Adult Chest Surgery

Chapter 46. Endoscopic Treatments 

In highly selected patient populations, endoscopic and endobronchial management offers effective treatment options for benign major airway disease (e.g., stenosis and malacia). These options are associated with less morbidity than other surgical treatments. Selection criteria focus primarily on the surgical candidacy of each individual patient. Patients can be deemed inappropriate candidates for resection for a variety of reasons: etiology, extent of disease, failed prior operation, confounding medical comorbidities, and patient preference. Lack of technical expertise at a given institution also may be a factor. Since each institute carries its own bias with respect to these parameters, a patient determined inoperable at one center, in fact, may be considered a reasonable candidate at another. Clearly, some patients benefit from less invasive management of their airway disease. Only rarely do patients present with life-threatening airway compromise (50% luminal compromise) requiring urgent endoscopic treatment. To this end, immediate endoscopic palliation of a high-grade stenosis may be part of a treatment strategy incorporating an elective staged resection.

Symptomatic subglottic and tracheal stenoses and tracheomalacias are indications for endoscopic therapy. These etiologies are listed in Table 46-1. Whether used as the primary therapy or as an adjunct to definitive surgery, the goal of endobronchial intervention is to restore airway patency and to provide a durable response while limiting morbidity. Procedures often involve collaboration between surgeons and interventional bronchoscopists. Critical elements of endoscopic treatments are careful patient selection, choice of an appropriate intervention based on indication, excellent postoperative care, and often, anticipation for serial procedures.

Table 46-1. Etiology of Airway Stenosis/Malacia

Location

Type

Disease

Subglottic

Congenital

Closed first ring

 

 

Membranous web

 

 

Cartilage deformity

 

Acquired

External trauma

 

 

Endoluminal trauma

 

 

Systemic illness

Tracheal

Congenital

Membranous web

 

 

Vascular anomaly

 

 

Congenital malacia

 

Acquired

External trauma

 

 

Endoluminal trauma

 

 

Systemic illness

 

 

Prior airway intervention

 

Modern endoscopic approaches are aimed at respiratory epithelial preservation while minimizing radial thermal and mechanical injury of the airway. Multimodality approaches are used often to affect these goals. Many procedures can be performed through an adult flexible bronchoscope (video or fiberoptic), whereas some require rigid instrumentation. General anesthesia is preferred for most procedures, although it is possible to perform some interventions in a bronchoscopy suite with conscious sedation and topical analgesia.

BENIGN SUBGLOTTIC STENOSIS

The subglottis lies between the vocal cords and the proximal trachea. Congenital causes generally present early in life and are characterized by an audible biphasic stridor or a persistent or recurrent croup-type cough. Historically, congenital subglottic stenosis required tracheotomy in over 40% of patients as an early palliative maneuver.1

Acquired subglottic stenosis is commonly associated with antecedent trauma, either externally (e.g., blunt-force injury to the anterior neck) or, more frequently, internally. There is little doubt that this represents an important, often delayed morbidity of laryngotracheal intubation. Airway injury can occur as a result of direct mucosal trauma sustained during intubation, endotracheal tube cuff pressure and mucosal necrosis, and tube motion and associated tracheitis.Percutaneous dilational tracheostomy and laryngotracheal reflux also have been implicated.3

Acquired systemic diseases such as amyloidosis, papillomatosis, tuberculosis, and Wegener's granulomatosis also may include subglottic stenosis as a component of their symptom complex. There is also a rare idiopathic syndrome, seen almost exclusively in younger women, that manifests as an obstructing subglottic web.4,5

BENIGN TRACHEAL STENOSIS

Fortunately, congenital causes of benign tracheal stenosis are quite rare and can include extrinsic narrowing or compromised development from complete vascular rings or partial vascular slings. Acquired diseases account for the majority of these occurrences. Specifically, intrinsic injuries caused by endotracheal intubation or tracheotomy are the most common and those best characterized. Table 46-2 summarizes the four most common locations related to posttracheotomy stenosis.2,6,7 Healing of these various injuries often results in a complex, asymmetric scar that can be difficult to palliate. Additionally, many tracheal stenoses are accompanied by some degree of tracheomalacia, which further complicates their management.

Table 46-2. Classification of Tracheal Stenosis after Tracheotomy

Relationship to Tracheostoma

Cause

Proximal

High tracheostomy and erosion into the anterior wall

At the stoma

Interaction polyps

 

Granulation tissue

Immediately distal to stoma

Excessive granulation response cuff

 

Necrosis

Distal to the endotracheal tube

Excessive motion or pressure of the tracheostomy tube

 

Adapted from references 1, 6, and 7.

ENDOBRONCHIAL AND ENDOSCOPIC INTERVENTIONS

Numerous techniques can be used to relieve central airway stenosis (Table 46-3). Classically, rigid tracheoplasty (dilation) was the only option available for high-grade proximal airway narrowing. More recently, however, although rigid instrumentation is still a critical element in the management of these conditions, endoscopic treatments have become favored because of the improved optics of flexible bronchoscopes and the development of a vast array of therapies that easily can be used through them. Very often procedures become an amalgam of both because the rigid scopes provide ventilatory support and stable airway access while flexible scopes are passed within them (Fig. 46-1).

Table 46-3. Endobronchial and Endoscopic Interventions for Benign Airway Stenosis

Conduit

Type

Effect

Flexible bronchoscope

Electrocautery

Thermal

 

Argon plasma coagulation

Thermal

 

Laser (CO2 or Nd:YAG)

Thermal

 

Pneumatic tracheoplasty

Mechanical

 

Self-expanding metallic stent

Mechanical

Rigid bronchoscope

Rigid tracheoplasty

Mechanical

 

Silastic stent

Mechanical

Suspension laryngoscope

All*

Both

 

*Primarily for subglottic and proximal tracheal therapies.

Figure 46-1.

 

The airway can be controlled by suspension laryngoscope, rigid bronchoscope, endotracheal tube, or laryngeal mask airway.

DILATION

By far the most common endobronchial intervention, dilation is seldom performed without another therapy. Depending on the complexity of the stenosis, however, repeated endobronchial dilations alone may be sufficient to effectively palliate an inoperable airway stenosis. Passage of graduated bougies through a suspension laryngoscope is an effective therapy for most simple (weblike) stenoses of the subglottis and proximal trachea. Because of the compliance of the bougienage tubes, this form of rigid tracheoplasty is gentler on the airway than a rigid bronchoscope used to affect the same result. As the complexity of the stenosis increases (i.e., asymmetric, denser scar, component of malacia, and lengthier), rigid tracheoplasty alone becomes far less effective, and its use may lead to unintended rupture of the airway. Rupture occurs because a spared membranous airway likely will be the point of least resistance for some dense asymmetric scars. Passage of a rigid dilator through these types of stenoses may split the posterior wall of the airway and leave the stenosis intact. This pitfall can be overcome by pretreating the stenosis with ablation therapy (see below).

With the development of graduated endobronchial balloons, pneumatic tracheoplasty can be performed bronchoscopically. Although this is a seemingly less traumatic approach, endobronchial balloons are often inflated to well above five times atmospheric pressure during a dilation. Thus this technique is no less traumatic than rigid dilation.

ENDOSCOPIC ABLATION THERAPIES

The use of thermal energy to disrupt or ablate diseased tissue has been reported for over 50 years. Its application within the respiratory system was limited until recent technologic advancements made impressive progress that permitted access. A number of delivery vehicles are now available for airway applications. For benign airway stenoses, there are two main goals of ablative therapies. First, endoscopic resection and vaporization of an obstructing granulation tissue mass or scar can be accomplished. Second, dense focal scars can be incised to create pathways of least resistance so that subsequent rigid or pneumatic dilations can be performed safely.

Several energy sources can create thermal injury and result in tissue ablation. The choice of source depends on the nature of the stenosis, which includes location, cause, thickness, and length of airway involvement. Having all the required instrumentation is vital. An institution must be committed to purchasing a therapeutic laser, argon plasma, and electrocautery sources, as well as flexible fiberoptic or video bronchoscopes with working channels of at least 2.3 mm (2.8 mm is preferred).

Laser

The development of lasers with short wavelengths that could be transmitted through thin quartz filaments made endoscopic application possible. The carbon dioxide laser operates at a longer wavelength (10.6 m), which limits its use to superficial structures.The neodymium:yttrium-aluminum-garnet (Nd:YAG) laser, however, operates at a wavelength one-tenth as long, making it the more common source used. Laser fibers can be passed through a flexible bronchoscope with a high degree of accuracy. Stenoses are endoscopically resected primarily by vaporization of tissues. Nd:YAG laser light is poorly absorbed by both water and hemoglobin, causing it to penetrate more deeply than other ablative therapies. Accordingly, the risk of airway perforation is higher. Also, the wider energy dispersion field results in effective coagulation.Unfortunately, as with other ablative therapies, although the mechanical obstruction can be partially relieved, the disease process continues and may accelerate because of the added effect of the mucosal thermal injury from the laser. A rare but important complication of endoscopic laser therapy is airway ignition.This is more commonly associated with laser procedures performed through the flexible bronchoscope rather than the rigid scope. Reduction of the inspired FIO2during laser use and awareness of this potential problem are critical.

Electrocautery and Argon Plasma Coagulation

Endoscopic electrocautery (diathermy) offers the technician the ability to rapidly snare and remove large granulomas or polyps bypassing the tedious process of vaporization. As an alternative, cautery can be used similarly to the laser. Risk of airway ignition is slightly less with electrocautery than with laser because less heat is generated by electrocautery. Depth of penetration of thermal injury depends on the contact time with tissues and, consequently, can vary by operator.

The flow of electrons through tissue generates heat for coagulation because of the high resistance within the target tissue. Electrocautery probes require direct contact with the target tissue to initiate this effect. Argon plasma coagulation (APC) uses ionized argon gas to conduct electrons into the target, providing a noncontact mode of treatment (lightning effect).Argon gas flows flexibly, and therefore it can travel in a nonlinear fashion to the desired target (i.e., bend around corners). Moreover, as tissues are coagulated, their intrinsic resistance rises, redirecting the argon beam to adjacent, nontreated, lower-resistance tissues.This feature distinguishes APC from the laser. Also, APC can treat more superficial tissues than either laser or diathermy.

TECHNIQUE

Endoscopic management of benign central airway stenosis involves a combination of endobronchial therapies. As discussed previously, dilation alone generally is insufficient to provide meaningful palliation. After identification of appropriate candidates for therapy, control of the airway is the initial step. Usually, general anesthesia will be required. In some patients, though rare, conscious sedation may be sufficient. The airway can be controlled by suspension laryngoscope (see Fig. 46-1), rigid bronchoscope, endotracheal tube, or laryngeal mask airway. The choice is predicated on location, etiology, and magnitude of the stenosis. For high-grade stenoses, rigid control of the airway is preferred but can be changed to endotracheal tube or laryngeal mask airway once the airway has been partially recanalized. If a subglottic lesion exists, suspension laryngoscopy provides excellent access.

Patients are ventilated with intermittent apnea or jet techniques. Ventilating rigid bronchoscopes are useful for these purposes. A thorough assessment of the airway is made, and if more than a simple weblike stenosis exists, an ablative therapy usually is required. Choice of ablative therapy is often guided by availability at a given institution. Laser, electrocautery, and APC probes are designed for a standard adult bronchoscope; familiarity with each is mandatory.9

Ablative therapies are used for three different purposes. Endoscopic photoresection (i.e., laser and electrocautery) is reserved for dense cicatricial stenoses or obstructing granulation tissue. The obstruction is vaporized, charred, and then debrided with biopsy forceps. Radial incisions (i.e., laser and electrocautery) can be made along suspected lines of tension to help guide the direction of fracture of the stenosis during dilation. Two or three full-thickness incisions are made within subcentimeter stenoses, and either endoscopic pneumatic dilation or rigid dilation follows. Endoscopic coagulation (APC) is used to treat diffuse superficial processes, such as benign polyposis. Regardless of the therapy, airway perforation and ignition are risks.

Topical endoscopic application of mitomycin C (0.4 mg/mL) appears to be a safe and moderately efficacious adjuvant therapy, although limited experimental10 and clinical data11–13 are available to support this. Mitomycin C can be applied topically to treated areas, and surprisingly, this does not appear to affect epithelial regrowth but rather only interferes with refibrosis.10 Treated areas should be surveyed regularly for squamous metaplasia.

TRACHEOBRONCHOMALACIA

Regardless of etiology, limited surgical procedures exist for long-segment central airway malacia. Consequently, endoscopic and endobronchial therapies have emerged as the main therapeutic options for these difficult-to-treat functional airway stenoses. Principal among these therapies is endobronchial stenting. Internal airway stents are ideal for airway collapse because they provide support for airway structures irrespective of the cause of malacia. Unfortunately, they themselves can lead to numerous complications relating to their migration and host foreign-body reactions.

In the context of benign disease, stents can be deployed as primary treatment for malacia or as an adjuvant after benign stenoses have been ablated. There are numerous stents from which to choose, although it is now apparent that silicone stents rather than metallic stents should be used for the treatment of benign disease.14

Placement of silicone stents requires rigid bronchoscopy and general anesthesia.15 Careful preoperative airway measurement is required to properly size the stent. To this end, a chest CT scan with three-dimensional reconstruction of the airway is useful (Fig. 46-2). Patients usually are treated with steroids to reduce the chance of bronchospasm during and immediately after the procedure.

Figure 46-2.

 
 

Careful measurement of the preoperative airway using a CT scan with three-dimensional reconstruction is required for placement of silicone stents. Before (A) and after (B) stent placement.

It is important to schedule frequent follow-up visits for patients with endobronchial stents. Follow-up visits should include surveillance flexible bronchoscopy. This is necessary because stent-related complications such as migration, mucus impaction, and granulation tissue occur frequently. All patients should be managed with mucolytic therapy (via nebulizer) two or three times daily. Patients also should be instructed that if any decline in respiratory function occurs, medical attention should be sought immediately. Asphyxia can occur with stent migration or occlusion.

SUMMARY

Endoscopic therapies are critical to the comprehensive management of benign airway stenosis and malacia. A multidisciplinary team, including airway surgeon and interventional pulmonologist, is necessary to identify candidates for these procedures. An institutional commitment to secure appropriate instrumentation and technical support is also required.

EDITOR'S COMMENT

Air embolism is an underappreciated complication of ablative therapy of the airways. It likely occurs as a result of high pressure near an open vessel. The incidence can be reduced by avoiding devices with high-gas-flow carriers as well as by minimizing ventilatory pressures and briefly reducing ventilation during ablative treatments.

–RB

REFERENCES

1. Holinger PH, Kutnick SL, Schild JA, Holinger LD: Subglottic stenosis in infants and children. Ann Otol Rhinol Laryngol 85:591–9, 1976. [PubMed: 791051]

2. Mehta AC, Harris RJ, De Boer GE: Endoscopic management of benign airway stenosis. Clin Chest Med 16:401–13, 1995. [PubMed: 8521696]

3. Lorenz RR: Adult laryngotracheal stenosis: Etiology and surgical management. Curr Opin Otolaryngol Head Neck Surg 11:467–72, 2003. [PubMed: 14631181]

4. Ashiku SK, Mathisen DJ: Idiopathic laryngotracheal stenosis. Chest Surg Clin North Am 13:257–69, 2003. [PubMed: 12755312]

5. Dedo H, Catten M: Idiopathic laryngotracheal stenosis: Findings and treatment in 52 patients. Ann Otol Rhinol Laryngol 110:121–5, 2001. 

6. Montgomery WW: Current modifications of the salivary bypass tube and tracheal T-tube. Ann Otol Rhinol Laryngol 95:121–5, 1986. [PubMed: 3963685]

7. Ossoff RH, Tucker GF Jr, Duncavage JA, Toohill RJ: Efficacy of bronchoscopic carbon dioxide laser surgery for benign strictures of the trachea. Laryngoscope 95:1220–3, 1985. [PubMed: 3930903]

8. Mehta AC: Laser application in respiratory care. In Stoller JK, Kacmarek RM (eds): Current Respiratory Care Techniques and Therapy. Ontario, Canada, BC Decker, 1988:100–6. 

9. Bollinger C, Sutedja T, Strausz J, Freitag L: Therapeutic bronchoscopy with immediate effect: Laser, electrocautery, argon plasma coagulation, and stents. Eur Respir J 27:1258–71, 2006. 

10. Cincik H, Gungor A, Cakmak A, et al: The effects of mitomycin C and 5-fluorouracil/triamcinolone on fibrosis/scar tissue formation secondary to subglottic trauma (experimental study). Am J Otolaryngol 26:45–50, 2005. [PubMed: 15635581]

11. Schweinfurth JM: Endoscopic treatment of severe tracheal stenosis. Ann Otol Rhinol Laryngol 115:30–4, 2006. [PubMed: 16466097]

12. Penafiel A, Lee P, Hsu A, Eng P: Topical mitomycin-C for obstructing endobronchial granuloma. Ann Thorac Surg 82:e22–3, 2006. 

13. Simpson CB, James JC: The efficacy of mitomycin-C in the treatment of laryngotracheal stenosis. Laryngoscope 116:1923–5, 2006. [PubMed: 17003706]

14. Murthy SC, Gildea TR, Mehta AC: Removal of self-expandable metallic stents: Is it possible? Semin Respir Crit Care Med 25:381–5, 2004. [PubMed: 16088481]

15. Dumon JF: A dedicated tracheobronchial stent. Chest 97:328–32, 1990. [PubMed: 1688757]



If you find an error or have any questions, please email us at admin@doctorlib.info. Thank you!