Introduction

Interventional pulmonology is an evolving discipline stemming from pulmonary medicine that concentrates on both diagnostic and therapeutic interventions for patients with advanced airway and pleural diseases. The interventional pulmonologist has taken an active role in developing potentially less invasive ways to perform diagnostic and therapeutic procedures in disorders of the airway and pleura.

Procedures encompassed within this expanding field include, but are not limited to, rigid bronchoscopy, endobronchial laser therapy, electrocautery, cryotherapy, balloon dilation (BD), brachytherapy (BT), and endotracheal or endobronchial stent placement. The question of which modality to use is influenced by many factors, including patient presentation, operator proficiency, anesthetic techniques, and the institution’s available equipment. The key to success in caring for patients with these disorders is careful patient selection and the complementary application of these techniques. In this review we will focus on describing these procedures, as well as outlining an active approach to the clinical disorders for which they are used.

Central Airways Obstruction

Obstruction or stenosis of the trachea and large bronchi can be a consequence of endobronchial obstruction, extraluminal compression, or a combination of both. Endoluminal or endobronchial lesions are most common. Extrinsic compression causing obstruction of the airway is less frequent, but can result in symptoms and outcomes similar to those of endobronchial obstruction. Most cases are secondary to bronchogenic carcinoma; however, both benign and malignant causes can produce significant morbidity and decreased life expectancy if left untreated. Table 16.1 shows the common etiologies of central airway obstruction.

The presenting symptoms of airway obstruction will differ depending on the anatomic location and severity of the obstruction. Symptoms range from chronic hoarseness, cough, dyspnea, and wheezing to more severe acute problems such as stridor, hemoptysis, and respiratory failure. When approaching the patient with upper airway obstruction, the pulmonologist must take into account the stability of the patient, the underlying pathologic condition, and the short-and long-term prognoses of the disease process. The location and severity of the lesion and the rate of progression of the obstruction are significant aspects that need to be considered when evaluating these difficult conditions. The availability of equipment and the expertise of the interventionalist are also important factors in deciding how to treat the individual patient. Most patients will require a combination of various techniques for the most successful outcomes.

Rigid Bronchoscopy

The rigid bronchoscope is an invaluable tool that allows the interventional pulmonologist to secure, evaluate, and manipulate the trachea and proximal bronchi, while controlling oxygenation and ventilation. It is the most rapid technique to relieve an obstruction of the central airways, whether it is an intraluminal or extraluminal obstruction.

Today, a majority of bronchoscopies are being performed with the flexible scope; making it the procedure of choice for most diagnostic and some therapeutic procedures. Despite this rapid expansion and widespread use of the flexible scope, however, the rigid scope still remains an imperative tool for therapeutic practice. Both flexible and rigid bronchoscopy have unique characteristics and offer specific advantages depending on the clinical situation. Table 16.2 compares rigid and flexible bronchoscopy and the best indications for specific clinical scenarios.

For patients with respiratory insufficiency secondary to central airways obstruction, reestablishment of the airway can be accomplished with intubation and advancement of the rigid scope. The airway can then be dilated by the advancement of the scope along the wall of the airway. This dilation may be temporary, but will allow oxygenation, ventilation, and time to evaluate the obstructed area for further therapy. If the airway is too narrow to allow advancement of the scope, balloons of increasing diameter can be passed through the scope for dilation. The scope can then be used as a tumor-debulking instrument, by “corkscrewing” the scope to core out large pieces of tumor. In patients with extrinsic compression causing airway obstruction, the rigid bronchoscope is required for the insertion of silicone stents in the trachea or proximal bronchi. Rigid bronchoscopy is also a vital tool in controlling massive hemoptysis. Hemorrhage can be controlled by tamponade with the scope and with the use of large suction catheters to remove blood or clots.

With proper technique and safe anesthesia, there are few complications associated with rigid bronchoscopy. The most common problems come during intubation or advancement of the scope, causing trauma to the teeth, oropharynx, trachea, or bronchial walls. Massive bleeding is rare. There are few contraindications to rigid bronchoscopy, and most are related to use of general anesthesia. These include unstable cardiopulmonary status and serious arrhythmias.

Laser

Laser therapy is a recognized endobronchial treatment that the interventional pulmonologist uses today. It is used extensively for the palliation of symptoms of airway obstruction secondary to malignancies, and it provides effective therapy for benign airway lesions and stenosis. In selected patients, laser therapy has been shown to improve quality of life and functional status, and, in some cases, to extend survival.

The most widely used laser in the tracheobronchial tree is the neodymium-doped yttrium aluminium garnet (Nd:YAG) laser because of its deep penetration into tissues (≤5 mm), superior coagulation characteristics, cutting ability, and versatility. It can be used through a flexible or rigid bronchoscope. The decision between using a flexible or rigid bronchoscope depends on the operator’s experience, the character of the lesion, and patient stability. Lesions that are favorable to laser therapy include tracheal and main stem lesions, polypoid lesions of short length (< 4 cm), lesions with a visible distal airway lumen, and functional lung distal to the obstruction. Lesions that are not favorable for laser resection have more than 80 percent obstruction of the airway and are those that destroy airway wall integrity and obliterate anatomical boundaries.

Palliation of symptoms from malignant airway obstruction is the most common indication for endobronchial laser therapy. It is also used for obstruction secondary to benign tumors such as hamartomas, papillomas, amyloidomas, and endobronchial endometriosis.

Bronchoscopic laser therapy is a relatively safe procedure. Most complications can be avoided by applying preventative safety measures. Perforation of a vascular structure, mediastinum, or esophagus is one of the most feared complications of laser therapy. Knowing the anatomic proximity of the aortic arch, pulmonary artery, and the esophagus is crucial when performing laser therapy near these areas. Another concerning complication is a laser-related endobronchial fire. Fires are uncommon when the rigid bronchoscope is used. Materials that ignite during laser therapy include the flexible scope sheath, endotracheal tubes, and silicone stents.

Contraindications to endobronchial laser therapy include extrinsic compression of the airway without an endobronchial lesion, involvement or compression of the pulmonary artery by tumor, tracheoesophageal fistula, and prolonged atelectasis for more than four weeks.

Electrocautery and Argon Plasma Coagulation

Although the Nd:YAG laser is recognized as the most widely used form of bronchoscopic intervention, its use may be limited by its expense, its relative lack of accessibility, and the belief that rigid bronchoscopy is required for its use. These factors have increased the appeal of a parallel procedure, electrocautery, which may be more available, more user friendly, and less expensive. Furthermore, there are many studies that present evidence that electrocautery has efficacy similar to that of laser therapy.

Bronchoscopic electrocautery, also called electrocoagulation (EC), unlike laser therapy, is usually performed in the contact mode, with the probe gently touching the tissue. A snare is available for polypoid lesions, and a standard probe is available for the bulky lesions. The indications, patient selection, and principles of application are essentially the same as for the Nd:YAG laser. Both benign and malignant lesions have proven to be amenable to electrocautery.

Complications are relatively similar to those of laser therapy, with hemorrhage, airway perforation, and (rarely) endobronchial fire. The EC probe needs to be cleaned from debris intermittently during the procedure, which is one disadvantage when comparing it with laser therapy. In general, however, EC has significant potential as an effective and cost-effective procedure for patients with endobronchial obstruction.

Argon plasma coagulation (APC) is a newer form of EC. It is used for both malignant and benign airway obstruction and endobronchial hemoptysis. It is used in the noncontact mode, similar to laser therapy. APC has the unique advantage of being able to treat lesions lateral to the probe. APC is less efficient than laser therapy at debulking large masses because it cannot generate as high of temperatures and provide as deep of tissue penetration.

Cryotherapy

Cryotherapy refers to the use of extreme cold for medical therapy. The goal of cryotherapy is to destroy pathologic tissue, while preserving normal mucosa. The basis of action relies on destruction of tissue by repeated cycles of freezing and thawing. Nitrous oxide (N₂O) is the most common cryogen used in endobronchial therapy.

There are many factors that influence tissue injury when cryotherapy is used. The absolute temperature, the rate of cooling and thawing, and the length of freezing time all affect the success of therapy. Freezing to −40 °C at the rate of −100 °C/min has been shown to cause >90 percent cell death. Tissue vascularity, the distance of tissue from the probe, the amount of water in the tissue, and the number of freeze–thaw cycles have also been found to be essential factors in the effectiveness of the therapy. The destruction of tissue by freezing occurs by both an immediate and delayed mechanism.

Tissues are either cryosensitive or cryoresistant, which is why certain tissues respond better than others to cryotherapy. Skin, mucous membranes, and granulation tissue (which arises histologically from mucous membranes) are cryosensitive, whereas fat cartilage and fibrous and connective tissue are cryoresistant. Tumor cells have been found to be more cryosensitive than are normal cells, making cryotherapy an attractive therapy for endobronchial malignancies.

The indications for cryotherapy are similar to those for laser and EC; however, each type of therapy has unique properties that may make one indicated over another in specific cases. Cryotherapy has been used most often for local therapy in the palliation of airway malignancies, and is also successfully used in benign airway conditions. It is effective in treating airway stenosis caused by excessive granulation tissue after lung transplant, and was reported to decrease the percentage of patients who required stent placement. Cryotherapy is excellent for papillomas as they are quite cryosensitive. It is successful in removing foreign bodies from the airway, especially objects that are friable or tend to fall apart with forceps. The object is frozen and then removed from the patient’s airway with the probe and scope as one unit. This technique can also be used when removing blood clots and mucous plugs. Cryotherapy can decrease the risk of hemorrhage if performed prior to the biopsy of a suspected carcinoid lesion.

The lesions best treated with cryotherapy (whether they are benign or malignant) tend to be polypoid in nature and short in length, and they have a large endobronchial component. Long tapering lesions, bulky endobronchial lesions, or those with extensive submucosal involvement are not as favorable. Cryotherapy offers no benefit to patients with obstruction from pure extrinsic compression of the airway.

The advantages of cryotherapy are that it is a procedure that is easy to learn, relatively inexpensive (as compared with laser therapy), and safe. In comparison with laser or electrocautery, it does not have the danger of causing endobronchial fire. It is superior to modalities for distal lesions, as the risk of airway perforation is much lower. The cryoresistance of the bronchial tissue surrounding the lesions explains the safety of using cryotherapy. The main disadvantage of cryotherapy is that its effects are not immediate. It can take up to 2–4 weeks to show its maximum benefit and usually requires repeated bronchoscopies for follow-up and retreatment.

Balloon Dilation

In the past, non-emergent cases of airway stenosis have been treated by introducing rigid bronchoscopes of increasing diameters or by dilation by semirigid dilator. These techniques have been largely replaced by the use of BD performed using either rigid or flexible bronchoscopy. BD is an effective procedure to restore patency of airways that are narrowed from either benign or malignant processes. The great benefit of BD is that it is a relatively nontraumatic and rapid procedure to use in airway strictures. It is most frequently used in combination with other endobronchial techniques, but may be used alone in selected cases.

The balloon catheter is passed through the working channel of the bronchoscope or threaded over a guide wire (using the Seldinger method) and placed across the stenosis, with the balloon protruding slightly beyond either end. The balloon, which is slightly larger than the stenotic area, is then gradually inflated with water for 30–120 seconds at increasing pressures. Fluoroscopy has traditionally been used to monitor the inflation, but has been shown to be unnecessary when the stenotic region is visualized bronchoscopically. Serial dilations are performed with the same balloon or with one of a larger diameter until the airway lumen is restored. It is best to be able to visualize the airway distal to the stenosis to assess which size balloon should be used. This therapy has been shown to be best suited for stenotic areas that are short in length. Patients with transmural strictures that occupy a long segment of the airway usually require either surgical or stent therapy.

The major disadvantage of BD is that, although it can immediately dilate both intrinsic and extrinsic lesions, the results are usually not sustainable. Complications are rare, but include chest pain during inflation, bronchospasm, or atelectasis. Other possible complications include airway rupture or laceration by excessive balloon inflation, pneumothorax, pneumomediastinum, or bleeding.