Abstract:
A dilator ( 10 ) for creating tracheostomies in one pass. Dilator ( 10 ) includes a generally linear shaft ( 12 ) extending from a proximal end ( 14 ) and beginning at a distance therefrom, gradually and continuously through a curved distal portion ( 16 ) of continuously decreasing diameter (from about 38 french) to a distal tip portion ( 18 ) of small diameter of about 12 french at distal end ( 20 ). The outer surface of the insertable portion is treated or hydrophilically coated to minimize friction, and the gradual taper gradually widens the tracheal entrance opening ( 44 ) between tracheal rings ( 46,48 ) with minimal trauma. The wall thickness gradually decreases from the linear shaft ( 12 ) to the soft distal tip portion ( 18 ). The continuing curve of the distal portion ( 16 ) enables the increasingly longer inserted portion of the dilator to remain situated in the trachea ( 50 ) during insertion and for the distal tip portion to clear the posterior tracheal wall.

Description:
RELATED APPLICATION INFORMATION  
       [0001]    This application claims priority of Provisional Application Serial No. 60/169,368 filed Dec. 7, 1999. 
     
    
     
       TECHNICAL FIELD  
         [0002]    This relates to the field of medical devices and more particularly to devices for percutaneous dilation.  
         BACKGROUND OF THE INVENTION  
         [0003]    Certain medical devices are known that are used in the atraumatic dilation into a patient, such as percutaneously accessing a patient&#39;s air passageway and dilating an opening thereto, and forming an ostomy in the tracheal wall. A tracheal tube is then inserted through the ostomy and into the trachea to establish a passageway for unobstructed air flow. To minimize trauma to the patient, it has been found desirable to initially incise only a small opening as an entrance, and thereafter to enlarge the opening with further dilation.  
           [0004]    Sold by Cook Critical Care, Division of Cook Inc., Ellettsville, Ind., is the “Ciaglia Percutaneous Tracheostomy Introducer Set”, used for controlled percutaneous introduction of tracheostomy tubes. Sequentially sized dilators (from 12 french to 38 french) are advanced over a wire guide/guiding catheter system to facilitate gradual dilation of the tracheal entrance site to an appropriate size; one such dilator is shown in FIG. 1 and herein below described. The tracheostomy tube is placed by fitting the tube over the appropriate size dilator and advancing the tube into position. Each of the dilators includes an elongated linear shaft for manual gripping and manipulation, and is provided with a curved distal end concluding in a tapered tip that in use is coated with lubricating jelly, all to minimize trauma. First, the smallest dilator (12 french outer diameter) is first selected and placed over a guiding catheter and guide wire that extend through the opening until the tip is adjacent to the opening. Then the tapered tip is urged gently into the percutaneous incision and between adjacent ones of the trachea rings, and is gently withdrawn and reinserted to gradually widen the opening. The first dilator is then withdrawn and removed, and replaced by the next larger sized dilator and the procedure is repeated until the appropriate sized ostomy has been created.  
           [0005]    It is desired to simplify the procedure used to create the ostomy and to shorten the length of time involved in its creation.  
         SUMMARY OF THE INVENTION  
         [0006]    The present invention is directed toward a single dilator that is used to define the ostomy in one pass, thus replacing the several sequentially sized dilators and eliminating the repeated changing thereof, and thereby greatly simplifying the procedure and substantially shorten the time to define the ostomy, all serving to minimize patient trauma. The single dilator includes a soft, pliant tapered tip identical in shape and size and in tip inner diameter to those of the prior art dilators, and additionally includes a curved distal portion extending from the tapered tip toward the proximal end, and the generally linear shaft. The curved distal portion is tapered to extend from a diameter of 12 french (for example) adjacent the tapered tip, to a diameter of 38 french adjacent the linear shaft. Preferably both the curvature and the taper of the curved tapered distal portion from the distal tip to the shaft is gradual with no discontinuities. Also preferably, the curved tapered distal portion has a gradual transition in flexibility from very flexible at the short distal tip portion to generally rigid at the generally linear shaft portion, such as by gradually changing its wall thickness.  
           [0007]    The resultant shape of the dilator of the present invention can be said to resemble the horn of a rhinoceros. Particularly useful for tracheostomies, the continuing curve of the distal end portion enables the increasingly longer inserted portion of the dilator to be situated in the trachea thus facilitating clearing the posterior tracheal wall.  
           [0008]    Preferably the curved tapered distal portion and the short distal tip portion are provided with a hydrophilic coating that obviates the need for lubricating jelly and provides a very low coefficient of friction when hydrated, thus facilitating insertion into and withdrawal from the tracheal opening.  
           [0009]    An embodiment of the invention will now be described by way of example with reference to the accompanying drawings. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]    [0010]FIG. 1 is an elevation view of a Prior Art dilator;  
         [0011]    [0011]FIGS. 2 and 3 are elevational and longitudinal section views of the dilator of the present invention; and  
         [0012]    [0012]FIG. 4 is an elevation view of the dilator in position over a guide wire and extending through an entrance to a trachea.  
     
    
     DETAILED DESCRIPTION  
       [0013]    Dilator  100  of FIG. 1 is a Prior Art dilator, namely, one of a series of dilators found in the “Ciaglia Percutaneous Tracheostomy Introducer Set” sold by Cook Critical Care, Division of Cook Inc., Ellettsville, Ind., used for controlled percutaneous introduction of tracheostomy tubes and having sequentially sized dilators (from 12 french to 38 french). Dilator  100  in particular is the largest of the series used last in the sequence to attain a tracheal entrance of about 38 french. Dilator  100  includes a shaft portion  112  extending from a proximal end  114 , a tip portion  118  adjacent to distal end  120 , and a curved intermediate section  130  extending between shaft portion  112  and tip portion  118 . An insertion depth marking  122  is defined a distance of about 50 mm (2.0 in) from distal end  120 , and on dilator  100  is positioned midway along curved intermediate section  130 . A central passageway  124  extends from proximal end  114  to distal end  120 .  
         [0014]    Tip portion  118  on Prior Art dilator  100  is about 20.0 mm (0.79 in) in length and has a taper along each side of about 0.223 mm per mm (0.223 in per in), or about 12.6 degrees. (On smaller dilators of the “Introducer Set” the length of tip portion  118  is shorter while the taper remains the same; the insertion depth marking  122  may be along the linear shaft portion  112  on the smaller dilators.) Curvature of the centerline of curved intermediate section  130  is a radius R of about 80 mm (3.15 in) over an angular distance θ of about 20° to 40°. Wall thickness immediately at the distal end  120  is about 0.406 mm (0.016 in), and thickens over the portion extending for 5.99 mm (0.236 in.) from distal end  120  to a thickness of about 1.09 mm (0.043 in), which is the wall thickness of curved intermediate section  130  and the shaft portion  112 , and at proximal end  114 .  
         [0015]    In Prior Art dilator  100 , the outer diameter from the location from tip portion  118  is constant to proximal end  114  and is 38 french or 12.7 mm (0.491 in) . Also, the wall thickness between tip portion  118  and proximal end  114  is constant at 1.09 mm (0.043 in). The durometer is measured at about 55 to 60 Shore D hardness.  
         [0016]    Dilator  10  of the present invention is shown in FIGS.  2  to  4  and includes a shaft portion  12  extending from a proximal end  14 , and a curved tapered distal portion  16  extending from shaft portion  12  to a small tip portion  18  at distal end  20 . Demarcation  22  denotes the location at which the outer diameter is 38 french. A central passageway  24  extends completely there through from proximal end  14  to distal end  20 . A marking  26  is identified toward proximal end  14  from demarcation  22  that indicates the recommended depth of maximum insertion into the skin, and that is at that location at which the shaft portion  12  and the curved tapered distal portion  16  meet.  
         [0017]    Preferred dimensions of dilator  10  for use especially in tracheostomy procedures are: an overall length of about 196 to 210 mm (7.75 to 8.25 in); a length of about 110 mm (4.33 in) from distal end  18  to insertion depth marking  26 ; an inner diameter at distal end  20  of about 2.79 mm (0.110 in) and that extends the short length of flexible tip portion  18 , about 3.18 mm (0.125 in); an outer diameter at distal end  18  of about 12 french or 4 mm (0.140 in); and an outer diameter at proximal end  14  of about 50 french or 16.5 mm (0.650 in), with an inner diameter of about 12.0 mm (0.473 in). The outer diameter at demarcation  22 , as mentioned above, is about 38 french or 12.7 mm (0.491 in) and is located at about a distance of 80 mm (3.150 in) from distal end  20 ; and the inner diameter at demarcation  22  is about 7.72 mm (0.304 in).  
         [0018]    The taper of the curved tapered distal portion  16  of the example described is about 0.056 mm per mm, or 3.19°. The taper may be within a range of tapers of between 1.7° and 10°. A very gradual taper such as about 1°00′ may also, if desired, be used for the shaft portion  12  for facilitating removal of the molded dilator from the molding apparatus. Continuation of the taper in the proximal direction from curved tapered distal portion  16  also serves to permit, if necessary, further widening of the ostomy beyond 38 french, such as to 40.5 french at the insertion limit  26 .  
         [0019]    The curvature of curved tapered distal portion  16  may be a series of curves of different radii, or a complex curve, from distal end  20  at least to demarcation  22 . The portion of dilator  10  between demarcation  22  and insertion limit  26  will extend, during use of the dilator, between the outer skin of the patient and the inside or anterior surface of the trachea of the patient. Also, the optimum curvature may be within a range such that the outer surfaces are within a zone of tolerance. While not susceptible of a precise mathematic definition, it is preferred that the curvature be complementary to the curvature of conventional curved tracheostomy tubes.  
         [0020]    Preferably, the curved distal portion  16  transitions gradually from a very flexible short tip portion  18  at distal end  20 , to a more rigid shaft  12  at insertion limit  26 , thus having increasing rigidity in the direction extending away from distal end  20 . Such flexibility transition may be generated such as providing a very small wall thickness at distal end  18  (e.g., 0.381 mm or 0.015 in) and greater wall thickness along shaft  12  of about 2.49 mm (0.098 in). Shaft  12  may also have a gradual taper, if desired. Dilator  10  may be made from polyurethane and be of softer durometer than prior art dilators, such as a durometer of about 43 Shore D hardness. Fabrication may be accomplished such as by molding the dilator initially in a linear tapered shape with appropriate wall thicknesses, and then inserting through the central passageway a rigid forming wire of stainless steel having an appropriate curved shape to elastically deform the dilator from its initial linear shape to generate the desired curve of the intermediate portion, and then post-curing the dilator at elevated temperatures with the forming wire in place, whereafter the dilator retains an appropriately curved shape. Sharp edges at the proximal end may be removed by abrasion, and the edges of the tip at distal end  20  may be rounded by careful application of localized heating and pressure to remove sharp edges.  
         [0021]    Preferably, dilator  10  has a hydrophilic coating along curved tapered end portion  16  such as PHOTO-LINK coating material commercially available from SurModics, Inc., Eden Prairie, Minn. The material is a liquid mixture of PV05 Photo-Polyvinylpyrrolidone copolymer, PA05 Photo-Polyacrylamide copolymer, 2-propanol and distilled water. Upon the intermediate and distal end portions of the dilator being dipped into a bath of the mixture, with the distal end being occluded to isolate the interior surfaces, the coating on the dilator is cured by ultraviolet light at 150 wpi. Dilator  10  is preferably of radiopaque material, and it may be blue in color to minimize glare when viewed by an endotracheal bronchoscope that is in position in the patient above the tracheal ring  46  to view the procedure within the trachea from above the tracheal entrance.  
         [0022]    [0022]FIG. 4 illustrates the use of dilator  10  positioned on and along a guide wire  40  that extends through incision  42  of a patient and in tracheal entrance  44  between adjacent tracheal rings  46 , 48 , to introduce a tracheostomy tube (not shown) into trachea  50 . Guide wire  40  includes a flexible J-shaped tip  52  and a guiding catheter  54  of 8.0 french over much of the guide wire. Guiding catheter  54  preferably includes an annular protrusion  56  there around to act as a stop for the distal end  20  of dilator  10 . Dilator  10  is inserted over guide wire  40  until distal end  20  abuts annular protrusion  56 .  
         [0023]    With the curved tapered distal portion  16  hydrated such as by being dipped into sterile saline or water to hydrate and thus activate the hydrophilic coating thereon, dilator  10  is moved along guiding catheter  54  and the distal tip portion of dilator  10  is inserted into tracheal entrance opening. The assembly is then gently urged repeatedly into and partially withdrawn from the tracheal entrance opening  44  and prying apart tracheal rings  46 , 48  in an iterative procedure, increasing the insertion depth gradually each time until tracheal entrance opening  44  has been made sufficiently wide to enable a tracheostomy tube of appropriate size to be inserted there through. Once hydrated by being immersed into sterile saline or water, the outer surface of curved tapered distal portion is made very slippery without the use of lubricating jelly, with a substantially lowered coefficient of friction to minimize trauma to the patient. Marking  26  indicates the safety limit of insertion of the dilator into the patient&#39;s incision  42 .  
         [0024]    Dilator  10  is then removed from guide wire  40 , and a loading dilator (not shown) of appropriate size is placed thereon, with the tracheostomy tube already placed on the loading dilator, extending through the widened tracheal entrance opening. Such a loading dilator may be similar to one of the larger Prior Art dilators as shown in FIG. 1. Thereafter, procedures are followed as with the prior art “Ciaglia Percutaneous Tracheostomy Introducer Set” instructions; the tracheostomy tube is translated along the loading dilator until fully inserted into the patient.  
         [0025]    The dilator of the present invention results in a simplified procedure with fewer steps and shortens procedure time.