Tracheobronchial Interventions

Central airway obstruction represents a great challenge to physicians from all subspecialties. Narrowing of the main tracheobronchial airways and proximal branches can cause significant and distressing symptoms for the patient and can be life-threatening. Signs and symptoms of large-airway compromise include breathlessness, wheezing, stridor, and recurrent infections. Treatment for airway obstruction varies depending upon the length of the lesion, etiology of the obstruction, and age and overall prognosis for the patient.

Malignancy is the most frequent cause of tracheobronchial obstruction in the adult population. Of the approximately 200,000 new cases of lung cancer diagnosed yearly in the United States, 20% to 30% will develop associated complications related to airway obstruction that can cause significant clinical problems such as resting and exertional dyspnea, atelectasis, postobstructive pneumonia, and hemoptysis.

Resection of the pathology and reconstructive airway surgery provide the most definitive therapy, but many of these patients are not amenable to curative or corrective surgery. External beam irradiation and endobronchial brachytherapy, laser therapy, argon plasma coagulation, cryotherapy, photodynamic therapy, and electrocautery have been used in this setting. Most of these treatment options provide only temporary relief of symptoms because of the rapid regrowth of residual tumor.

Most benign strictures of the trachea and major bronchi are due to iatrogenic causes, but prior infections, sarcoidosis, amyloid disease, vascular rings, trauma, or disease processes that affect the integrity of the cartilaginous rings of the trachea can also lead to airway stenosis. Short, circumscribed, benign lesions of the cervical trachea are usually best treated by surgical resection and reanastomosis. Long strictures (>5–7 cm in length) are more difficult to treat, but can occasionally be treated by experienced thoracic surgeons.

Surgical options, although rarely feasible, should always be explored first for both malignant and benign lesions, but a large number of patients with symptomatic and life-threatening airway pathology are not candidates for definitive surgical correction because of the extent of the disease or comorbidities. A multidisciplinary approach to obstructing malignancies, with bronchoscopic debulking or removal of the obstructing lesion, balloon dilation of the airway, stenting of the airway, or a combination of techniques, has proved to be highly effective in reestablishing functional airway patency and palliating patient symptoms. Benign lesions have been treated with a variety of endoscopic and fluoroscopic techniques. These therapeutic modalities usually provide immediate improvement and occasional long-term successes, but recurrences are the general rule. The etiology for the obstruction will determine the need for bronchoscopic tumor debulking, airway stenting (covered or uncovered), balloon dilation, or a combination of these techniques. Central airway obstruction can be divided into four main categories: intraluminal, extraluminal or extrinsic, dynamic (due to loss of airway integrity and dynamic collapse causing obstruction), or mixed. Although intraluminal obstruction typically requires tumor debulking before stent placement, pure extraluminal or extrinsic compression and dynamic airway collapse will mainly benefit from airway stenting, with or without prior bronchoscopic balloon dilation. On occasion, intraluminal benign scar tissue (e.g., lung transplant anastomosis or postinflammatory synechiae) can be treated with balloon dilation alone, but often stenting will be necessary.

There are three major indications for airway stenting ( Table 106.1 ). Two of these are for (1) enhancing airway patency by stenting an obstructed bronchus or trachea and creating a barrier for further tumor ingrowth (by using a covered stent) and (2) preventing extrinsic compression or dynamic obstruction by serving as a scaffold or supporting weakened airway walls (due to chondromalacia) and preventing airway collapse related to the static and dynamic behaviors of the stent. A third indication for using stents in the airway is for sealing airway dehiscences and fistulas.

There have been no recent major advances in airway stent technology. The ideal stent should have limited migration, be easily removed if necessary, demonstrate long-term luminal patency without causing ischemia, be nonallergic, not erode into adjacent structures, induce minimal granulation tissue, be easy to accurately position, allow patency of bronchial branches, be durable, and allow for continued functioning of the mucociliary system. However, such an ideal stent is not yet available. A variety of stents are available from many different manufacturers ( Table 106.2 ). Tracheobronchial stents can be divided into two main categories according to materials used in their construction: silicone and metallic-based stents. Hybrid stents result from the combination of these two major categories.

In 1965, Montgomery described the use of a T-shaped silicone tube designed to be used both as a tracheal stent and as a tracheostomy tube. The tube is positioned in the trachea, with the side arm of the T projecting through the tracheostomy. The side arm prevents tube migration and provides access for clearance of secretions. In 1990, Dumon developed the first silicone stent that could be inserted with a bronchoscope and did not require a tracheostomy. It was designed with no external components and could be inserted using a rigid bronchoscope. The outside surface of this stent had rounded studs protruding from its surface. The studs are designed to prevent the stent from sliding or turning. The Dumon stent is available in several sizes for both tracheal and bronchial applications. Different types or designs of silicone stents are also available.

Silicone stents are fairly well tolerated and have been shown to be effective in relieving respiratory symptoms; they have the advantage of being easily removed and exchanged when necessary. The most frequent problems associated with silicone stents are migration and mucous plugging of the stents. Migration is most likely to occur in short conical stenoses with intact smooth mucosa or in the presence of tracheobronchomalacia. In both situations, the underlying anatomy does not permit firm anchorage of the stent. The mucosa under most silicone stents undergoes a metaplastic alteration, reducing the effectiveness of the mucociliary clearance mechanism, leading to recurrent stent plugging. In most cases, migration or mucous plugging of the stent can be managed by frequent endoscopic repositioning or replacement of the silicone stent.

Metallic tracheobronchial devices have been in use since the early 1950s, but were refined when metallic stents were developed for use in the vascular system. Metallic stents offer several potential advantages over silicone stents for treatment of complex airway obstruction. Metallic stents have a small profile and are fairly easy to insert; the open lattice design allows treatment of more peripheral bronchi with less fear of causing obstructive pneumonia and/or atelectasis. After placement of a metallic stent, the normal respiratory epithelium can protrude through the open lattice, and metaplastic squamous epithelium overgrows and incorporates the stent into the wall of the airway. The neoepithelium overlying the stent also appears to maintain some rudimentary ciliary function ( Fig. 106.1 ). However, granulation tissue and tumor can grow through the open lattice of these stents and lead to recurrence of airway obstruction. In addition, once metallic stents become incorporated into the wall of the airway, they are difficult to remove without surgery. Covered stents are used to prevent intraluminal tumor ingrowth or when a fistula has to be excluded or sealed. Covered stents also have the advantage of relatively easy removal or exchange compared with uncovered stents ( Table 106.3 ). However, covered stents may prevent neoepithelialization and compromise the mucociliary clearance mechanism of the airway.

Open full size image

(A) Microscopic section of autopsy specimen from patient with endobronchial Palmaz stent in place for 27 months shows stent strut ( arrow ) with overlying granulation tissue ( G ). (B) Further magnification of specimen reveals ciliated neoepithelium ( arrow ) along luminal surface of airway.

Photos courtesy of Maria I. Almira-Suarez, MD.

Balloon dilation has been proposed for management of benign stenoses of the airways. The noncompliant balloon dilates the stenotic trachea or bronchus by stretching, tearing, and expanding scar tissue and the airway wall. Balloon dilation is associated with little morbidity and mortality, but this technique is of little value in the treatment of malacic segments or airway narrowing secondary to tumor ingrowth or extrinsic compression. In addition, balloon dilation has failed to be of durable benefit for lung-transplant anastomotic strictures.

Increased availability and ease of delivery of metallic balloon-expandable or self-expanding stents has resulted in a lower threshold for considering placement of airway stents. However, other therapeutic modalities and possible long-term complications inherent with the use of a metallic stent should be considered, because these patients will likely require lifelong management and revision. Indeed, an increasing number of adverse events reported in association with use of metallic stents for treatment of patients with benign airway disease led the US Food and Drug Administration (FDA) to publish an advisory in 2005 on their use. These were the recommendations:

• • Appropriate patient selection is crucial.

  • Use metallic tracheal stents in patients with benign airway disorders only after thoroughly exploring all other treatment options (e.g., tracheal surgical procedures or placement of silicone stents).

  • Using metallic tracheal stents as a bridging therapy is not recommended, because removal of the metallic stent can result in serious complications.

  • If a metallic tracheal stent is the only option for a patient, insertion should be done by a physician trained or experienced in metallic tracheal stent procedures.

  • Should removal be necessary, the procedure should be performed by a physician trained or experienced in removing metallic tracheal stents.

  • Always review the indications for use, warnings, and precautions.

  • Be aware of the guidelines from professional organizations regarding recommended provider skills and competency for these procedures (i.e., training requirements and clinical experience).

Tracheobronchial Balloon Dilation

Indications and Contraindications

The primary indication for using balloon dilation is for treatment of benign tracheobronchial strictures. Postintubation tracheal stenosis, postoperative anastomotic stenosis, chemical aspiration–induced scarring, granulation tissue due to granulomatous disease (tuberculosis, sarcoidosis, histoplasmosis), postinflammatory stricture, and stenosis induced by radiation therapy are the principal etiologies for benign airway stenosis. Balloon dilation can also be used either before or after stent placement to optimize airway patency. Presence of an active inflammatory process or infection of the tracheobronchial tree is a relative contraindication to balloon dilation, owing to the potential for aggravating the underlying process.

Outcomes

Small case series and limited reports in which balloon dilation was the only treatment used for benign tracheobronchial stenoses have shown a high initial technical success rate, but recurrence of symptoms necessitated further treatment with additional dilation, stenting, or laser therapy in 71% to 80% of patients. ^{, ,} Ipsilateral bronchial stenosis is found in 7% to 15% of lung transplant recipients, and ischemic damage (which often affects the bronchial anastomosis), rejection, and infection have been considered as individual and/or concomitant predisposing causes. In one retrospective study of lung-transplant bronchial stenoses, bronchoscopic balloon dilation showed effective results in only 50% (5 of 10 bronchial stenoses) after an average of four balloon dilation procedures, suggesting that single or multiple sessions of balloon dilation could be used as a possible approach to management of bronchial stenoses after lung transplantation. In cases of bronchial stenosis refractory to repeated sessions of balloon dilation, stent placement was often employed.

Postintubation tracheal stenosis is caused by either cuff-induced ischemic damage to the trachea and/or stomal injury from a tracheostomy, and is primarily managed with surgical resection and reconstruction. However, balloon dilation or other bronchoscopic treatment options have been used in select patients with severe comorbidities and very debilitated health status, or for stenoses less than 2 cm in length. In one report based on long-term follow-up of 14 patients, 71% of the patients showed relief of symptoms after additional balloon dilation.

For treatment of benign bronchial strictures resistant to conventional balloon dilation, use of a cutting balloon has shown some preliminary promise. Kim et al. reported successful use of the cutting balloon, no major complications, and a demonstrated clinical benefit of approximately 60% (11 patients) at 2 years ( Fig. 106.2 ).

Endobronchial brachytherapy has also been used to treat benign bronchial strictures resistant to conventional balloon dilation or as an adjuvant treatment to treat granulation tissue formation after airway restoration.

Equipment

The optimal setup for performing fluoroscopic-guided tracheobronchial balloon dilation includes an all-purpose fluoroscopy room with a rotating C-arm. Flexible standard bronchoscopes with an outer diameter of 4.9 to 5.9 mm at the distal tip and a working channel of 2 to 2.8 mm diameter are usually available. Devices used include any standard 5F 65-cm multipurpose shaped catheter (Cook Medical, Bloomington, IN; Boston Scientific, Natick, MA; Cordis Endovascular, Warrenton, NJ; AngioDynamics, Glen Falls, NY) and either a steerable nonhydrophilic 0.035-inch guidewire that comes with a locking wire extension component (Wholey wire [Mallinckrodt, Hazelwood, MO]), a 0.035-inch J nonhydrophilic guidewire (Cook Medical, AngioDynamics), or Magic Torque guidewire (Boston Scientific) and the appropriate-diameter balloon catheter. A hydrophilic guidewire should not be used because it might inadvertently pass too peripherally and cause a pneumothorax, and it is too slippery to adequately control during catheter exchanges. In adults, balloon catheters 8 to 12mm in diameter are used in the bronchi, and 14 to 28 mm in diameter in the trachea. The diameter of the balloon is chosen to be closest to that of the lumen measured at the proximal-region normal airway, which is determined based upon a pretreatment computed tomography (CT) scan. It is helpful to partner with a pulmonologist to allow bronchoscopy to be combined with the fluoroscopic procedure to provide additional guidance and assessment of the stenosis before and after balloon dilation.

Technique

Before balloon dilation, stenosis severity, proximal and distal extent of the lesion, tapering in size of the airways, and location of the stricture relative to the vocal cords and branch airways should be evaluated by conventional radiography, pretreatment CT scans, including three-dimensional and multiplanar reconstructions, and/or bronchoscopy. The presence of malignancy or a benign tumor should have already been excluded, even if a bronchoscopic biopsy is necessary.

The pharynx and larynx are topically anesthetized with lidocaine aerosol spray 3 to 5 minutes before the procedure. Patients are sedated using intravenous administration of midazolam and fentanyl and their oxygen saturation, electrocardiogram, blood pressure, and pulse are monitored throughout the procedure. General anesthesia is rarely indicated for simple balloon dilation. Bronchoscopy is first performed to localize the airway obstruction and assess for the presence of a secondary infection. A guidewire is inserted through the working channel of the bronchoscope and is passed through the obstruction. With the guidewire held in place, the bronchoscope is withdrawn and a sizing catheter (Accu-Vu sizing catheter [AngioDynamics, Latham, NY]) is passed over the guidewire to the distal part of the stricture to measure the lesion length, although this calculation can often be performed based upon measurements from the CT scan and the virtual bronchoscopic reconstructions. Alternatively, use of a calibrated guidewire (Magic Torque [Boston Scientific]) can be used as an internal reference for calibration. The degree and length of the stricture can be further evaluated in detail by selective tracheobronchography by injecting approximately 5 mL of water-soluble nonionic contrast medium (Visipaque 270 [GE Healthcare, Milwaukee, WI]) mixed 1:1 with lidocaine through the sizing catheter while the catheter is pulled back proximal to the lesion, without withdrawing the catheter through the vocal cords. Fluoroscopy is performed, and digital spot images are obtained without moving the image intensifier. This maneuver may cause the patient to cough, and it will also necessitate passage of the guidewire through the lesion again. However, the tracheobronchogram can be used as a reference such that radiopaque markers can be placed on the surface of the patient’s skin to allow fluoroscopic identification of the proximal and distal limits of the stricture. Again, to minimize misregistration of the reference image due to parallax, the image intensifier and patient should not be moved. Tracheobronchography could be skipped in cases where exact position of the balloon dilation catheter is not critical or the location of the stricture is seen with simple fluoroscopy. An angioplasty balloon catheter is then passed over the guidewire under fluoroscopic guidance, correctly positioned across the stenosis, and inflated with diluted water-soluble contrast medium at inflation pressures as high as 20 atm. Use of a noncompliant balloon (e.g., Dorado [Bard Peripheral Vascular, Tempe, AZ] or Ultrathin Diamond [Boston Scientific]) is recommended to optimize translation of the dilating forces to the lesion.

If the stenosis is too narrow to allow passage of a balloon catheter of 10 mm or more in diameter (which is extremely rare), a 6-mm-diameter balloon catheter can be used first to provide a passage for the larger balloon catheter. Two to three serial balloon inflations are performed for 60 to 120 seconds during balloon bronchoplasty until the balloon waist formed by the stenosis disappears, or until the patient cannot tolerate further inflations. For a tracheal stenosis, balloon inflation and deflation should be very quick (e.g., <20 seconds) because patients cannot tolerate longer inflations within the trachea. As the balloon catheter is being deflated, it is helpful to push the balloon catheter distally to allow improved air flow at the stenotic area. After the procedure, another bronchoscopy is performed to evaluate procedure results and assess for complications such as bleeding or a mucosal laceration.

When catheterization with a guidewire and conventional vascular catheter is not successful because a bronchial stricture is tight or complete, catheterization with an angled-tip introducer set (Flexor Check Flo Introducer Set [Cook Medical]) could be very effective to negotiate the guidewire into the stricture ( Fig. 106.3 ; also see Fig. 106.2 ). The inner dilator has a suitable angle to allow passage of the tapered end of the dilator into the bronchus.

On occasion, some patients do not tolerate balloon dilation of the trachea and/or bronchial segment. In these situations, it may be necessary to employ general anesthesia for the procedure. It is helpful to use a no. 8 endotracheal tube, which is large enough to allow continued ventilation during flexible bronchoscopy. It is also helpful to use an adapter on the back end of the endotracheal tube through which the bronchoscope can be inserted without having the anesthetic gases leak. During the catheter-based endotracheal/bronchial intervention, a 14F 11-cm vascular sheath can be inserted into the port of the endotracheal tube adapter to minimize back-leakage of the anesthesia gases.

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