INNER CANNULA FOR TRACHEOSTOMY TUBE

Abstract: The present invention relates to a new, superior inner cannula (10) for insertion into a tracheostomy tube. The inner cannula according to the present invention is formed of a material that allows the inner cannula to have a smooth lumen, while avoiding kinking or collapse when inserted into the tracheostomy tube.

Description: Inner Cannula For Tracheostomy Tube Background Tracheostomy tubes are normally inserted into the trachea of a patient through an opening cut in the front of the throat. The tracheostomy tube is generally designed to include a relatively straight proximal and distal end portion connected by a curved central portion. Alternatively, the tracheostomy tube may be formed entirely in an arced configuration. The distal end portion of the tracheostomy tube extends down into the trachea, while the proximal end portion extends through the cut in the throat. An inflatable cuff may be included around the distal end portion and may be used to seal the space between the tube and the surrounding wall of the trachea, so that all ventilation occurs through the tracheostomy tube. During use, mucous and other secretions collect and dry within the tracheostomy tube causing obstruction of the ventilation path. Therefore, it is necessary to periodically remove the tracheostomy tube for cleaning, followed by reinsertion into the patient's trachea. This removal and reinsertion is traumatic to the patient, and increases the risk of injury to the trachea and surrounding membranes. In addition, a skilled practitioner is required to administer the procedure. To overcome the disadvantages of removal and reinsertion, it has been proposed to include a second, removable, tube or cannula which can be inserted into the tracheostomy tube. This inner cannula may easily be removed from the tracheostomy tube and cleaned or replaced by a new inner cannula, without disturbing the tracheostomy tube. The inner cannula must be flexible enough to be inserted into the proximal end of the tracheostomy tube and then pushed around the curved central portion into the distal end. However, the inner cannula must also be rigid enough to avoid collapse or kinking in the curved portion, which would restrict or close off the ventilation pathway. One type of inner cannula is described in US Patent 3,443,564 to Oehmig, and includes a spirally wound wire along a portion of its length which will correspond to the curved portion of a tracheostomy tube when inserted. This inner cannula has several disadvantages including the lack of a solid wall where the wound wire exists. This is disadvantageous because gaps will be present between convolutions of the wire, which will gather mucous and other secretions. Also, such an inner cannula is relatively expensive, so as not to be suitable as a disposable unit. Therefore, this inner cannula must be cleaned every time it is removed, which is a difficult task because of the wire and grooves formed there between. Another known inner cannula is shown in US Patent 3,948,274 to Zeldman et al, such inner cannula comprising a normally straight one-piece flexible tube of plastic having circumfirentially formed corrugations along a portion of its length. The corrugations enable the inner cannula to have enough flexibility to be pushed through the curved portion of a tracheostomy tube while maintaining structural integrity and preventing collapse of the inner cannula when inserted. However this inner cannula also has disadvantages associated with the corrugations. In particular, the corrugations will allow relatively rapid buildup of mucous and other secretions. This buildup creates a need for relatively frequent removal of the inner cannula for cleaning or replacement. While this inner cannula is low in cost, cleaning may still be preferred to replacement, by some patients. Cleaning is made difficult because the mucous and other secretions may become embedded in the corrugations. This in turn may lead to excessive build up and possible infection. Therefore, there remains a need in the art for an inner cannula which overcomes all of the above problems. Objects Of The Invention It is one object of the present invention to provide a superior inner cannula for use in tracheostomy tubes. It is another object of the present invention to provide a flexible inner cannula having a smooth lumen and which possesses sufficient strength to avoid kinking and collapse. Summary Of The Invention The objects above and others are accomplished according to the present invention, by providing an inner cannula made from a material which allows for a minimum outside diameter (OD) to inside diameter (ID) ratio, while maintaining structural integrity. In particular, the objects of the present invention are accomplished by providing an inner cannula formed from a expanded polytetrafluoroethylene (EPTFE) material or other compound of similar polymer matrix. Brief Description Of The Drawings Fig. 1 is a plan view of an inner cannula for a tracheostomy tube according to the present invention. Detailed Description Of The Invention Fig. 1 shows an inner cannula, generally designated by reference numeral 10, according to the present invention. The inner cannula 10, comprises a flexible tube 20, having a distal end 30, and a proximal end 40. The flexible tube 20, has a single lumen extending the entire length thereof. An end piece 50, is attached to the proximal end 40. The end piece 50, is formed so as to fit securely into the distal end of a tracheostomy tube when inserted. The flexible tube 20, is formed of a material which has sufficient flexibility to allow for insertion into the lumen of a tracheostomy tube while maintaining structural integrity and avoiding kinking and collapse. In particular, the flexible tube 20, is formed of a material as described above which also allows the flexible tube 20, to have a smooth lumen. In a preferred embodiment, the flexible tube 20, is formed of a EPTFE material or another compound of similar polymer matrix. The end piece 50, may be attached to the proximal end 40, by any suitable means, such as adhesive bonding, compression fitting or an insert molding process. An inner cannula according to the present invention provides several advantages over those known in the prior art. In particular, the use of a material as described above for the flexible tube of the inner cannula provides a low ratio of OD to ID. In other words, the walls of the inner cannula can be very thin, e.g. about 0.4mm thick. In a particular example, the wall thickness of an inner cannula for a 9mm tracheostomy tube is from about 0.3mm to 0 . 5mm. The inner cannula according to the present invention may have any suitable OD, so as to fit snugly and securely within any standard tracheostomy tube. In addition, the inner cannula can be of any suitable length to correspond with the length of the tracheostomy tube in which it is to be inserted. The use of the material described above for the inner cannula according to the present invention provides several other advantages. In particular, less drag is exerted on the tracheostomy tube during insertion of the inner lumen. Also, there may be less drag exerted on instruments which may be inserted through the inner cannula and used for suctioning of the airway of the patient by an attending practitioner. In addition, there is less resistance to airflow when the inner cannula is inserted. This is attributable both the relatively low friction coefficient of the material used, and because the OD to ID ratio can be minimized making the ID as large as possible. Because the inner cannula according to the present invention can be formed with a smooth lumen, other advantages are realized over prior art devices. In particular, it is believed that less build-up of mucous and other secretions may occur. Therefore, it may not be necessary to remove and clean or replace the inner cannula as frequently as needed by prior art devices. The relatively low cost of the inner cannula according to the present invention makes replacement highly feasible and affordable. However, cleaning of the inner cannula according to the present invention is also possible. The smooth lumen and low friction coefficient make cleaning easier and more efficient. There are no corrugations or wires for mucous and secretions to become embedded in. Therefore, cleaning is more thorough and creates less risk of subsequent contamination and infection. The foregoing has been a description of certain preferred embodiments of the present invention, but is not intended to limit the invention in any way. Rather, many modifications, variations and changes in details may be made within the scope of the present invention.

Claims: What is claimed is: 1 An inner cannula for insertion into a tracheostomy tube, said inner cannula comprises a flexible tube having a smooth lumen. 2 An inner cannula according to claim 1, wherein said flexible tube is formed of a flexible material having sufficient strength to avoid kinking and collapse when inserted into a tracheostomy tube. 3 An inner cannula according to claim 2, wherein said flexible material is a expanded polytetrafluoro- ethylene material or other material having a similar polymer matrix. 4 An inner cannula for inserting into a tracheostomy tube, wherein said inner cannula comprises a flexible tube having a wall thickness of 0.3mm to 0.5mm. 5 An inner cannula according to claim 4, wherein said wall thickness is about 0.4mm.

Inventors: BENWAY CHERYL A, HORTON DUANE L, MAHONEY MICHAEL R, BENWAY, CHERYL, A., HORTON, DUANE, L., MAHONEY, MICHAEL, R.
Applicants: MALLINCKRODT MEDICAL INC, MALLINCKRODT MEDICAL, INC.
Application year: 1993
Main classification: A61M16
IPC codes: A61M16