Endobronchial lesions are caused by a variety of benign and malignant disease processes. When such lesions obstruct the central airways, trachea, or mainstem bronchi, they quickly turn life threatening. The incidence of central airway obstruction (CAO) has increased largely because of the prevalence of lung cancer. It causes significant morbidity and, without treatment, may lead to suffocation and death. This chapter reviews the gamut of available endobronchial techniques for managing acute CAO, including endobronchial resection with electrocautery, argon plasma coagulation, laser therapy, photodynamic therapy, cryotherapy, external beam radiation and brachytherapy, and airway stents. The most comprehensive use of these techniques should be offered at centers experienced in the management of complex airway disorders with the full array of endoscopic and surgical options at their disposal.

CAO causes significant morbidity and mortality in patients with malignancies that affect the upper airways. Although the precise incidence and prevalence of CAO are unknown, current lung cancer rates suggest that an increasing number of patients experience complications of proximal endobronchial disease.¹ It has been estimated that approximately 20% to 30% of patients with lung cancer develop complications associated with airway obstruction (i.e., atelectasis, pneumonia, or dyspnea)² and that up to 40% of lung cancer deaths are caused by locoregional disease.³ With increased use of temporary artificial airways, such as endotracheal intubation, in a growing elderly population, the incidence of CAO from malignant, nonmalignant, or iatrogenic complications is also predicted to rise.

The most frequent cause of malignant CAO is by direct invasion of an adjacent tumor, chiefly bronchogenic carcinoma, secondarily esophageal and thyroid carcinoma. Primary tumors of the central airway are relatively uncommon. Most primary tracheal tumors are squamous cell carcinoma or adenoid cystic carcinoma. Distal to the carina, the carcinoid tumors account for the majority of primary airway tumors.⁴ Distant tumors, such as renal cell, breast, and thyroid, also may metastasize to the airway. Although the epidemiologic data are limited, the most commonly encountered nonmalignant causes of CAO are stenosis from the proliferation of granulation tissue resulting from prior endotracheal or tracheostomy tubes, airway foreign bodies, and tracheo- or bronchomalacia.⁵

The clinical presentation of patients with CAO secondary to endobronchial lesions depends not only on the underlying disease but also on the location and rate of progression of the airway obstruction, the patient’s underlying health status, and other associated symptoms, such as postobstructive sequelae. Mild airway obstructions may have only slight effect on airflow; hence, the patient may be asymptomatic. However, the inflammation associated with even mild respiratory tract infections can cause mucosal swelling and mucous production, which may further occlude the lumen. For this reason, patients sometimes are misdiagnosed with exacerbations of chronic obstructive pulmonary disease or asthma, especially when symptoms such as wheezing and dyspnea improve with therapy aimed at treating the superimposed infection.

Typically, the trachea must be significantly narrowed (<8 mm) before exertional dyspnea is noted. The lumen diameter must be less than 5 mm before symptoms occur at rest.⁶ As a consequence of the dramatic loss of lumen diameter necessary for the development of symptoms, there is no forewarning, and up to 54% of patients with tracheal stenosis present in respiratory distress.

When evaluating patients with suspected CAO, in addition to spirometric tests including forced expiratory volume in 1 second (FEV₁), functional vital capacity (FVC), and FEV₁/FVC ratio, it is crucial to examine the shape of the flow-volume loop. The characteristic blunting of the flow-volume loop that signals the presence of a CAO typically is seen before spirometry yields abnormal results but may not be recognized until the airway is already narrowed to approximately 8 to 10 mm.⁷

Although often obtained as the initial radiologic test, conventional chest radiographs are rarely diagnostic. Recent advances in airway imaging with CT scanning now permit multiplanar and three-dimensional reconstruction with internal (virtual bronchoscopy) and external rendering.^8,9 Excellent image quality can be achieved with low-dose techniques.¹⁰ These new imaging protocols are better able to characterize whether the lesion is intraluminal, extrinsic to the airway, or has features of both. Moreover, with the newer techniques, one can detect whether the airway distal to the obstruction is patent. Measurements of length, diameter, and relationship to other structures such as blood vessels are also more accurate.

Bronchoscopy (either rigid or flexible; see Chapter 54) is a necessary component of the preinterventional workup. Bronchoscopy provides the means for obtaining a tissue diagnosis, and nothing replaces direct visualization to assess the nature and extent of the obstruction. Other information useful for treatment planning, such as the relative amount of intraluminal and extraluminal diseases, is also obtained. Endobronchial ultrasound can be useful for the diagnostic workup of tracheal invasion and can aid in planning therapeutic interventions.¹¹

When the obstruction is severe, bronchoscopy may be difficult and potentially dangerous to perform because the instrument further diminishes the diameter of the remaining lumen and does not accommodate ventilatory support. In addition, conscious sedation may depress ventilation and relax the respiratory muscles, causing a relatively stable airway to become unstable. Access to a team skilled in advanced airway management is essential when undertaking flexible bronchoscopy.

Many of the ablative endoscopic techniques presented below are used together clinically. An algorithm is provided for endoscopic management and decision making in CAO (Fig. 67-1).

Bronchoplasty—Dilation of the Airways

In urgent cases, the airways may be dilated using the barrel of the rigid bronchoscope. In more controlled situations, sequential dilation with balloons is preferred. Sequential balloon dilation produces less mucosal trauma and limits the subsequent formation of granulation tissue. The technique has been used successfully for patients with airway stenosis after lung transplantation and surgical resection of the airway, patients with postintubation tracheal stenosis, and patients with malignant airway obstruction. It also has been shown to be safe, effective, and well tolerated in awake patients undergoing flexible bronchoscopy with conscious sedation.

Balloon bronchoplasty is particularly effective in preparing stenotic airways for stent placement, for expanding stents after insertion, and for placement of brachytherapy catheters that otherwise would be impeded by high-grade stenoses. Dilation alone is immediately effective for intrinsic and extrinsic compression, but the results are not sustained. The mucosal trauma itself may lead to granulation and, in fact, accelerate restenosis. For this reason, dilation is commonly followed by laser or stenting procedures.

The microdebrider, a tool borrowed from otorhinolaryngology, can be used to perform mechanical tumor excision in the trachea and mainstem bronchi. The microdebrider has a spinning blade that is contained in a rigid suction catheter and provides the ability to cut with suction to remove blood and tumor or granulation tissue.¹²

Electrocautery

The “active ingredient” of electrocautery is heat, which is generated by passing current from the probe to the tissue. The electric current leaves the body through a grounding plate. The amount and type of current, the characteristics of the tissue, and the contact area between the probe and the tissue all determine the amount of heat generated. The clinical result can vary from simple desiccation to tissue vaporization.

Since most commercially available bronchoscopes are not electrically grounded, the bronchoscopist may “become” the grounding electrode if the unipolar probe tip touches the scope while the current is on.¹³ Newer bipolar probes have been developed to eliminate this risk as the current completes the arc through the probe.

Electrocautery with a snare device is well suited for removing pedunculated lesions. By cauterizing the stalk of the lesion, most of the tissue can be removed without destruction and therefore is available for pathologic review. This method has been used with curative intent for patients with early-stage and intraluminal squamous cell lung cancer, as well as in advanced malignancies, combined with other modalities.¹⁴ The side effects of electrocautery include bleeding, airway perforation, endobronchial fire, and damage to the bronchoscope.

Argon Plasma Coagulation

Argon plasma coagulation is a form of noncontact electrocoagulation that can be used as an alternative to contact electrocautery and noncontact laser therapy. The plasma is formed when a 5000- to 6000-V spark created at the tip of the probe by a tungsten electrode ionizes argon gas released at the probe tip. The plasma seeks the nearest grounded tissue, producing coagulative necrosis. Argon plasma coagulation can be used to treat lesions lateral to the probe or to reach around corners to access pathology that otherwise would be inaccessible by laser therapy. Used endoscopically, a coagulation depth of 2 to 3 mm can be achieved.¹⁵ The technique produces excellent hemostasis and is associated with minimal risk of airway perforation. As the tissue coagulates and becomes desiccated, the resistance increases, suppressing further current conduction and limiting penetration.¹⁶ Argon plasma coagulation is not as useful on large, bulky tumors because, unlike laser therapy, tumor vaporization does not occur, and other modalities typically are required to achieve satisfactory tumor debulking.

Laser Therapy

Light amplification by stimulated emission of radiation (laser) technology was first described in the 1960s. With introduction of the neodymium:yttrium-aluminum-garnet (Nd:YAG) laser in 1975, laser tumor debulking became a mainstay of clinical practice. Before that time, CO₂ and argon lasers were the only available options, and for technical reasons, neither could be adapted for use with the bronchoscope. The Nd:YAG laser has a wavelength of 1064 nm and produces an invisible beam that lies in the infrared region and can be used with the flexible bronchoscope.¹⁷ Since there is less absorption by hemoglobin with the Nd:YAG laser, tissue penetration up to 10 mm can be achieved. Less precise than a CO₂ laser, the Nd:YAG laser treats a greater volume of tissue. The laser typically is used at a power of approximately 20 to 40 W. Pulse duration is 0.1 to 1.2 seconds. The laser is always aimed tangentially to the airway. A conservative approach is advised because the depth of penetration is not immediately apparent to the endoscopist, and frequent reanalysis of the lesion and reapplication of the laser are recommended.