Since the introduction of the first percutaneous dilational tracheostomy (PDT) technique in 1985 , posterior tracheal wall injury has been reported by several authors [2–4]. Posterior tracheal wall injury is a disadvantage of any percutaneous tracheostomy with the anterior dilatational approach. Recently, a new percutaneous tracheostomy dilator set has been introduced: PercuTwist (dilator set for controlled percutaneous tracheostomy; Rusch, Kernen, Germany) [5,6]. It uses a self-tapping screw as the dilator to create an access through the tracheal wall without the need of excessive pressure on the posterior tracheal wall; therefore, in theory, it reduces the risk of posterior tracheal wall injury .
The real incidence of posterior tracheal perforation is difficult to ascertain as this complication varies from less than 1% up to 12.5% . Posterior tracheal lesions may develop after incidental puncture of the posterior wall by the introducer needle, by kinking of the guide wire or during dilatation of the stoma using either dilatational or screw-like devices. Young people and women are particularly susceptible to developing posterior tracheal lesions because the anterior tracheal wall may collapse against the posterior wall when the introducer needle is inserted into the trachea due to the high elasticity of the tracheal wall. Therefore, protection of the posterior tracheal wall during tracheostomy is desirable. Moreover, some difficulties may be encountered when puncturing the anterior tracheal wall because of the presence of the distal portion of the tube or the cuff itself. As a consequence, the endotracheal tube (ETT) cuff is necessarily deflated and withdrawn so that the cuff is just seen at the vocal cords. Failure to place the ETT just before the vocal cords may result in cuff puncture, tube perforation by means of the needle or accidental extubation, with a consequential airway loss : this situation occurs most often in patients with a short neck. To overcome these problems, the use of a laryngeal mask airway (LMA) has been proposed as an alternative to the ETT . Nevertheless, even if the ETT provides a complete and clear view of the whole procedure , it does not prevent the posterior wall injuries related to the procedure itself. From May 2002 to June 2006, we performed percutaneous tracheostomy using the PercuTwist method in 130 patients on a neurosurgical ICU . We observed the following procedure-related complications: seven fractures of the tracheal rings, one kinking of the J guidewire, two mild episodes of bleeding and two tracheoesophageal fistulas. In performing the PDT, we often encounter the following difficulties or possible complications:
- Dislocation of the ETT: to allow a better view of the procedure and provide space to easily puncture the trachea, it is necessary to withdraw the ETT, placing the cuff just before or in between the vocal cords. Such a manoeuvre often compromises the stability of ETT.
- Frequent puncture of the ETT cuff: among the cases investigated, we had a high percentage of cuff puncturing, especially in patients with a short neck. Such an anatomical feature increases the chances of puncturing the tracheal wall because the ETT is in the way.
- Viewing difficulties throughout the procedure: we routinely perform PDT with direct vision by means of a fibreoptic bronchoscope. The view is incomplete and sometimes difficult because the ETT is in the way, limiting vision.
- Posterior tracheal wall damage introducing needle, kinking of the guidewire and rotation of the dilator may accidentally damage the inner mucosa of the trachea without necessarily perforating the entire posterior wall. In our clinical practice, we limited the damage by the use of fibreoptic visualization during the entire procedure.
Aim of the study
We developed a dedicated tube for percutaneous tracheostomy procedures by modifying a commercially available ETT in order to improve the view of the procedure, to insert the introducer needle and to protect the posterior tracheal wall while maintaining tube stability and airway control.
The procedure is described as follows (Fig. 1):
- Using a surgical knife, the distal extremity of the cuff is cut around its entire circumference.
- The inflation channel is punctured 1 cm above the proximal extremity of the cuff using a needle, with the optional help of a magnifying glass.
- The excised distal end of the cuff is turned inside out and wrapped carefully to prevent any air leak.
- The distal anterior part of the tube (dotted) is cut 2–3 cm in order to shape the distal posterior portion of the tube as a gutter-shaped shield: its edge is smoothened by using a very hot needle.
- The distal hole of the inflation channel is sealed using cyanoacrylate glue.
Modification of the ETT can be easily performed in less than 10 min. The effectiveness of this modified tube was tested on a manikin model.
Replacement of the ETT with the dedicated one was accomplished by direct laryngoscopy or by means of a tube exchanger. A single operator, expert in intubations, was asked to perform the procedure 10 times by means of a laryngoscope and again with a tube exchanger. He was asked to evaluate the difficulty encountered during the manoeuvres using a three-point scale: 1, easy; 2, difficult; 3, impossible.
The operator rated the tube replacement as easy by direct vision with a traditional laryngoscope (scale grade 1). At all times, the dedicated tube was easily placed in the trachea, with the cuff inflated in the hypopharynx, and gently pushed against the vocal cords to avoid any air leak. Misplacement of the dedicated tube would be detected nine times out of 10 using a tube exchanger, and the operator would experience problems with the procedure, rating it difficult (scale grade 2). We observed that the distal part of the dedicated tube could be easily placed outside the larynx in the laryngopharyngeal tract, as shown in Fig. 2. To avoid this, we introduced a simple modification: the ETT was introduced into the patient's trachea taking care to have the gutter-shaped shield of the dedicated tube slide anterior to the tube exchanger, as shown in Fig. 3. After introducing this modification, the operator was able to correctly replace the tube nine times out of 10, rating the procedure as easy (scale grade 1).
The whole PDT procedure was performed on the manikin model with the ordinary tube and with the dedicated prototype. When using the dedicated tube, we observed: optimal global visualization during the whole procedure with the fibreoptic device; transillumination tracing was always possible to better orientate the puncture spot; no puncturing of the cuff occurred; and the posterior tracheal wall was covered by the shield at all times (Fig. 4). Having the distal portion of the dedicated tube below the cuff for longer than the ordinary tubes, the airway control and tube stability was considered optimal in all cases. Protection of the posterior tracheal wall was accomplished by the newly designed portion of the dedicated tube that acted as a shield to the posterior tracheal wall.
We believe that the dedicated tube for tracheostomy designed by our team may be of help in speeding up the PDT. It eliminates puncturing of the cuff and distal portion of the ETT; it avoids multiple punctures of the anterior tracheal wall, thus reducing tracheal wall injuries. Moreover, the protection provided by the gutter-shaped shield portion prevents accidental lesions of the posterior tracheal wall, allowing a safer procedure to be performed during the learning curve period of any operator. Even though the endotracheal cuff is placed in the upper portion of the larynx, above or in between the vocal cords, the stability of the ETT is maintained by the modified distal portion of the tube below the cuff being located in the trachea by at least 6 cm (Figs 1–4).
On the basis of our preliminary experience obtained during practice on the manikin, we believe that the use of this tube will result in a significant improvement in the safety and time taken to learn how to perform PDT in teaching hospitals. The ultimate improvement would probably be given by the replacement of the overturned cuff with a large pharyngeal one such as the cuffs of the cuffed oropharyngeal airway (COPA), Esophageal–Tracheal-Combitube (Kendall Sheridan Catheter Corp., Argyle, New York, USA) or Laryngeal Tube (VBM, Medizintechnik, Germany) devices.
The results obtained by using the dedicated tube on the manikin allow us to confidently state that the ETT modifications and the placement of the cuff in the hypopharynx would eliminate puncturing of the ETT, rupture of the cuff and difficult limited direct vision in clinical practice. Because the portion of the ETT below the cuff is longer than in a standard ETT, we observed optimal stability of the tube during the whole procedure.
Such technical modifications may reduce the duration and could improve the efficacy and safety  of the procedure, limiting posterior and anterior tracheal wall injuries due to multiple punctures [4,5]. When residents attempt PDT for the first time, we believe that it would be safer and more practical to perform such a technique with the modified ETT.
The modified ETT gives its best results when used with a traumatic tracheostomy device for PDT; the different, new balloon percutaneous tracheostomy introducer seems to be safer and minimizes patient risk by combining balloon dilation and transtracheal tube insertion .
The modified ETT could be developed by using the ETView tracheoscopic ventilation tube (TVT; ETView Ltd, Misgav, Israel), an ordinary ETT equipped with a tiny camera at its tip, connected to a monitor, buried within the tube. Such a continuous view would avoid the need for a bronchoscope, making the procedure safer and faster.
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