Abstract:
An instrument for providing ventilation access to the trachea has a hollow needle with a sharp tip, a tube extending within the needle and a spring urging the tube to project a short distance from the patient end of the needle. The rear end of the tube carries two colored flags one of which is visible at a time in a transparent window towards the machine end of the needle. When the patient end of the instrument is pushed through neck tissue overlying the trachea the inner tube is pushed rearwardly so that a flag of one color is visible. When the patient end of the instrument enters the trachea the spring can push the inner tube forwardly so that the other flag is visible. In one embodiment the instrument carries a dilator and tracheostomy tube that can be slid off the needle after penetration. In another embodiment, ventilation equipment is connected to the rear of the inner tube and the patient is ventilated through the instrument itself.

Description:
BACKGROUND OF THE INVENTION 
   This invention relates to medico-surgical instruments. 
   Various procedures and instruments are used to ventilate patients via the trachea. Tracheostomies can be made by a conventional surgical technique or by a percutaneous technique, which is quicker and more suited to emergency situations. In the usual percutaneous technique a needle is pushed through the skin of the throat into the trachea. Entry of the needle to the trachea is detected by a loss-of-resistance technique involving a syringe filled with air connected to the needle hub. The tip of the needle is blocked while it is passing through the neck tissue so that manual pressure applied to the needle plunger encounters a resistance to movement. When the tip of the needle enters the trachea air can flow and the plunger can move forwardly, enabling entry to be detected. The syringe is then removed and a guidewire is slid along the needle. The needle is then pulled out along the guidewire, leaving the guidewire in position. The opening into the trachea is then enlarged by sliding a dilator or a series of dilators of increasing size along the guidewire into the trachea. When the opening has been enlarged sufficiently, a tracheostomy tube is slid along the guidewire, following which the guidewire can be removed. Although the apparatus involved in this technique has been used successfully for many years, the number of different components and steps is not ideal for adverse situations, such as at the site of a trauma incident, and it may not be suitable for less experienced clinicians or paramedics. 
   An alternative technique used in emergency situations is percutaneous transtracheal ventilation. In this technique a sharp-tipped needle penetrates the trachea and the external, machine end of the needle is connected to a jet ventilation machine so that breathing gas is supplied to the trachea via the needle, which is left in position. This arrangement can be used to provide emergency ventilation for up to about one hour, which is usually sufficient time for the patient to be provided with alternative ventilation. The advantage of this procedure is that it can be carried out relatively easily by ambulance crew and paramedics and it does not involve the need for cutting with a scalpel. The procedure does, however, have several disadvantages. First, there is a risk that the needle will not be inserted to the correct depth, because of variations in thickness of neck tissue overlying the trachea. If the needle is not inserted far enough its tip may be located in the anterior tissues surrounding the trachea instead of in the trachea itself. If inserted too far, the needle may damage the posterior wall of the trachea. Second, because the ventilation gas emerges through the open tip of the needle and the bore of the needle is relatively small compared with a tracheal tube, the gas emerges as a jet directed longitudinally of the needle and towards the posterior wall of the trachea. Where the gas jet impinges on the tissue of the trachea it may cause drying and necrosis. 
   Another problem with emergency ventilation instruments is that it is usually necessary to hyperextend the neck in order to provide access to the trachea. Where the patient has suffered neck injury, or is suspected of having suffered a neck injury it is important that there is minimal movement of the neck. This is a particular disadvantage because patients requiring emergency ventilation are often those that have been involved in an accident of the kind that can cause neck injury. 
   BRIEF SUMMARY OF THE INVENTION 
   It is an object of the present invention to provide alternative medico-surgical instruments for ventilating a patient via the trachea. 
   According to one aspect of the present invention there is provided a medico-surgical instrument for ventilation via the trachea comprising a hollow needle having a sharp tip adapted to penetrate the trachea through neck tissue, an elongate inner member located within the needle such that the member can slide along its length relative to the needle, means for urging the inner member forwardly resiliently relative to the needle, such that the forward end of the inner member is located forwardly of the needle tip before use but is displaced rearwardly during passage through the neck tissue by engagement with the tissue and moves forwardly relative to the needle when the trachea is penetrated, and indicator means towards the rear end of the needle for indicating the position of the elongate member relative to the needle so that the user knows that the trachea has been penetrated. 
   The instrument may include a tracheostomy tube extending along the outside of the needle so that the needle can be removed to leave the tracheostomy tube in the trachea after penetration of the trachea. The instrument may include a dilator with a tapered patient end mounted on the needle, the tracheostomy tube being mounted on the outside of the dilator with the tapered end of the dilator projecting from the patient end of the tracheostomy tube. The tracheostomy tube is preferably helically reinforced and may be cuffed. The inner member may be hollow and provide a gas passage along the member. The inner member may be closed at its patient end and open through a side opening adjacent the patient end. The inner member preferably opens through two side openings adjacent the patient end and the or each side opening may be longitudinally elongated. The instrument may include a coupling towards the machine end of the inner member by which gas can be supplied to the inner member. The indicator preferably includes a visual indicator, which may include a colored flag movable behind a transparent window. 
   According to another aspect of the present invention there is provided apparatus for ventilating via the trachea including a hollow needle having a sharp tip adapted to penetrate the trachea through neck tissue, an inner, elongate, hollow member opening towards its patient end and slidably mounted within the needle, means urging the inner member forwardly relative to the needle, such that a forward end of the inner member is located forwardly of the needle tip before use but is displaced rearwardly during passage through neck tissue by engagement with the tissue and moves forwardly relative to the needle when the trachea is penetrated, an indicator towards the rear end of the needle for indicating position of the elongate member relative to the needle so that the user knows that the trachea has been penetrated, and ventilation equipment connected with the rear end of the elongate inner member by which ventilation gas is supplied to the trachea via the inner member. 
   Instruments according to the present invention will now be described, by way of example, with reference to the accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a side elevation view of an instrument in the form of tracheostomy apparatus; 
       FIG. 2  is a cross section along the line II-II of  FIG. 1 ; 
       FIG. 3  is a side elevation view of an alternative ventilation instrument; and 
       FIG. 4  is a cross section along the line IV-IV of  FIG. 3 . 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   With reference first to  FIGS. 1 and 2 , the tracheostomy apparatus comprises a needle assembly  1 , a dilator assembly  2  mounted on the outside of the needle assembly and a tracheostomy tube  3  mounted on the outside of the dilator assembly. These components are supplied mounted with one another and are used with one another during the initial stage of the tracheostomy procedure. 
   The needle assembly  1  is similar to a Veress needle used in chest surgery and laparascopy. The assembly  1  has a straight, rigid steel needle  10  of circular section which opens axially at its patient end  11  through a cutting tip  12 . An inner elongate member in the form of a hollow tube  13  extends along the needle  10  as a sliding fit. The tube  13  may be of a rigid plastics material and has a rounded, open forward or patient end  14 . The rear end  15  of the tube  13  projects from the needle  10  and carries an indicator in the form of two colored flags  16  and  17  spaced axially of one another. The forward flag  16  is red; the rear flag  17  is green. The assembly  1  also includes a helical spring  18  mounted between the needle  10  and the tube  13 , urging the tube forwardly relative to the needle. The force of the spring  18  is sufficient to push the tube  13  forwardly against friction with the inside of the needle  10  and to overcome obstructions caused by tissue fragments or fluid at the tip of the needle. The force of the spring  18 , however, is not sufficient to prevent the tube  13  being pushed rearwardly relative to the needle  10  when this is pushed against patient tissue. The rear end  19  of the needle assembly  1  projects at the rear of the tracheostomy assembly and the needle assembly can be withdrawn rearwardly from the tracheostomy assembly by pulling on the rear end. The passage through the inner tube  13  opens through the rear end of the needle assembly  1 . 
   The dilator assembly  2  comprises a shaft  20  of a plastics material with a tapered forward end  21 . The shaft  20  is a close sliding fit on the needle assembly  1  with its forward end being located about 10 mm to the rear of the patient end  11  of the needle  10 . The natural shape of the dilator assembly  2  is curved but, while mounted on the needle assembly  1 , it is maintained straight by the straight shape of the needle assembly. At its rear end, the dilator assembly  2  has a handle  22  and a hub  23  in which the rear end  19  of the needle assembly  1  is received. The hub  23  has a transparent window  24  in one side located in alignment with the flags  16  and  17  on the inner tube  13 . The position of the window  24  is such that, when the inner tube  13  is in its natural, forwards position relative to the needle  10 , the rear, green flag  17  is visible through the window and the forward, red flag  16  is not visible. When the inner tube  13  is pushed rearwardly, the red flag  16  becomes visible in the window  24  in place of the green flag  17 . 
   The tracheostomy tube  3  may be of conventional construction, comprising a flexible, helically-reinforced shaft  30 , which is naturally curved but is held straight when mounted on the needle assembly  1 . At its rear end  31  the tube  3  has a neck flange  32  and a standard 15 mm hub or female connector  33 . The tube  3  is a close sliding fit on the dilator assembly  2  with its forward, patient end  34  spaced from the forward end  21  of the dilator by about 20 mm. The shaft  30  may have an inflatable sealing cuff (not shown) of the usual kind close to its patient end  34 . The rear end of the dilator assembly  2  is received in the connector  33 . 
   The tracheostomy assembly is provided as shown in  FIGS. 1 and 2  with the tracheostomy tube  3  loaded on the dilator assembly  2  and with the dilator assembly loaded on the needle assembly  1 . Initially, therefore, the assembly is straight, the needle assembly  1  projects from its patient end and the green flag  17  is visible. To make a tracheostomy, the cutting tip  12  of the needle assembly  1  is brought up to the skin of the throat over the trachea, usually in the cricothyroid region, with the assembly generally orthogonal to the skin surface. As pressure is applied, the inner tube  13  is pushed rearwardly by the skin surface and the red flag  16  becomes visible in the window  24 . Further pressure causes the tip  12  of needle  1  to penetrate the skin and underlying tissue. The needle  10  enters the neck tissue followed by the forward, tapered end  21  of the dilator  2 . When the tip  12  of the needle  1  enters the trachea, its open end  11  is no longer occluded by tissue so the spring  18  can move the inner tube  13  to its forward position, causing the green flag  17  to be visible. This provides an indication to the clinician that the trachea has been entered. When the needle  10  enters the trachea a gas passage is provided into the trachea via the passage through the inner tube  13 . If the tracheostomy assembly should be inserted too far, so that it contacts the posterior wall of the trachea, this will push back the inner tube  13  and cause the red flag  16  to appear as a warning to the clinician. This warning flag  16  will also appear if the tip  12  of the assembly should contact an obstruction within the trachea. 
   The clinician then angles the assembly so that the tip  12  points down the trachea, that is, towards the patient&#39;s feet. He then continues to push in the assembly until the tip  34  of the tracheostomy tube  3  is adjacent the skin surface, at which point the tip  21  of the dilator  2  should be located in the trachea. He then pulls out the needle assembly  1  by gripping its rear end  19  while holding the handle  22  so that the dilator  2  is not pulled out. After the needle assembly  1  has been removed he continues to push in the assembly of the dilator  2  and the tracheostomy tube  3 . The taper  21  on the dilator  2  enlarges the opening through the neck tissue sufficiently for the tracheostomy tube  3  to be pushed in. As the dilator  2  emerges into the trachea it bends to its natural shape pointing down the trachea. This helps guide the tracheostomy tube  3 , which also bends as it is inserted. Once the tracheostomy tube  3  has been fully inserted, with its flange  32  abutting the skin surface, the dilator  2  is removed and the cuff on the tracheostomy tube is inflated to seal with the trachea. 
   The instrument of the present invention provides a clear indication of entry into the trachea without the need to use a loss-of-resistance syringe. It also provides an indication of contact with the posterior wall. The apparatus can be provided ready assembled for immediate use making it ideally suited for emergency applications. The apparatus is easy to use making it safe for use by less skilled people. 
   The instrument could be modified in various ways. For example, the elongate member extending along the bore of the needle need not be a tube but could be a rod or the like. Instead of a visual indicator, the indicator could provide an audible indication such as by completing an electrical circuit on sliding forwards or rearwards. 
   The instrument need not have a tracheostomy tube and dilator but could be used itself to provide ventilation in the manner shown in  FIGS. 3 and 4 . Components of the instrument equivalent to those of the instrument shown in  FIGS. 1 and 2  are given the same reference numeral with the addition of 100. 
   The instrument has a needle  110  assembly with an inner hollow tube  113  that differs from the tube  13  in that its patient end  114  is closed, the needle opening through two longitudinally-elongated side openings  214  located diametrically opposite one another close to the tip. The rear end  115  of the tube  113  projects from the needle  110 , is open and communicates with a bore  215  extending rearwardly along a handle  122   
   The rear end  115  of the inner tube  113  also carries two colored flags  116  and  117 , which are movable behind a transparent window  124  in the handle  122 . The handle  122  terminates at its rear, machine end in a male coupling  119  through which opens the bore  215 . Jet ventilation equipment  216  is connected to the connection  119 , and hence to the inner tube  113  by tubing  217 . 
   The instrument does not carry a tracheostomy tube or dilator as does the instrument shown in  FIGS. 1 and 2 . 
   The instrument is used initially in the same manner as the instrument shown in  FIGS. 1 and 2  to provide access to the trachea, usually in the cricothyroid region. During insertion the red flag  116  becomes visible in the window  124  until the trachea is penetrated when the green flag  117  become visible. 
   When the tip  112  of the needle  110  is correctly located in the trachea, the openings  214  in the inner tube  113  are exposed and breathing gas can be supplied to the instrument from the ventilation equipment  216  emerging into the trachea via the openings in the inner tube. The instrument remains in place while ventilation takes place and is not removed as with the instrument shown in  FIGS. 1 and 2 . 
   The instrument is easy to use making it safe for use by less skilled people. Because the gas emerges from side openings there is less risk of tracheal tissue being damaged by exposure to a gas jet. Another advantage of the instrument is that it enables ventilation without having to hyperextend the neck so that it lends itself particularly for use with patients having a neck injury or a suspected neck injury. 
   The instrument could have an adjustable flange, such as of the kind described in GB 2227941, to enable it to be secured to the neck after insertion. 
   It is not essential that the inner tube open through side apertures since it could open through its end, although this would give rise to jetting problems. These problems might be reduced by having side apertures in addition to an open end so that some of the gas pressure is dissipated by lateral flow from the side apertures. Where side apertures are used, the instrument could be arranged so that the side apertures are totally blocked by the needle when the inner tubular member is in its retracted position. In this way, gas could be supplied to the instrument continuously but would be prevented from emerging at the patient end of the instrument during passage through neck tissue, and would automatically emerge into the trachea when the trachea is penetrated.