Introduction: Many patients with carcinoma of the lung are not candidates for curative pulmonary resection. Chemotherapy and radiotherapy have been shown to improve survival among these patients; however, a significant number of them will present with, or develop, symptomatic bronchial obstruction. This bronchial obstruction manifests as progressive dyspnea with or without cough, hemptysis and fever. Many of these patients can receive symptomatic relief of their bronchial obstruction and potential survival benefit from endobronchial treatments.

Bronchoscopic laser ablation of the obstructing tumor, endobronchial stent placement and endobronchial radiobrachytherapy are the primary treatment modalities at the physician's disposal today. Exciting new gene therapy treatments in development at Allegheny General Hospital may also provide benefit to these patients. In this section of the newsletter, we describe the clinical indications, basic technique and our clinical experience with these bronchoscopic approaches to airway obstruction treatment.

Patient evaluation for bronchial obstruction: Patients at risk for endobronchial obstruction include those individuals with lung cancer presenting with a hilar mass, patients with mediastinal malignancies (i.e. lymphoma, thyroid carcinoma, and metastatic visceral malignancies to the mediastinum such as renal cell, breast or colorectal carcinoma), and individuals who have undergone an airway anastomoses (lung transplantation patients, sleeve lobectomy patients and repair sites of bronchial trauma). Occasionally, individuals with tuberculous tracheitis or unrecognized blunt bronchial trauma may present with delayed airway obstruction requiring endobronchial treatment.

The primary complaint of these individuals is progressive difficulty breathing; however, increased sputum production and fever related to an obstructive pneumonitis and/or hemoptysis may also be part of the patient's clinical presentation. Physical examination may be unrevealing but for diminished auscultory breath sounds over the affected lung and wheezing. The patient may present with an obvious tracheal shift toward the lung with the obstructed airway, or a tracheal shift may be related to compression from a central mediastinal mass affecting the patency of the trachea. Vascular bruits may be auscultated, and upper thoracic and cervical venous distension may be present from venous drainage impairment by a mediastinal mass lesion that is also compressing the airway.

The principal diagnostic modality to evaluate potential airway obstruction is the upright PA and lateral chest roentgenographic examination. Partial or total lung collapse may be seen. A significant mediastinal or hilar mass may be evident. At times, only subtle findings such as obscuration of the tracheo-bronchial silhouette are present. Subsequent, computed tomographic examination of the chest is indicated when tracheo-bronchial obstruction is suspected. This examination will usually delineate the nature of the airway obstruction. An intravenous contrast-enhanced CT study can aid in differentiation of vascular structures from mass lesions and can also provide information regarding the integrity of the pulmonary blood supply, which may be occluded/thrombosed by a central tumor mass. When the pulmonary blood supply is compromised, there is little likelihood that relief of the patient's airway obstruction will result in improvement in the patient's dyspnea, as the involved lung cannot participate in effective gas exchange.

Ultimately, bronchoscopic examination is required to assess the nature and scope of the airway obstructive process. The clinician caring for these patients should have a high index of suspicion for such a potential airway problem and proceed with this definitive work-up expeditiously.

Patient selection and general considerations for endobronchial treatment of airway obstruction: Appropriate patient selection for bronchoscopic treatment of airway pathology is critical. Careful review of all roentgenographic studies is essential prior to the bronchoscopic procedure. As mentioned above, the CT scan can provide critical evidence regarding the potential utility of a particular bronchoscopic intervention. The chronicity of the airway obstruction must also be taken into account. As a rule of thumb, bronchial obstruction of more than a month duration will be difficult to reverse. This reality speaks for expeditious diagnosis and management of bronchial obstructions, which may be amenable to endobronchial management.

The patient being considered for bronchoscopic airway treatment should have a normal coagulation profile and also be physiologically able to undergo a general anesthetic should that be required. The clinical management team should include a thoracic surgeon and pulmonologist, adequate intensive care nursing support, and the necessary anesthesia support to safely perform the intervention. Although localized and limited intrinsic tumor masses obstructing the airway can be managed with Nd:YAG laser fulguration under conscious sedation in the bronchoscopy suite, more extensive disease processes are probably best treated under general anesthesia in the operating room.

The therapeutic team of pulmonologist and thoracic surgeon should be well-versed in fiberoptic and rigid bronchoscopic airway management approaches. Similarly, the anesthesia team should be comfortable with high-frequency "jet" ventilation techniques, which may be required to maintain adequate gas exchange during rigid bronchoscopic interventions. Cooperation and communication between the bronchoscopist and anesthesiologist before and during these potentially difficult interventions is vital to ensure patient safety and procedural efficacy.

A variety of bronchoscopic treatments of bronchial obstructing and/or bleeding lesions is available today. Each of these approaches has specific advantages and shortcomings. It is also important to realize that these interventions are not mutually exclusive with regard to developing a therapeutic plan for the patient with endobronchial pathology. Indeed, the bronchoscopic team can apply one or more of these interventions during the several phase of the patient's airway management. Commonly, two or more of these treatments may be performed under the same anesthetic management.

We now describe the specific bronchoscopic treatment modalities used by our team at Allegheny General Hospital to control benign and malignant airway obstruction with or without hemoptysis. During the last decade, our team has performed more than 300 therapeutic bronchoscopic interventions aimed at relieving endobronchial obstructive/bleeding lesions.

Rigid bronchoscopic mechanical fulguration of the airway obstruction: In some circumstances, the primary use of rigid bronchoscopic techniques to provide rapid removal of obstructing airway lesions is primarily indicated. This approach is most effective in the management of large and bulky lesions involving the tracheal and very proximal main stem bronchi associated with impending total loss of the airway.

The bronchoscope essentially acts as a shoveling and dilating instrument, which also stents the airway once the tip of the instrument is negotiated beyond the major point of the tracheobronchial obstruction. Large, grasping forceps and suction equipment are available to rapidly debride the airway of loose tumor debris (Figure 1). Direct electrocautery control of sites of airway bleeding can be accomplished. Alternatively, the Nd:YAG laser can be introduced into the rigid bronchoscopic lumen through a fiberoptic bronchoscope to coagulate sites of bleeding and residual tumor mass within the airway.

Laser ablation of obstructing/bleeding endobronchial tumors

Nd:YAG laser
The Neodynium: Yttrium Aluminum Garnet laser has a wavelength of 1,064 nanometers and absorption upon the red/black light spectrum. This makes this particular laser wavelength particularly suited for coagulation and fulguration of most vascular endobronchial lesions. The laser wavelength has a penetration of 2 to 3 millimeters. Care must be taken to apply the laser energy parallel to the lateral bronchial wall to avoid potential perforation of the airway and injury to the pulmonary vasculature. This is of particular importance when lasing peripheral bronchial lesions, as the wall thickness of the bronchus is reduced and the proximity of the pulmonary vasculature is nearer to the bronchial wall.

The Nd:YAG laser energy is delivered through a fiberoptic, which is introduced through the biopsy channel of the bronchoscope. The energy can be delivered in a "free beam" shooting mode toward the tumor mass or by using a "contact tip" applied to the tumor surface. Both methods are effective in coagulating the tumor mass obstructing the bronchus; however, the "contact tip" approach is a little more time-consuming and may require secondary bronchoscopic treatment to remove the devitalized tissue that remains in place. We usually apply this Nd:YAG laser approach for less extensive endobronchial lesions that are not compromising a major airway.

The "free beam" approach actually fulgurates/vaporizes the endobronchial tumor immediately. Rapid clearance of a large obstructing lesion can be accomplished with this technique in expeditious fashion. The potential drawback of this latter approach is the increased amount of laser plume that is created with immediate fulguration of the tumor mass. This can lead to significant bronchospasm when used upon the patient undergoing laser therapy under conscious sedation in the bronchoscopy suite. Because of this, we usually perform the "free beam" Nd:YAG laser approach in the operating room under general anesthesia. We will also frequently utilize a rigid bronchoscopic technique to secure the airway and allow for large suction/ biopsy forcep removal of devitalized tissues during these "free beam" laser treatments.

Endobronchial lesions amenable to these laser techniques are those with a primary intrinsic bronchial growth obstructing the lumen of the bronchus (Figure 2). Along these lines, obstructive lesions with a primary extrinsic component to their disease are poor candidates for Nd:YAG laser therapy. The lesion should spare the more peripheral airways, as long-term control of the obstruction is less good and the risk of complications is significant. Lesions associated with mild to moderate hemoptysis can be treated with the Nd:YAG laser approach in many circumstances.

Carbon dioxide laser
The carbon dioxide laser (10,600 nm wavelength) was first used to ablate benign central laryngotracheal tumors. The primary disadvantage of this laser is the inability to transmit the laser energy through flexible optic fibers. Instead, the laser light energy is directed to the target tissue by reflecting it across precisely positioned mirrors within the laser instrumentation and endoscopic equipment. This limits the use of the carbon dioxide laser to rigid bronchoscopic access to the airway.

The carbon dioxide laser is readily absorbed upon tissues with a high water content, which enables its use as a valuable surgical cutting tool. Hemostat- ic/coagulative properties are limited compared to the Nd:YAG laser. These precise cutting/vaporization properties allow for vaporization of relatively avascular tumors of the central airway with little injury to surrounding normal tissues.

Photodynamic therapy with tunable dye lasers
Photodynamic therapy utilizes a variety of laser sources to obtain light energy that is then passed through a dye system to obtain a selected wavelength for optimal absorption upon a patient's tissues. The patient is administered a drug known as a "photosensitizer", which is absorbed within the tissues to be treated by the laser energy. The accumulation of the drug within the tissues "sensitizes" the target cells selectively to the effect of the laser energy.

The most commonly utilized sensitizer is hematoporphyrin, which is an analogue to hemoglobin. This drug is injected intravenously, 48 hours prior to the timing of the laser treatment. Malignant tissues tend to retain the hematoporphyrin to a much greater extent than normal surrounding tissues. This results in a much greater laser effect upon these malignant tissues compared to the normal tissues next to the tumor. The laser light activates the hematoporphyrin within the tumor cells, leading to a chemical reaction (peroxidation) within the cells, which results in cell membrane disruption and cellular death. This novel form of laser therapy is being used by our team and others to manage malignant airway and esophageal obstructions. We consider this laser treatment technique when other more conventional endobronchial therapies (Nd:YAG laser, brachytherapy, stents) have failed or when considering primarily treating microscopic diffuse malignant airway changes (carcinoma in situ).

Endobronchial stenting of airway obstruction: Endobronchial stenting (or internal strutting) is an effective means of restoring airway integrity for a variety of benign and malignant bronchial conditions. This is particularly applicable for the management of bulky lung tumors with a significant extra-bronchial component that compresses and compromises the airway. These stenting procedures can also be effective in managing bronchomalacia (floppy, collapsible central bronchial passages) or tracheobronchial strictures developing from benign or malignant diseases.

These airway stents are available in two varieties. Soft silastic plastic stents, which are introduced into the airway across the narrowing with rigid bronchoscopy, are available in variable lengths but with a limited diameter option. These stents can be easily repositioned or removed if the airway obstruction changes or resolves with therapy (i.e. chemotherapy or radiotherapy). The other airway stent available is the expandable wire variety, which has a larger available diameter selection for the management of more central airway lesions (Figure 3). We commonly utilize rigid bronchoscopic equipment and fluoroscopic guidance to position these expandable stents because of superior airway visualization and more accurate stent deployment; however, some patients can have the stent placement accomplished using fiberoptic bronchoscopic techniques under topical analgesia and intravenous sedation.

These airway stents are immediately effective in relieving the patient's dyspnea if a more peripheral airway problem is absent. If peripheral airway narrowing from more diffuse tumor involvement is present, only marginal recovery for the patient can be expected. Indeed, when the obstructive airway process is primarily within the peripheral bronchial passages, airway stenting is of little utility. Other means of relieving the airway obstruction (i.e. laser ablation, external beam radiotherapy plus chemotherapy, or endobronchial brachytherapy) must be primarily considered.

Endobronchial radio-brachytherapy: Endo- bronchial brachytherapy is a means of providing supplemental radiotherapy directly through the airway obstructive lesion. In contrast to conventional external beam radiotherapy, brachytherapy focuses the radiation effect specifically at a limited area of airway disease. This often allows for salvage of the airway integrity when tumor recurrence is seen following full-dose external beam radiotherapy.

The details of endobronchial brachytherapy are intriguing. The patient undergoes bronchoscopic examination and introduction of a thin sheathing catheter through the nostril into the airway (Figure 4). 

This catheter is positioned through the airway obstruction under bronchoscopic and fluoroscopic guidance. The patient is then transported  to the radiation therapy unit where the high-dose remote afterloading radiation therapy equipment is located. A robotically controlled radiation source is placed within the catheter and then quickly guided directly to the site of the airway obstruction (Figure 5). The radiation source is left in place at the appropriate location of the obstruction for several seconds to achieve an adequate dose of treatment. After the treatment has been accomplished, the radiation source is quickly retracted from the catheter and back into the protective lead housing in which it is stored. This remarkable technology allows for the performance of this endobronchial radiotherapy under local/topical analgesia on an outpatient basis. Usually, four outpatient visits are required at weekly intervals to complete the brachytherapy.

Conclusions: During the last 15 years, our group has treated more than 300 patients with the modalities described above. This extensive experience has allowed us to streamline our approach to provide patients with the most efficient and effective palliation of their airway obstruction. In many circumstances, we will utilize a combination of two or more of these endobronchial treatments (i.e. laser and stent, stent and brachytherapy) to maximize the patient's airway therapy. Systemic therapy and external beam radio therapy are also commonly employed in the patient's general treatment schema. We emphasize the importance of a flexible approach to this airway management, which tailors the therapy to the specific needs of the patient so as to optimize his or her overall care.

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