pressure at an outlet of a lymphatic duct decreases, which promotes the drainage of lymph and relief from edema. 
       FIG.  7    diagrams a method  701  for treating edema. The method  701  includes operating  710  a pump to increase flow through an innominate vein  939  of a patient and—subsequent to the operating step—deploying  717  a restrictor upstream of the pump to thereby restrict flow from a jugular vein to the innominate vein  939  in order to balance  729  pressure downstream of the pump. The method  701  may include operating the pump and then restricting the flow once the increased flow through the innominate vein  939  affects pressure in the jugular vein. 
     The method  701  preferably includes sensing  715 , with a pressure sensor  805 , an increase in pressure in the jugular vein that results from the increased flow and restricting the flow in response to sensing the increased pressure in the jugular vein. 
       FIG.  8    shows the restrictor  801  and a pressure sensor  805 . In fact, as shown in  FIG.  8   , the device  101  includes pressure sensors  805  along the catheter  105  at locations both proximal and distal to the restrictor  801 . In the depicted embodiment, the pressure sensors  805  include pressure sensing lumens extending along the catheter  105  and terminating at the skive-cut sensing apertures along the side of the catheter  105 . The sensing lumens extend proximally along the catheter to the motor housing  401 , where the sensing lumens preferably exit the housing  401  and make fluidic contact with a mechanical pressure sensor device such as a piezoelectric pressure sensor. The interior of the pressure sensing lumens preferably establish at least substantial hydrostatic equilibrium from the skive-cut sensing apertures along the side of the catheter  105  to the mechanical pressure sensor devices such that a reading from the sensing device(s) is informative of pressure in an area around the restrictor  801 . Thus the pressure sensors  805  provide information that can feedback into the method  701  and be used as information to control deployment  717  of the restrictor  801 . The method  701  preferably includes inserting  705  the device  101  comprising the pump into vasculature of a patient prior to the operating  710  step. 
       FIG.  9    shows a device  101  inserted  705  into vasculature of a patient. The device  101  comprises a catheter  105  dimensioned to be at partially implanted within the vasculature and the pump comprises an impeller assembly  201  disposed at a distal portion  115  of the catheter  105 . The distal portion  115  is inserted through the jugular vein and down and into the innominate vein  939 . Preferably a proximal portion  109  of the catheter  105  is connected to a motor housing  401  and the device  101  one or more pressure sensor  805  and the deployable restrictor  801  attached to the catheter  105  proximal to the pump. 
     Once the impeller assembly is at least partially within the innominate vein  939 , the impeller  205  is spun, which pumps blood through the impeller housing  203 . This causes a decrease in pressure around an outlet of a lymphatic duct  907 . The decrease in pressure causes lymph to drain from the lymphatic duct  907  and into the circulatory system. That drainage of lymph relieves edema or alleviates congestive heart failure. The method  701  further includes deploying  717  a restrictor  801  upstream of the impeller assembly  201  to thereby restrict flow from a jugular vein to the innominate vein  939  in order to balance  729  pressure downstream of the impeller assembly  201 . The method  701  may further include sensing  715  pressure and adjusting  735  restriction of the flow according to pressure sensed  715  via one or more of the pressure sensors  805 . 
     In some embodiments, the restrictor  801  includes an inflatable balloon and restricting  717  the flow includes inflating the restrictor. Optionally the sensing  715  is performed using a computer system communicatively connected to the pressure sensor(s)  805 . The method  701  may include periodically or continually adjusting  735  inflation of the restrictor according to the sensed pressure. 
       FIG.  10    diagrams a related method  1001  for treating edema. The method  1001  includes inserting  1005  a pump into an innominate vein and operating  1010  the pump to increase flow through an innominate vein  939  of a patient. A pressure change in a jugular vein of the patient that results from the increased flow is sensed  1015 , and a restrictor  801  is adjusted  1029  to restrict flow from the jugular vein to the innominate vein  939  based on the sensed pressure. Preferably, the method  1001  includes inserting  1005  a catheter  105  into the innominate vein  939 . The catheter  105  comprises the pump, a pressure sensor  805 , and the restrictor  801 . The restrictor may include an inflatable balloon and adjusting  1029  the restrictor may include at least partially inflating and/or deflating the balloon. The sensing  1015  may be performed using the pressure sensor  805 . The method  1001  preferably includes periodically or continually adjusting inflation of the restrictor according to the sensed pressure. The method  1001  may include adjusting  1029  the inflation in order to balance pressure downstream of the pump. In preferred embodiments, the pump comprises an impeller assembly  201  disposed at a distal portion  115  of the catheter  105 . A proximal portion  109  of the catheter  105  is connected to a motor housing  401  having a motor  405  therein operably coupled to the impeller assembly. In certain embodiments, the catheter  105  is coupled to a computer system operable to read the pressure or control the inflation. 
     Aspects and embodiments of the disclosure relate to a purge-free system, which may be understood to refer to or include methods and devices for the treatment of edema that do not use a purge system or a purge liquid. 
       FIG.  11    is a detail view of features that provide for a purge-free system. The purge-free system may be provided by a device  101  that includes a catheter  105  comprising a proximal portion  109  and a distal portion  115 , an impeller  205  connected to the distal portion  115  of the catheter  105 , a motor  405  connected to the proximal portion  109  of the catheter  105 , a drive cable  411  extending through the catheter  105  from the motor  405  to the impeller  205 , and an impermeable sleeve  121  extending through the catheter  105  over the drive cable  411 . 
     The sleeve  121  has a distal seal  435  at the impeller. With reference back to  FIG.  4   , the sleeve  121  may have a proximal seal  433  at the motor  405 . Due to the sleeve  121  and at least the distal seal  435 , a body fluid external to the impermeable sleeve  121  is prevented from entering the impermeable sleeve  121  and contacting the drive cable  411 . The sleeve  121  and at least the distal seal  435  exclude fluid from the drive cable  411 . 
     With reference back to  FIG.  4   , the proximal seal  433  (see  FIG.  4   ) may include one or more O-rings. Similarly, the distal seal  435  between the sleeve  121  and the drive cable  411  may be provided by an O-ring, or a collar or press-fit, or extended, friction-fit tube. Any suitable seal may be included that prevents blood or bodily fluid from entering the sleeve and making contact with the drive cable  121 . The drive cable  121  may be provided by any suitable material including, for example, a nickel-titanium alloy or a braided steel cable. Contact with blood would present a risk of hemolysis or clotting that could interfere with an ability of the drive cable  411  to rotate freely (e.g., at &gt;5,000 rpm) within the sleeve  121  and within the catheter  105 . The sleeve excludes blood and thus obviates concerns about clotting or hemolysis, allowing the drive cable  411  and impeller  205  to operate freely without impediment. 
     Embodiments of the device  101  may include multiple lumens. For example, the device  101  may include a first and second inflation lumen  415  (or a single inflation lumen  415 ). The device may include a medicament lumen  251  extending through the catheter  105 . In preferred embodiments, the device  101  includes at least a first inflation lumen  415  and a second inflation lumen  415 , both extending through the catheter  105 . The first inflation lumen  415  and the second inflation lumen  415  have respective first and second proximal ends  416  (see  FIG.  1   ) accessible outside of the motor housing  401 . The first lumen and the second lumen are preferably symmetrically disposed about the drive cable  411  to impart balance to the device  101 . As shown, the catheter  105  does not include a purge system or a purge fluid. 
     With reference back to  FIGS.  1  and  3   , the device  101  may include an impeller  205  sitting in an impeller housing  203 . The device  101  includes at least a first expandable member  301  connected to the distal portion  115  of the catheter  105 . The first expandable member  301  may be connected to the impeller housing  203 , wherein the device  101  further comprises a second expandable member  801  disposed along the catheter  105 . The first expandable member  301  may use a toroidal balloon connected directly to a surface of the impeller housing  203 . The device  101  may further include at least one pressure sensor  805  disposed along the catheter  105  proximal to the impeller. In purge-free embodiments, the distal seal  435  may be provided using a fitting  1107  between the impermeable sleeve  121  and a portion of the impeller  205 , in which the fitting  1107  excludes fluids and allows the impeller  205  and drive cable  411  to rotate within the device  101 . The depicted device  101  is useful for the treatment of edema, and may be characterized as a purge-free device. The purge-free device may be used in a method of treating edema. 
       FIG.  12    diagrams a method  1201  of treating edema using a purge-free device. The method  1201  includes inserting  1205  into an innominate vein  939  of a patient a distal portion  115  of a catheter  105  and driving  1210  an impeller  205  connected to the distal portion  115  of the catheter  105  by means of motor  405  at a proximal portion  109  of the catheter  105 . The motor  405  is connected to the impeller  205  by a drive cable  411  extending through the catheter  105 , to thereby decrease pressure  1217  at a lymphatic duct  907 . An impermeable sleeve  121  extends through the catheter  105  over the drive cable  411  such that body fluid external to the impermeable sleeve is prevented from entering the impermeable sleeve and contacting the drive cable. The impermeable sleeve  121  and at least the distal seal  435  exclude  1215  fluid from entering into the impermeable sleeve  121  and making contact with the drive cable  411 . 
     The method  1201  may include inflating  1229  a restrictor disposed along the distal portion  115  of the catheter  105  to restrict flow from a jugular vein into the innominate vein  939 . The inflation  1229  may be performed using an inflation lumen  415  extending through the catheter  105  outside of the impermeable sleeve  121 . In some embodiments, blood and bodily fluid is excluded  1215  from the drive cable  411  using a repulsive gap between the drive cable  411  and the impermeable sleeve  121 . For example, the repulsive gap may include a hydrophobic material (PTFE) on one side of the gap, a smooth metallic shaft  411  on the other and a gap dimension that prevents influx of blood components. For example, a gap dimension of about 0.5 μm should prevent influx of red blood cells, leukocytes, and platelets. It may be found that a gap dimension of 0.1 μm excludes  1215  all blood and bodily fluid. The drive cable  411  may not lie concentric with the sleeve  121  so preferably the gap dimension is the largest gap between the two. 
     The decreased pressure at a lymphatic duct  907  promotes drainage from a lymphatic system into a circulatory system. Preferably, the impermeable sleeve  121  comprises a proximal seal  433  at a housing of the motor  405  and a distal seal  435  at the impeller  205 . The proximal seal  433  prevents the blood and bodily fluid from escaping the patient through the motor housing  401  or the proximal portion  109  of the catheter  105 . In some embodiments, the distal seal  435  comprises a fitting between the impermeable sleeve and a portion of the impeller, wherein the fitting excludes fluids and allows the impeller and drive cable to rotate within the device  101 . The method  1201  may include inflating at least one balloon  301 ,  801  disposed along the catheter  105  by means of an inflation lumen  415  having a proximal end accessible outside of the motor housing  401  while the distal portion  115  of the catheter  105  is inserted into the innominate vein  939 . In various embodiments, the proximal seal  433  uses an O-ring; the impermeable sleeve  121  comprises PTFE; the drive cable  411  comprises a metal such as a nickel-titanium alloy; either or both of balloon  301  and restrictor  801  may comprises polyvinyl chloride, cross-linked polyethylene, polyethylene terephthalate (PET), or nylon; or any combination of the those materials are included. Employing the method  1201 , blood and bodily fluid are excluded  1215  from the drive cable  411  without the use of a purge fluid or purge system. 
     Other features and benefits are provided by or within the scope of the disclosure. 
     Methods and devices of the disclosure avoid problems with thrombosis or hemolysis that may otherwise interfere with the functioning of mechanical systems or form surface irregularities that lead to other complications. For example, mechanical system may be most beneficial medically when blood clots or other coagulation-related phenomena are avoided. Accordingly, embodiments of devices and methods of the disclosure are provided that inhibit coagulation, thrombosis, hemolysis, or other issues that may present when treating edema. 
     Certain embodiments provide a device that operates with benefit from an anticoagulant. The device may include a pump (e.g., an impeller assembly) that is washed with a solution or suspension that comprises an anticoagulant such as, for example, heparin. Where the pump or impeller assembly is provided via a catheter, the catheter may include a lumen, reservoir, port, or other such feature to release the coagulant at or near the pump. 
       FIG.  13    illustrates a portion of an intravascular device  101  for treatment of edema that releases an anticoagulant at an intravascular pump. The device  101  includes a catheter  105 , an impeller assembly  201  mounted at a distal portion  115  of the catheter  105 , and a medicament lumen  251  extending through the catheter  105  and terminating substantially at an inlet  255  of the impeller assembly  201 . When the device  101  is used (e.g., when the impeller  205  is operated within a blood vessel of a patient), a medicament released from the medicament lumen  251  flows through the inlet  255  and impeller assembly  201 . Preferably, the catheter  105  and impeller assembly are dimensioned for insertion through a jugular vein of a patient The device  101  may include a reservoir in fluid communication with the medicament lumen  251 . The reservoir may be, for example, a solution bag (aka an “IV bag”) on a rack near the treatment gurney and in fluid communication with the medicament lumen  251  (e.g., via a Luer lock). 
     In certain embodiments of an anticoagulant delivery device  101 , the impeller assembly  201  has an impeller housing  203  with an impeller  205  rotatably disposed therein. The device  101  preferably includes a motor  405  connected to a proximal end of the catheter  105  and operably connected to the impeller  205  via a drive cable  411  extending through the catheter  105 . The medicament lumen  241  preferably extends through the catheter  105  (e.g., outside of a sleeve  121  surrounding the drive cable  411 ) and may terminate at a port  252  such that an anticoagulant released therefrom washes the impeller  205  or impeller assembly  201 . Preferably, the port  252  is located at the impeller housing  203 , proximal to the impeller. 
     To define the inlets  255 , the catheter  105  may include a tube with a drive cable extending there through with a cap  249  connected around a terminal portion of the tube, with the impeller housing  203  mounted to the cap by a plurality of struts to define inlets  255  into the impeller housing  203 . In some embodiments, the cap  249  seals a terminus of the flexible tube to a shaft of the impeller, and the port  252  is located in the cap  249 . Preferably, the impeller housing  203  includes one or more outlets  258  around a distal portion  115  of the impeller, such that operation of the impeller  205  within a blood vessel drives blood into the impeller assembly  201  via the inlets  255  and out of the impeller assembly via the outlets  258 . 
     The device  101  may include an anticoagulant in the reservoir. When the device  101  is inserted into a blood vessel of a patient and the impeller  205  is operated, the anticoagulant is released from the port  252  in the impeller cage  201  and the released anticoagulant mixes with blood and washes over the rotating impeller  205 . Any suitable anticoagulant may be used. For example, the anticoagulant may include one or any combination of heparin, tirofiban, warfarin, rivaroxaban, dabigatran, apixaban, edoxaban, enoxaparin, and fondaparinux. Due to the anticoagulant, the device  101  may be used for the treatment of edema, using the impeller to cause drainage of a lymphatic duct or vessel. 
     Using such a device, aspects of the invention provide a method for treating edema. The method includes operating a pump to increase flow through an innominate vein  939  of a patient and releasing an anticoagulant at or adjacent an inlet of the pump. The pump may include an impeller  205  in a cage  203  at a distal portion  115  of a catheter  105  and the anticoagulant is released from a port  252  in or adjacent a proximal portion of the cage. Preferably, a proximal end of the catheter  105  terminates at a housing comprising a motor  405 , and the motor  405  is operably coupled to the impeller by a drive cable extending through the catheter  105 . In this method, the catheter  105  includes a medicament lumen extending therethrough and terminating at the port. This method may include providing the anticoagulant in a reservoir in fluid communication with the medicament lumen; inserting the catheter  105  into vasculature of the patient to position the impeller in the innominate vein  939 ; operating the motor  405  to drive the impeller; and washing the anticoagulant over the impeller by releasing the anticoagulant from the port. Preferably, this method includes operating the pump decreases pressure at a lymphatic duct  907 , thereby draining lymph from a lymphatic system of the patient. The pump may include an impeller on a distal portion  115  of a catheter  105 . This method may include releasing the anticoagulant from a port at a proximal portion  109  of the impeller, preventing clotting or thrombosis from interfering with operation of the impeller by the release of the anticoagulant, or both. The anticoagulant may include heparin, warfarin, rivaroxaban, dabigatran, apixaban, edoxaban, enoxaparin, or fondaparinux. Using a restrictor  801 ,  301 , the method may include restricting flow from a jugular vein to the innominate vein  939  to thereby promote flow from a subclavian vein to the innominate vein  939 . 
       FIG.  16    is a partial cutaway view of an impeller assembly  1601 . The impeller assembly  1601  includes an impeller housing  1603  with an impeller  1605  rotatably disposed therein. An expandable member  1607  is attached to an outside of the impeller housing  1603 . The expandable member  1607  is depicted in an expanded state. 
     The impeller assembly  1601  is may be designed to facilitate a blood flow through the impeller housing  1603 . To facilitate blood flow, the impeller housing  1603  may include proximal inlets  1655 . Preferably, the impeller housing  1603  includes at least four proximal inlets  1655 . The proximal inlets  1655  may be substantially rectangular and may include rounded corners. The impeller assembly  1601  may also include distal outlets  1658 . For example, the impeller assembly  1601  may include four to five distal outlets  1658 . Preferably, the proximal inlets  1655  and distal outlets  1658  include substantially rounded features, such as, rounded corners. Rounded features are preferable because rounded features provide smooth contact surfaces for blood that flows through the impeller housing  1603 . This may reduce incidences of damage to particles in blood, e.g., blood cells, that occurs when blood strikes a sharp surface. 
     In preferred embodiments, an expandable member  1607  is attached to an outer surface of the impeller housing  1603 . The expandable member  1607  may comprise a shape that facilitates a flow of blood into the impeller housing  1603  when the expandable member  1607  is in an expanded state. In some embodiments, the expandable member  1607  forms a D shaped ring around a circumference of the impeller housing  1603 . In other embodiments, the expandable member  1607  forms an Omega shaped ring around a circumference of the impeller housing  1603 . In other embodiments, the expandable member  1603  forms a substantially circular ring around the impeller housing  1603 . 
     In an expanded state, a proximal face  1613  of the expandable member  1607  may be substantially aligned with a distal portion  1615  of the proximal inlets  1655 . A distal face  1617  of the expandable member  1607  may be substantially aligned with the proximal extent  1619  of the distal outlets  1658 . 
     In preferred embodiments, the expandable member  1607  comprises an elastomeric membrane, for example, a polyurethane membrane. The expandable member  1607  may be a balloon. The balloon may comprise a low durometer material, for example, a durometer of &lt;80 shore D hardness, or &lt;70 shore D hardness, or less than 60 shore D hardness, or between 60 shore A hardness and 60 shore D hardness. 
     The expandable member  1607  may include a fluidically sealed space, i.e., an inflation space  1623 , that is radially expandable relative to the impeller housing  1603 . The impeller assembly  1601  may include an inflation tube  1627  connecting the inflation space  1623  to a lumen of the catheter  1602 . The inflation tube  1627  may extend between the catheter  1602  and the inflation space  1623 , for example, parallel to a proximal strut  1633 . The inflation tube  1627  may extend exterior of the proximal strut  1633  (as shown). Alternatively, the inflation tube  1627  may extend interior to the proximal strut  1633 . The inflation tube  1627  may connect with the inflation space  1623  by extending through a wall of the expandable member  1607 . Alternatively, the inflation tube  1627  may connect with the inflation space  1623  by extending through an interface between the expandable member  1607  and the impeller housing  1603 , or by extending through a wall of impeller housing  1603 . The fluidically sealed space  1623  may comprise an inflation port for expanding the expandable member  1607 . 
     The inflation tube  1627  may comprise an outer surface and a lumen. The inflation tube  1627  preferably provides a sealingly penetrate into the inflation space  1623 . The penetration of the inflation tube  1627  into the inflation space  1623  may comprise a seal of the region of penetration. The seal may comprise a melting or bonding operation. 
       FIG.  17    is a side view of an impeller assembly  1701 . An expandable member  1707 , e.g., a balloon, is attached to an outer surface of an impeller housing  1703 . The expandable member  1707  may be substantially torpid in shape. The expandable member  1707  is depicted with muted lines to reveal structures beneath the expandable member  1707 . A proximal face  1713  of the expandable member  1707  extends over a distal inlet region  1715 . In this configuration, the proximal face  1713  of the expandable member  1707  provides a funnel to converge blood flow towards inlets of the impeller housing  1703  thereby facilitating blood flow through the device. 
     The impeller assembly  1701  is dimensioned for inserting into an innominate vein. The expandable member  1707  is dimensioned such that in a deployed state, the expandable member  1707  opposes walls of the innominate vein to impede, guide, or direct a flow of blood into the impeller housing  1703 . In some embodiments, an inner diameter of the expandable member  1707  is substantially equivalent to the outer diameter of the impeller housing  1703 . The inner diameter of the expandable member  1707  may extend over a portion of the proximal inlets. This arrangement helps funnel blood into the impeller assembly  1701  without the distal edge of the inlets disrupting blood flow. In some embodiments, the proximal inlets are substantially D shaped with rounded features to prevent shearing of blood cells. 
     The expandable member  1707  may comprises a bonded region, the bonded region comprising a substantially cylindrical section where the expandable member  1707  is bonded to the impeller assembly  1701 . In some embodiments, the inlet region may comprise a conical element  1737  coaxial with the impeller. The conical element  1737  may be proximal to the impeller and may be configured to minimize flow recirculation regions. 
       FIG.  18    shows an exemplary inlet region  1855  of an impeller assembly  1801 . The inlet region  1855  comprises a conical element  1837  with flow directing features projecting radially outward from a surface of the conical element  1837 . The flow directing features may be aligned with proximal struts. A drive element  1839  may extend through the conical element  1837  and connect with an impeller disposed inside the impeller assembly  1601 . In the shown embodiment, an inflation lumen  1827  is exterior of the impeller assembly  1801 . 
       FIG.  19    shows an inlet region  1955  with an internal inflation lumen. The inflation lumen is internal to the impeller housing  1903 . The inflation lumen may connect to and extend through the conical element  1937 . The inflation lumen may, for example, extend through a wall of the impeller housing  1903 . Alternatively, the inflation lumen may be interiorly located within the impeller housing  1903 . 
       FIG.  20    is a detailed view of a proximal inlet  2055 . The proximal inlet  2055  is defined by proximal struts  2033 . The proximal struts  2033  extend parallel to one another connecting a proximal portion  2041  of the impeller housing  2003  to a distal portion  2043  of the impeller housing  2003 . The proximal struts  2033  are designed such that when the catheter is operating inside a patient&#39;s body, the proximal struts  2033  may separate and direct a flow of blood into the impeller housing  2003  without inducing a recirculation flow pattern. The proximal struts  2033  may include a proximal and distal rim  2045 ,  2047 . The proximal struts  2033  and rims  2045 ,  2047  may, for example, define a generally rectangular inlet region  2055 . In some embodiments, the generally rectangular inlet region  2055  comprises a curved rectangular inlet. The curved rectangular inlet may have, for example, a bevel around at least a portion of a rim  2045 ,  2047  of the inlet  2055 . The bevel may provide a gentle transition region for blood to flow into the impeller housing  2003 . 
     In some embodiments, the proximal struts  2033  comprise a substantially constant width along a length of the proximal strut  2033 . In other embodiments, the width of the proximal struts  2033  may vary, for example, the width of the proximal struts  2033  may be greater at a proximal end than at a distal end, or vice versa. The proximal struts  2033  may comprise a first wall thickness and a second wall thickness, wherein said first wall thickness is greater than said second wall thickness. In some embodiments, the proximal struts  2033  may comprise a tapered wall thickness. 
     Preferably, the impeller housing  2003  is substantially cylindrical in shape for easy passage through an innominate vein. The impeller housing  2003  may comprise a plurality of inner diameters for manipulating a flow of blood through the impeller housing  2003  and such that the flow of blood experiences minimal disturbances such as recirculation or vortices within, or near, the impeller assembly  2001 . For example, the impeller housing  2003  may comprise a first inner diameter D 1  and at least a second inner diameter D 2  wherein the first inner diameter is greater than said at least second diameter. In some embodiments, the impeller housing  2003  may comprise stepped portions defined by changes in inner diameters. In some embodiments, the impeller housing  2003  may comprise, for example, a tapered diameter, defined by a diminished or reduced internal diameter along the length of the impeller housing  2003  toward one end. 
       FIG.  21    shows a side view of an impeller assembly  2101  with rectangular proximal inlets  2155 . This configuration may reduce recirculation of blood at a proximal area of the impeller assembly  2101  by providing a larger inlet area at the distal-most region of the inlet  2147 . 
       FIG.  22    shows an impeller assembly  2201  with arcuate proximal struts  2233 . The arcuate proximal struts  2233  extend longitudinally and radially. In some embodiments, the arcuate proximal struts  2233  comprise tubular members. The tubular members may be welded to the impeller assembly  2201 , connecting a proximal portion  2241  of the impeller housing  2203  to a distal portion  2243  of the impeller housing  2203 . The arcuate proximal struts  2233  may connect to a proximal portion  2241  of the impeller housing  2203  integral with the catheter shaft. The arcuate proximal struts  2233  may comprise a monolithic structure. The monolithic structure may comprise a 3D printed structure. 
     The impeller assembly  2201  may be distally mounted to a catheter shaft (not shown) comprising a plurality of lumens and at least one of the lumens sealingly connected to an expandable member  2207  attached to an outer surface of the impeller housing  2203 . 
       FIG.  23    shows a side view of a proximal portion of an impeller assembly  2301 . The proximal portion of the impeller assembly  2301  includes a proximal hub  2383 , a proximal inlet  2355 , and a body section  2385 . The proximal hub  2383  may be configured to facilitate a smooth flow pattern as fluids, e.g., blood, are directed into the proximal inlet  2355 . The hub  2383  may comprise a substantially circular outer geometry in axial cross section for easy movement within a vein. The hub  2383  may comprise a tapered geometry. For example, a cross-sectional diameter of the hub  2383  may decrease along a length of the hub  2383  from a first end to a second end. The hub  2383  may have a tapered outer geometry that may comprise a proximal diameter, an intermediate diameter, and a distal diameter wherein the intermediate diameter is greater than either the proximal diameter or the distal diameter and the transition between proximal, intermediate, and distal diameters is substantially smooth. The curve between the proximal, intermediate, and distal diameters may be without an inflection point. 
       FIG.  24    shows an impeller assembly  2401 . The impeller assembly  2401  includes an impeller housing  2403  with an impeller  2405  rotatably disposed therein. An expandable member  2407  depicted with ghosted lines is attached to an outer surface of the impeller housing  2403 , the expandable member  2407  is shown in an expanded state. 
     The impeller assembly  2401  is designed to facilitate the flow of blood through the impeller housing  2403 . The impeller assembly  2401  may include fillets  2435  under the proximal end of the proximal struts  2433  to provide mechanical support and prevent recirculation of blood in these regions when the catheter is inside a vein. In some embodiments, the proximal struts  2433  taper towards their distal ends. 
       FIG.  25    shows an elongated impeller assembly  2501 . The elongated impeller assembly  2501  includes an expandable member  2507  spaced apart from a proximal inlet region  2555 . The expandable member  2507  may be, for example, approximately 1-25 cm from the proximal inlet region  2555 . Preferably, the expandable member is at least 1 cm from the proximal inlet region  2555 . 
       FIG.  26    shows a cross-sectional view of an impeller assembly  2601 . The impeller assembly  2601  includes an impeller housing  2603  with an impeller  2605  rotatably disposed therein. The impeller assembly  2601  includes a distal portion  2645 . The distal portion  2645  may include a tip  2647  that is substantially disc shaped. The distal portion  2645  may have at least a partially flat surface. The disc-shaped tip  2647  may be spaced apart from a proximal surface of the distal portion  2645 . 
     The impeller  2605  may comprises a substantially fixed axial position relative to the impeller housing  2603 . The distal portion  2645  may comprise a substantially fixed axial position relative to the impeller housing  2603 . The fixed axial positions of the impeller  2605  and the distal portion  2645  may define a distal gap  2651  between the distal portion  2645  and the impeller  2605 . The gap  2651  is preferably greater than 5 um. The gap  2651  may be greater than 10 um or 20 um. The gap  2651  may be preferably less than 150 um, 120 um, or 100 um. Ideally, the gap  2651  is between 25 um and 50 um. 
       FIG.  27    is a cross-sectional view of an impeller assembly  2601  inside a vein  2756 . The impeller assembly  2701  comprises an impeller housing  2703  with an impeller  2705  inside. The impeller housing  2703  has an expandable member  2707  attached to an outer surface of the impeller housing  2703 . 
     The impeller  2705  includes at least one blade  2753 . The blade  2753  comprises a proximal end and a distal end. A core diameter of the impeller  2705  comprises a proximal end and a distal end. The core diameter proximal end is proximal of the proximal end of the blade  2753 . The core diameter distal end and the blade distal end terminate substantially at the same axial region. The core diameter is smallest at the proximal end of the impeller  2705  and largest near the distal end of the core diameter. The core diameter may comprise a curved tapered surface. 
     The proximal end of the impeller  2705  core diameter may be spaced apart from the distal end of a cuff  2761 . The proximal end of the impeller  2705  core diameter and the distal end of the cuff  2761  comprise a controlled proximal gap. The gap  2751  is preferably greater than 5 um. The gap  2751  may be greater than 10 um or 20 um. The gap  2751  may be preferably less than 150 um, 120 um, or 100 um. Ideally, the gap  2751  is between 25 um and 50 um. 
     The impeller  2705  may comprise an inner diameter, the inner diameter extending through at least a portion of the length of the impeller  2705  and being coaxial with the impeller  2705 . The impeller  2705  may comprise a bearing arrangement distal of the distal surface. The bearing surface may include a ball bearing arrangement, for example, a ceramic bearing arrangement or a PTFE or PEEK bearing surface arrangement. 
       FIGS.  28 A-F  illustrates attachment and folding of an expandable member  2807 . In particular, these drawings detail attachment of the expandable member  2807  to an outer surface of an impeller housing  2803  as wells as folding of the expandable member  2807  when the expandable member is inflated or when the catheter is being delivered or retrieved. 
       FIG.  28 A  is a partial cross-sectional view of an impeller assembly  2801 . A portion of the cross-section demarcated by dashed lines and labeled B shows a portion of the expandable member  2807  and is enlarged in  FIG.  28 B . The expandable member  2807  includes at least one coupling  2863  attaching the expandable member  2807  with the impeller housing  2803 . The coupling  2863  may create a sealed annular space in the expandable member  2807 . 
     The coupling  2863  may comprise a laser weld joint, a solvent weld joint, an adhesive weld joint, a hot air or heated surface weld joint, or any other similar type of attachment. The coupling  2863  may comprise a prepared outer surface of the impeller housing  2803  onto which the expandable member  2807  is attached. For example, the impeller housing  2803  may be prepared such that the impeller housing  2803  includes at least one of a primed surface, a chemically activated surface, a plasma activated surface, a mechanically abraded surface, a laser ablated surface, an etched surface, or a textured surface. The prepared outer surface of the impeller housing  2803  may comprise a surface roughness, a patterned surface, or a high energy surface. 
     Referring to  FIG.  28 B , the expandable member  2807  may include at least one neck  2867 , the neck  2867  may be dimensioned for joining with the impeller housing  2803 . The expandable member  2807  may comprises a joint distal end  2831  and a joint proximal end  2832 . The shape of the distal end  2831  may be configured to change as the expandable member is inflated/deflated (compare  FIGS.  28 B,  28 D, and  28 E ) or when the catheter is moved inside a vein. In particular, the joint distal end  2831  may comprise a distal neck segment joined to the impeller housing  2803  and a distal transition segment  2845  that is integral with the neck  2867  but not attached to the impeller housing  2803 . As the expandable member  2807  is inflated, the distal transition segment  2867  may fold inward. The joint proximal end may comprise a neck  2832  joined to the impeller housing  2803  and a proximal transition segment that is integral with the neck but not joined to the impeller housing. The expandable member  2807  may be configured to be substantially rigid in the expanded configuration. The expandable member  2807  may be configured to be conformable in the expanded configuration. The expandable member  2807  may be made from a polyurethane, or pebax or nylon material. The expandable member  2807  may be made from polytetrafluoroethylene. 
       FIG.  28 C  is a partial cross-sectional view of the impeller assembly  2801  in which the expandable member  2807  is partially inflated. The portion of the partial cross-section showing the expandable member  2807  (labeled D) is enlarged in  FIG.  28 D . Notably, the shape of the distal neck changes as the expandable member  2807  is inflated (compare  FIG.  28 D  in which the expandable member is partially inflated to  FIG.  28 B  in which the expandable member is fully inflated). 
       FIG.  28 E  is a partial cross-sectional view of the impeller assembly  2801  with moderately inflated expandable member  2807 . The portion of the partial cross-section showing the expandable member  2807  (labeled F) is enlarged in  FIG.  28 F . In particular, the expandable member  2807  is inflated more than the expandable member  2807  illustrated in  FIG.  28 D . Upon inflating the expandable member  2807 , the distal transition segment  2845  may fold outward eliminating a potential recirculation zone at the interface between the balloon and housing  2803 . 
       FIG.  29    shows an impeller assembly  2901  with an expandable member  2907  having an elongated surface  2974  for interfacing with a wall of a blood vessel. The elongated surface  2974  increases an interaction between the blood vessel and the impeller assembly  2901  to restrict movement of the impeller assembly inside the blood vessel. The expandable member  2907  may comprise a compliant material. The compliant material may be a polyurethane or silicone. The compliant material may stretch 100% to 800%, thus creating an elongated surface  2974 . In other embodiments, the expandable member  2907  may comprise a non-compliant material, which may expand to one specific size or size range, even as internal pressure increases. 
       FIG.  30    shows an impeller assembly  3001  with a two-part expandable member  3007 . The two-part expandable member  3007  includes a first part  3065  comprising a compliant material and a second part  3066  comprising a non-compliant material. The first part  3065  and second part  3066  may be attached to each other and to the impeller housing  3003  to define an annular space for inflation. Preferably, the first part  3065  of the expandable member  3007  comprises a portion of the expandable member  3007  that interacts with a wall of a blood vein during operating of the catheter. 
       FIG.  31    is a partial cross-sectional view of a distal portion of a catheter  3101 . The distal portion of the catheter  3101  is attached to an impeller housing  3103  with an expandable member  3107  mounted to an outer surface of the impeller housing  3103 . The impeller housing  3103  is connected to a distal portion of a catheter  3101  by a plurality of proximal struts  3133 . The proximal struts  3133  preferably comprise a flexible material, for example, latex, silicone, or Teflon, to provide for easier navigation inside a vein of a patient. The proximal struts  3133  may be configured to conform to anatomical curvatures. A drive shaft  3139  connecting a motor to an impeller disposed inside the impeller housing  3103  may comprise a flexible drive cable. 
       FIG.  32    is a partial cross-section of a self-expanding impeller assembly  3201 . The impeller assembly  3201  comprises an impeller housing  3203  with an impeller  3205  disposed therein. An expandable body  3207  is attached to a surface of the impeller housing  3203  between proximal inlets  3255  and distal outlets  3258 . 
     In an expanded configuration, the expandable body  3207  is configured to oppose a wall of a vein over a longitudinal segment of the vein. The longitudinal segment of apposition extends proximal of the proximal inlets  3255 . The longitudinal segment of apposition extends distal of the distal inlets  3258 . The expandable body  3207  is configured to provide a proximal flow directing funnel that extends from a region of apposition with the vessel wall to the distal end of the inlets  3255 . The proximal flow directing funnel is configured to promote converging flow pattern at the entrance to the proximal inlets  3255 . The expandable body  3207  may be configured to provide a distal flow directing funnel that extends from a proximal region of the outlets  3258  to a region of apposition with the vessel wall to the distal end of the outlets  3258 . The distal flow directing funnel may be configured to promote diverging flow pattern distal of the exit of the outlets  3258 . The diverging flow pattern may be configured so as to impart a gradual deceleration of fluid distal of the outlets and maintain a larger proportion of the pressure gain developed by the impeller  3205  by reducing recirculating or negative velocity flow patterns. 
     The expandable body  3207  may comprise a nitinol membrane, a non-compliant membrane, or a porous membrane. The longitudinal segment of the expandable body  3207  may comprise a compliant material. Preferably, the flow directing funnels of the expandable body  3207  comprise a relatively less compliant material (or a semi compliant material or a non-compliant material). 
     The catheter  3200  may comprise a plurality of pull wires  3279  attached to the expandable body  3207  and configured to facilitate collapse of the expandable body  3207  in preparation for the removal of the catheter  3200  from the body. 
       FIG.  33    shows a partial cross-section of an impeller assembly  3301 . The impeller assembly  3301  comprises proximal struts  3333  attaching a proximal portion  3341  of the impeller assembly  3301  to a distal portion  3343  of the impeller assembly  3301 . At least one proximal strut  3333  comprises an inflation lumen, i.e., an integrated inflation channel, extending through the proximal strut  3333  to an interior of an expandable member  3307  that is attached to an outer surface of the impeller assembly  3301 . The inflation lumen provides a structure for inflating the expandable member  3307 . The inflation lumen is preferably terminated within the inlet to minimize disruption to the flow inside the housing. This is facilitated by the more proximally positioned expandable member  3307 . 
       FIG.  34    shows an inlet  3433  of an impeller assembly  3401 . The inlet  3433  is configured to provide easier fluid flow into the assembly  3401 . This configuration includes a proximal hub  3480  with at least one flow basin  3481 . The flow basin  3481  extends from a proximal region of the proximal hub  3480  and terminates at the inlet  3433 . The flow basin  3481  extends between a first and second strut  3433 ,  3434 . The flow basin  3481  may be configured to modulate a flow of blood upstream of the inlets. For example, the flow basin  3481  may progressively slope inwards along the length of the flow basin  3481  towards the inlet  3433 . 
       FIG.  35    is an exemplary catheter system  3500 . In particular,  FIG.  35    illustrates a catheter  3500  according to aspects of the invention to show interactions between an impeller assembly  3501  of the catheter  3500  and a blood vessel wall  3556 . The catheter  3500  includes the impeller assembly  3501 , a catheter shaft  3581 , a proximal expandable member  3508 , a hub  3583  and a motor (not shown). 
     The impeller assembly  3501  is dimensioned for placement inside a blood vessel with a shaft  3581  extending from the impeller assembly  3501  to a position exterior of the patient. The shaft  3581  may comprise a multilumen shaft. A first proximal expandable member  3508  is attached to the shaft  3581  and may be configured to restrict a flow of blood to the impeller assembly  3501 . 
     A motor may be connected to an impeller housed within the impeller assembly  3501  and may be configured to drive the impeller at high RPMs. The impeller assembly  3501  may comprise a distal expandable member  3507  mounted onto an outer surface of an impeller housing  3503  and wrapping around the impeller housing  3503 , for example, like an expandable ring. The distal expandable member  3503  may be configured to appose a vessel wall  3556  during operation of the catheter. 
     The proximal expandable member  3508  may be mounted on the catheter shaft  3581  proximal of the impeller assembly  3501 . The proximal expandable member  3508  may be spaced apart from the impeller assembly  3501 . For example, the proximal expandable member  3508  may be a distance of 1-10 cm upstream of the impeller assembly  3501 , preferably about no more than about 5 cm. 
     The proximal expandable member  3508  may be dimensioned for placement (inflation) between the vessel access site and an outflow port of a thoracic duct  3585 . The expandable members  3507 ,  3508  are preferably configured to atraumatically contact a vessel wall. 
     In some embodiments, a proximal expandable member  3508  may be configured to reduce a volume of blood flowing in the vessel by impeding a flow of flood. The proximal expandable member  3508  may be configured to adjust the volume of blood flowing in the vessel by impeding, restricting, guiding, or directing the flow of blood. For example, the proximal expandable member  3508  may include an orifice for fluid to flow across the expandable member  3508  while the expandable member  3508  is in an expanded state. For example, the orifice may substantially comprise one of an annular ring or a crescent shape with a lumen through a body of the expandable member  3508 . The orifice may comprise a valley or a recess in the outer surface of the expandable member  3508 . The orifice may comprise a channel underneath the expandable member  3508 . The expandable member  3508  may comprise a shape that defines the orifice. For example, the expandable member  3508  may be shaped at least partially as a spherical, conical, or cylindrical shape and the orifice comprises an annular ring or a crescent. The expandable member  3508  shape may comprise, for example, a double D shape and the orifice may be defined by surfaces between the two joining shapes. The expandable member  3508  may comprise a helical shape wrapped around the catheter shaft  3581  and the orifice may comprise a channel defined by a space between adjacent spirals. 
     The proximal expandable member  3581  may comprises a compliant material and the compliant material may comprise a compliance-pressure relationship. The expandable member  3581  may be processed so the compliance pressure relationship is repeatable. The expandable member  3581  may comprise an annealed member. The expandable member  3581  may be configured to achieve a precise diameter at a given pressure. The expandable member  3581  may be configured to have minimal hysteresis when inflated, deflated and inflated again. 
     The hub  3583  may be configured to facilitate inflation of a distal expandable member  3507 , and may be configured to at least partially inflate the proximal expandable member  3508 . For example, the hub  3583  may include access to one or more lumens that extend through the catheter shaft  3581  and connect to a proximal and/or distal expandable member  3508 ,  3507 . The expandable members can be inflated by infusing a fluid into the lumens at the hub  3583 . The hub  3583  may be configured to inflate the proximal expandable member  3508  into apposition with an innominate vessel. 
     The device may comprise a connector cable  3585  configured to connect the catheter to a console (not shown), the console may comprise a computer with hardware, software and a user interface. The console can be configured to operate the device. 
       FIG.  36    shows a catheter  3600  with an expandable member  3608  slidably mounted along a shaft  3681  of the catheter  3600 . The catheter  3600  comprises a first catheter shaft  3681  and a second catheter shaft  3682 . The catheter  3600  includes an impeller assembly  3601  attached to a distal end of the first catheter shaft  3681 . The proximal expandable member  3608  mounted near a distal end of said second catheter shaft  3682 . 
     The first catheter shaft  3681  may comprise a multilumen tubing wherein a first lumen is configured to facilitate inflation of a distal expandable member  3607  and a second lumen is configured to transmit mechanical or electrical energy to facilitate the operation and control of an impeller disposed within the impeller assembly  3601 . 
     The second catheter shaft  3682  may comprise a multilumen tubing wherein a first lumen is configured to encapsulate the first catheter shaft  3681  and a second lumen is configured to inflate the proximal expandable member  3608 . The first and second catheter shafts  3681 ,  3682  may be configured to facilitate relative axial movement (indicated by arrows) between the distal expandable member  3607  and the proximal expandable member  3608 . The relative axial movement may be limited distally. The relative axial movement may be is limited proximally. 
     The catheter  3600  may include a first stop and a second stop and axial movement of second shaft  3682  may be limited by the first and second stops. The first and second stops may be mounted on the first shaft  3681 , exterior of the patient (inside or around the hub). The axial movement may comprise fine movements. The fine movements may comprise, for example, a thread or ratchet mechanism. 
     Relative axial movement between the distal expandable member  3607  and the proximal expandable member  3608  may provide better anatomical placement, i.e., accurate placement of the distal expandable member  3607  in the innominate vein and then accurate placement of the proximal expandable member  3608  between the vessel wall access site and the thoracic duct. 
     The first and second shafts  3681 ,  3682  may extend exterior of the patient. The second shaft  3682  may be coupled and decoupled to the first shaft during use. In a collapsed state, the catheter may be dimensioned for advancement through a valve and lumen of a sheath. The second shaft  3682  may comprise a distal segment and a proximal segment. The distal segment may comprise a tubular member and an inflation lumen with the proximal expandable member sealingly welded (bonded) to a distal segment so as to create an inflation space in the expandable member  3607  that is in fluid communication with the inflation lumen. 
     The proximal segment of the second shaft may comprise an inflation lumen and a member configured to transmit axial push and pull forces to the distal segment of the second shaft  3682 . The proximal segment of the second shaft may be concentric or eccentric with the first shaft. The inflation lumen of the proximal segment may be integral with a wall of the proximal segment of the second shaft. 
       FIG.  37    shows a fluid channel across an expandable member  3708  that allows a controlled amount of blood flow. The proximal expandable member  3708  may be configured to oppose a wall of a vessel. The proximal expandable member  3708  may comprise a flow channel  3706 , the flow channel  3706  defining a lumen through the body of the expandable member  3708 . Flow is indicated by black arrows. The flow channel  3706  may comprise a collapsed state and an expanded configuration. The flow channel  3706  may be configured to expand when the expandable member  3708  is inflated. The expandable member  3708  may comprise at least one inner membrane, the inner membrane may be configured to support the body flow channel  3706  in the expanded state. The proximal expandable member  3708  may be configured to allow 100 ml or more fluid to cross the expandable member  3708  per minute. 
       FIG.  38    shows a catheter  3800  with an alternative bypass channel  3806 . A second shaft  3882  comprises a tubular member with a distal end and a proximal end and a lumen  3883  extending through both distal and proximal ends. The lumen  3883  may be sized to provide a fluid flow pathway underneath the inflated expandable member  3808  in a distal segment. The second shaft  3882  may comprise an entry port  3885  at the proximal end of the distal segment of the second shaft  3882 , the entry port may be configured to facilitate blood flow into said fluid flow pathway. 
       FIG.  39    shows a patient interface  3900  with a sheath  3904  in situation. A proximal expandable member, a flow entry port, and pressure sensor, may be on the sheath. The catheter system may comprise a catheter and a flow control sheath  3904 , the catheter comprising an impeller assembly at a distal end of an elongated shaft, the flow control sheath  3904  comprising a flow restrictor, a fluid channel and a pressure sensor. 
     The system may be configured for transdermal insertion into a vein of a patient  3908 . Insertion of the catheter comprises transdermal insertion in a region of the neck. The flow control sheath  3904  may be configured for placement so as to provide an access platform for other components of the system. The flow control sheath  3904  may comprise a flow restrictor adjacent a tip. The flow restrictor may comprise an expanded state and a collapsed state. In the collapsed state the flow restrictor may be configured to collapse completely onto the shaft of the sheath. In the collapsed state, the OD of the flow restrictor may be substantially the same as the shaft of the sheath. The restrictor may sit in an annular recess in a diameter of the shaft of the flow control sheath in the collapsed configuration. In the expanded configuration, the flow restrictor may be configured to at least partially restrict fluid flow through the jugular vein. The flow restrictor may be configured to control the rate of flow through the jugular vein. The flow restrictor may be configured to prevent inadvertent displacement of the flow control sheath during the procedure. 
     The flow control sheath may comprise a pressure sensor, the pressure sensor may be configured to measure pressure in a vein upstream of the restrictor. The sheath may comprise a lumen in a wall of the sheath and the pressure sensor may be positioned in said lumen. The pressure sensing lumen may comprise a port, the port may be configured to establish a hydrostatic connection between blood in the vein and the pressure sensor. The pressure sensor and the pressure sensing lumen may be sized to prevent blood flow ingress into the pressure sensing lumen. 
       FIG.  40    shows a patient interface  4000  with a sheath  4004  held in situation by an adhering membrane  4010 . The adhering member  4010  helps maintain a sterile region around an access site and secures a hub  4080  of the sheath  4004  to the skin. This reduces irritation to the patient by movement of the hub  4080  made by accidental forces. The membrane  4010  may be shaped so as to allow second or tertiary layers to be added to tie all of the various system elements of the sheath  4004  or catheter together or to the skin. 
       FIG.  41    shows a flow control sheath  4150 . Shown are various features of the flow control sheath  4150  according to some preferred embodiments. In particular, the flow control sheath  4150  may include a restrictor  4151  (shown in an inflated state), a sheath tip  4152 , a port  4153 , a pressure sensor  4154 , a sheath shaft  4155 , and a hub  4159 , the hub  4159  including a pressure sensor lead  4156 , an inflation side port  4157 , a flushing and infusion side port  4158 . At least one suturing hole may be added to the hub  4159  to facilitate fixation to the patient. 
       FIG.  42    shows a proximal portion of a catheter system  4200 . A catheter  4269  that is similar to the catheter described in  FIG.  40    is disposed within a catheter sheath  4280 . The catheter  4269  includes a shaft  4270 , a proximal expandable member  4271  (depicted in an expanded state), and a catheter pressure sensor  4273 . The sheath  4280  includes a sheath tip  4272 , a sheath pressure sensor  4274 , a sheath shaft  4275 , a pressure sensor lead  4276 , an inflation side port  4277 , and hub  4278 . 
       FIG.  43    illustrates a locking mechanism  4300  for fixing a catheter shaft  4392  to a hub  4391  of a sheath  4390  during therapy. The locking mechanism  4300  includes an arm  4396  with a catheter shaft grip  4395  attached to a distal end of the arm  4396 . When engaged, the catheter shaft grip  4395  attaches to the catheter shaft  4392  preventing movement. The locking mechanism  4300  is advantageous because it prevents migration of a distal expandable member of the catheter system, described above, during therapy. The locking mechanism  4300  is configured to lock the catheter shaft  4392  to the sheath  4390  during at least a portion of the procedure. 
     The locking mechanism  4300  may be configured for easy engagement and disengagement. The locking mechanism may be configured to prevent relative movement between the catheter distal balloon and the access sheath  4390 . The locking mechanism  4300  may comprise a clip  4395  on locking mechanism  4300 ; the clip on mechanism  4300  may be configured to be clipped onto the catheter shaft  4392  from one side of the shaft  4392 . The locking mechanism  4300  may be pre-mounted on the catheter shaft  4392  such that the locking mechanism  4300  may slide into position when fixation is required. 
     The locking mechanism may be integral with the sheath. The locking mechanism may optionally attach to the sheath. Preferably, the locking mechanism may be a Tuohy Borst type locking mechanism. 
       FIG.  44    shows the locking mechanism  4300  engaged with the catheter shaft. 
       FIG.  45    shows a schematic of a push lock mechanism  4500 . 
       FIG.  46    shows an alternative locking mechanism  4600 . The locking mechanism  4600  includes an arm  4696  attached to a hub  4691  of a sheath  4690 . The arm  4696  includes a catheter shaft grip  4695  attached to a distal end of the arm  4696 . When engaged, the catheter shaft grip  4695  attaches to the catheter shaft  4692  preventing movement. A further embodiment of a locking system may include a C shaped shaft which may be secured over the catheter shaft proximal to the sheath. The shaft would be configured so that when the shaft is slid into the sheath hub it creates an interference lock between the catheter shaft OD and Sheath ID. 
       FIG.  47    is a partial cutaway of a jugular vein  4752  showing a flow control sheath  4750  inserted therein. The restrictor  4751  of the sheath  4750  is shown in a deployed state with the restrictor  4751  opposing a wall of the jugular vein  4752 . In a preferred position, the shaft  4755  of the sheath  4750  terminates adjacent to a junction of the subclavian vein  4753  and the thoracic duct  4756 . The hub  4759  is external to the jugular vein  4752 . 
       FIG.  48    shows an indwelling catheter system  4800  according to aspects of the invention. The indwelling catheter system  4800  includes a catheter shaft  4851  with an impeller assembly  4861  mounted to a distal portion thereof. The catheter shaft  4851  includes a proximal expandable member  4850  attached to an outer surface of the catheter shaft  4851 . The proximal expandable member  4850  comprises a flow channel  4854  that allows fluid to bypass the proximal expandable member  4850  at a controllable rate. 
       FIG.  49    is a cross-section taken along line A-A of  FIG.  48    to reveal internal lumens of the catheter shaft  4851 . The internal lumens extend internally through the catheter shaft  4851 . Shown is a proximal expandable member lumen  4901  for delivering fluids, i.e., gas or a liquid, used to inflate the proximal expandable member  4850 . A separate distal expandable member lumen  4902  is provided for delivering fluids to inflate the distal expandable member  4862 . The separate lumens allow the proximal and distal expandable members  4850 ,  4862  to be manipulated independently of one another during therapeutic treatments. A pressure sensor lumen  4966  is provided for sending and receiving electrical signals with one or more pressure sensors disposed on the catheter system  4800 . One or more reinforcement lumens  4930  may be provided to reinforce the catheter  4800  so that the catheter  4800  can be more easily navigated through the body. 
       FIG.  50    is an indwelling catheter  5000 . The catheter  5000  includes mechanical components, e.g., an impeller  5005  and/or drive shaft  5007 , and a purge system. The purge system operates to exclude biological fluids and materials from the catheter  5000  and mechanical components operating within the catheter  5000 . In that manner, body fluids are prevented from entering the crevasses of the catheter  5000 , ensuring smooth and efficient operation of the mechanical parts, e.g., impeller  5005  and drive shaft  5007 , within the catheter  5000  while also preventing the patient&#39;s body fluid from travelling to a proximal portion of the catheter  5000  outside of the patient&#39;s body, where it could leak out of the catheter. The purge system would further prevent air entering the vein though the same channels. 
     The catheter  5000  may be used to reduce pressure in a region of a venous system. The catheter  5000  includes an impellor assembly  5009  mounted at the distal end of the catheter  5000 . The impellor assembly  5009  comprises an expandable member  5013 , a cage  5015  with an inlet region  5017  and an outlet region  5019  and an impellor therein. The impellor  5005  may rotate at high RPMs within the cage  5015 . The impellor  5005  may further include a distal surface, a proximal surface and an impellor blade surface. The distal surface, proximal surface and impeller blade surface configured to rotate in close proximity to adjacent surfaces inside the cage, but without contacting said adjacent surfaces. 
     The impellor assembly  5009  may further comprise a cuff  5023 . The cuff  5023  may include a distal surface  5025  and a proximal surface  5027 . The impeller  5005  rotates in clearance of the distal surface of a cuff  5023 . 
     The clearance between the cuff distal surface  5025  and the impeller  5005  comprises a proximal gap  5029  and the proximal gap  5029  is configured to remain fixed during operation. The proximal gap  5029  is configured to define a transition between a static cuff and a rotating impeller  5005 . The proximal gap  5029  is configured to allow blood to flow across the proximal gap  5029  without flow disturbance, flow recirculation, or vortices. The proximal gap  5029  may be in fluid communication with a catheter lumen which is in fluid communication with a fluid reservoir exterior of the patient. The proximal gap  5029  may be configured to prevent blood flow from entering the proximal gap  5029 . 
     In preferred embodiments, the proximal gap  5029  includes a resistive fluid pressure configured to prevent blood from entering the proximal gap. For example, the resistive fluid may be a purge fluid delivered from a fluid reservoir external to the patient. The purge fluid can be used to purge or flush the proximal gap  5029  clearing debris; for example, as described in co-owned U.S. Provision Application 62/629,914, which is incorporated herein by reference. The resistive fluid pressure may comprise a hydrostatic fluid pressure, which may include a pulse of fluid pressure. The fluid pressure comprises a solution that may include saline, dextrose or a heparin solution. 
     The viscosity of the purge solution may be tailored to effectively purge small gaps and orifices. The solution may also be immiscible with blood to prevent blood contact with the purges surfaces. For example, the solution may be a hydrophobic solution. In some embodiments, the proximal gap  5029  may include a seal, such as, for example, a spring loaded seal. 
     A clearance between a distal-most surface of the impellor  5005  and a tip  5031  comprising a bearing housing  5033  may comprise a distal gap  5041  and the distal gap  5041  may be configured to remain fixed during operation. The distal gap  5041  may be configured to define a transition between a rotating impeller  5005  and a static tip  5031 . The distal gap  5041  may be configured to allow blood to flow across the distal gap without flow disturbance, recirculation, or vortices. 
     In preferred embodiments, the distal gap  5041  is in fluid communication with a catheter lumen which is in fluid communication with a fluid reservoir exterior of the patient. The distal gap  5041  may be configured to prevent blood flow from entering the distal gap, for example, by providing a purge from the fluid reservoir as discussed above. The distal gap  5041  may comprise a resistive fluid pressure configured to prevent blood from entering the distal gap. The resistive fluid pressure comprises a hydrostatic fluid pressure. The resistive fluid pressure comprises a pulse of fluid pressure. The fluid pressure comprises a solution, for example, a saline, dextrose or a heparin solution. The viscosity of the purge solution may be tailored to effectively purge small gaps and orifices. The solution may also be immiscible with blood to prevent blood contact with the purges surfaces. The solution may be a hydrophobic solution. The distal gap  5041  may comprise a seal, such as, for example, a spring loaded seal. 
       FIG.  51    is an expanded view of dotted circle B of  FIG.  50    according to an embodiment of the invention. In this embodiment, fluid is delivered from a purge channel  5101  extending along a central lumen of the device. The purge channel may be external to a PTFE liner that surrounds a central lumen of the catheter. 
       FIG.  52    is an expanded view of dotted circle B of  FIG.  50    according to another embodiment of the invention. In this embodiment, purge fluid is delivered from the reservoir exterior of the patient via a purge channel  5201  that travels through a lumen used for inflating the expandable member  5013 . The purge channel  5201  is external to a PTFE liner of a drive cable. 
       FIG.  53    is an expanded view of dotted circle B of  FIG.  50    according to a different embodiment of the invention. In this embodiment, purge fluid is delivered from a purge channel  5301 , the purge channel  5301  extending through a PTFE liner that surrounds a drive lumen. 
       FIG.  54    illustrates a distal flush of an indwelling catheter  5400 . The flush, i.e., purge fluid, is delivered via a lumen  5403  of the expandable member  5407 . The purge travels through the lumen  5403  and through a distal bearing housing  5411 , preventing blood flood flow into bearings of the catheter. The purge fluid flows into the distal gap  5431  flushing and preventing blood from filling the distal gap  5431 . The purge fluid travels down a second lumen  5437  to a proximal gap  5439  and flushes blood from the proximal gap  5439 . 
       FIG.  55    illustrates distal flush of an indwelling catheter  5500  according to a different embodiment. In this embodiment, the purge fluid is delivered via a purge lumen  5505  that is separate and distinct of the lumen for inflating the expandable member  5507 . The purge travels through the purge lumen  5505  and into a distal bearing housing  5511 , thereby preventing blood flood flow into bearings of the catheter. The purge fluid flows into the distal gap  5531  flushing and preventing blood from filling the distal gap  5531 . The purge fluid then travels down a second lumen  5537  to a proximal gap  5539  to flush blood from the proximal gap  5539 . 
       FIG.  56    shows an indwelling catheter  5600  with a purge system. The catheter  5600  includes a central lumen  5603  optimized for transporting purge fluid and maintaining concentricity of the catheter  5600  assembly. The internal structures of the central lumen  5306  can have various configurations some of which are detailed below in cross-sections taken through a cuff  5606  along line A-A. 
       FIG.  57    shows a cross-section of the central lumen  5603  taken along line A-A of  FIG.  56    according to one embodiment of the invention. In this embodiment, a purge channel  5709  is external to a drive shaft  5711  that connects a motor to an impeller of the device. Between the purge channel and the drive shaft  5711  is a profiled extrusion  5713 . The profiled extrusion  5713  includes a number of projections  5715 , for example, at least two projections  5715 , and preferably three projections  5715 , the projections  5715  extend outward from a central hub  5717  that encases the drive shaft  5711 . The profiled extrusion  5713  optimizes a purge cross sectional area and also helps to maintain assembly concentricity. 
       FIG.  58    shows a cross-section of the central lumen  5603  taken along line A-A of  FIG.  56    according to a different embodiment of the invention. In this embodiment, a purge channel  5809  is in association with the drive shaft  5711  connecting the motor to the impeller of the device. The purge channel  5809  is defined by a profiled extrusion  5813 . The profiled extrusion  5813  includes a number of projections  5815 , for example, at least two projections  5815 , and preferably three projections  5815 , the projections  5815  extending inward from an outer hub  5817  that encases the drive shaft  5711 . The profiled extrusion  5813  defines and optimizes a purge cross-sectional area and maintains assembly concentricity. 
       FIG.  59    shows a cross-section of the central lumen  5603  taken along line A-A of  FIG.  56    according to another embodiment of the invention. In this embodiment, the central lumen  5603  houses a coil drive shaft  5905  connecting the motor to the impeller of the device. A purge channel  5909  surrounds the coil drive shaft  5905 . The purge channel  5909  is defined by an outer hub  5911  that encases the coil drive shaft  5905 . 
       FIG.  60    shows an optimized guide surface  6001  of a cage inlet  6003 . With reference to  FIG.  27   , the optimized guide surface  6001  comprises a portion of a cuff  6007  that tapers towards the impeller  6011  in harmony with an outer boundary surface  6015 . The optimized guide surface  6001  maintains axial momentum and prevents recirculation of fluid  6017  flowing into the cage assembly  6021 . In particular, the optimized guide surface  6001  tapers in a manner that creates a flow field convergence and minimizes fluid divergence in the inlet region  6003 . The optimized guide surface  6001  may comprise a curved tapered section. The optimized guide surface  6001  may be configured to smoothly reduce the cross sectional area along the length of the inlet  6003 . For example, the change in cross sectional area of the optimized guide surface  6001  along the length of the inlet  6003  may be less than or equal to about 1 mm 2 . The optimized guide surface  6001  may comprise a curved taper. The optimized guide surface  6001  may comprises a cylindrical section. The optimized guide surface  6001  may comprise a substantially conical section. 
     In some embodiments, the outer boundary surface  6015  tapers over at least a portion of the inlet region  6003 . With reference to  FIG.  17   , the outer boundary surface  6015  may comprise a proximal surface of an expandable member. Alternatively, the outer boundary surface  6015  may comprise an inner surface of the cage. 
       FIG.  61    shows a suboptimal guide surface  6105 . The suboptimal guide surface  6105  may cause disturbances in flow  6107  of fluid flowing into the inlet region  6111 . In particular, the suboptimal guide surface  6105  comprises a steeper profile as compared to the optimized guide surface  6017  of  FIG.  60   . The steeper profile causes changes in axial momentum and fluid divergence of blood flowing into the inlet region  6111 . These disturbances in flow  6107  are prevented by with the optimized guide surface  6017 . 
       FIG.  62    shows a cage inlet  6201 . Illustrated is an optimal configuration where fluid flow  6207  is aligned with the inlet  6201  along an optimized guiding surface  6017 . The flow  6207  is primarily in the X-direction with no rotational component which promotes a smoothly flowing inlet  6201 . 
       FIG.  63    shows a suboptimal inlet  6301  configuration. This suboptimal configuration includes a steep guide surface  6105  that causes recirculation and stalls the flow in the inlet. A rotational component of the velocity dominates and carries the flow underneath the inlet struts  6215 . This phenomenon creates disrupted flow  6217  in the inlet  6301  and reduces the effectiveness of the inlet  6301  to guide flow towards the impeller. 
     Incorporation by Reference 
     References and citations to other documents, such as patents, patent applications, patent publications, journals, books, papers, web contents, have been made throughout this disclosure. All such documents are hereby incorporated herein by reference in their entirety for all purposes. 
     Equivalents 
     Various modifications of the invention and many further embodiments thereof, in addition to those shown and described herein, will become apparent to those skilled in the art from the full contents of this document, including references to the scientific and patent literature cited herein. The subject matter herein contains important information, exemplification and guidance that can be adapted to the practice of this invention in its various embodiments and equivalents thereof.