Laryngeal and Tracheal Stents Treatment & Management

The placement of stents in the larynx or trachea is usually performed under anesthesia. Transcervical or transthoracic approaches provide exposure to place the stents under direct vision. Stents can be sutured in place or affixed in other ways.

Depending on the clinical situation, laryngeal and tracheal stents can be placed transluminally under endoscopic view in the OR by a surgeon or they can be placed under fluoroscopic control in the radiology suite by a radiologist.

Laryngeal stents

See the list below:

• Aboulker stent

  • The most common stent used for stability following LTR in children is the Aboulker stent. In the early 1960s, Aboulker introduced this cigar-shaped prosthesis, which is available in several different outside diameters at a length of 120 mm, as in the image below. Aboulker originally used his stents in adults, after cricoid plate reconstructions. In the late 1960s, Aboulker used a stent to decannulate 3 of 5 children after airway reconstructions. In the early 1970s, Grahne, Cotton, and Crysdale also used this stent following LTR in children.

    Representative (noninclusive) sample demonstrating various sizes of Aboulker stents, ranging from 15 mm in diameter on the left to 3 mm in diameter on the right. These stents are hollow and coated with Teflon.

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  • Zalzal noted that one of the benefits of the Aboulker stent is that the stent is made of highly polished Teflon, which minimizes irritation and granulation tissue formation compared with other stents. ^[12] However, the stent has been shown to cause some mucosal irritation, with granulation tissue formation occurring at the superior or inferior end. Not uncommonly, the base of the epiglottis is affected, and granulation tissue often forms in this area.

  • The Aboulker stent has been shown effective for counteracting scar contracture and for keeping reconstructed areas stable during healing. Zalzal, Cotton, and others have had good success decannulating children with severe LTS using the Aboulker stent in association with LTR.

  • The Aboulker stent can be used in both a short and long form. In the short form, the stent is used for 6 weeks or less and is placed in the larynx and upper trachea. As with all laryngeal stents, place it between the true and false vocal cords superiorly and suture it in place with a large Prolene stitch tied externally to the strap muscles. Place a portion of an angiocatheter or small feeding tube over this suture to decrease the chance of erosion through the strap muscles. Throw multiple knots for identification during later stent removal.

  • The Aboulker stent can also be used in the long form. When the long form is used, suture the stent to a metal Holinger tracheotomy tube (Holinger T-tube); see the images below. Long stents are used when the suprastomal area needs support or when long-term stenting (ie, > 6 wk) is necessary. Long stents help prevent granulation tissue and secondary stenosis in the suprastomal area.

    Radiographic lateral neck view of a long stent connected to a metal Jackson tracheotomy tube at the bright inferior portion of the picture. The stent is seen in the airway as an oblong translucent area, with a rim of opacification around it that extends up through the larynx. A thin wire is seen connecting the stent and the tracheotomy tube.

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    A long Aboulker stent wired to a metal Jackson tracheotomy tube.

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    A Jackson tracheotomy tube wired to a long Aboulker stent.

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• Montgomery stent

  • The Montgomery T-tube, shown in the image below, is a silicone stent with a long center lumen and a smaller lumen projecting from the side of the stent at either a 90° or 75° angle. Ensure that the upper end extends through the true and false vocal cords. The lower end can extend all the way to the carina, depending on the length of the trachea and stent. The side lumen extends through the tracheostoma. If long-term stenting is required, this tube can be an alternative to a wired stent-tracheotomy complex.

    Montgomery T-tube (7 mm) stent with caps.

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  • The Montgomery T-tube has been used successfully to stent the adult larynx and trachea following reconstruction and to stent areas of malacia and stenosis. Concern exists regarding the safety of the stent in children because the internal diameter of the stent is small and the tube could become plugged with dried secretions, which could result in obstruction of the stent and could end in airway obstructive symptoms and death if not promptly removed. With an indwelling Montgomery T-tube, plug the side lumen as much as possible and intermittently perform proper suctioning to prevent plugging.

  • Stern and Cotton evaluated the Montgomery T-tube in children, reporting on 26 children who underwent laryngeal procedures including LTR and cricotracheal resection. ^[13] Most of the stents used had lumens wider than 8 mm in diameter; only 1 had a diameter of 6 mm. Stern et al used the stents from 2 weeks to almost 2 years and did not observe increased granulation tissue formation in children who had stents for longer periods of time. The researchers concluded that the Montgomery T-tube is safe to use in children. In France, Froehlich et al used Montgomery T-tubes in 12 children for an average of 6 months and noted that complications include removal of the T-tube by the child, forward migration resulting in tube expulsion, formation of granulation tissue, and clogging. ^[14] Neither set of researchers reported deaths from stent malfunction.

  • A retrospective study by Prasanna Kumar et al supported the use of the Montgomery T-tube in laryngotracheal stenosis, finding no mortality and minor, manageable complications in patients who underwent stenting. Among 39 patients in the study, 82% were successfully decannulated, although in 44% of patients, crusting occurred within the tube, and in 33%, granulation at the subglottis occurred. In addition, one instance of tracheomalacia and another of stenosis at both ends of the T-tube occurred. ^[15]

• Silastic sheet (Swiss roll)

  • This stent, shown in the image below, was reported by Evans in 1977 as a form of stenting for laryngotracheoplasty. ^[16] The silastic sheet was initially one of the main stents used following reconstructive efforts in children. The silastic sheet is rolled up and inserted into the larynx and upper trachea, where it is fixed in place with a suture. The roll has a constant tendency to unroll, producing general pressure on the mucosa. This pressure allows obliteration of any dead space and allows mucosal regeneration to occur. Because of its propensity to form granulation tissue, the silastic sheet was replaced by the Teflon Aboulker stent.

    Roll of silastic sheeting.

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  • Foam and a finger cot were used initially in the larynx, especially following acute laryngeal traumatic injuries. Most of these stents have been replaced by Aboulker stents, Montgomery T-tubes, or Montgomery laryngeal stents.

• Endotracheal tubes: Originally reported by Brick in 1970, the use of endotracheal tubes made from polyvinyl chloride was reported again from a series in India in 1995. These tubes were used to stent the laryngotracheal area following LTR. Fibrosis, inflammation, and granulation tissue occurred after 4 weeks. Brick believed these stents should only be used for 4 weeks or less to prevent permanent laryngeal damage.

• Silicone stents: Silicone stents used in the larynx have mainly been reported in adults. These stents are placed endoscopically after dilating the larynx up to 18 mm. If dilation does not enlarge the larynx enough to place the stent, carbon dioxide laser excision of the scar is occasionally performed to enlarge the subglottic stenosis. Suspend the patient in the OR, and place the stent through the vocal cords into the subglottis. Place an external stitch by passing it through the skin into the stent and then out to the skin again, and secure it in position. In adults, place stents 5-30 mm below the vocal folds. Complications and concerns of this stent include transient vocal fold edema, stent migration, and recurrence of stenosis following stent removal, which has occurred even after leaving stents for 11 months.

• Inflatable stents: Over the last few years, inflatable stents composed of a small balloon attached to a port to allow expansion with air have been evaluated at the Cleveland Clinic. These stents have been used only in experimental canine models. ^[17] Inflatable stents are inflated slowly and expanded over 3-46 days. Complications included small superficial ulceration of the true vocal cords, minor polypoid changes, and granulomas. Of these experimental dogs, 20-30% exhibited inflammation extending into the underlying cartilages. Based on this information, the stent was associated with minimum local tissue reaction.

Tracheobronchial stents

Tracheobronchial stents can be broadly divided into metal or silicone stents. General differences exist between these 2 categories.

Silicone stents were the first developed in the mid 1960s. Most studies report that the tracheal mucosa tolerates long-term use of these stents relatively well. Silicone stents can be left in place for several years and, generally, are easily removable. Because this stent has the propensity to slide well over the mucosa, stent migration is the most common problem. Metal stents are usually composed of a mesh and become incorporated into the mucosa, making them extremely difficult to remove in some cases.

This same propensity for mucosa to grow around the metallic stents allows for better mucociliary clearance and function. Mucociliary flow is hindered by the silicone stents, which are mostly solid. Silicone stents are thicker than metallic stents and, thus, cause more restrictive airflow than the thin metal stents that can self-expand or be expanded to adhere closely to the tracheal wall. Additionally, metal stents have the potential to be expanded intermittently as the airway enlarges or changes. Metal stents are more distensible and conform better to the airway than silicone stents, especially if the airway is somewhat tortuous.

Generally, more reaction and granulation tissue is seen with metallic stents than with silicone stents, although reports vary, some significantly. Metallic stents can be coated with various materials that seem to reduce the rate of granulation tissue formation.

Metal stents are easier to use in the distal trachea and bronchi because they are mesh and do not obstruct primary or secondary bronchi that come into contact with the side of the stent. A bronchus could become obstructed with a silicone stent, unless a port has been fashioned into the side of the stent. The Dumon stent, shown in the image below, comes with some stents open to the side.

The Dumon stent with its opening for the right mainstem bronchus.

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Generally, both types of stents are structurally strong, and they resist forces that cause stent collapse. Metal stents are usually used in the radiological suite because they are radiopaque; silicone stents are used in the OR because they are radiolucent, do not expand, and generally require some type of affixation.

Specific stents are discussed below. Metal stents include the categories of balloon- and self-expandable stents. Bioabsorbable stents are also discussed and compared.

• Balloon-expandable metallic stents

  • Palmaz stent

    • This stent (Johnson & Johnson; New Brunswick, NJ and Interventional Systems; Warren, NJ) was initially developed as a vascular prosthesis. The Palmaz stent reportedly is the most common stent used in children, in part because of its small size.

    • The stent consists of 150-µm slotted stainless steel in a tubular mesh configuration with lengths varying from 10-40 mm. A balloon of 6- to 10-mm diameter fits inside the stent for manual expansion of as much as 6-12 mm. An appropriate size for expansion of the trachea and bronchi in children is 8 mm and 6 mm in diameter, respectively. After balloon expansion, the stent does not exert a continual outward pressure on the airway wall.

    • The stent has been used in primary tracheomalacia or bronchomalacia, external compression of the trachea or bronchi, or collapse of the trachea or bronchi from previous surgery.

    • Fraga et al from the Hospital for Sick Children in Toronto, Ontario, Canada, reported results in 16 patients who required 30 stents. Half of these patients had primary tracheomalacia, and all did well, with relief of symptoms following stent placement. The stents were easily removable, and granulation tissue was seen in approximately 20% of the group. Additionally, the children who required stenting following stenosis at the site of a previous surgical repair did well and underwent stent removal without complications, except for some granulation tissue. In the 4 children who had stents placed for external compression, 2 had stent migration and 1 had bronchial erosion. Three patients died of underlying cardiac disease, but stenting provided good palliation of respiratory symptoms. Sommer and Forte believe use of this stent is the preferred management for significant tracheobronchomalacia in children.

  • Strecker stent

    • This stent is made of a tantalum filament that is structured into a cylindrical wire mesh. The stent is flexible, whether compressed or expanded. When expanded, the stent does not change length.

    • The Strecker stent is 2-4 cm long and can be expanded from 8 to 11 mm.

    • This stent is being used successfully in tracheobronchial obstructions.

• Self-expanding metallic stents: These stents have "memory" that allows a return to normal shape after compression for placement in the airway. The device self-expands but occasionally requires balloon inflation for complete expansion. Self-expanding metallic stents include the Gianturco-Z (William Cook, Bjaeverskov, Denmark), the Wallstent (Boston Scientific; Natick, Mass), and the Nitinol.

  • Gianturco-Z stent

    • Developed by Cesare Gianco in the 1980s, this stent was initially designed for stenting obstructions in the vascular system; it has been the most widely used of the expandable metallic stents in adults. The Gianturco-Z is composed of 460-µm stainless steel filaments arranged in a zigzag configuration. The stent has been modified several times since initial development. One modification added small hooks to the outer perimeter to prevent migration, but they contributed to difficulty with stent removal.

    • The diameter of the stent when expanded is 15-40 mm. The stent is available in 2- and 2.5-cm lengths. Two stents can be combined to double the length.

    • The Gianturco-Z stent has been used to expand benign disease and with posterior anastomotic strictures, tracheal stenosis, and tracheobronchomalacia. The stent exerts good radial force and does not shorten when deployed, but it has a tendency to spring forward if released too quickly.

    • Complications are sometimes reported and include breakdown or unraveling of the stent and fatal hemoptysis after erosion into the pulmonary artery 10 days after insertion.

  • Wallstent

    • The Wallstent (Schneider; Minneapolis, Minn) is a stainless steel device composed of approximately 15-20 braided (100-µm diameter) filaments. The filaments are arranged in a criss-cross fashion to form a cylindrical mesh. The individual alloy filaments make a precise number of turns to maintain the mesh pattern and are good in tortuous airways because they maintain shape.

    • Stent diameters range from 6-25 mm; lengths range from 2-7 cm. Ensure that the diameter of the stent is at least 2 mm wider than the diameter measured at the proximal region of the normal airway. The stent exerts good radial force and good flexibility but shortens to 20-40% upon deployment. The Wallstent can be delivered with a rigid bronchoscope or flexible telescope.

    • Initially, this stent had difficulty with tumor in-growth, and a silicone body covering was developed. An important advantage of this stent is the ability to cut small openings into the mesh of a stent that lies across bronchial openings.

  • Nitinol/InStent/Ultraflex stent

    • This stent is thermally triggered and changes shape in response to temperature changes. This response is known as a Marmen effect and occurs in certain metals or alloys that distort at low temperatures (martensitic state) then revert to the original shape when reheated (austenitic state).

    • The Nitinol wire is heated and made into a helical shape and is then cooled for deployment. With release into the target site, high body temperature causes the Nitinol stent to coil back to its original helical shape. Alternatively, a current of 1.5-3 amperes or 3-5 volts can be applied to this stent for 1-2 seconds to heat it to 40°C, thus converting it to the fully expanded state.

    • A group from Japan noted that Teflon coating of this stent decreased tissue reactivity. The stent was found to have poor visualization under fluoroscopy. Haeck compared this stent to the Strecker stent and found it preferable because of ease of use, greater flexibility, and faster deployment.

• Silicone stents: Available stents include the Montgomery T-tube, Dumon (Novatech; Aubagne, France), Reynder (Reynder's Medical Supply; Lennik, Belgium), dynamic (Rusch AG; Duluth, Ga), Polyflex (Rusch AG; Duluth, Ga), and Nova (Novadis; Saint-Victoret, France). The Montgomery T-tube and laryngeal stents were discussed earlier. A form of the Montgomery T-tube can be extended to include the trachea and upper bronchi.

  • Dumon stent

    • In the late 1980s, Dumon introduced a tracheobronchial stent that could be inserted through a bronchoscope. This stent is a cylindrical silicone stent with external studs placed at regular intervals to prevent stent migration and to reduce mucosal ischemia by limiting contact with the airway wall. The Dumon is the most widely used silicone stent. The stent is widely available in varying widths and lengths from 10-35 mm. Once placed in the airway, the stent can be adjusted with a forceps and bronchoscope.

    • These stents have been used more commonly in the adult population. Dumon's series of 574 stents placed between 1987 and 1994 indicated the stents were tolerated for as long as years. The Dumon stent has a thick wall, but a thin-walled stent in pediatric sizes has been developed.

  • Reynder stent: This stent is a cylindrical silicone prosthesis that is more rigid than regular silicone tubes but requires a special introducer and a bronchoscope for placement.

  • Dynamic stent: The dynamic stent is a silicone Y-stent with anterior and lateral walls reinforced to simulate the tracheal wall. Special forceps are available for insertion within the rigid laryngoscope.

  • Polyflex: This device is a self-expandable stent made of polyester wire mesh within layers of silicone.

  • Novastent: The Novastent is a thin silicone sheet containing a small metallic hoop of Nitinol alloy. The silicone bands on the ends are designed to prevent migration.

• Bioabsorbable tracheal stents: Corpela from Finland described absorbable stents in animal models. These stents have been efficacious in preventing airway collapse in rabbit models and in created tracheomalacia, although no current publications report studies on the use of bioabsorbable stents in humans.

When using stents for the larynx or trachea, special equipment for placement must be at hand. Different stents require different placement methods, and common sense mandates that different stent sizes be available for different airway sizes. If stents are to be placed under fluoroscopic guidance in the radiology suite, a mechanism to correct airway obstruction must be in place before the procedure.

The deployment methods must be available along with airway rescue equipment and techniques.

Patients who require laryngeal stents require a postoperative evaluation based on the stent placed and the procedure performed. Airway problems patients experience or potentially may experience dictate whether in-hospital observation is necessary. The need for a feeding tube to continue nutrition is important in patients without a gastrostomy and who have significant dysphagia that prevents adequate oral intake.

For tracheal stents, perform in-hospital observation until airway symptoms resolve.

The follow-up for laryngeal stents is based on the type of surgery performed, not necessarily the stent. The type of stent usually depends on the procedure performed, so they are often associated. Frequently evaluate patients with tracheal stents, even when asymptomatic. Perform periodic bronchoscopy to assess for complications and to intervene before significant obstruction or problems occur. When patients are symptomatic, perform an emergent evaluation.

Laryngeal stents

Complications from laryngeal stents, regardless of type, are usually in the form of granulation tissue. Granulation tissue can lead to scar formation. Various studies by Grahne, Cotton, Evans, and Crysdale show that the Aboulker stent induces less granulation tissue formation than other forms of stenting, such as Montgomery T-tubes or silastic sheets (Swiss roll). In 1975, Thomas and Stevens showed that stenting after laryngeal trauma in a canine model increased inflammation and irritation of the larynx as opposed to no stenting after laryngeal trauma. ^[18]

Zalzal reported complications with the Aboulker stent. ^[12] He found broken stents, stent infection, stent migration, and granulation tissue formation. In fact, Zalzal found broken Aboulker stents in 3 of 17 children who had received them. Granulation tissue formed at the ends of the stent in the suprastomal area inferiorly and at the base of the epiglottis superiorly. The granulation tissue formed in the base of the epiglottis had not been a significant cause of stenosis. However, the granulation tissue formed at the distal end of the stent in the suprastomal area can cause collapse or stenosis.

When a stent is required for longer than 6 weeks, place a long stent through and supporting the suprastomal area. This practice decreases the complication rate or stenosis in that area.

For an Aboulker stent wired to a Jackson metal tracheotomy tube, airway obstructive complications could occur if the inner cannula of the tracheotomy tube is occluded. The Jackson tube is the only pediatric tracheotomy tube with an inner cannula that can be removed if obstructed. This characteristic is important because the tube cannot be removed easily because it is wired to the trachea and tissues of the larynx, trachea, and neck have healed around it.

When the tracheotomy tube is left in place for 3-6 months (often the indicated duration for long stents), it can become corroded and crusted. This corrosion causes the inner cannula to adhere to the body of the indwelling tracheotomy tube, making removal of the inner cannula difficult or impossible. Because of this problem, small-sized endotracheal tubes that can be pushed through the internal diameter of the Holinger T-tube must be sent home with the patient so that any crusting can be dislodged from the inner cannula if the inner cannula cannot be removed easily. This scenario must be taken into consideration when placing an Aboulker stent.

With stents in place, dysphagia and aspiration occasionally occur. According to Cotton, aspiration is worse within the Montgomery T-tube stent than the Aboulker stent. When stents are placed higher than the level of the arytenoids, aspiration usually occurs; however, when the stent is placed lower than the arytenoids, glottis and subglottis granulation tissue and scarring may ensue. These observations certainly seem to indicate that higher placement is more beneficial over the long-term.

Erosion at the base of the epiglottis is not uncommon and is usually seen in patients whose stent is placed high in the larynx so that it chronically irritates the base of the epiglottis. Formation of granulation tissue occurs despite adequate placement of the stent. Granulation tissue and scarring in this area are much less likely to cause long-term sequelae or scarring compared to granulation tissue or scarring in the suprastomal area. Despite the frequent formation of granulation tissue in the distal end of a short stent in the suprastomal area if left too long, granulation tissue rarely forms at the distal end of a long stent. Most likely, irritation of the short stent results from movement, especially if the proximity of the indwelling tracheotomy tube leads to more granulation tissue. Polishing the cut end of the Aboulker stent removes the sharp edge and helps prevent irritation.

Place the superior end of Aboulker stents, as with all current laryngeal stents, above the true and false cords to prevent scarring. When placed through the true and false cords, widening and blunting of the anterior commissure and pressure damage to the mucosal folds of the vocal cords could occur. A softer stent does not cause this particular problem.

Tracheal stents

Not infrequently, complications have been reported with the Gianturco stent, possibly because it is the most widely used stent in adults for expansion of tracheal collapse. Russ reported a 31% migration rate over a 10-month follow-up. In 35 stents, 14 deaths were attributed to migration of the stent causing respiratory distress. Hramiec and Haasler reported metallic fracture in the stent and do not recommend its use for tracheomalacia. Other reports include partial unraveling of the stent after a suction catheter became lodged in the device and a report of a fatal hemoptysis after erosion of a stent into the pulmonary artery 10 days after insertion.

Granulation tissue formation has been seen in 15-20% of patients with Palmaz stents. Stent migration has occurred in children in whom the stent was used to expand the airway against external compression. A bronchial erosion without perforation occurred in 1 patient. Reports have noted granulation tissue formation and partial collapse of Palmaz stents in 45% of patients; persons with these stents require frequent monitoring and stent adjustment. In experimental studies in cats, the Palmaz stent was found to cause inflammation in 75-85% of animals. The inflammatory tissue reaction was clinically insignificant, except for the granulation tissue seen in overexpanded stents. Because of its small size, the Palmaz stent has mainly been used in children.

Metallic stents often become incorporated into the bronchial mucosa. Stents are then very difficult to remove; often, they can be removed only by destruction of the stent and piecemeal removal of the wires endoscopically or through an external open approach. In fact, death has been reported during an attempt at metallic stent removal.

Concern has been expressed that the Palmaz stent may cause recompression and collapse with strong external pressure, such as from enlarging tumor masses or adjacent vascular structures. This stent's nonelastic nature does not allow significant reexpansion, and it has also been observed to migrate. Superficial laceration of the bronchial mucosa during balloon dilatation and partial dehiscence of the stent from the bronchial wall has occurred.

A retrospective study by Lee et al indicated that in patients who undergo stent insertion for tracheal stenosis occurring either post intubation or post tracheostomy, restenosis following stent removal is less likely in individuals who underwent trauma-induced intubation and in those with a stent length of under 50 mm. ^[19]

The decision to use a laryngeal or tracheal stent and the type of stent used is based on the experience and knowledge of the surgeon or physician.

Which stent should be used in the larynx or trachea is still controversial. Most authors stress the specific nature of each patient's often unique problem and clinical presentation.

Controversy exists regarding whether stents should be used at all. In 1975, Thomas and Stevens compared the effectiveness of 3 stented materials versus no stents in the management of acute laryngeal injury to dogs. These researchers found that dogs healed better and had fewer complications when no stents were used. ^[18]

Tracheal stents are even more controversial. Because of the risks (including death) presented by the stent itself, other surgical corrections must be attempted first. When choosing the optimal stent for the problem at hand, consider all factors, including comparisons of complications and respective uses of each stent.

A retrospective, observational cohort study by Marchioni et al indicated that stenting with rigid bronchoscopy more effectively stabilizes tracheal patency than does balloon dilatation via direct laryngoscopy, in patients with benign tracheal stenosis, when there is complex stenosis, an idiopathic etiology, and a degree of stenosis greater than 70%. However, stenting was also associated with a higher rate of adverse events. ^[20]

Many authors have discussed attributes of an ideal stent. This future stent should be easy to insert and remove and should not cause significant complications. The ideal stent also maintains airway patency, expands or is available in multiple sizes for different-sized airways, elicits no disturbance in normal homoeostasis and mucociliary transport, and causes minimal tissue reaction (ie, is biocompatible).

A reactivated, recoverable, temporary Nitinol stent has been used in the coronary arteries; this stent may be applicable to the airway. Alternatively, biodegradable stents made of self-reinforced poly-L-lactate may be beneficial. In addition to their use as airway expanders, stents also may be developed that can be used for pharmacological applications (eg, drug delivery).