The tube consists of a vertical column of flexible medical silicone, which resides in the airway and is intended to span the entire length of a stenosis or other obstructive pathology. A sidearm of the same material emerges from the tube at a right angle and passes to the surface. A plug or stopper of silicone is provided to occlude the sidearm. Tubes are made in a variety of outer diameters ranging from 6 to 16 mm. The size numbers of tubes correspond to their outer diameter. Tubes are provided in pediatric, standard, long, and extra-long lengths (up to 15 cm) (Figure 39-2). The tubes may be trimmed to precisely the size required for the individual patient but care must be taken to smooth the cut edges. Densely radiopaque tubes are available.
Following an instance of airway obstruction, when an entire tube including the sidearm was inexplicably aspirated into the distal trachea, Montgomery produced a model of a tube characterized by a ridged sidearm over which a circular ring of silicone is passed to prevent such aspiration. I have never observed this problem using the modified T tube.
The technique of placement is conceptually simple, but in individual cases with very varied pathology, fitting a T tube may be difficult and time-consuming and demands close cooperation between the anesthetist and surgeon. Preliminary standard tracheal x-rays provide maximum information about the lesion, including precise and relative dimensions of the diseased airway, distances between the glottis and superior margin of the lesion, and relationship of the lesion to the carina and to an existing stoma. T tube placement is best done under general anesthesia with spontaneous respiration. Rigid bronchoscopy is performed initially, a stenosis is dilated, and tracheal measurements are made as described in Chapter 5, "Diagnostic Endoscopy." The diameter of the tube is selected on the basis of radiologic findings and observations. I prefer to select a tube of larger size to provide the patient with the best possible airway palliation, but which will not fit too tightly against the mucosa proximally or distally. A tight fit can produce inflammation of normal trachea above and below the lesion. In many patients, a standard or long T tube will suffice to span the lesion without creating additional problems such as laryngeal irritation. If a tracheostomy is already present, it is usually used for the sidearm of the T tube. In some patients, because of the obliquity of the tracheostomy tube tract, a T tube sidearm will not rest appropriately, and it is necessary to modify the stomal tract and the opening into the trachea so that the sidearm will emerge without kinking (Figure 39-3). If the stoma is insufficiently large, it may be dilated with Hegar uterine dilators. During these manipulations, the ventilating bronchoscope is withdrawn to a point above the stoma, but it is not removed from the airway. The rigid bronchoscope provides a safe airway for these maneuvers. A flexible endotracheal tube should also be available to be slipped into the stoma for direct distal ventilation, intermittently if necessary. Liberal suctioning keeps the airway free of blood. Profuse granulations at the tracheal stoma and within the stomal tract and trachea are removed. In some patients, opportunity is taken at this point to transfer a tracheostomy stoma that may have been placed below a cervical stenotic lesion to a location in the stenotic lesion. This will permit the stoma that was within normal trachea to heal and so recapture this portion of trachea for later reconstruction (see Chapter 24, "Tracheal Reconstruction: Anterior Approach and Extended Resection"). The sidearm of the T tube should never rest against the brachiocephalic artery any more than a tracheostomy tube should.
In most patients, the T tube must be modified at one or both ends to obtain a precise fit. The proximal end of the T tube should not abut the conus elasticus of the subglottic larynx, to avoid inciting a ring of potentially obstructive granulations. It is acceptable to seat the proximal end of the tube within the sub-glottic larynx, but below the curve of the conus. Distally, the tube should extend below the lesion, but not so far that evacuation of secretions is made more difficult, or that the lower tip of the tube abuts and irritates the carina, giving the potential for forming granulations.
Final tube lengths are determined in the following manner. After initial approximation of the length from bronchoscopy, the tube is trimmed conservatively, inserted into the trachea, and position observed carefully. The proximal end is examined with the 0° Hopkins telescope. If a short (25 cm) ventilating bronchoscope is used at this point, then the telescope can be passed through the longest of T tubes and the location of the distal end of the T tube observed. Alternatively, a flexible bronchoscope is passed through a sealing gasket via the rigid bronchoscope to check the position of the distal end of the T tube relative to the lesion and carina. The lower end of the tube must lie lower than the obstructing lesion, or granulations will form distal to the tube.
Trimming the tips of the tube may be done in a number of ways. The tube is cut sharply with a scalpel, resting the tube on a firm surface while this is being done. A sterile paper millimeter ruler included in the kit permits precise measurement of lengths removed and lengths remaining. The cut end of the
figure 39-3 Modification of existing tracheostomy tract for T tube placement. A, Oblique tract in a longstanding tracheostomy. The dotted line shows the modifying incision. B, Corrected stomal tract with a T tube in place through the dilated stenosis.
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