Patent Publication Number: US-11040160-B2

Title: Compressible connector for an inner cannula

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of prior U.S. application Ser. No. 14/683,515, filed Apr. 10, 2015, which is a continuation of prior U.S. application Ser. No. 13/565,273, filed Aug. 2, 2012 (patented as U.S. Pat. No. 9,010,326), the specification of which is incorporated herein by reference in its entirety for all purposes. 
    
    
     BACKGROUND 
     The present disclosure relates generally to the field of tracheal tubes and, more particularly, to a tracheal tube including an inner cannula with a compressible end. 
     This section is intended to introduce the reader to various aspects of art that may be related to various aspects of the present disclosure, which are described and/or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present disclosure. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art. 
     A wide variety of situations exist in which artificial ventilation of a patient may be desired. For short-term ventilation or during certain surgical procedures, endotracheal tubes may be inserted through the mouth to provide oxygen and other gasses to a patient. For other applications, particularly when longer-term intubation is anticipated, tracheostomy tubes may be preferred. Tracheostomy tubes are typically inserted through an incision made in the neck of the patient and through the trachea. A resulting stoma is formed between the tracheal rings below the vocal chords. The tracheostomy tube is then inserted through the opening. In general, two procedures are common for insertion of tracheostomy tubes, including a surgical procedure and a percutaneous technique. 
     Such tubes may include an inner cannula, such as a reusable inner cannula, or a disposable inner cannula. The inner cannula may be disposed inside the tracheostomy tube and used as a conduit for liquids or gas incoming and outgoing into the patient&#39;s lungs. The inner cannula may be removed for cleaning and for disposal of secretions without disturbing the placement of the tracheostomy tube. A connector is typically provided at an upper or proximal end where the tube exits the patient airway, suitable for coupling the ventilator with the inner cannula. In one embodiment, the inner cannula may be removed, cleaned, and reused. In another embodiment, the inner cannula may be disposable, and a new inner cannula may then be positioned inside of the tracheal tube. By enabling the cleaning and/or replacement of the inner cannula, a ventilation circuit may be kept clean and free of secretions. 
     Standard connectors have been developed to allow the tracheal tube to then be fluidly coupled to artificial ventilation equipment to supply the desired air or gas mixture to the patient, and to evacuate gases from the lungs. One difficulty that arises in the use of tracheal tubes, and tracheostomy tubes in particular, is in the connection of the tube to the ventilation equipment. For example, an inner cannula may not be installed, or may be installed improperly. This may lead to difficulties with ventilation when a connection is made to ventilation equipment. 
     There is a need, therefore, for improved tracheal tubes, and particularly for improved tracheostomy tubes. It would be desirable to provide a tube that allows for ease of placement and connection of the inner cannula during ventilation. 
     BRIEF DESCRIPTION 
     This disclosure provides a novel tracheal tube designed to respond to such needs with a low insertion force and a high retention force. The tracheal tube may be a tube with a separate inner cannula and outer cannula. The inner cannula includes a compressible end, such as a pinch end, that allows for ease of insertion into the outer cannula. In contrast to other types of inner cannula connectors, such as threaded or snap-on connectors, the disclosed embodiments may provide inner cannulas that may be inserted and connected in a single movement and that also resist axial or rotational displacement relative to the outer cannula. In particular embodiments, the entire proximal end of the inner cannula, including any cap or lip portion, is smaller in diameter than the widest portion of the outer cannula connector when properly inserted. In this manner, the outer cannula connector forms the connector portion (e.g., a standard 15 mm connector) for attachment to upstream medical tubing and/or devices. This is in contrast to disposable inner cannulas that, when inserted into an outer cannula and connector, have integral 15 mm connectors. Accordingly, in the disclosed embodiments, the standard connector resides on the outer cannula portion of the tracheal tube, which may allow the outer cannula assembly to be connected to upstream medical tubing with or without an inserted inner cannula. 
     Further, the compressible end of the inner cannula may be adhered to or otherwise affixed to the inner cannula to form its proximal end region or may be manufactured as a unitary assembly, such as a single molded piece, which may be a cost-effective manufacturing technique. The disclosed tracheal tubes provide improved inner/outer cannula connection while also maintaining standard connections to other medical tubing, such as ventilator tubing. 
     Thus, in accordance with a first aspect, a tracheal tube assembly includes an outer cannula configured to be positioned in a patient airway. The assembly further includes a flange member secured about the outer cannula and an outer cannula connector coupled to a proximal end of the outer cannula. The assembly further includes an inner cannula configured to be disposed inside the outer cannula such that the inner cannula and the outer cannula are coaxial. The inner cannula features a compressible proximal region that is configured to be positioned inside the outer cannula connector. The compressible proximal region is capable of assuming a compressed configuration and an uncompressed configuration. The compressed configuration is assumed when the compressible proximal end region is positioned in the outer cannula connector, and the uncompressed configuration is assumed when the compressible proximal end region is not subjected to any biasing forces. 
     In accordance with another aspect, a tracheal tube inner cannula includes a conduit configured to be inserted into an outer cannula to transfer gas to a patient, the conduit comprising a flared proximal region, wherein the flared proximal region is configured to be inserted in an outer cannula connector. The flared proximal region includes a first ear and a second ear separated by opposing notches formed in a wall of the flared proximal region, wherein the opposing notches extend from the flared proximal region towards a distal end of the inner cannula such that an outer circumference of a proximal end of the inner cannula is a broken annulus and wherein the first ear and the second ear are configured to be biased towards one another when the flared proximal region is inserted in the outer cannula connector. 
     Also disclosed herein is a tracheal tube assembly kit that includes an outer cannula configured to be positioned in a patient airway; a flange member secured about the outer cannula; an outer cannula connector coupled to a proximal end of the outer cannula; and an inner cannula configured to be disposed inside the outer cannula comprising: a conduit configured to be inserted into an outer cannula to transfer gas to a patient, the conduit comprising a flared proximal region, wherein the flared proximal region is configured to be inserted in an outer cannula connector and wherein the flared proximal region comprises a first ear and a second ear separated by opposing gaps formed in a wall of the flared proximal region, wherein the first ear and the second ear are configured to be biased towards one another when the flared proximal region is inserted in the outer cannula connector. 
     Also disclosed herein is a tracheal tube inner cannula mold. The mold includes a mold form defining a conduit, wherein the conduit comprises: a distal end; a flared proximal region comprising a first ear and a second ear separated by opposing notches formed in a wall of the flared proximal region, wherein the opposing notches extend from the flared proximal region towards a distal end of the inner cannula such that an outer circumference of a proximal end of the inner cannula is a broken annulus; a first protrusion formed on an outer surface of the first ear and a second protrusion formed on an outer surface of the second ear, wherein the opposing notches extend distally past the first protrusion and the second protrusion. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Various aspects of the disclosed techniques may become apparent upon reading the following detailed description and upon reference to the drawings in which: 
         FIG. 1  is a perspective view of a tracheal tube with a compressible inner cannula connector inserted into a patient in accordance with embodiments of the present disclosure; 
         FIG. 2  is a perspective view of the tracheal tube of  FIG. 1 ; 
         FIG. 3  is a perspective view of a separate inner cannula and outer cannula assembly of the tracheal tube of  FIG. 1 ; 
         FIG. 4  is a partial perspective view of a tracheal tube with the inner cannula inserted in the outer cannula connector; 
         FIG. 5  is perspective view of an inner cannula with a compressible connector in accordance with embodiments of the present disclosure; 
         FIG. 6  is a partial perspective view of the compressible connector region of the inner cannula of  FIG. 5 ; 
         FIG. 7  is a top view of the compressible connector region of the inner cannula of  FIG. 5   
         FIG. 8  is a partial perspective view of an inner cannula inserted into the outer cannula connector component; 
         FIG. 9  is a perspective view of an outer cannula connector component; 
         FIG. 10  is a cross-sectional view of the outer cannula connector component of  FIG. 9 ; and 
         FIG. 11  is a perspective view of a tracheal tube assembly including an inner cannula with a compressible connector used in conjunction with an obturator. 
     
    
    
     DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS 
     One or more specific embodiments of the present techniques will be described below. In an effort to provide a concise description of these embodiments, not all features of an actual implementation are described in the specification. It should be appreciated that in the development of any such actual implementation, as in any engineering or design project, numerous implementation-specific decisions must be made to achieve the developers&#39; specific goals, such as compliance with system-related and business-related constraints, which may vary from one implementation to another. Moreover, it should be appreciated that such a development effort might be complex and time consuming, but would nevertheless be a routine undertaking of design, fabrication, and manufacture for those of ordinary skill having the benefit of this disclosure. 
     The tracheal tubes as provided herein are disposable rather than reusable, capable of providing differential mechanical ventilation to either or both lungs, and capable of supporting all other functions of standard tracheal tubes (e.g. sealing, positive pressure generation, suctioning, irrigation, drug instillation, etc). The tracheal tubes can be used in conjunction with all acceptable auxiliary airway devices such as (e.g. heat and humidity conservers, mechanical ventilators, humidifiers, closed suction systems, scavengers, capnometers, oxygen analyzers, mass spectrometers, PEEP/CPAP devices, etc). Furthermore, although the embodiments of the present disclosure illustrated and described herein are discussed in the context of tracheal tubes such as tracheostomy tubes, it should be noted that presently contemplated embodiments may include a tracheal tube assembly including an inner cannula with a compressible end used in conjunction with other types of airway devices. For example, the disclosed embodiments may be used in conjunction with a single-lumen tube, an endotracheal tube, a double-lumen tube (e.g., a Broncho-Cath™ tube), a specialty tube, or any other airway device with a main ventilation lumen. Indeed, any device with a ventilation lumen designed for use in an airway of a patient may include an inner cannula with a compressible end as provided. As used herein, the term “tracheal tube” may include an endotracheal tube, a tracheostomy tube, a double-lumen tube, a bronchoblocking tube, a specialty tube, or any other airway device. 
     Turning now to the drawings,  FIG. 1  is a perspective view of an exemplary tracheal tube  10  placed in a patient&#39;s airway in accordance with aspects of the present disclosure. The tracheal tube assembly  10  represented in the figures is a tracheostomy tube, although aspects of this disclosure could be applied to other tracheal tube structures, such as endotracheal tubes. The application to a tracheostomy tube is apt, however, insomuch as such tubes tend to be worn for longer periods of time and, thus, may include a removable and/or disposable inner cannula disposed inside of an outer cannula  12 , which is useful in maintaining a clean ventilation circuit. 
     The tracheal tube  10  includes an outer cannula  12  that defines a ventilation lumen and that facilitates the transfer of gases to and from the lungs. The tracheal tube  10  includes an inflatable cuff  16  disposed on the outer cannula  12 . However, certain embodiments of the disclosure may be used in conjunction with cuffless tubes. A proximal end of the tracheal tube  10  may connect to upstream airway devices (e.g., a ventilator) via the appropriate medical tubing and/or connectors. In embodiments that include a cuff  16 , a pilot balloon and inflation line assembly  18  is coupled to the cuff  16 . 
     The outer cannula  12  is illustrated extending both distally as well as proximally from a flange member  20 . A pair of side wings of the flange  20  extend laterally and serve to allow a strap or retaining member (not shown) to hold the tube assembly  10  in place on the patient. In one embodiment, apertures formed in each side of the flange member  20  allow the passage of such a retaining device. In many applications, the flange member  20  may be taped or sutured in place as well. During intubation, the tracheal tube assembly  10  is placed through an opening formed in the neck and trachea of a patient and extending into the patient airway. In certain embodiments, the tracheal tube assembly  10  is curved to accommodate the curved tracheal passageway. For example, the outer cannula  12  may be curved in an unbiased state (i.e., outside the patient) such that an inner curve  22  is generally positioned on a ventral side of the patient while the outer curve  24  is positioned on the dorsal side of the patient when the tracheal tube assembly  10  is inserted in the patient. Further, while a distal portion of the outer cannula  12  is inserted within the patient, a proximal portion of the outer cannula  12  forms an outer cannula connector  28 . As provided herein, the outer cannula connector  28  receives a compressible end region of the inner cannula and forms a secure connection. 
       FIG. 2  is a perspective view of the tracheal tube assembly  10  showing an inner cannula  30  inserted in the outer cannula  12  and forming a connection with the outer cannula connector  28 . The compressible end region  32  is disposed within the outer cannula connector  28  such that a proximal end  34  is exposed (i.e., is not within the outer cannula connector  28 ). The inner cannula  30  is generally coaxial with the outer cannula  12  and is shaped to fit within the outer cannula  12  to form the gas conveying passageway to the patient. In this manner, the inner cannula  30  may be removed and replaced while the outer cannula  12  is retained. This reduces stress on the stoma while permitting cleaning of the passageway. 
     The inner cannula  30  may be manually inserted into the outer cannula  12 . As shown in  FIG. 3 , the inner cannula  30  may be inserted by pushing the distal end  40  through the proximal end  44  of the outer cannula  12 , e.g., in the direction of arrow  46 . The insertion is complete when the distal end  40  is generally located at or near the distal end  48  of the outer cannula  12 . In certain embodiments, the distal end  40  of the inner cannula  30  terminates short of the distal end  48  of the outer cannula and is disposed entirely within the outer cannula. When the inner cannula  30  is inserted, the compressible end region  32  is disposed at least in part within the outer cannula connector  28 . In embodiments in which the outer cannula forms a curve, such as a Magill curve, the inner cannula  30  may also be curved in a complementary fashion. Accordingly, the insertion may be directional such that proper insertion involves an inner curve  50  of the inner cannula  30  located proximate to or corresponding with the inner curve  22  of the outer cannula  12 . Similarly, the outer curve  52  of the inner cannula  30  will be located proximate to the outer curve  24  of the outer cannula  12 . The positioning of the inner cannula  30  in the outer cannula  12  may be facilitated by operator technique and, in particular embodiments, with the aid of markings, instructions, or other visual indicators. 
     The inner cannula  30  forms a conduit from which liquids or gases, including medications, may enter through the proximal end  34 . Both the inner cannula  30  and the outer cannula  12  have dimensions selected to fit easily through the stoma. In practice, a range of such tubes may be provided to accommodate the different contours and sizes of patients and patient airways. Such tube families may include tubes designed for neonatal and pediatric patients as well as for adults. By way of example only, the outer cannula  12  of the tube  10  may range from 4 mm to 16 mm. The inner cannula  30  may be sized to correspond with an appropriate outer cannula  12 . The outer cannula  12  and the inner cannula  30  may be characterized by their inner diameters (referring to the diameter of the interior of the passageway) or their outer diameters (referring to the diameter as measured from the exterior outside wall to exterior outside wall). 
     Because the inner cannula  30  fits within the outer cannula  12 , the outer cannula  12  features a larger inner diameter  60  relative to an outer diameter  64  of the inserted portion  54  of the inner cannula  30 . The outer diameter  64  of the inner cannula  30  may be selected to allow sufficient air flow while also fitting comfortably within the outer cannula  12  and allowing for appropriate insertion force. The inner diameter of the outer cannula  12  is less than the outer diameter  64  by the thickness of the walls of the inner cannula  30 . For example, an inner cannula  30  sized to 6.5 mm may have an outer diameter  64  of about 6.5 mm and an inner diameter of about 5.5 mm. In such an embodiment, the inner cannula walls are about 1 mm thick in the inserted portion of the inner cannula  30  (e.g., in portions distal of the compressible end region  32 ). Similarly, a 10 mm inner cannula  30  may have an inner diameter of about 9 mm. Accordingly, tubes sized to 6.5 mm, 7.0 mm, 7.5 mm, 8.0 mm, 8.5 mm, 9.0 mm, or 10 mm may feature smaller inner diameters that define the airflow passage. 
     Further, the inner diameter  62  at the proximal end  44  of the outer cannula  12  is typically larger than the inner diameter  60  and is selected to couple to appropriate tubing. That is, the outer cannula  12  is narrower in the inserted portion and is wider at the connector. The compressible end region  32  also has a larger outer diameter  70  relative to the inserted portion  54 . In certain embodiments, the compressible end region may flare or taper outwards gradually such that the diameter increases gradually, with the largest diameter  70  at the proximal end  34 . In other embodiment, the compressible end region  32  may include a generally barrel-shaped region with an outer diameter  70 . It should be understood that the compressible end region  32  may change under compression. Accordingly, the outer diameter  70  refers to the uncompressed configuration. Further, in embodiments in which the proximal end  34  forms a broken annulus (i.e., is not a continuous element), the outer diameter  70  refers to a diameter between the solid portions of the proximal end  34 . When the compressible end region  32  is within the outer cannula connector  28 , the outer cannula connector  28  provides a biasing force that compresses the compressible end region  32  into a compressed configuration that is sized to fit within the inner diameter  62  of the outer cannula connector  28 . The outer diameter  70  is larger than a largest outer diameter of the inner cannula  30  in the compressed configuration. 
     The compressed configuration of the inner cannula  30  is shown in  FIG. 4 , which is a partial perspective view of the proximal region  80  of the tracheal tube assembly  10 . In the compressed configuration, the compressible end region  32  is constrained by the wall  82  of the outer cannula connector  28 . Accordingly, the outer diameter  84  is smaller than the outer diameter  70  (see  FIG. 3 ) of the uncompressed configuration. In one embodiment, the outer diameter  84  is about 15 mm or slightly smaller. That is, uncompressed outer diameter  70  is about the outer diameter of a 15 mm connector. The resulting proximal opening  86  of the inner cannula  30  is also smaller. In a specific embodiment, the material of the compressible end region  32  is selected so that an operator is capable of changing the configuration of the compressible end region  32  through the application of a biasing force. Similarly, the wall  82  of the outer cannula connector  28  is sufficiently strong to maintain the compressible end region  32  in the compressed configuration. In another embodiment, the compressible end region  32  includes one or more notches or openings  90  that facilitate the change from the uncompressed configuration to the compressed configuration. In the compressed configuration, the gap  92  formed by the opening  90  is smaller than in the uncompressed configuration. 
     The opening  90  allows the proximal end  34  of the inner cannula  30  to form a smaller compressed diameter  84  under a compression force without wrinkling and while maintaining a generally circular cross-section over the inserted portion of the compressible end region  32  that corresponds with the generally circular cross-section of the outer cannula connector  28 . The size and number of openings  90  may be selected according to the size and manufacturing of the inner cannula  30 . In one embodiment, the compressible end region has two openings  90 . In embodiments with only one opening  90 , the size of the gap  92  in the uncompressed configuration may be relatively larger to facilitate the change from uncompressed to compressed with fewer openings. In another embodiment, if more openings  90  are used, the corresponding gaps  92  may be smaller. That is, in certain embodiments, the total space accounted for in the gaps  92  is about the same regardless of the number of openings. The size of the gaps  92  may be measured in either the compressed or the uncompressed configuration, and may be a largest space between the adjacent portions of the inner cannula wall  94 . 
     The outer cannula connector  28  may be formed in accordance with industry standards to permit and facilitate connection to ventilating equipment (not shown). By way of example, the outer cannula connector  28  is a 15 mm connector, although other sizes and connector styles may be used. Additionally, the tracheal tube assembly  10  may be connected to other medical devices, such as a suction device, a T-junction, a medicine delivery system, and so forth. Indeed, the outer cannula connector  28  may enable the attachment of one or more medical devices to the tracheal tube assembly  10 . To accommodate such a connection, the compressible end region  32  may be formed such that, when inserted, the inner cannula  30  does not interfere with coupling via the outer cannula connector  28 . To that end, in particular embodiments, the widest diameter  84  of the inner cannula  30 , including any protruding portions, is smaller than the widest outer diameter (e.g., 15 mm) of the outer cannula connector  28 . It should be understood that, the inserted portions of the compressible end region  32  press against the interior wall  93  of the outer cannula connector  28  and feature an outer diameter that is slightly smaller (e.g., 12 mm or smaller) than the inner diameter of the outer cannula connector  28 . Further, the inner cannula  30  may feature regions with different outer diameters along its length in either configuration. 
     Because the inner cannula  30  is configured to be inserted and/or removed by an operator, the proximal end  34  may protrude from the outer cannula connector  28  to allow the compressible end region  32  to be manipulated while the inner cannula  30  is in place. For example, the proximal end  34  protrudes proximally or along a rotational axis  95  of the outer cannula connector  28 . The axis  95  is generally orthogonal to the axis  98  along a longest dimension of the flange member  20 . When inserted in the patient, the inner cannula  30  may be positioned so that the operator grips the proximal end and pushes laterally (e.g., along the axis  98 ). Accordingly, the openings  90  may be positioned to correspond with a dorsal and ventral side of the tube  10  (e.g. to correspond with the inner curve  50  and the outer curve  52  of the inner cannula, see  FIG. 3 ) when inserted to encourage lateral compression. In other embodiment, the openings  90  may be positioned to encourage dorsal-ventral compression. 
       FIG. 5  is a perspective view of an inner cannula  30  in the uncompressed configuration. In the depicted configuration, the proximal end  34  assumes its largest unbiased outer diameter  70 . When force is applied along arrows  110 , the first ear  112  and the second ear  114  move towards one another (e.g., along axis  98 , see  FIG. 4 ) and the gaps  92  formed by the openings  90  decrease as the compressible end region  32  assumes the smaller, compressed outer diameter  84  (see  FIG. 4 ). For example, an application of  5 N of force or less may be applied to achieve sufficient compression to insert the inner cannula  30 . In other embodiments, the compressible end region  32  may form a single gripping structure or more than two ears. 
       FIG. 6  is a detail view of the compressible end region  32 . In particular embodiments, the compressible end region  32  may include mating features that couple to complementary features on the interior wall  93  of the outer cannula connector  28  (see  FIG. 4 ). Such mating features may prevent rotational movement of the inner cannula  30  relative to the outer cannula connector  28 . In addition, the mating features may provide additional alignment to facilitate correct alignment of the curve of the inner cannula  30  with the curve of the outer cannula  12  (see  FIG. 3 ). As depicted, the mating features may be protrusions, such as protrusion  122  formed on an exterior surface  120  of the inner cannula  30 . The protrusion  122  may be formed in any suitable shape or combination of shapes, such as a rounded bump, a ramp shape, a pyramid structure, etc. Further, the compressible end region  32  may include any number of protrusions  122  positioned about a circumference. For example, the compressible end region  32  may include two protrusions  122  that oppose one another. In specific embodiments, opposing protrusions  122  may be circumferentially centered on the ears  112  and  114 . In such embodiments, the protrusions  122  may serve as guides for an operator to press against to bias the ears  112  and  114  towards one another. In another embodiment, the protrusions  122  may be about 90 degrees from opposing notches  90 . In another embodiment, respective protrusions  122  may be provided as a partial ring with an arc having less than 45° of circumference of the compressible end region  32 . In another embodiment, the protrusion  122  may form a ring about the circumference of the compressible end region  32 . 
     It should be understood that the mating features may also be implemented as recesses or a combination of protrusions and recesses. The size of the protrusion  122  may be selected to fit into a corresponding recess in the outer cannula connector  28  and may be less than a thickness of the wall of the outer cannula connector  28 . In one embodiment, the protrusion  122  may protrude less than about 1 mm, less than about 1.5 mm or less than about 2 mm from the exterior surface  120 . In particular embodiments, the protrusions  122  protrude less than a widest diameter  70  in an uncompressed configuration. Alternatively, the protrusion  122  may fit into complementary windows formed in the outer cannula connector. In such embodiments, the protrusion  122  may be larger. The inner cannula  30  may also include additional support structures, such as one or more ribs  124 . In the depicted embodiment, the rib  124  may provide structural support to the protrusion  122 . In addition, the compressible end region  32  may feature regions of varying outer diameters that form a slope  126 . The slope  126  may be formed proximate to the protrusion  122  to facilitate insertion of the relatively larger protrusion  122  into the outer cannula connector  28 . 
       FIG. 7  is a top view of the inner cannula  30  showing the position of two opposing protrusions  122  relative to the proximal end  34 . The position of the protrusions  122  may be measured from the midpoint  130  or the distal-most point  132 . In one embodiment, the distance  140  from the proximal end  34  of the inner cannula  30  to the distal-most point  132  of the protrusion  122  may be selected to place the protrusion  122  within the interior of the outer cannula connector  28  (see  FIG. 4 ). In another embodiment, the protrusion  122  may be positioned relative to a distal terminus  142  of opposing openings  90 . As depicted, the openings  90  are generally oriented along the rotational axis  95 . However, it should be understood that the openings  90  may be irregularly shaped. Accordingly, the distal terminus may be the distal-moist point of the opening  90  from the proximal end  34 . 
     In one embodiment, the protrusion  122  is located proximally relative to the distal terminus  142 . In other words, the distance  140  is less than a distance  144  (the distance from the proximal end  34  to the distal terminus  142 ). Further, the ratio of the distance  140  to the distance  144  may be selected such that the protrusions  122  are generally closer to the distal terminus  142  than the proximal end  34 . For example, the ratio may be greater than 0.5 or greater than 0.75. Such an implementation may allow the protrusions  122  to be biased sufficiently toward one another to ease insertion in the outer cannula connector  28 . That is, if the proximal end region  32  is flared, positions closer to the distal terminus  142  may be within smaller diameter regions. In certain embodiments, the distal terminus  142  is also positioned within the outer cannula connector  28 . Depending on the size and length of the outer cannula connector  28 , in particular embodiments, the distance  144  may be less than about 15 mm, less than about 12 mm, less than about 10 mm, less than about 9 mm, less than about 8 mm, less than about 7 mm, less than about 6 mm, or less than about 5 mm. 
     The proximal end  34  may also terminate in a lip  150  that is formed in the wall  94 . The relatively thicker lip  150  may also extend at least partially towards the distal terminus  142  and terminate in an abutment surface  152 . The abutment surface  152  is configured to abut the proximal end  44  of the inner cannula connector and prevent further movement of the inner cannula  30  distally, which may assist in aligning the inner cannula  30  within the outer cannula  12 . In certain embodiments, a distance  160  from the abutment surface  152  to the proximal end  34  is less than the distance  140  and the distance  144 . In particular embodiments, the distance  160  is less than 50% of the distance  144  or is less than 50% of the distance  140 . In a particular embodiment, the distance  160  is about 4 mm. Further, in another embodiment, the distance between a midpoint  130  and the abutment surface  152  may be less than the distance  160 , e.g., may be about 3 mm. 
     As noted, the proximal end  34  of the inner cannula  30  is positioned outside of the outer cannula connector  28 , which facilitates operator manipulation of the inner cannula  30 .  FIG. 8  is a partial perspective component view of the interaction between the outer cannula connector  28  and the proximal end  34 . The position of the abutment surface  152  determines how much the proximal end  34  protrudes from the proximal end  44  of the outer cannula connector  28 . A more distal abutment surface  152  results in greater protrusion. The length  170  of the protrusion may be about 4 mm or less. In other embodiments, the length  170  of the protrusion is selected to avoid interference with couplings formed by the outer cannula connector  28 . In addition, the inner cannula  30  may include features that facilitate gripping by an operator. The thickness  172  of the lip  150  may be selected to maintain the desired outer diameter  84  and also form a gripping end. The lip  150  may be slightly thicker than the inserted portion of the compressible end region  32 . 
     In certain embodiments of the present techniques, the inner cannula  30  is retained in place by the compression force of the compressible proximal end  32  against the interior surface  93  of the outer cannula connector  28 . That is, the force against the outer cannula connector  28  reflects the material and geometric properties of the compressible end region  32  and a tendency of the compressible end region  32  to return to a default uncompressed configuration. In one embodiment, the compression force is sufficient to form a seal between the compressible end region  32  and the outer cannula connector  28 . In one embodiment, the compressible end region  32  has one or more mating features that may align the inner cannula  30  within the outer cannula  12  and/or may prevent rotational dislodgment. 
       FIG. 9  is a perspective view of an outer cannula connector  28  that includes complementary features to such mating features. The -outer cannula connector  28  is typically coupled to the outer cannula  12  (see  FIG. 1 ) at its distal end  180 . The outer cannula connector  28  may also include distal features  182  for coupling to the flange member  20  (see  FIG. 1 ), such as threading connectors, snap-in features, and/or one or more windows or recesses to facilitate heat bonding. In certain embodiments, the outer cannula connector  28  may include one or more recesses (e.g., recesses  184  and  186 ) that are sized and shaped to accommodate complementary protrusions on a compressible end region  32  of an inner cannula  30 . It should be understood that the complementary features may be selected based on the characteristics of the mating features. Accordingly, if the mating features are protrusions, the complementary features are recess or windows and vice versa. Similarly, the position of the complementary features may be selected to facilitate proper alignment and insertion of the inner cannula  30 .  FIG. 10  is a cross-section of the outer cannula connector  28  of  FIG. 9 , showing the position of the recess  184 . 
     It is envisioned that the tracheal tube assembly  10  as provided herein may be provided as an assembly and/or as a kit. A kit may include a packaging that encloses an inner cannula  30  sized for an outer cannula  12 , which may include an affixed outer cannula connector  28  and flange member  20 . The kit may also include a neck strap for retaining the tracheal tube  10  in place. The kit may also include an obturator  190 , shown in  FIG. 11 . Other components of the kit may include a cap configured to be placed on a proximal end  34  while the obturator  190  is in use and that may be part of the obturator  190 . The tube assembly  10  components (e.g., outer cannula  12 , flange member  20 , outer cannula connector  28 , cuff  16 , and pilot balloon assembly  18 ) may be assembled prior to in situ assembly of the inner cannula  30  into the outer cannula  12 . Indeed, the user or clinician may perform final assembly of the tracheal tube  10  by selecting a desired inner cannula  30  from a selection of inner cannulas and then inserting the inner cannula  30  into the outer cannula  12  prior to intubation. Thus assembled, the tracheal tube  10  may then be inserted into the patient&#39;s trachea. 
     Components of the tube assembly  10  may be manufactured according to suitable techniques. For example, the inner cannula and/or outer cannula  12 , including the outer cannula connector  28 , may be molded, overmolded, two shot molded, computer numerical control (CNC) machined, milled, or otherwise formed into the desired shape. In one embodiment, a mold or mold form may be used to manufacture the inner cannula  30 . In one embodiment, the mold or other manufacturing technique may facilitate a speckled outer surface of the inner cannula  30 , which may facilitate insertion. One or more components may be manufactured of materials such as a polyethylene (e.g., low density polyethylene), polypropylene, PTFE, expandable PTFE, polyvinyl chloride (PVC), a PEBAX silicone, a polyurethane, thermoplastic elastomers, a polycarbonate plastic, a silicon, or an acrylonitrile butadiene styrene (ABS). In particular embodiments, the material of the inner cannula  30  may be selected to be 60 Shore D. 
     While the disclosure may be susceptible to various modifications and alternative forms, specific embodiments have been shown by way of example in the drawings and have been described in detail herein. However, it should be understood that the embodiments provided herein are not intended to be limited to the particular forms disclosed. Indeed, the disclosed embodiments may not only be applied to airway devices, but these techniques may also be utilized for connections between inner and outer conduits for other types of medical devices and medical connective tubing. Rather, the various embodiments may cover all modifications, equivalents, and alternatives falling within the spirit and scope of the disclosure as defined by the following appended claims.