Abstract:
Unwanted separation of an inner cannula from an outer cannula in tracheostomy devices can be achieved by installing a retaining ring which prevents the inner cannula from unwantingly being unlatched from the outer cannula. The retaining ring allows the air supply elbow to be separated which, in turn, permits the sensory alarms to properly sound when a disconnection of the air supply arises.

Description:
This non-provisional application claims the benefits of provisional application Serial No. 60/229,622 entitled the same and filed Aug. 31, 2000 on behalf of Craig D. Linderoth. 
    
    
     FIELD OF INVENTION 
     The present invention relates to a medical safety device and, more particularly, to a tracheostomy safety device and its use. 
     BACKGROUND OF THE INVENTION 
     Tracheostomy devices are extensively used within the medical field to ventilate or assist patients with respiratory problems. Many patients with advanced stages of gas exchange impairment (e.g. COPD, multiple sclerosis, emphysema, etc.) are dependent upon effective utilization of the tracheostomy devices to supply oxygen and discharge exhaled gases from the respiratory system. Any inadvertent or unwanted cessation of the respiratory exchange by the tracheostomy devices within the medical unit can lead to irreparable injury or death of the patient. 
     The ventilator units are usually equipped with sensory or alarm systems designed to detect certain abnormalities such as gas pressure loses within the device. Typically a sudden operational decrease in back pressure activates a remote alarm system so as to alert the medical staffing so that the device may be restored to a life sustaining operation. 
     One of the most popular tracheostomy devices is a device referred to as a Shiley disposal cannula low pressure cuffed tracheostomy device manufactured and distributed by Mallinokrodt, Inc. (St. Louis, Mo. 63134) fitted with a rigid neck plate and what is referred to as a STRONGHOLD retainer for harnessing the tracheostomy device so that the inner cannula cannot be inadvertently separated from the outer cannula. 
     The SHLEY device includes an inner cannula and an outer cannula operatively connected to an oxygen or air supply and a low pressure sensory for the alarm system. The outer cannula includes a larger tubular section with an inflatable cuff encompassing a distal end section of the tube and a notched flanged rim at a proximate tube end with a flared seating collar for connecting to the inner cannula. The inner cannula comprises a tubular passageway fitted with a projecting tubular portion and a collared seat for seating and sealing onto the flanged collar of the outer cannula. The projecting tubular portion of the inner cannula is sized to concentrically fit within the outer cannula passageway. The inner cannula functions as an air passageway for ventilating the patient. An enlarged hollow cylindrical extension capped with a brim which anchors the stem of the projecting tubular portion completes the air pathway of the inner cannula. The enlarged tubular air line cylindrical extension having a larger external diameter than the outer diameter of the outer cannula serves as a connecting site for a ventilator connecting elbow which connects the ventilator gas supply lines to the tracheostomy device. 
     The cylindrical extension also serves as a mounting site for mounting the outer cannula onto the inner cannula. The brim of the cylindrical extension includes a pair of aligning ledges which mate onto notched sections of the notched rim. The extension has the appearance of a hollow cylindrical member with the tubular section spouting outwardly from the stem of the opposite end. The cylindrical member serves as a connecting site for a connecting elbow for the air supply lines. 
     The cylindrical extension includes a flared seat on the latching side which sealingly fits against flared collar of the outer cannula. A pair of jutting ledges extending outwardly from the top edge of brim of the cylindrical extension of the inner cannula serves as a support for the latching assembly. The cylindrical member is equipped with a pair of latching assemblies which latched the outer cannula to the inner cannula. The latching assemblies outwardly extending ledges are laterally positioned at a sufficient outwardly position so as to provide annular clearance for the latches from the outer cannula rim. The undersides of the extending bridges are notched with channeled grooves to impart improved hingeability to the latches. 
     The latching assemblies of the inner cannula include a pair of flexible latches in the form of extending arms along the outer peripheral margin of the jutting ledges which extend upwardly and inwardly terminated by L-shaped latching tab or claw which engage onto the notched rim of the outer cannula so as to snuggly hold the outer cannula rim onto the inner cannula rim. The arms extend downwardly and outwardly from the ledges to form depressing tabs which, when depressed, place the latches in an unlatched position. 
     When used, the outer cannula is inserted into the trachea of the patient with the inflatable cuff inflated to seal the outer cannula to the trachea. The inner cannula tube with the connected or unconnected gas supply lines is then inserted onto the outer cannula in a seating position and then latched together with the latches. Normally the harness for the neck plate is secured to the patient to hold the tracheostomy unit in place when ventilation of the patient is commenced. A ventilating elbow connector forms a connecting elbow between the inner cannula and the air lines to the air sources. When the STRONGHOLD anti-disconnect device is used, it straps the elbow connector to the neck plate so as to prevent the elbow connector and the inner cannula from being inadvertently separated from the outer cannula. 
     Unfortunately, the aforementioned tracheostomy device creates problems for an impaired patient which, if uncorrected, can cause irreparable damage or death to the patient. The ventilating device, with or without the STRONGHOLD, creates serious health risks to patients using the Shiley ventilating device. Without the STRONGHOLD, the latches for latching the inner cannula to outer cannula can become unlatched causing a disruption of the crucial air supply to the patient. Obese patients with excessive neck fat or double chins can unknowingly manipulate the latches with the neck excess sufficiently to unlatch the latching system. This causes a break in the air passageway and a severance of air supply to the patient. Since the inner cannula remains connected to the air source, the sensing system will not detect any appreciable decrease in gas back pressure and, therefore, will not sound the alarm system. Consequently, the medical staffing will be unaware that the patient is in distress and will die if the problem remains uncorrected. 
     Another particularly serious problem arises in the case of those tracheostomy devices equipped with the STRONGHOLD when the unattended patient becomes restless, startled or panicked by respiratory or ventilating irregularities. Panicky or startled patients will often grasp the connecting elbow of the tracheostomy device with such force so as to pull the entire device, including the inflated cuff, from the trachea causing the ventilating gases to escape into the atmosphere. Since the inner cannula remains connected, there is no detectable back pressure decrease so that the alarm system will not normally detect and sound the alarm under these life-threatening conditions. When an ambulatory patient coughs to clear a plug in the throat, the startled patient will often unconsciously grasp or elbow the device so as to dislodge the entire device, including inflated cuff, from the trachea often causing serious harm or injury to the patient. Thus, the addition of the STRONGHOLD anti-disconnect device does not alleviate those problems associated with the tracheostomy device. 
     There exists a need to avoid unwanted disconnection of the inner cannula from the outer cannula. There exists a need for an anti-disconnect device which prevents unlatching but yet permits a detectable separation at the connecting elbow. There exists a need for an anti-disconnect device which prevents unwanted unlatching of the inner cannula from the outer cannula and unwanted disengagement of the entire tracheostomy device including the inflated cuff from the patient&#39;s trachea. If the latching system could be maintained latched until knowingly unlatched by hospital or medical staffing, patients needlessly suffering of loss of life or serious injury could be avoided. Crucial notice of a failure of a patient&#39;s tracheostomy unit by timely sounding of the alarm system would avoid catastrophic injury or death to the user of the device. 
     SUMMARY OF THE INVENTION 
     Safety of using a tracheostomy device by preventing unauthorized or undetected separation of the inner cannula from the outer cannula can be achieved by installing a latching stop against the latches so as to prevent unwanted unlatching. An annular retaining ring buttressed against the latches effectively prevents an unlatching movement of the latches and maintains the latches in the latching position. The latch retaining ring is positioned so as to prevent a patient from intentionally or unintentionally removing the latching stop from the unlatching position. This allows only the authorized personnel to remove the latching stop from the latching position. The latch retaining ring prevents only separation or unlatching of the inner cannula from the outer cannula. If separation of ventilating passageway occurs, it occurs at the connecting elbow, thus, preserving the inflated trachea cuff and the alarm system. 
     The latching stop mechanism allows the low pressure alarming system to perform its intended function of alarming medical personnel in crucial life-threatening situations. Failure of the alarming system to notify medical staffing of an undetectable separation of the inner cannula from the outer cannula is effectively avoided by the inclusion of the latching stop mechanism of this invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a frontal view of an assembled tracheostomy unit equipped with the safety locking embodiments of this invention. 
     FIG. 2 is a frontal view of the unit shown in FIG. 1 attached to a patient. 
     FIG. 3 is a top view showing in part the assembled tracheostomy unit of FIG.  2 . 
     FIG. 4 depicts FIG. 3 without the safety locking attachment. 
     FIG. 5 is a side view of the tracheostomy unit shown in FIG.  1 . 
     FIG. 6A is a side view of the locking attachment used to interlock the outer cannula to the inner cannula as shown in FIGS. 1-3 and  5 . 
     FIG. 6B is a top view of the interlocking attachment shown in FIG.  6 A. 
     FIG. 7 is a side view of the inner cannula shown in FIGS. 1-5. 
     FIG. 8 is a cross-sectional view taken along line  8 — 8  of FIG.  1 . 
     FIG. 9 is a partial cross-sectional view as shown in FIG. 8 with the inner cannula being shown as separated from the outer cannula 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Pursuant to the present invention, there is provided a tracheostomy device (generally referred as  1 ) equipped with an interlocking stop (generally referenced as a  40  series number) which prevents an inner cannula  20  from being accidentally separated from an outer cannula  30  without first removing the interlocking stop  40  from the assembled inner  20  and outer  30  cannulas. The tracheostomy device as depicted without the interlocking  40  stop as shown in FIG. 4 is manufactured and distributed by Mallinokrodt, Inc., Critical Care Division, St. Louis, Mo. 63134, in various sizes (e.g., men, women, children, etc.) such as a Shiley adult model fitted with a rigid neck plate  34  and a neck strap  34 S which straps the tracheostomy device to the patient&#39;s neck. An anti-disconnect accessory identified as STRONGHOLD (not shown) for strapping elbow E to neck plate  34  has heretofore been used to anchor the inner cannula  20  and the outer cannula  30  together and, thereby, prevent unlatching. The present invention incorporates an interlocking stop  40  which avoids inadvertent disconnection of the inner cannula  20  from the outer cannula  30  while allowing the connecting elbow E to separate from the inner cannula  20 . 
     The inner  20  and outer  30  cannulas comprise concentric tubular members adapted to interlock onto one another when the tracheostomy device  1  is assembled for use by a patient. The outer cannula  30  comprises an outer tube  31  fitted with an inflatable cup  33  or bag, which circumscribes the distal end of the outer tubular section cannula  30  and, when inserted in the trachea of a patient P, may be inflated via pumping air pressure bulb  32  to pump air through inflating lines  22 A so as to seal the tracheostomy device  1  against the trachea opening of the patient P. The opposite (proximate) end of tube  31  includes a flanged rim  35  equipped with a pair of seating grooves  36  which, as explained later, seat onto mating ledges of latching legs  26 L and  26 R of the inner cannula  20 . A beveled annular flared female seat  38  buttressed against the inward side of rim  35  forms airtight union when drawn snuggly against a mating male flared fitting  28  of the inner cannula  20 . An attachable neck rest  34  seated onto the outer cannula tube  31  permits the device  1  to be attached to the patient&#39;s neck with drawstrings  34 S as illustrated in FIG.  2 . 
     The inner cannula  20  comprises a hollowed cylindrical base  25  and tubular section  21  adapted to sealingly seat within an open passageway  37  of the outer cannula  30 . The inner cannula  20  thus includes a smaller diameter tubular section  21  adapted to seat within passageway  37  of the outer cannula  30  and open at both ends so as to provide a passageway  21 A for gases from and to the trachea to flow therethrough. 
     The proximate end of the inner cannula  20  comprises a hollowed cylindrical base  25  equipped with a brim  29  of a larger diameter than the outer cannula tube  31 . Brim  29  includes a centrally disposed spouting orifice  23 C spouting and connecting tubular section  21  to hollowed base  25  at stem  23 . Circumscribing tubular section  21  at stem  23  (the interfacing of base  23  and tubular section  21 ) is a flared male seat  28  for seating onto a mating female flanged seat  38  of the outer cannula  30 . Cylindrical base  25  is hollowed in the center so as to provide an air passageway  21 B which interconnects onto air passageway  21 A of the inner cannula  20 . The cylindrical base  25  supports the inner cannula tube  20 . The anterior portion of cylindrical base  25  extends perpendicularly outwardly from the stem  23  of the inner cannula tube  21  to form brim  29  and the interfacing top surface of cylindrical base  25  closure which spouts onto the stem  23  of the inner cannula tube  21 A. The interfacing top surface of brim  29  is circular and flat (except for seats  28 ) so as to rest flushly against outer cannula rim  35  and form a sealed passageway therewith. The perimeter of cylindrical top surface of brim  29  is equipped with a pair of outwardly extending ledges or bridges  22 B and  24 B which respectively support latching legs  26 L and  26 R. 
     The brim  29  of cylindrical base  25  of the inner cannula  20  includes a pair of hinged latches  22  and  24  which latch the inner cannula  20  onto the outer cannula  30 . Latches  22  and  24  are positioned about the peripheral margin of brim  29  of inner cylindrical base  25  cannula. Latches  22  and  24  respectively include bridged sections  22 B and  24 B of molded plastic which interconnect legs  26 L and  26 R of latches  22  and  24  to the cylindrical base  25  with each of legs  26 L and  26 R of the latches  22  and  24  including a projecting legged tab  22 T and  24 T of legs  26 L and  26 R which extends outwardly and downwardly from hinged bridges  22 B and  24 B. The underside of bridged regions  22 B and  24 B include notched grooves  22 V and  24 V which impart hingeability and flexibility to latches  22  and  24 . Notched grooves  24 V and  26 V also serve as a nesting channel for retaining stop ring  40  so as to prevent hinging and downward depression of tabs  22 T and  24 T. The terminating end of each latching member  22  and  24  is equipped with a latching hook  22 H and  24 H adapted to engage onto lip  35 L of flanged rim  35  of the outer cannula  30  and connect the inner cannula  20  and outer cannula  30  together as shown in FIGS. 3-5 and  8 . Interconnecting latching legs  26 L and  26 R project upwardly and inwardly from the hinged bridged regions  22 B and  24 B at a sufficiently outwardly distance for latching hooks  22 H and  24 H to hook and latch onto lip  35 L of rim  35  of the outer cannula  30 . 
     When the inner cannula  20  and outer cannula  30  are connected in this manner without the protective unlatching stop of this invention as shown in FIG. 4, the inner  20  and outer  30  cannula may be inadvertently separated from one another by disconnecting neck movement of the patient. When the patient P unwantedly disconnects the inner cannula  20  from the outer cannula  30 , the inner cannula  20  remains connected to the vent tubing or elbow E which, in turn, fails to create sufficient back pressure to activate the ventilator&#39;s low pressure alarm circuitry which, in turn, if not corrected, can cause serious injury or death to the patient. 
     By inserting the interlocking stop  40  (e.g. in the form of a detachable annular ring such as a snap ring shown in FIGS. 6A,  6 B, and  9 ) into the recesses of notched grooves  22 V and  24 V (as shown in FIGS. 1-3,  5  and  7 - 8 ), inadvertent or unwanted separation of the inner cannula  20  from the outer cannula  3  is prevented. As may be seen with reference to FIGS. 1-3,  5 , and  7 - 8 , the latching stop  40  biases the latching members  22  and  24  into a secure latching position, which requires an advertent removal of latching stop  40  in order to effectuate any separation of the inner cannula  20  from the outer cannula  30 . 
     As may be observed in particular from FIGS. 1-3 and  8 , the latching stop  40  prevents the latching tabs  22 T and  24 T of the inner cannula  20  from being depressed downwardly and inwardly towards the cylindrical base  25  which, in turn, unlatches the latching lips or hooks  22 H and  24 H of the latching members  24  of the inner cannula  20  from latching lip  35 L of the flanged rim  35  of the outer cannula  30 . Thus, as may be observed from the embodiments of the invention as disclosed, if the latching stop  40  is not removed from the tracheostomy device  1 , inner cannula  20  cannot be dislodged from the outer cannula  30 . Separation of the air supply can occur if connecting elbow E is removed from the interconnecting cylindrical base  25  passageway  21 B which, in turn, creates a sufficiently low pressure so as to sound the low pressure alarming units within the hospital staffing or nursing unit. Unlike the conventional anti-disconnecting devices which cannot be separated at the connecting elbow causing tearing away of the inflated cuff and the whole tracheostomy assembly, separation occurs at the elbow E which also allows the alarm system to sound. 
     A rigid annular latching and seating member serves as a mounting site for mounting the inner cannula  20  onto the outer cannula  30  and an air line connecting site for connecting the air line to the tracheostomy device  1 . The annular latching and seating member is laterally positioned inwardly from the terminating end of the cannula so as to provide a connecting site for mounting and latching the outer cannula  30  thereto. An inward beveled seat configured so as to matingly seal the corresponding flanged passageway seating site of the outer cannula provides an airtight seal when the outer cannula  30  and inner cannula  20  are coupled together.