Patent Publication Number: US-2021178045-A1

Title: Flow chamber with helical flow path

Description:
FIELD 
     Exemplary embodiments of the invention relate to a flow chamber for use in, for example, a hemodialysis system. The flow chamber has a helical flow path. 
     BACKGROUND 
     Patients with kidney failure or partial kidney failure typically undergo hemodialysis treatment in order to remove toxins and excess fluids from their blood. In hemodialysis treatment, blood is taken from the dialysis patient through an intake needle or catheter which draws blood from an artery or vein located in a specifically accepted access location, for example, a shunt surgically placed in an arm, thigh, subclavian artery, or the like. The needle or catheter is connected to extracorporeal tubing that is fed to a peristaltic pump and then to a dialyzer that cleans the blood and removes excess fluid. The dialyzed blood is then returned to the patient through additional extracorporeal tubing and another needle or catheter. Sometimes, a heparin drip is located in the hemodialysis loop to prevent the blood from coagulating. 
     As the drawn blood passes through the dialyzer, it travels in straw-like tubes within the dialyzer that serve as semi-permeable passageways for the unclean blood. Fresh dialysate solution enters the dialyzer at its downstream end. The dialysate surrounds the straw-like tubes and flows through the dialyzer in the opposite direction of the blood flowing through the tubes. Fresh dialysate collects toxins passing through the straw-like tubes by diffusion and excess fluids in the blood by ultra filtration. Dialysate containing the removed toxins and excess fluids is disposed of as waste. The red cells remain in the straw-like tubes and their volume count is unaffected by the process. 
     It is desirable to avoid mixing air into the blood when the blood is outside of the patient&#39;s body, as the presence of air in the blood can have various negative consequences for the patient when the dialyzed blood is returned to the patient&#39;s body. Accordingly, hemodialysis systems may also include one or more components intended to separate entrained air from the blood. 
     SUMMARY 
     A flow chamber for use in a dialysis treatment is provided. The flow chamber can include a tube section having a first end and a second end. A tube section longitudinal axis extends between the first end and the second end. The tube section has an inner wall and outer wall. A helical flow path disposed in the inner wall of the tube section. The helical flow path extends along at least a portion of the tube section longitudinal axis. 
     In an embodiment of the flow chamber, the helical flow path extends radially outward from the inner wall of the tube section. 
     In an embodiment of the flow chamber, the helical flow path has a rounded cross-section. In an embodiment of the flow chamber, the helical flow path has a hemispherical cross-section. 
     In an embodiment of the flow chamber, the tube section has a first outer diameter at the first end of the tube section and a second outer diameter at the second end of the tube section, the first outer diameter being greater than the second outer diameter. 
     In an embodiment of the flow chamber, the tube section tapers from the first end of the tube section to the second end of the tube section. 
     In an embodiment of the flow chamber, the helical flow path extends from the first end of the tube section to the second end of the tube section. 
     In an embodiment of the flow chamber, the flow chamber further includes a flow inlet disposed at the first end of the tube section. In an embodiment of the flow chamber, the helical flow path extends into the flow inlet. 
     In an embodiment of the flow chamber, the flow chamber further includes a flow outlet disposed at the second end of the tube section. 
     In an embodiment of the flow chamber, the helical flow path is at a first angle with respect to the tube section longitudinal axis. In an embodiment of the flow chamber, the first angle is 75°. 
     In an embodiment of the flow chamber, the helical flow path includes a first helical flow path portion at a first angle with respect to the tube section longitudinal axis and a second helical flow path portion adjacent to the first helical flow path portion. The second helical flow path portion is at a second angle with respect to the tube section longitudinal axis. The second angle is different than the first angle. In an embodiment of the flow chamber, the second angle is greater than the first angle. 
     A fluid management system for use in a dialysis treatment is also provided. The fluid management system can include a flow chamber. The flow chamber can include a tube section having a first end and a second end. A tube section longitudinal axis extends between the first end and the second end. The tube section has an inner wall and outer wall. A flow inlet is disposed at the first end of the tube section. A flow outlet is disposed at the second end of the tube section. A helical flow path is disposed in the inner wall of the tube section. The helical flow path extends along at least a portion of the tube section longitudinal axis. The fluid management system can also include an end cap arranged on the flow inlet. 
     In an embodiment of the fluid management system, the helical flow path extends radially outward from the inner wall of the tube section. 
     In an embodiment of the fluid management system, the helical flow path has a rounded cross-section. 
     In an embodiment of the fluid management system, the tube section has a first outer diameter at the first end of the tube section and a second outer diameter at the second end of the tube section, the first outer diameter being greater than the second outer diameter. 
     In an embodiment of the fluid management system, the helical flow path extends from the first end of the tube section to the second end of the tube section. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Exemplary embodiments of the present invention will be described in even greater detail below based on the exemplary figures. The invention is not limited to the exemplary embodiments. All features described and/or illustrated herein can be used alone or combined in different combinations in embodiments of the invention. The features and advantages of various embodiments of the present invention will become apparent by reading the following detailed description with reference to the attached drawings which illustrate the following: 
         FIG. 1  is a schematic diagram of a hemodialysis system including a flow chamber according to an exemplary embodiment of the invention; 
         FIG. 2  shows a perspective view of a flow chamber according to an exemplary embodiment of the invention; 
         FIG. 3  shows a cross-sectional view of the flow chamber of  FIG. 2  along line  3 - 3 ; 
         FIG. 4  shows a perspective view of an embodiment of a flow chamber with a flow outlet according to an exemplary embodiment of the invention; 
         FIG. 5  shows a cross-sectional view of the flow chamber of  FIG. 4  along line  5 - 5 ; 
         FIG. 6  shows an end view of a flow chamber according to an exemplary embodiment of the invention; 
         FIG. 7  shows a perspective view of a flow chamber according to an exemplary embodiment of the invention; 
         FIG. 8  shows a perspective view of a fluid management system according to an exemplary embodiment of the invention; 
         FIG. 9  shows a cross-sectional view of the fluid management system of  FIG. 8  along line  9 ,  10 - 9 ,  10 , wherein the helical flow path of the tube section does not extend into the flow inlet; 
         FIG. 10  shows a cross-sectional view of the fluid management system of  FIG. 8  along line  9 ,  10 - 9 ,  10 , wherein the helical flow path of the tube section extends into the flow inlet; 
         FIG. 11  shows a cross-sectional view of the fluid management system of  FIG. 9  with fluid therein; 
         FIG. 12  shows a flow chamber according to another exemplary embodiment of the invention, wherein a helical flow path of the flow chamber has helical flow path portions at two different angles with respect to the tube section longitudinal axis; and 
         FIG. 13  shows a cross-sectional view of the flow chamber of  FIG. 4  along line  5 - 5  with exemplary dimensions. 
     
    
    
     DETAILED DESCRIPTION 
     Exemplary embodiments of the present invention provide a flow chamber with improved fluid management. The flow chamber may be used, for example, in a hemodialysis system, which dialyzes blood. The flow chamber reduces oxygenation of the dialyzed blood before the dialyzed blood is returned to the dialysis patient. The flow chamber also minimizes coagulation of the blood therein, and, correspondingly, the risk of introducing a blood clot in the patient upon return of the dialyzed blood to the patient. 
     The flow chamber of exemplary embodiments of the present invention provides improved fluid management through the provision of a helical flow path in an inner wall of a tube section of the flow chamber. In practice, the flow chamber receives, in drop form, dialyzed blood at a first end of the flow chamber. For example, at the beginning of a dialysis session with a patient, the dialyzed blood begins to accumulate within the flow chamber so as to partially fill the flow chamber with dialyzed blood. Eventually the flow of blood into and out of the flow chamber reaches an approximately steady state, such that the flow chamber is partially filled with blood and the remainder of the flow chamber is filled with air. 
     The helical flow path is disposed in an inner wall of the tube section of the flow chamber. In an embodiment, the helical flow path can be formed by debossing the inner wall of the tube section. In this manner, the helical flow path extends radially outward from the center of the tube section such that the inner diameter of the tube section at the helical flow path is increased due to the presence of the helical flow path. The helical flow path can have a rounded cross-section. The helical flow path can also have hemispherical cross-section. A rounded cross-section may be desirable because it reduces the creation of additional turbulence within the flow in the flow chamber. However, in other exemplary embodiments, the cross-section of the helical flow path may not be rounded. 
     As the blood drips into the flow chamber, the drops fall onto the helical flow path in the inner wall of the tube section, either directly contacting at least one of the inner wall or the helical flow path or after a minimal free fall distance within the flow chamber. The drops then progress, at least in part, along the helical flow path. In this manner, the helical flow path reduces the velocity of the drops as they progress through the tube section. Reducing the velocity of the drops helps to minimize the formation of foam that would occur within the flow chamber if the drops were allowed to free fall for longer distances or if the drops moved at a faster velocity. It is desirable to limit the formation of foam within the blood chamber so as to minimize coagulation of the blood and blood clots within the flow chamber. 
     The flow chamber according to exemplary embodiments of the present invention may be fitted with a flow inlet at the first end of the flow chamber. The flow inlet can act as an extension of the flow chamber. In an embodiment, the helical flow path can extend into the flow inlet, lengthening the helical flow path. The flow inlet may be similar in structure to the flow chamber in that the flow inlet is also tubular. The flow inlet may also be tapered in the same manner as the flow chamber. The flow inlet can be made of the same or a different material as the flow chamber. 
     An end cap can be attached either to the flow chamber or to the flow inlet if the flow chamber is provided with a flow inlet. The end cap includes one or more ports that facilitate fluidic connection of the flow chamber to the hemodialysis system vis-à-vis extracorporeal tubing. 
     The flow chamber may be fitted with a flow outlet at the second end of the flow chamber. The flow outlet allows the flow chamber to be connected to standard diameter extracorporeal tubing. Dialyzed blood flows from the flow chamber, through the flow outlet, into the extracorporeal tubing, and then into the return needle or catheter so that the dialyzed blood can be returned to the patient. The flow outlet may be similar in structure to the flow chamber in that the flow outlet is also tubular, at least in part. Accordingly, the flow outlet may also be tapered in the same manner as the flow chamber. The flow outlet then transitions to a nozzle shape to facilitate connection to the standard diameter extracorporeal tubing. The flow outlet can be made of the same or a different material as the flow chamber. 
       FIG. 1  is a schematic diagram of a hemodialysis system in which a patient  10  is undergoing hemodialysis treatment using a hemodialysis machine  12 . An input needle or catheter  16  is inserted into an access site of the patient  10 , such as in the arm, and is connected to extracorporeal tubing  18  that leads to a peristaltic pump  20  and to a dialyzer  22  (or blood filter). The dialyzer  22  removes toxins and excess fluid from the patient&#39;s blood. The excess fluids and toxins are removed by clean dialysate liquid which is supplied to the dialyzer  22  via a tube  28 , and waste liquid is removed for disposal via a tube  30 . The dialyzed blood is returned to the patient  10  from the dialyzer  22  through the extracorporeal tubing  24  and a return needle or catheter  26 . In the context of exemplary embodiments of the present invention, a flow chamber  40  is fluidically disposed between the extracorporeal tubing  24  and the return needle or catheter  26 . The flow chamber  40  can include a flow inlet  56 , a flow outlet  58 , and an end cap  60 , as discussed in further detail below, so as to provide a fluid management system. 
       FIG. 2  shows the flow chamber  40 . The flow chamber  40  comprises a tube section  42 , which has a first end  44  and a second end  46 . The second end  46  is disposed opposite the first end  44  on tube section  42 . A tube section longitudinal axis  48  extends along tube section  42  between the first end  44  and the second end  46 . The tube section  42  has an inner wall  50  and outer wall  52 . A thickness of the tube section (i.e., a distance between the inner wall  50  and the outer wall  52 ) is relatively small compared to an overall diameter of the tube section  42 . For example, in an embodiment, a thickness of the tube section  42  (e.g., at first end  44 ) could be 1651 μm±127 μm. 
       FIG. 3  shows the flow chamber  40  of  FIG. 2  in cross-section along line  3 - 3  in  FIG. 2 . The tube section longitudinal axis  48  defines an axial direction A, to which radial direction R is perpendicular. A helical flow path  54  is disposed in the inner wall  50  of the tube section  42 . The helical flow path  54  extends along at least a portion of the tube section longitudinal axis  48 . In this embodiment, the helical flow path  54  extends over an entire length of tube section  42  (i.e., from first end  44  to second end  46 ). The helical flow path  54  extends radially outward from the inner wall  50  of tube section  42  (i.e., in a radial direction R with respect to tube section longitudinal axis  48 ). In this manner, the helical flow path  54  forms a recessed channel in the inner wall  50  of the tube section  42 . For example, in an embodiment, the helical flow path extends radially outward 952.5 μm±12.7 μm from the inner wall  50  of the tube section  42 . The helical flow path  54  helps reduce the velocity of drops of blood that enter the flow chamber  40 , as discussed above. 
     As seen in  FIG. 3 , the tube section  42  has a first outer diameter OD 1  at its first end  44  and a second outer diameter OD 2  at its second end  46 . The first outer diameter OD 1  is greater than the second outer diameter OD 2 . The outer wall  52  and the inner wall  50  of the tube section  42  can taper, or continuously narrow, from its first end  44  to its second end  46 . For example, in an embodiment, the angle or slope of the taper is 1°±0.2°. Such narrowing of the tube section  42  along its length (i.e., along axial direction A) also facilitates reducing the velocity of drops of blood that enter the flow chamber  40  by ensuring that blood drops input into the flow chamber  40  (e.g., from drip outlet  68  as shown in  FIG. 9 ) will directly contact at least one of the inner wall  50  or the helical flow path  54  without free falling through the flow chamber  40  or after a minimal free fall distance within the flow chamber  40 . 
       FIG. 3  shows the helical flow path  54  at a first angle α with respect to the tube section longitudinal axis  48 . Adjusting the first angle α of the helical flow path  54  with respect the tube section longitudinal axis  48  affects how quickly the flow chamber  40  reduces the velocity of drops of blood as the drops progress through the tube section  42 . In general, a helical flow path  54  having smaller first angle α will cause the flow chamber  40  to more gradually reduce the velocity of the drops than if the helical flow path  54  has a larger first angle α. Conversely, a helical flow path  54  having larger first angle α will cause the flow chamber  40  to more quickly reduce the velocity of the drops than if the helical flow path  54  has a smaller first angle α. 
       FIG. 4  shows the flow chamber  40  with a flow outlet  58  disposed at the second end  46  of the tube section  42 . The flow outlet  58  further narrows the passageway through which the dialyzed blood flows. The end of the flow outlet  58  that does not abut the second end  46  of the tube section  42  may be attached to tubing so as to fluidically transport dialyzed blood from the flow chamber  40  to the return needle or catheter  26 , as shown in  FIG. 1 .  FIG. 5  shows the flow chamber  40  of  FIG. 4  in cross-section along line  5 - 5  in  FIG. 4 . 
     As shown in  FIGS. 6-7 , the helical flow path  54  has a rounded cross-section. A rounded cross-section helps mitigate turbulence within the flow of the blood within the tube section  42 . The cross-sectional geometry of the helical flow path  54  can vary. For example, the helical flow path  54  can have a hemispherical cross-section. 
       FIG. 8  shows a fluid management system according to an exemplary embodiment of the invention, the fluid management system comprising the flow chamber  40  with the flow outlet  58  disposed at the second end  46  of the tube section  42 , a flow inlet  56  disposed at the first end  44  of the tube section  42 , and an end cap  60  arranged on the flow inlet  56 . The flow inlet  56  is a longitudinal extension of the tube section  42 , in that the flow inlet  56  acts as a continuation of both the inner wall  50  and the outer wall  52  of the tube section  42 . The end cap  60  facilitates connection of the flow chamber  40  to extracorporeal tubing  24 , as shown in  FIG. 1 . The end cap  60  is secured to the flow inlet  56 , for example, by tolerance fit. Alternatively, in the absence of the flow inlet  56 , the end cap  60  may be secured to the first end  44  of the tube section  42 , for example, by tolerance fit. 
       FIGS. 9-10  show the fluid management system of  FIG. 8  in cross-section along line  9 ,  10 - 9 ,  10  in  FIG. 8 . As shown in  FIGS. 9-10 , the end cap  60  includes a drip tube  62  having a drip tube inlet  66  and a drip tube outlet  68 . A drip tube longitudinal axis  70  extends between the drip tube inlet  66  and the drip tube outlet  68 . The drip tube longitudinal axis  70  is parallel to the tube section longitudinal axis  48 . The drip tube  62  is positioned radially outward (i.e., in radial direction R) from the tube section longitudinal axis  48 . In this manner, the drip tube  62  is positioned such that the drip tube outlet  68  is proximal to or in contact with the inner wall  50  of the flow chamber  40 . This helps to ensure that blood drops input into the flow chamber  40  from drip outlet  68  will directly contact at least one of the inner wall  50  or the helical flow path  54  without free falling through the flow chamber  40  or after a minimal free fall distance within the flow chamber  40 . Then, immediately or soon after the drops enter the first end  44  of the tube section  42 , the drops are carried along the helical flow path  54  so as to reduce the velocity of the drops as they progress through the tube section  42 , as previously discussed. 
     As shown in  FIG. 9 , the helical flow path  54  of tube section  42  ends at the first end  44  of the tube section  42  such that the helical flow path  54  does not extend into the flow inlet  56 . In  FIG. 10 , in contrast, the helical flow path  54  extends into the flow inlet  56 , such that inclusion of the flow inlet  56  in the fluid management system can lengthen the helical flow path  54 . 
       FIG. 11  shows the fluid management system of  FIG. 9  in operation. Drops D exit the drip tube  62  at drip tube outlet  68 , moving in the axial direction A (i.e., from the first end  44  of the tube section  42  toward the second end  46  of the tube section  42 ). The drops D directly contact at least one of the inner wall  50  of the tube section  42  or the helical flow path  54  without free falling through the flow chamber  40  or after a minimal free fall distance within the flow chamber  40 , reducing the velocity of the drops D and minimizing the creation of foam within the flow chamber  40 . After a number of the drops D enter the flow chamber  40 , fluid F, which comprises drops D, accumulates in the lower portion of the flow chamber  40 . The fluid F ultimately exits the flow chamber  40  through the flow outlet  58  and passes to the return needle or catheter  26  to be returned to the patient  10 , as shown in  FIG. 1 . 
       FIG. 12  shows another embodiment of the flow chamber according to an exemplary embodiment of the invention. In contrast to the embodiment shown in  FIG. 3 , the helical flow path  54  comprises a first helical flow path portion  72  arranged adjacent to a second helical flow path portion  74 . The first helical flow path portion  72  is at a first angle α with respect to the tube section longitudinal axis  48  while the second helical flow path portion  74  is at a second angle β with respect to the tube section longitudinal axis  48 . The second angle β is different than the first angle α. For example, in an embodiment, the second angle β is greater than the first angle α. Varying the first angle α and the second angle β affects how quickly the flow chamber  40  reduces the velocity of drops of blood as the drops progress through the tube section  42 , as described in connection with  FIG. 3 . For example, in an embodiment, the first angle α is 75°±2° and the second angle β is 80°±2°. 
     In an alternative embodiment, the first angle α with respect to the tube section longitudinal axis  48  can, over the length of the tube section  42  (i.e., from first end  44  to second end  46 ), gradually change to the second angle β so that the helical flow path  54  provides a smooth reduction in velocity of the drops as the drops progress through the flow chamber  40 . 
       FIG. 13  shows the flow chamber  40  of  FIG. 4  in cross-section along line  5 - 5  in  FIG. 4 , adding exemplary dimensions in centimeters and degrees. The exemplary dimensions are intended to be illustrative and not limiting in any way. For example, in the embodiment of the flow chamber  40  shown in  FIG. 13 , a turn-to-turn distance along tube section longitudinal axis  48  from the center of one turn of the helical flow path  54  to the center of an adjacent turn of the helical flow path  54  along axial direction A is 0.48 cm, while the first angle α is 75°. The turn-to-turn distance can range from 0.4673 cm-0.4927 cm, while the first angle α can range from 73°-77°. If  FIG. 13  were not shown in cross-section, a distance from the center of one turn of the helical flow path  54  to the center of an adjacent turn of the helical flow path  54  along axial direction A would be half as much, namely 0.24 cm, due to the presence of the helical flow path  54  on the other half of the flow chamber  40 . 
     While exemplary embodiments of the invention have been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive. It will be understood that changes and modifications may be made by those of ordinary skill within the scope of the following claims. For example, the present invention includes further embodiments with any combination of features from the different embodiments described above. 
     The terms used in the claims should be construed to have the broadest reasonable interpretation consistent with the foregoing description. For example, the use of the article “a” or “the” in introducing an element should not be interpreted as being exclusive of a plurality of elements. Likewise, the recitation of “or” should be interpreted as being inclusive, such that the recitation of “A or B” is not exclusive of “A and B,” unless it is clear from the context or the foregoing description that only one of A and B is intended. Further, the recitation of “at least one of A, B and C” should be interpreted as one or more of a group of elements consisting of A, B and C, and should not be interpreted as requiring at least one of each of the listed elements A, B and C, regardless of whether A, B and C are related as categories or otherwise. Moreover, the recitation of “A, B and/or C” or “at least one of A, B or C” should be interpreted as including any singular entity from the listed elements, e.g., A, any subset from the listed elements, e.g., A and B, or the entire list of elements A, B and C.