Abstract:
A tool for assisting a medical professional in inserting an endotracheal tube in the trachea of a patient comprises a relatively rigid rod in the shape of an offset spiral. The tool has a mandrel section, a curved arc section smoothly transitioning from the mandrel section, and a tip section smoothly transitioning from the arc section. The arc section is an arc of a three dimensional spiral, and angularly and spatially offsets the tip section with respect to the mandrel section.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    An endotracheal (e/t) tube is a medical device in the form of a tube that is inserted to extend through a patient&#39;s glottic opening and into the trachea to assist breathing. An e/t tube for an adult patient typically comprises a soft, pliable plastic hose, perhaps 10-11.5 mm. OD and 6.5-8.0 mm. ID with a uniform cross section, and with a length typically ranging from 30-35 cm. A pediatric e/t tube may be approximately two-thirds the length and OD of an adult e/t tube. An infant e/t tube may be one-half the size of an adult e/t tube. E/t tubes must be pliable so that they can conform to the shape of the patient&#39;s throat, and so they can bend within the mouth to protrude from the patient&#39;s lips. 
         [0002]    An e/t tube has a leading end that a medical professional inserts in the patient&#39;s throat and pushes into the trachea to a distance of 2-4 cm. The length of the e/t tube allows a trailing end of an inserted e/t tube to project from the patient&#39;s mouth. 
         [0003]    To keep the e/t tube in place, an e/t tube typically has near the leading end and surrounding the outer surface, a balloon-like cuff that is blown up once the e/t tube is inserted into the trachea. A small tube that passes through the wall of the e/t tube between the leading and trailing ends and extends from the patient&#39;s mouth, provides a means for inflating the balloon. A trailing end of the e/t tube has a fitting for attachment to an air supply. 
         [0004]    When a medical professional inserts an e/t tube in a patient&#39;s trachea to provide airflow through a closed or restricted breathing passage, often the patient is already unconscious. The e/t tube must rapidly and accurately enter the trachea during placement, since time is precious when breathing is difficult for a person. At the same time, inserting the e/t tube should not cause scraping or tearing of the soft throat tissue. 
         [0005]    It is difficult for a medical professional to consistently place the e/t tube in the trachea. The flexibility of typical e/t tubes sometimes makes it difficult to insert the e/t tube in a trachea that may already be somewhat constricted. Also, the esophageal opening is very close to the glottal opening to the trachea, sometimes causing the e/t tube to enter the esophagus instead of the trachea. For all of these reasons, personnel cannot always place an e/t tube in a trachea as quickly and accurately as is desirable. This is caused by some patients&#39; anatomy. The professional can usually detect improper e/t tube placement, but the delay is undesirable. 
         [0006]    Tools currently exist for assisting e/t tube placement. Laryngoscopes are one type of such tools. These provide for viewing the glottic opening at the entrance to the trachea during e/t tube placement, using either an optical system or a video camera. They do allow placement accuracy around 90-95%. 
         [0007]    An endobronchialscope (e/b scope) may be a better alternative than a laryngoscope for intubating patients with more difficult anatomy. An e/b scope is a long, thin, flexible tube with a video camera at the tip. The e/b scope is thin enough to be inserted completely through the e/t tube duct from the trailing end to the leading end prior to starting the placement. The video camera in the e/b scope tip allows a good view of the glottic opening. Once the e/b scope tip is properly positioned, the e/t tube is pushed off the e/b scope and into the trachea. The inventor estimates that an e/b scope allows 96-98% e/t tube placement accuracy. E/b scopes cost thousands of dollars, and hence are not disposable devices. Therefore, they require sterilization between uses, which may some times be inconvenient. 
         [0008]    For all of these reasons, a better tool for inserting e/t tubes in patients&#39; throats is desirable. 
       BRIEF DESCRIPTION OF THE INVENTION 
       [0009]    A tool in the nature of a stylet temporarily placed into the duct of an e/t tube is an effective means for assisting in rapidly and accurately inserting an e/t tube in the throat of a living being. Such a tool comprises a relatively rigid rod in a general shape referred to hereafter as an offset spiral. The tool has mandrel and handle sections that a medical professional holds during the insertion procedure. A curved arc section of the tool has a generally spiral configuration and smoothly transitions from the mandrel section. A tip section of the tool smoothly transitions from the arc section. The tip section may be curved or may also be nearly straight. The arc section angularly offsets the tip section with respect to the mandrel section. Preferably, the mandrel, arc, and tip sections are unitary, and are formed from a single piece of rod or wire. 
         [0010]    The term “offset spiral” in this context means that the curved arc section does not lie in a plane. 
         [0011]    The term “relatively rigid” means that the tool comprises a rod formed from material that is stiff enough to allow a skilled medical professional to properly place the e/t tube at the glottic opening of a patient without permanently bending the tool from the specified shape. It is convenient to form the stylet tool from heavy gauge, relatively straight, metal wire or rod by bending into the specified shape, which inherently makes the tool relatively rigid. 
         [0012]    The term “angularly offset” means that a portion of the tip section adjacent to the tip is at an acute angle to a plane in which at least a part of the mandrel section lies. 
         [0013]    The arc section is in the general shape of an arc of a three dimensional spiral. The mandrel and tip sections may also have a similar three dimensional spiral shape, or may be substantially linear. 
         [0014]    The mandrel section may have a first end and a second end. The second end of the mandrel section is unitary with the arc section. A handle section of the tool may be attached to the mandrel section&#39;s first end. 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]      FIGS. 1 ,  2 , and  3  are respectively, top, end and side orthographic projections of an e/t tube placement tool. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0016]      FIGS. 1 ,  2 , and  3  collectively show an e/t tube placement tool  10  in the form of a stylet for inserting an e/t tube  25  in a patient&#39;s trachea.  FIGS. 1-3  are aligned as orthographic projections of the top, end, and side of tool  10 .  FIG. 3  shows e/t tube  25  in phantom at  25 ′ mounted on tool  10  to form a tool assembly  11  that is prepared for use by a medical professional to insert e/t tube  25  in a patient&#39;s trachea. For simplicity, tube  25  is omitted from  FIGS. 1 and 2 . For the same reason, the balloon and attachment fitting mentioned in the Background section are omitted from e/t tube  25 . E/t tube  25  has leading and trailing ends  28  and  30  respectively. 
         [0017]    Principles of descriptive geometry teach that three orthographic projections are sufficient to completely describe the shape of a simple curved line. Tool  10  may be represented as a simple curved line. Hence, the orthographic projections of  FIGS. 1-3  are sufficient to define the shape of tool  10  in a manner allowing one with skill in the art to understand and reproduce tool  10 . 
         [0018]    Tool  10  preferably is formed from a straight section of a unitary, round rod or wire with a substantially uniform diameter. This piece of rod may be from 35-40 mm. long and made of a material whose yield strength and ductility allow bending into the shape shown in  FIGS. 1-3 . The diameter of the rod from which tool  10  is formed may be around 2.25-2.5 mm., and surely substantially smaller than the ID of e/t tube  25 , so as to allow tool  10  to easily slip into and from e/t tube  25 . 
         [0019]    Tool  10  may comprise a non-toxic, inert material such as stainless steel that is relatively stiff, but yet bendable into a shape having gentle curves using sufficient force. Tool  10  should have sufficient stiffness to resist distortion when subjected to moderate bending load but be bendable into the shape shown when subjected to a greater bending load when tool  10  is formed into the shape of  FIGS. 1-3 . Materials with a modulus of elasticity approximately in the range of 15-40×10 6  psi. and a yield strength of approximately 20,000-80,000 psi, such as 300 or 400 series stainless steel are suitable for the purpose. Tool  10  may also be molded from hard plastic having suitable strength and modulus of elasticity. 
         [0020]    One version of tool  10  suitable for use with adult patients comprises at least four distinct sections. Each of the sections smoothly transitions and merges into the adjacent section(s). Forming tool  10  from a single length of rod simplifies the making of smooth transitions and curves. 
         [0021]    A handle section  22  may be bent in an approximate hook shape as seen in  FIG. 3 . A mandrel section  19  perhaps 7-10 cm. long connects handle section  22  to an arc section  16 . The mandrel section  19  may be straight or nearly so. 
         [0022]    Arc section  16  may have an average radius of curvature of from 6-12 cm. and be approximately 15-20 cm. long. Arc section  16  may subtend a total angle of 150-220°. A pediatric version of tool  10  for older children might be ⅔d the size of an adult version and scaled to the size of a pediatric e/t tube. An infant version of tool  10  for very young children might be roughly ½ the size of an adult version and scaled appropriately for use on an infant patient. A similar device for veterinary practice should have the various dimensions changed to match the physiology of the animal involved. 
         [0023]    A tip section  13  is connected to arc section  16  and supports the leading end of e/t tube  25 . The tip section  13  and the adjacent portion of arc section  16  may also be nearly straight, perhaps with a radius of curvature in the range of 10-20 cm. 
         [0024]    An important feature of tool  10  is that arc section  16  is angularly offset from the plane of  FIG. 3 , as can be seen in  FIG. 2 . The offset results from twist in the arc section  16  along the axis thereof.  FIG. 1  shows the offset as an angle β that may in practice range from 15-45°. The offset spacing or distance shown in  FIGS. 1 and 2  may be on the order of 5-10 cm. The angle a at which tip section  13  is pointed may range from +15 to +45°, so that the projection of tip section  13  may make an angle of 195-225° with at least a portion of the projection of mandrel section  19 . 
         [0025]    This offset feature allows a medical professional to easily and safely insert an e/t tube  25  mounted on tool  10  into a patient&#39;s trachea. E/t tube  25  is shown mounted on tool  10  in  FIG. 3  as a phantom image  25 ′. It is easy to mount an e/t tube  25  on tool  10  by sliding tool  10  into the duct of e/t tube  25  at the trailing end until the end of tool  10  nears the leading end of e/t tube  25 , to thereby form the tool assembly  11 . Preferably, the leading end of e/t tube  10  should project past the tip of tool  25  by a distance d. The value d may range from approximately 0.3 to 2.5 cm. The overall length of a tool  10  may be chosen so that an amount of tool  10  protrudes from the trailing end of e/t tube  25  sufficient to provide a handle section  22  to be held by a medical professional while placing the e/t tube in a patient&#39;s trachea. 
         [0026]    To place or insert an e/t tube  25 , the medical professional first inserts tool  10  into e/t tube  25  to form a tool assembly  11 , although it may be convenient to commercially provide complete tool assemblies  11 . Next, she places the leading end of e/t tube  25  in assembly  11  at the glottic opening near the entrance to a patient&#39;s throat. The topology of tool  10  as shown in  FIGS. 1-3  allows the medical professional to place the handle section  22  and mandrel section  19  near the patient&#39;s right cheek and outside his or her mouth during this positioning of e/t tube  25 . 
         [0027]    Next, the professional uses handle  22  to hold tool  10  relatively stationary and slowly slides e/t tube  25  off tool  10  and into the patent&#39;s trachea. The shape of tool  10  allows the medical professional to point tip section  13  directly into the patient&#39;s trachea during placement, so that e/t tube  25  slides easily into the patient&#39;s trachea with minimal discomfort or trauma. Further, the tool  10  allows the medical professional to place the e/t tube  25 ′ in the patient&#39;s trachea to the proper depth almost every time on the first try. Of course, the sense of the spiral and offset in arc section  16  can be reversed so that tool  10  is deployed with the mandrel section  19  near the patient&#39;s left cheek during placement of e/t tube  25 . Current standard practice is to approach patients during intubation from their right side. 
         [0028]    The offset angle feature in arc section  16  allows the user to position the handle  22 , mandrel section  19 , and perhaps a small portion of the arc section  16  adjacent to the mandrel section  19 , near the cheek and jaw of the patient. When the professional sees or feels that e/t tube  25  is positioned properly in the patient&#39;s trachea, the professional holds e/t tube  25  near the trailing end, and then rotates tool  10  clockwise ( FIG. 3  view) to withdraw tool  10  from e/t tube  25 . After tool  10  is removed from e/t tube  25 , the cuff (not shown) is inflated to hold e/t tube  25  securely in the patient&#39;s trachea. 
         [0029]    Of course, many variations of tool  10  providing similar functionality are possible.