Patent Publication Number: US-2019167968-A1

Title: Fluid line connectors

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation application of and claims priority to U.S. application Ser. No. 13/778,655, filed on Feb. 27, 2013. 
    
    
     TECHNICAL FIELD 
     This disclosure relates to fluid line connectors. 
     BACKGROUND 
     Dialysis is a treatment used to support a patient with insufficient renal function. During hemodialysis, the patient&#39;s blood is passed through an extracorporeal hemodialysis circuit that includes a dialysis machine. In particular, the patient&#39;s blood is passed through a dialyzer of a dialysis machine while also passing a dialysis solution or dialysate through the dialyzer. A semi-permeable membrane in the dialyzer separates the blood from the dialysate within the dialyzer and allows diffusion and osmosis exchanges to take place between the dialysate and the blood stream. These exchanges across the membrane result in the removal of waste products, including solutes like urea and creatinine, from the blood. These exchanges also regulate the levels of other substances, such as sodium and water, in the blood. In this way, the dialysis machine acts as an artificial kidney for cleansing the blood. 
     In hemodialysis and many other medical procedures, luer connectors are used to obtain leak-free connections in fluid lines between a male fitting and a corresponding female fitting. For example, luer connectors are used to connect fluid lines to needles, syringes, catheters, fluid reservoirs, laboratory instruments, and other medical devices. In hemodialysis treatments in particular, male luer connectors are used to connect the flexible tubing of an extracorporeal blood circuit to and from a female luer connector that accesses a patient&#39;s circulatory system during the dialysis treatment. 
     SUMMARY 
     In some aspects, a male fluid line connector is configured to engage a female fluid line connector. The male fluid line connector includes a body having a first end configured to be connected to a fluid line, a tapered second end opposed to the first end, the second end configured to be inserted into and form a fluid-tight connection with the female fluid line connector, and a body longitudinal axis that extends between the first end and the second end. The male fluid line connector also includes a locking collar having a locking collar first end, and a locking collar second end opposed to the locking collar first end. The locking collar first end is connected to the body in a manner such that the locking collar can rotate about the longitudinal axis, and the locking collar is configured such that when the second end of the body is inserted into the female fluid line connector, the locking collar second end engages an outer surface of the female fluid line connector and is deformed by the engagement. 
     In some implementations, the locking collar includes internal threads that engage corresponding threads provided on the outer surface of the female fluid line connector, and the locking collar internal threads deform when engaged with the threads provided on the outer surface of the female fluid line connector. 
     In some implementations, the locking collar internal threads have a thread angle that is greater than a thread angle of the threads provided on the outer surface of the female fluid line connector. 
     In some implementations, a major diameter of the locking collar internal threads is less than a major diameter of the threads provided on the outer surface of the female fluid line connector. 
     In some implementations, the locking collar is more flexible than the female fluid line connector. 
     In some implementations, the locking collar is formed of a material that is more flexible than the material used to form the female fluid line connector. 
     In some implementations, the locking collar has a durometer value that is less than the durometer value of the female fluid line connector on a given durometer scale. 
     In some implementations, the locking collar includes through holes that are elongated in a direction parallel to the longitudinal axis. 
     In some implementations, an interior surface of the locking collar includes a region that engages a region of the outer surface of the female fluid line connector, and the region of the locking collar has a maximum inner diameter that is less than the maximum outer diameter of the female fluid line connector region. 
     In some implementations, each through holes is spaced apart from the adjacent through holes along a circumference of the locking collar. 
     In some implementations, the body is formed of a material having a first coefficient of friction and the locking collar is formed of a material having a second coefficient of friction, and the first coefficient of friction is less than that of the second coefficient of friction. 
     In some implementations, the first coefficient of friction has a range of 0.1 to 0.3. 
     In some implementations, the second end of the body does not protrude beyond a plane that is transverse to the longitudinal axis and includes an end face of the locking collar. 
     In some implementations, the internal threads of the locking collar are arranged to begin at a predetermined distance from the locking collar end face, and the predetermined distance is selected so that when the second end of the body is inserted into the female fluid line connector, a leading edge of threads provided on the outer surface of the female fluid line connector abuts a leading edge of the internal threads of the locking collar before an outer surface of the second end of the body forms a connection with an internal surface of the female fluid line connector. 
     In some implementations, the second end of the body is recessed within the locking collar. 
     In some implementations, the second end of the body is recessed within the locking collar by 0.5 mm to 2 mm. 
     In some implementations, the second end of the body is configured to form a luer-slip connection with the female fluid line connector. 
     In some aspects, a male fluid line connector is configured to engage a female fluid line connector. The male fluid line connector includes a body having a first end configured to be connected to a fluid line, a tapered second end opposed to the first end, the second end configured to be inserted into and form a fluid-tight connection with the female fluid line connector, and a body longitudinal axis that extends between the first end and the second end. The male fluid line connector also includes a locking collar having a locking collar first end configured to engage the body so as to rotate relative to the body about the longitudinal axis and a locking collar second end configured to receive the female fluid line connector. The second end of the body does not protrude beyond a plane that is transverse to the longitudinal axis and includes the locking collar second end. 
     In some implementations, the second end of the body is recessed within the locking collar. 
     In some implementations, the locking collar second end is aligned with the second end of the body when viewed in a direction perpendicular to the longitudinal axis. 
     In some implementations, when the second end of the body is inserted into the female fluid line connector, the locking collar engages an outer surface of the female fluid line connector in such a way that the locking collar is deformed. 
     In some implementations, the locking collar includes internal threads that engage corresponding threads provided on the outer surface of the female fluid line connector, and the locking collar internal threads deform when engaged with the threads provided on the outer surface of the female fluid line connector. 
     In some implementations, the locking collar internal threads have a thread angle that is greater than a thread angle of the threads provided on the outer surface of the female fluid line connector. 
     In some implementations, a major diameter of the locking collar internal threads is less than a major diameter of the threads provided on the outer surface of the female fluid line connector. 
     In some implementations, the locking collar is more flexible than the female fluid line connector. 
     In some implementations, the locking collar is formed of a material that is more flexible than the material used to form the female fluid line connector. 
     In some implementations, the locking collar has a durometer value that is less than the durometer of the female fluid line connector on a given durometer scale. 
     In some implementations, the locking collar includes through holes that are elongated in a direction parallel to the longitudinal axis. 
     In some implementations, an interior surface of the locking collar includes a region that engages a region of the outer surface of the female fluid line connector, and the locking collar region has a maximum inner diameter that is less than the maximum outer diameter of the female fluid line connector region. 
     In some implementations, each through hole is spaced apart from the adjacent through holes along a circumference of the locking collar. 
     In some implementations, the body is formed of a material having a first coefficient of friction and the locking collar is formed of a material having a second coefficient of friction, and the first coefficient of friction is less than that of the second coefficient of friction. 
     In some implementations, the first coefficient of friction has a range of 0.1 to 0.3. 
     In some implementations, the second end is configured to form a luer-slip connection with the female fluid line connector. 
     In some aspects, a male fluid line connector is configured to engage a female fluid line connector. The male fluid line connector includes a body having a first end configured to be connected to a fluid line, a tapered second end opposed to the first end, the second end configured to be inserted into and form a fluid-tight connection with the female fluid line connector, and a body longitudinal axis that extends between the first end and the second end. The male fluid line connector also includes a locking collar having a locking collar first end, and a locking collar second end opposed to the locking collar first end. The locking collar first end is connected to the body in a manner such that the locking collar rotates about the longitudinal axis, the locking collar includes internal threads that are configured to engage corresponding threads provided on the female fluid line connector outer surface, and the locking collar internal threads deform when engaged with the threads provided on the female fluid line connector outer surface, the locking collar is more flexible than the female fluid line connector, the body is formed of a material having a first coefficient of friction and the locking collar is formed of a material having a second coefficient of friction that is greater than that of the second coefficient of friction, and the second end of the body does not protrude beyond a plane that is transverse to the longitudinal axis and includes the locking collar second end. 
     A male luer connector is described that provides improved connection security relative to some conventional male luer connectors that include a threaded, rotating locking collar used to secure the collar to mating threads on a corresponding female luer connector. The locking collar is intended to provide additional security to the male-to-female luer connection. However, in some conventional male luer connectors, inadvertent disconnection between male and female luer connectors can occur if a rotational force is applied to the male luer connector and the female luer connector independent of the collar. For example, torque applied to the male and female luer connectors by the fluid line tubing can cause the locking collar to unscrew and allow the male-to-female luer connection to separate. An advertent disconnection can also occur if the male and female luer tapers are engaged without properly securing the locking collar of the male luer connector to the female luer connector threads. Security of the connection between the male luer connector and the corresponding female luer connector is particularly important in some medical procedures and/or treatments since if the connection fails during treatment, a potentially fatal problem can arise. For example, if the mail luer connector inadvertently becomes disconnected from the female luer connector on the venous side of a hemodialysis blood circuit, the patient can quickly become exsanguinated. 
     In some implementations, the male luer connector includes a locking collar that is configured to be more compliant than the female luer connector. The relative compliance can be achieved through appropriate selection of materials used to form the locking collar and female luer connector. Alternatively, it can be achieved by providing the locking collar with physical features, such as longitudinally-extending slits, that allow the locking collar to deform more easily than the female luer connector. Since the locking collar is more compliant than the female luer connector, the locking collar can secure the connection between the male luer connector body and the female luer connector regardless of dimensional variations in either the locking collar or the threads of the female luer connector, while maintaining a slight friction between the male and female luer threads. 
     In some implementations, the locking collar includes internal threads having dimensions that are designed to provide a slight interference with the external threads of the female luer connector. Advantageously, this feature can permit the locking collar internal threads to remain engaged with the external threads of the female luer connector even when the fluid lines extending from each of the male and female luer connectors are counter-rotated. 
     In some implementations, the male luer connector body is formed of a material having a lower coefficient of friction than that of the material used to form the locking collar. This configuration can allow the male luer connector body to rotate relative to the locking collar without imparting a rotational force to the locking collar. This can in turn prevent the locking collar internal threads from disengaging from the external threads of the female luer connector even when the fluid lines extending from each of the male and female luer connectors are counter-rotated. 
     In some implementations, the luer tip of the male luer connector body is slightly recessed within the locking collar. As a result, the locking collar internal threads must be engaged with the external threads of the female luer connector in order to achieve engagement and sealing between the luer tip of the male luer connector body and the luer socket of the female luer connector. Thus, it is ensured that both the locking collar and luer tip are securely engaged with the female luer connector during use. This is advantageous relative to conventional male luer connector configurations including a luer tip that protrudes beyond an end of the locking collar. In such conventional connectors, since the luer tip protrudes beyond an end of the locking collar, it is possible to obtain a connection between the luer tip and the socket portion of the female luer connector without obtaining an engagement of the locking collar with the external threads of the female luer connector. In some cases, it is possible to overlook that the locking collar has not been engaged, whereby the resulting connection can be insecure and easily disconnected. 
     Other aspects, features, and advantages will be apparent from the description and drawings, and from the claims. 
    
    
     
       DESCRIPTION OF DRAWINGS 
         FIG. 1  is a schematic illustration of an extracorporeal hemodialysis circuit including a male-to-female luer connection that joins a fluid line of the extracorporeal hemodialysis circuit to a patient catheter. 
         FIG. 2  is a partially cut away exploded perspective view of the male-to-female luer connection of  FIG. 1 . 
         FIG. 3  is an exploded side sectional view of the male luer connector of  FIG. 1 . 
         FIG. 4  is a perspective view of the male luer connector of  FIG. 1 . 
         FIG. 5  is an enlarged view of the second end of the male luer connector of  FIG. 1 . 
         FIG. 6  is an enlarged view of the second end of a prior art male luer connector. 
         FIG. 7  is a perspective view of another male luer connector including a locking collar having axially elongated through holes. 
         FIG. 8  is an enlarged view of the threaded portions of the locking collar and female luer connector illustrating thread definitions as used herein. 
     
    
    
     DETAILED DESCRIPTION 
     Referring to  FIG. 1 , an extracorporeal hemodialysis circuit  100  includes a flexible tubing fluid line  118  connected to a patient catheter assembly  120  via a first male-to-female luer connection  1 . The fluid line  118  receives arterial blood removed from the patient via the first male-to-female luer connection  1  and the patient catheter assembly  120 . The fluid line  118  conveys the blood to an arterial blood pressure monitor  102 , a blood pump  104 , such as a peristaltic pump, a pressure sensor  108  that monitors dialyzer inflow pressure, and then to the dialyzer  110 . After the blood is filtered within the dialyzer  110 , the fluid line  118  conveys the blood to a pressure sensor  112  that monitors venous blood pressure, through an air trap/detector device  114 , a valve  116 , and back to a vein of the patient via another patient catheter assembly  122  that is connected to the fluid line  118  by a second male-to-female luer connection  1 . 
     Referring to  FIG. 2 , the male-to-female luer connection  1  includes a male luer connector  10  and a female luer connector  140 . The male luer connector  10  is configured to engage the female luer connector  140  to obtain a leak-free connection. The male luer connector  10  includes a luer tip  28  having a tapered outer surface that is press fit within a correspondingly-tapered socket  142  of the female luer connector  140 . This connection is referred to as a luer-slip connection. In some embodiments, the taper is a 6 percent taper, and the luer-slip connection along the tapered surfaces is maintained by friction. To ensure that the luer-slip connection is maintained, the male luer connector  10  also engages an outer surface of the female luer connector  140 . In particular, the male luer connector  10  includes a locking collar  50  having internal threads  62  that are configured to engage external threads  144  provided on the female luer connector  140 , as further discussed below. 
     The female luer connector  140  is a tubular member having a first end  150  that engages the male luer connector  10 , and a second end  152  opposed to the first end  150 . The second end  152  includes a tubing connection portion  146  that permits the female luer connector  140  to be connected to a fluid line (e.g., fluid line  118 ). Between the first end  150  and the second end  152 , the outer surface  156  of the female luer connector  140  is provided with finger grips  148  to facilitate manual gripping of the female luer connector  140 . The female luer connector first end  150  includes the socket  142  defining a conical inner surface that has an inward 6 percent (Luer) taper so as to be widest at the connector first end  150 . The socket  142  is in fluid communication with the tubing connection portion  146 , providing a fluid flow passageway through the female luer connector  140 . The outer surface of the female luer connector first end  150  is provided with the external threads  144  that engage the internal threads  62  of the male luer connector  10 . The tapered socket  142  and external threads  144  are shaped and dimensioned according to requirements specified in industry standards, for example the international standard ISO 594-2: 1998(E), “Conical Fittings with 6% (Luer) Taper For Syringes, Needles and Certain Other Medical Equipment, Part 2: Lock Fittings,” Second Edition, 1998 Sep. 1, the contents of which are incorporated herein by reference. 
     Referring to  FIGS. 3 and 4 , the male luer connector  10  includes a connector body  12  and the locking collar  50  that is rotatably connected to the connector body  12 , as discussed below. The connector body  12  is a generally cylindrical tube that has a first end  18 , a second end  20  opposed to the first end  18 , and a longitudinal axis  32  that extends between the first end  18  and the second end  20 . The male luer connector first end  18  includes a tubing connection portion  22  that permits the male luer connector  10  to be connected to a fluid line (e.g., fluid line  118 ). In the illustrated embodiment, the tubing connection portion  22  has an enlarged diameter relative to that of the body  12 , and includes an opening  36  dimensioned to receive an end of a fluid line therein. In some embodiments, the fluid line is press fit within the opening  36  and retained within the opening  36  via friction. In other embodiments, the fluid line may be retained within the opening  36  using adhesives, by welding, etc. 
     The connector body  12  includes a collar seat  26  disposed between the first end  18  and the second end  20  at a location spaced apart from the tubing connection portion  22  along the longitudinal axis  32 . The collar seat  26  is configured to receive and retain a first end  56  of the locking collar  50 . In particular, the collar seat  26  is a region of reduced outer diameter relative to an outer diameter of the body  12 , whereby a shoulder  40  is formed at one end of the collar seat  26 . In addition, the outer surface of the connector body  12  is tapered in the vicinity of the collar seat  26  so that the collar seat  26  has a minimum outer dimension at the shoulder  40  and a maximum outer dimension adjacent the luer tip  28 . The reduced diameter and tapered configuration of the collar seat  56  facilitates retention of the locking collar  50  on the connector body  12 , as discussed further below. 
     The male luer connector second end  20  includes the luer tip  28 , which extends between the collar seat  26  and an end face  38  of the connector body  12 . The luer tip  28  has a conical outer surface that has an inward 6 percent (Luer) taper. In particular, the luer tip  28  has a maximum outer dimension adjacent the collar seat  26  and a minimum outer dimension at the end face  38 . This configuration corresponds to the shape and dimensions of the female luer connector socket  142  such that a leak-free luer slip connection can be formed when the luer tip  28  is press fit within the socket  142  of the female luer connector  140 . In some implementations, leak-free refers to a liquid-tight connection. In other implementations, leak-free refers to a fluid-tight connection. The male luer connector  10  includes an internal fluid passageway  30  that extends longitudinally and provides fluid communication between the tubing connection portion  22  and the end face  38 . 
     The locking collar  50  is a hollow cylinder that includes a first end  56  and a second end  58  that is opposed to the first end  56 . Finger grips  66  are provided on the outer surface  54  of the locking collar  50  adjacent to the locking collar first end  56 . The finger grips  66  improve manual gripping of the locking collar  50 . In the illustrated embodiment, the finger grips  66  are outwardly-protruding elongated ribs that extend in parallel to the longitudinal axis  32 . The ribs are provided at regular intervals about the circumference of the locking collar  50 . In addition, internal threads  62  are provided on an inner surface  52  of the locking collar  50  adjacent to the locking collar second end  58 . The internal threads  62  are configured to engage the external threads  144  of the female luer connector  140  and thereby provide a secure connection between the male fluid line connector  10  and the female fluid line connector  140 . 
     As discussed above, the locking collar first end  56  is connected to the body  12  in a manner such that the locking collar  50  rotates about the longitudinal axis  32  and is prevented from movement along the direction of the longitudinal axis  32 . To this end, resilient fingers  60  are formed on the inner surface  52  of the locking collar  50  adjacent to the first end  56 . The fingers  60  protrude radially inward at an angle relative to the inner surface  52  and toward the locking collar first end  56 . When the locking collar  50  is assembled with the body  12 , the luer tip  28  is inserted into the locking collar first end  56  and through an opening defined by the free ends of the fingers  60  until the locking collar first end  56  abuts the shoulder  40 . The fingers  60  are configured to pass over the body second end  20  including the luer tip  28  during assembly with minimal finger deflection. However, the fingers  60  are configured to be deflected outward (e.g. toward the collar inner surface  52 ) by the collar seat  26 , whereby the fingers  60  are snap-fit on to and retained by the collar seat  26  via cooperation between the collar seat taper and the inwardly-directed resiliency of the fingers  60 . The engagement of the resilient fingers  60  with the collar seat  26  substantially prevents longitudinal movement of the collar  50  relative to the body  12 , while permitting the locking collar to rotate relative to the body  12  about the longitudinal axis  32 . 
     Referring to  FIGS. 5 and 6 , when the locking collar  50  is assembled with the body  12  such that the locking collar first end  56 , including the resilient fingers  60 , is disposed within the collar seat  26 , the end face  38  of the connector body  12  does not protrude beyond a plane P that is transverse to the longitudinal axis  32  and includes an end face  70  of the locking collar  50  ( FIG. 5 ). In some embodiments, the connector body end face  38  is recessed within the locking collar  50  relative to the plane P. For example, the connector body end face may be recessed within the locking collar  50  by 0.5 mm to 2 mm relative to the plane P. The configuration in which the end face  38  of the body second end  20  is recessed within the locking collar  50  can be compared to some conventional male luer connectors  10 ′ in which the luer tip  28 ′ including the end face  38 ′ protrudes outward beyond the plane P ( FIG. 6 ). In particular, male luer connectors formed according to ISO standard 594-2 have an end face  38 ′ that protrudes 2.1 mm beyond the plane P. In such conventional male luer connectors  10 ′, since the luer tip  28 ′ protrudes outward, it is possible to obtain a luer slip connection between the luer tip  28 ′ and the female luer connector socket without securing the locking collar  50 ′ to the external threads of the female luer connector. For example, since the locking collar  50 ′ overlies the external threads, it can appear to be secured even if the locking collar  50 ′ has not yet been rotated to engage the external threads. However, by providing a male luer connector  10  in which the end face  38  of the connector body  12  does not protrude beyond the plane P, the locking collar  50  must be rotated in order to obtain engagement of locking collar internal threads  66  and the female luer connector external threads  144  before the luer slip connection between the luer tip  28  and the female luer connector socket  142  can be made. This arrangement helps to ensure that both the locking collar  50  and the luer tip  28  form a connection with the female luer connector  140 , resulting in a reliable and secure male-to-female luer connection. 
     The male luer connector  10  may include other features to improve connection security between the male luer connector  10  and the female luer connector  140 . In some aspects, the materials used to form the male luer connector  10  are selected so that the locking collar  50  rotates freely relative to the connector body  12 . In particular, the materials of the connector body  12  and locking collar  50  are selected so that the locking collar fingers  60  rotate freely relative to the collar seat  26 . 
     For example, in some embodiments, the body  12  is formed of a material having a coefficient of friction that is less than (e.g., about 0.2 to about 0.4 less than) the coefficient of friction of the material used to form the locking collar  50 . In some embodiments, the body  12  is formed of acrylic including an additive of two percent polypropylene, whereby the body  12  has a coefficient of friction of 0.1. Other possible materials that may be used to form the body  12  include, but are not limited to, polypropylene, polyethylene, and polyester. In some embodiments, the coefficient of friction of the material used to form the body  12  is in the range of 0.1 to 0.3. This can be compared to the coefficient of friction of materials conventionally used to form fluid line connectors, including ABS and polyvinylchloride (PVC), having a coefficient of friction in a range of 0.2 to 0.5. In some embodiments, the locking collar  50  is formed of a common thermoplastic such as acrylonitrile butadiene styrene (ABS), having a coefficient of friction of 0.5. 
     By providing the body  12  of a material having a relatively low coefficient of friction compared to that of the locking collar  50 , the locking collar  50  can rotate freely relative to the body  12 . As a result, if a rotational force is applied to the body  12 , it becomes difficult for the body  12  to transfer the rotational force to the locking collar  50 , enhancing the security of the connection between the male luer connector  10  and the female luer connector  140 . 
     In some embodiments, the internal threads  62  of the locking collar  50  are arranged to begin at a predetermined distance d from the locking collar end face  70 . This distance d is selected so that when the second end  20  of the connector body  12  is inserted into the female fluid line connector  140 , a leading edge  144   a  of threads provided on the outer surface of the female fluid line connector  140  abuts a leading edge  62   a  of the internal threads  62  of the locking collar  50  before the outer surface of the luer tip  28  of the body second end  20  forms a connection with female fluid connector socket  142 . 
     This feature, in combination with selecting the materials used to form the male luer connector  10  so that the locking collar  50  rotates freely relative to the connector body  12 , can prevent a user from connecting a female luer connector  140  to a male luer connector by merely inserting the second end  20  of the connector body  12  into the female fluid line connector  140  and rotating the female luer connector  140 . Such a procedure can result in formation of a luer slip connection, but in some cases does not also result in a secure threaded engagement between the internal threads  62  of the locking collar  50  and the external threads  144  of the female luer connector  140 . In addition, in such a procedure, the user may mistakenly assume that the rotation of the female luer connector was sufficient to achieve a secure connection between the internal threads  62  of the locking collar  50  and the external threads  144  of the female luer connector  140  since the female luer connector  140  is manually rotated relative to both the connector body  12  and locking collar  50 . By providing the locking collar threads as described in combination with the with forming the locking collar  50  with a low coefficient of friction relative to that of the connector body  12 , when the second end  20  of the connector body  12  is inserted into the female fluid line connector  140  and the female luer connector  140  is rotated, the locking collar  50  rotates in concert with the female luer connector  140 . Since the locking collar  50  rotates together with the female luer connector  140 , the internal threads  62  of the locking collar  50  do not engage the external threads  144  of the female luer connector  140 . That is, connection between the male luer connector  10  and the female luer connector  140  is not made until the user manually rotates the locking collar  50 , whereby the internal threads  62  of the locking collar  50  engage the external threads  144  of the female luer connector  140 , and the male luer tip  28  is drawn into a luer-slip connection with the female socket  142 . 
     To further improve connection security between the male luer connector  10  and the female luer connector  140 , in some embodiments, the locking collar  50  is configured to be deformed when the male luer connector body second end  22  is inserted into the female fluid line connector  140 . In particular, when the locking collar internal threads  62  engage the corresponding external threads  144  of the female luer connector  140 , the locking collar internal threads  62  deform. The compliance of the locking collar  50  permits accommodation of dimensional variations between the locking collar  50  and the female luer connector  140 , while maintaining a slight friction between the locking collar internal threads  62  and the female luer connector external threads  144 . This friction allows the locking collar  50  to remain securely in place (e.g., the locking collar internal threads  62  remain securely engaged with the female luer connector external threads  144 ) if the male luer connector  10  is rotated relative to the female luer connector  10  during use. 
     In some embodiments, the locking collar  50  is formed to be more flexible than the the female luer connector  140  to allow the threads  62  to deform when engaged with the female luer connector external threads  144 . The flexibility of a component depends on the flexibility of the material used to form the component, the component thickness and component shape. Thus, for implementations where the locking collar shape and thickness are maintained, the locking collar  50  is formed of a material that is more flexible than the material used to form the female luer connector  140  to allow the threads  62  to deform when engaged with the female luer connector external threads  144 . For example, the locking collar  50  can be formed of polyethylene or polypropylene having a durometer value in the range of 55 to 70 Shore D, as compared to the female luer connector  140  which may be formed of ABS having a durometer value of about 75 Shore D. For example, in some embodiments, the locking collar  50  has a durometer value that is less than (e.g., about 5 to about 15 less than) the durometer value of the female luer connector  140  for a given durometer scale. 
     In some embodiments, the locking collar  50  includes structural features that increase the compliance of the locking collar itself. For example, in the embodiment illustrated in  FIG. 7 , the locking collar  50  includes through holes  68  extending between the inner surface  52  and outer surface  54  of the locking collar  50 . The through holes  68  are elongated in a direction parallel to the longitudinal axis  32 , and reside adjacent the collar second end  58  so as to interrupt the internal threads  62 . In addition, each through holes  68  is spaced apart from the adjacent through holes  68  along a circumference of the locking collar  50 . Since the locking collar includes the through holes  68 , the locking collar  50  can be more easily deformed during engagement of the locking collar internal threads  62  with the external threads  144  of the female luer connector  140 . 
     The flexibility and/or compliance of the locking collar  50  allows the locking collar  50  to self-adjust to minor dimensional differences of various female luer connectors  140 , and still impart a slight friction between the components. The connection and disconnection of the two connectors is still easily made in the normal manner by manually turning the locking collar  50 , but the slight friction between the locking collar internal threads  62  and the external threads  144  of the female luer connector  140  increases resistance to relative rotation, and thus can prevent accidental disconnection. This is advantageous when compared to some prior art male luer connectors that are more rigid. Due to their rigidity, the prior art male luer connectors are typically formed having sufficiently large tolerances to accommodate the minor dimensional differences of various female luer connectors. As a result, the engagement between the prior art male luer connectors and the female luer connectors tends to be less secure. 
     To still further improve connection security between the male luer connector  10  and the female luer connector  140 , in some embodiments, the internal threads  62  of the locking collar  50  are shaped and/or dimensioned to provide slight interference when engaged with the external threads  144  of the female luer connector  140 . For example, the locking collar internal threads  62  may be formed having a thread angle θ 1  ( FIG. 8 ) that is greater than the thread angle θ 2  of the external threads  144  of the female luer connector  140 . In another example, the locking collar internal threads  62  may be formed having a slightly different pitch γ 1  than the pitch γ 2  of the external threads  144  of the female luer connector  140 . In another example, the major diameter α 1  of the locking collar second end  58  (e.g., the inner diameter of the locking collar second end  58 ) is slightly less than the major diameter α 2  of the external threads  144  of the female luer connector  140  (e.g., the outer diameter of the female luer connector first end  150 ). Since the internal threads  62  of the locking collar  50  are shaped and/or dimensioned to provide slight interference when engaged with the external threads  144  of the female luer connector  140 , the relatively compliant locking collar internal threads  62  are further deformed when engaged with the female luer connector external threads  144 . As a result of the interference, friction between the locking collar internal threads  62  and the female luer connector external threads  144  is further increased, further increasing the resistance to rotation and allowing the locking collar  50  to remain more securely in place if the male luer connector  10  and the female luer connector  140  are inadvertently rotated during use. 
     Each of the male luer connector improvements described herein can be implemented individually or in various combinations to achieve improved fluid line connection security. 
     Although the male luer connector  10  has been described with respect to connection to a female luer connector  140  that accesses a patient&#39;s circulatory system via a catheter assembly during hemodialysis, the male luer connector  10  can be connected to other types of female luer connectors, and/or the female luer connector can provide connection to other access devices such as fistula needles. 
     The locking collar first end  56  is connected to the body  12  in a manner such that the collar  50  is retained in a desired axial position relative to the body  12 , while the locking collar can rotate relative to the body  12  about the longitudinal axis  32 . Although the cooperative engagement of the resilient fingers  60  with the collar seat  26  serves this function in the illustrated embodiment, the locking collar  50  may be connected to the body  12  using other structures that serve this function. For example, an outer surface of the body  12  may be formed having resilient members that engage a seat formed on an inner surface of the locking collar  50 . In another example, an outer surface of the body  12  may be formed having an outwardly protruding annular flange, and the locking collar may receive the flange therewithin and include an inwardly extending lip that engages the flange and retains the locking collar on the body  12 . 
     Although an embodiment was described in which the body  12  is formed of a material having a coefficient of friction that is less than the coefficient of friction of the material used to form the locking collar  50  so that the locking collar  50  rotates freely relative to the connector body  12 , free rotation of the locking collar  50  relative to the connector body  12  can be achieved in other ways. For example, in some embodiments, the locking collar  50  is formed of a material having a coefficient of friction that is less than (e.g., about 0.2 to about 0.4 less than) the coefficient of friction of the material used to form the body  12 . In another example, in some embodiments, both the locking collar  15  and the body  12  are formed of materials that have a low coefficient of friction. In some embodiments, the coefficient of friction of the materials used to form both the body  12  and the locking collar are in the range of 0.1 to 0.3. In this case, the materials used to form the body  12  may be, but are not required to be, the same as the materials used to form the locking collar  50  as long as both are formed of materials having a low coefficient of friction. 
     Although an implementation was described in which the locking collar  50  is formed of a material that is more flexible than the material used to form the female luer connector  140  to allow the collar threads  62  to deform when engaged with the female luer connector external threads  144 , increasing the flexibility of the locking collar  50  (for example, to be more flexible than the female luer connector  140 ) can be achieved by other techniques. For example, in some implementations, the locking collar material is conventional, and the locking collar shape is modified to increase the flexibility of the locking collar  50  by reducing the wall thickness of the locking collar  50 . 
     A number of embodiments have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the disclosure. Accordingly, other embodiments are within the scope of the following claims.