Insertion technique
Implantation of the helical stent is in every respect identical to that of a 14 mm straight stent. That is, it will be loaded into a tracheoscope if its destination is the trachea, or into a wide bronchoscope if the helical stent is to be left in the right main bronchus, which is ultimately larger than the left one, in keeping with the lung it ventilates, and which has one additional segment from the outset.
The procedure is then performed under general anesthesia. The implant can be carried out directly through the internal working channel of the tracheoscope or bronchoscope, or by using an introducer for silicone prostheses.
We repeat here that the length to be covered with the stent must be properly known. A simple method to determine the length of the affected area is to mark the tracheoscope or bronchoscope when its tip has been positioned at the end of the lesioned zone. The marking is then repeated after withdrawing it back to the beginning of the lesion. The diameter must be estimated—when the trachea is the recipient of the stent, or of the bronchus in which it will be lodged—by comparing these with the already known diameter of the endoscope being used.
Retrograde implantation method
- Lubricate the mouthpiece of the introducer with lidocaine gel.
- Fold the Stening® along its axial axis and insert it into the prosthesis introducer through the mouthpiece.
- Remove the mouthpiece.
- Advance the tracheoscope or bronchoscope tube beyond the lesioned area and place its distal end or bevel on healthy mucosa, exceeding the affected zone by about 5 to 7 mm.
- Place the introducer inside the endoscope.
- Press the ejector while withdrawing the tracheoscope or bronchoscope by the same amount the plunger is advanced inside the ejector.
- As delicate as it is important: the plunger of the stent loader is pressed by the same amount that the endoscope is withdrawn. Any inequality of coordination will result in a precision error.
Once the stent is thus released, it can be repositioned with a forceps, the maneuver being simpler if the stent is placed “below” the lesion; that is to say, if we must pull on it to settle it into its final site, rather than push it.
Antegrade implantation method
Steps 1, 2 and 3 are repeated. Now stop the tracheoscope or bronchoscope containing the introducer and the prosthesis 5 mm before the lesion to be treated, and then slowly press the ejector plunger. In this way, the prosthesis will be expelled toward the affected trachea.
Some stent loader models are not introduced inside the rigid endoscope, but are attached to it at its proximal end, from where the stent is propelled. For this purpose, the endoscope will have been stopped proximally or distally to the lesion as explained above, before pushing the prosthesis with the plunger. The stent will then travel through the entire interior of the tracheoscope or bronchoscope until reaching the trachea or bronchus. At this point, a sudden reduction in resistance to the pressure exerted on the plunger will be perceived, which reveals that the stent has begun to leave the interior of the endoscope and to occupy the bronchial lumen, which will be of larger diameter and therefore the cause of the mentioned decrease in the force needed to push the prosthesis.
Having described both methods, it nonetheless appears that antegrade implantation has prevailed pragmatically for two presumed reasons that will not be discussed here, as this is neither their purpose nor their place.
Correction of the stent position
The stent may require additional maneuvers in order to correct or adjust its final position. It is preferable to correct a stent that has been installed beyond the desired position than the opposite, since it is highly inconvenient to advance a prosthesis that has been released “before” the affected area.
To move a stent in a proximal direction, it can be grasped by its edge and pulled gently. We strongly recommend, for its precision, a maneuver consisting of grasping the stent by its edge as mentioned, and then advancing with the direct-vision optics inside the stent until visualizing its final end. Then pull the forceps and you will see the stent ascend through the airway. Stop the traction when you consider the position to be optimal.
Removal technique
Intubation is performed with a tracheoscope or rigid bronchoscope as appropriate. It is a virtue and a rule of silicone stents not to offer obstinate resistance to their removal. It must be grasped by its edge with an alligator forceps with sufficient firmness. It can be pulled and its docile removal awaited. If this does not occur, the forceps must be rotated about 360° so that the stent folds into an omega shape and loses, by this method, its radial resistance to compression and, with it, its fixation. Then the forceps is pulled, extracting the prosthesis together with the tracheoscope.
The proximal end of the stent may be introduced inside the tracheoscope or bronchoscope. With this maneuver, the vocal cords are protected during the passage of the stent through them. Other methods of implantation and removal are also possible depending on the experience and preferences of each operator.
