Abstract:
There is provided a tubular workpiece for blow-molding into an inflatable balloon component. The tubular workpiece is a raw tube having a lumen and composed of a thermoplastic polymer, the tube having an asymmetric wall thickness such that when the tube is preheated in a mold to a temperature sufficient to soften the material of the tube and inflated with a gas to generally uniformly stretch the material of the tube, the tube forms a balloon component. The balloon may be non-uniform in wall thickness depending on the type of mold used. The balloon may be attached according to conventional means to a hollow tube to produce a tracheostomy device.

Description:
[0001]    This application claims the benefit of commonly assigned U.S. provisional application 60/994,664, filed Sep. 20, 2007 and having attorney docket number 64391725US01. 
     
    
     BACKGROUND 
       [0002]    Balloons or “cuffs” for tracheostomy (trach) tubes are sized to obdurate the trachea of a patient after they are inflated so that breathing takes place only through the lumen of the trach tube. The trach tube is designed to be inserted into the trachea from the front of the throat after it has been punctured and dilated to receive the tube. The balloon is located near the distal end of the tube and is typically inflated using a small conduit or inflation lumen after the tube has been inserted into the tracheal stoma and is in place in the trachea. The proximal end of the tube may be connected to a mechanical ventilator or respirator if necessary to provide assisted breathing. 
         [0003]    Trach tube balloons are desirably soft and compliant so that damage to the tracheal tissue is kept to a minimum. Prior trach tube balloons that operated at relatively high pressures and had relatively thick walls caused considerable damage to the trachea. Newer designs having much thinner walls and that operate at lower pressures have reduced the trauma considerably. One example of such a balloon is that taught by Gobel in U.S. Pat. No. 6,526,977 which provides a thin (at most 20 micron) balloon wall and which is effective at low pressures; 30 mbar or less. 
         [0004]    Recent work by Fauza (U.S. Pat. No. 6,612,305) provides a shaped balloon that is elongated so that it adheres to a larger area of the internal lining of the trachea to provide for better control over the location of the balloon, i.e. better “anchorage”. This balloon appears to completely block the tracheal stoma and so inhibit the ability to drain any secretions that may pool above the balloon. 
         [0005]    The draining of secretions from above the balloon is important because they are a prime suspect in the cause of ventilator assisted pneumonia (VAP). VAP is a serious and sometimes fatal problem that may occur in patients intubated for long periods of time. While VAP is generally less common in patients having trach tubes as contrasted with endotracheal tubes, it is still a serious concern. 
         [0006]    While the previous balloons designed by Gobel and Fauza perform well, it would be quite desirable to have the ability to control the wall thickness of the balloon at various points or areas on the balloon. It may be desired for certain applications, for example to produce a balloon that is thicker or thinner at the front or rear of the trachea. Current balloon making technology uses generally symmetrical polymeric tubing that is blown into a balloon shape. This process results in a balloon having generally symmetrical wall thicknesses or results in predictable (but uncontrollable) thickness changes based on the degree of blowing of each wall section. 
         [0007]    It would be desirable to give the balloon designer another dimension of control in order to tailor the balloon design more precisely or to allow for creative development of even more improved balloons. 
       SUMMARY 
       [0008]    This disclosure concerns a tubular workpiece having a lumen that may be used to make balloons for use on a tracheostomy tube. The workpiece is asymmetrical, allowing the balloon designer to more precisely control the thickness of the walls of the balloon in different areas. 
         [0009]    The tubular workpiece may further include a lengthwise marking or line that is visible to a user, to help show the orientation of the workpiece in the mold. 
         [0010]    The balloon may be made by placing the workpiece in a mold, heating the mold to soften the workpiece and pressurizing the tube internally (i.e. blowing) to force it to expand and conform to the walls of the mold. Rotating the asymmetrical tubular workpiece within the mold prior to blowing the balloon can change the location of thinner and thicker areas of the walls of the formed balloon. 
         [0011]    The tracheostomy tube device includes a conventional hollow tube having a proximal end portion, a distal end portion, and a bend region intermediate of the end portions. The distal end portion of the tube is arranged for insertion through a patient&#39;s throat and tracheal stoma and into the tracheal lumen such that the distal end portion of the tube extends in a first direction within the tracheal lumen when the proximal end portion extends in a second direction through the tracheal stoma. The balloon that may be produced from the tubular workpiece may be attached to the hollow tube by conventional means. The balloon has a distal balloon portion substantially centered about and attached to the distal end portion of the tube. The balloon also has a proximal balloon portion attached to the bend region of the tube and positioned substantially off-center about the bend region below the proximal plane of the device. Upon inflation, this configuration provides for expansion of the balloon around the distal end portion of the tube and the proximal end portion of the tube below the proximal plane of the device to seal the trachea below the tracheal stoma and avoid sealing the trachea above the tracheal stoma. Desirably, this configuration of the balloon will allow secretions to exit the stoma. 
         [0012]    The device further includes means for inflating and deflating the balloon. These means for inflating and deflating the balloon may be conventional flexible tubing placed along the trach tube and through the flange of the trach tube. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0013]      FIGS. 1A  and  FIG. 1B  are each an illustration of cross-section of an exemplary asymmetric raw tube having a lumen. 
           [0014]      FIG. 2  is a perspective view of an inflatable balloon component. 
           [0015]      FIG. 3  is an illustration of an exemplary device in which the balloon is inflated to seal the trachea in the region below the tracheal stoma while avoiding sealing the trachea in the region above the tracheal stoma. 
       
    
    
     DETAILED DESCRIPTION  
       [0016]    The asymmetrical tubular workpiece described generally above is illustrated in  FIGS. 1A and 1B  wherein the raw tube  300  has a lumen  302 . The lumen is asymmetrical, meaning that the lumen is not exactly centered in the tube but is off center, resulting in varying wall thickness. The tube  300  may further have a line  304  that is located where the lumen is closest to the outside wall of the tube. The optional line  304  may be located at other locations, of course, depending on the needs of the user. The line  304  may be used to align the tube in a mold as desired. 
         [0017]    The tube may be placed in a mold for forming into a balloon or “blow molding”.  FIG. 2  shows and example of a balloon that may be formed (blown) using the asymmetrical tube.  FIG. 2  is, of course, necessarily a representation of the interior of the mold as well since the tube expands to contact the entire interior of the mold. The raw tube may be placed in the mold so that it lies in a straight line and so that either end protrudes from the mold. The mold and tube are heated by conventional means, pressure is applied to the tube internally (in the lumen), and the tube expands to fill the mold, forming the balloon. After the balloon is formed, the mold and balloon are cooled and the balloon is withdrawn from the mold. The balloon may be attached to a tracheostomy tube by means known in the art. 
         [0018]    As should be clear from  FIG. 2 , the balloon  250  has a distal end  255 , a distal attachment zone  260 , a proximal end  265 , a proximal attachment zone  270  and walls on either side  275 ,  280  joining the distal end and the proximal end of the balloon, the walls being asymmetrical or not symmetrical. The asymmetrical design of the mold in this case results in the tubular workpiece (tube) being offset from the centerline (i.e., a central line or plane “C” along the longest dimension of the balloon or mold dividing the balloon or mold into two equal volumes), resulting in expansion of the tube that is not uniform. Generally speaking, the central line “C” is equidistant from the side  275  and the side  280 . If the mold or balloon has dimensions that were generally the same from a front region to a back region and from side to side or if the mold or balloon were generally spherical, the central line “C” would generally be a line that divided the mold or balloon into two equal volumes. An asymmetrical mold is one in which one or both openings in the ends of the balloon produced from it are not centered on the ends or on the centerline. In an asymmetrical mold, the side of the tube that forms the larger side  280  of the balloon expands more than the side of the tube that forms the smaller side  275  of the balloon. A symmetrical raw tubing that is used to form a balloon in this manner will result in a balloon having differential wall thickness with the larger side  280  being much thinner than the smaller side  275 . 
         [0019]    The overall dimensions of balloons produced using the asymmetrical workpiece disclosed herein for tracheostomy tubes generally, from the upper region  275  to the lower region  280 , may range from about 50 millimeters to about 25 millimeters and may desirably be between about 35 millimeters to about 30 millimeters. The dimensions from the distal end  405  to the proximal end  415  may range from about 60 millimeters or more to about 25 millimeters and may desirably be between about 40 millimeters to about 30 millimeters. Of course, it is contemplated that the dimensions may be larger or smaller. 
         [0020]    If an asymmetrical tube is placed in an asymmetrical mold with the thicker part of the tube aligned to face the large side of the to-be-formed balloon, the balloon so formed will have wall thicknesses that are more uniform than those formed from a symmetrical tube. Should it be desired to produce an asymmetrical balloon having walls  275 ,  280  that are approximately the same in thickness, the asymmetrical tube disclosed herein should be used. 
         [0021]    Alternatively, the asymmetrical tube may be aligned in the mold so that the thinner part of the tube is facing the large side. This will result in a differential thickness of the balloon walls being increased beyond that formed by the symmetrical tube. 
         [0022]    A symmetrical mold may also be used with the asymmetrical tube disclosed herein. A symmetrical mold is one producing a balloon having its openings approximately centered on either end and with an approximately cylindrical shape. The balloon formed using asymmetrical tube will have differential wall thicknesses where one side of the balloon has thinner walls and the other side of the balloon has thicker walls even though the shape of the balloon so formed is symmetrical. Typical dimensions for such symmetrical balloons are from between 20 and 60 mm in length and 20 to 30 mm in diameter, though balloons for pediatric patients may be smaller. Wall thicknesses are desired to be less than 30 microns at the thickest location and more desirably less than 20 microns. 
         [0023]    Turning to  FIG. 3 , there is shown a cross-section of a tracheostomy tube device  150  in the trachea  200  of a patient. The tracheostomy tube device  150  may have balloon walls that are non-uniform thickness made using the asymmetrical tube disclosed herein. For example, the device may have a first portion “A” of the balloon in which the walls have a thickness of about 20 to 30 micrometers and a second portion “B” of the balloon in which the walls have a thickness of about 5 to about 15 micrometers. 
         [0024]    The measurement of balloon wall thicknesses may be made using a Litematic device. An exemplary device is the series 318 Model VL-50A by Mitutoyo America Corporation. According to the manufacturer, the Litematic device measures thicknesses between 0 and 50.8 mm with a resolution of 0.01 micron, using a probe tip and an inflexible ceramic base. The measuring force used is 0.01 N (1 gram). The probe tip used for testing herein was a 3 mm diameter carbide ball contact point which was provided as the “standard” probe tip with the Litematic device. 
         [0025]    Strips of single-ply foils or membranes may be used to determine the thickness of each sample. Balloon specimens (not attached to a trach tube) from each sample may be cut to prepare the strips: first the ends should be cut off to leave a uniform band of about 30 mm in width; then each band should be cut in the width direction to form a strip. Thickness measurements at 10 locations along the length of each strip should be made, the individual measurements of strips for each sample (with at least 6 strips measured) should be averaged together, and the respective standard deviations calculated. 
         [0026]    It is desirable that the first portion “A” of the balloon  180  is the portion of the balloon contacting the upper portion of a cross-sectional region of the tracheal lumen  200  and the second portion “B” of the balloon is the portion of the balloon contacting the lower portion of the same cross-sectional region of the tracheal lumen. More specifically with reference to  FIG. 3 , the inflated balloon  180  is adapted to seal the trachea (i.e., the tracheal lumen  200 ) in the region  205  below the tracheal stoma  210  and avoid sealing the trachea in the region above the tracheal stoma. Desirably, this configuration of the balloon allows secretions to exit the stoma at opening  215  and provides increased control over the location of the balloon in the trachea, i.e. better “anchorability”. 
         [0027]    Although the inventors should not be held to a particular theory of operation, it is generally thought that having the relatively thinner second portion “B” of the balloon contacting the lower wall  195  of the trachea will provide a better seal in that region where secretions may be more prone to collect due to gravity when a patient is resting horizontally on his or her back. The relatively thicker first portion “A” of the balloon contacting the upper wall  190  of the trachea where secretions may be less prone to collect due to gravity when a patient is resting horizontally on his back. 
         [0028]    Desirable inflation pressures for tracheostomy tube balloons of the type disclosed herein is generally between 20 and 30 mbar. 
         [0029]    According to the invention, the raw tubular workpiece may be formed from thermoplastic polyurethane polymers, thermoplastic polyolefin elastomers, thermoplastic polyolefin block copolymers, SBS di-block elastomers, SEBS tri-block elastomers, polyvinyl chloride (PVC), polyethylene terephthalate (PET) and blends and mixtures thereof. More desirably, polyurethane may be used because it has been found to cause less irritation to tissues than other materials. Useful polyurethanes include those from the Dow Chemical Company (Dow Plastics) available under the tradename Pellethane®. Pellethane® thermoplastic polyurethane elastomer is available in a number of grades and hardnesses and the particular one selected for a specific use will depend on the properties desired in the final product. The hardness of a polymer, for example, is an attribute that may be varied to meet the requirements of various applications. One exemplary polyurethane is designated Pellethane® 2363-90A and has a durometer hardness of 90A (ASTM D-2240). This polyurethane has a softening temperature of 110° C. (ASTM D-790) and a melt index of 30 g/10 min. at 224° C., 2160 g (ASTM D-1238). The asymmetrical tubular workpiece disclosed herein may have dimensions for the outside diameter (OD) between 6 and 11 mm. The wall thickness may be between 70 and 150 microns. One example of an asymmetrical tubular workpiece may have an OD of 8.6 mm and a wall thickness varying between 80 and 120 microns. Of course, other dimensions for the raw tubular workpiece are contemplated and may be varied as required depending on the size dimensions and wall thickness dimensions desired for the resulting balloon. 
         [0030]    The present invention also encompasses an inflatable balloon that has been blow molded from the tubular workpiece described above. The inflatable balloon has a distal end, a proximal end, distal attachment zone, a proximal attachment zone, a first wall and a second wall joining the distal end and the proximal end, wherein the first wall and the second wall are asymmetrical. 
         [0031]    This application is one of a group of commonly assigned patent application which are being filed on the same day. The group includes application Ser. No.: ______ (attorney docket no. 64391725US02) in the name of Brian Cuevas and is entitled “Improved Balloon Cuff Tracheostomy Tube”; application Ser. No.: _______ (attorney docket no. 64391725US03) in the name of Brian Cuevas and is entitled “Improved Balloon Cuff Tracheostomy Tube with Greater Ease of Insertion”; application Ser. No.: ______ (attorney docket no. 64391725US04) in the name of Brian Cuevas and is entitled “A Tubular Workpiece for Producing an Improved Balloon Cuff Tracheostomy Tube”; application Ser. No.: _______ (attorney docket no. 64391725US05) in the name of Brian Cuevas and is entitled “A Method of Making an Improved Balloon Cuff Tracheostomy Tube”. 
         [0032]    Modifications and variations of the present invention will be obvious to those of skill in the art from the foregoing detailed description. Such modifications and variations are intended to come within the scope of the following claims.