BT is performed using the Alair Bronchial Thermoplasty System^® (Boston Scientific, Marlborough, MA). The system is composed of two principle components (Figs. 33.1 and 33.2):

The Alair catheter is a sterile, single-use device that is introduced into the airways through the working channel of an RF-compatible bronchoscope. The bronchoscope should ideally have an outer diameter of 4.9–5.2 mm and a working channel ≥2.0 mm [17]. The catheter has a distal 4-arm electrode wire array that expands to contact the airway wall when the proximal actuator is activated. The catheter is connected to the RF controller by a cable attached to its proximal end. The controller also has inputs for the footswitch and the patient return electrode. The footswitch allows the bronchoscopist to initiate delivery of RF energy. The return electrode completes the circuit, providing a pathway for the return of electrical current. This gel electrode is typically placed on the patient’s chest or thigh. The RF controller delivers RF energy to the expanded 4-arm array in contact with the airway wall for a duration of 10 s. The RF controller utilizes sensory data from the catheter to limit current, power, voltage, time, and temperature of the RF energy delivered. This allows for the proper intensity and duration of RF energy to be applied while minimizing collateral airway damage. If the bronchoscopist determines that early termination of RF energy is needed, the footswitch can be pressed and released a second time to cease energy delivery [19]. The RF controller also safeguards against incorrect device setup. If any of the individual components are incorrectly connected, or the catheter electrodes fail to contact the airway wall, the device will not deliver RF energy.

BT is performed under conscious sedation to a moderate level or general anesthesia. Visible airways distal to the main stem bronchi are treated by activation of the RF probe against nonoverlapping adjacent airway segments. Airways between 3 and 10 mm in diameter are systematically targeted, starting distally and moving proximally, being careful to avoid overlap with areas already treated [16, 19, 20]. Three sequential procedures are performed with a minimum interval of 3 weeks between each procedure. This allows for adequate healing of the airways between treatments and minimizes the likelihood of an asthma exacerbation [17]. Each treatment addresses a separate lobe, with the exception of the right middle lobe (RML). The RML remains untreated due to its narrow opening and the theoretical concern that inflammation related to the procedure may result in the development of RML syndrome [21]. However, recent experience suggests that the RML can be treated safely [22]. The right lower lobe is treated first, followed by the left lower lobe. Finally, both the right and left upper lobes are addressed in a single treatment. Each treatment takes approximately 45 min to 1 h to perform [16].

In order to facilitate successful BT, adequate pre-procedure preparation is essential. Pre-procedure preparations include (1) reassessing asthma stability and status on the day of each procedure; (2) administration of oral steroids (prednisone 50 mg daily) 3 days before, on the day of, and after each procedure; and (3) administration of inhaled bronchodilators, antisialagogues, anxiolytics, sedatives, and topical anesthetics to facilitate an uneventful procedure.

Clinical assessment of the patient on the day of the procedure is the first step in performing BT. The patient should have no contraindications to routine bronchoscopy. It is imperative to rule out current respiratory tract infections and ensure that the patient has not had a severe asthma exacerbation within 2 weeks of performing the procedure. Finally, the patient should be at baseline with respect to their asthma symptoms and pulmonary function testing performed on the day of the procedure by confirming that the patient’s FEV₁ is within 15% of their baseline value [18, 23]. If any of the recommended criteria are not met, bronchoscopy should be postponed.

To reduce inflammation resulting from the application of thermal energy, patients are prescribed oral corticosteroids (equivalent to 50 mg/day of prednisone) starting 3 days prior to the procedure, on the day of the procedure, and for one day following the procedure [17]. Patients on chronic oral steroids should be increased to the level used to treat their exacerbations. Antisialagogues are administered on the day of the procedure to reduce salivary and tracheobronchial secretions. At our institution, the antimuscarinic agent glycopyrrolate (0.2–0.4 mg IV/IM) is administered a minimum of 30 min prior to initiation of the procedure. Lastly, bronchodilators are administered prior to the procedure to help ameliorate bronchospasm. We make use of nebulized albuterol (2.5–5.0 mg), but albuterol may also be dispensed through a metered-dose inhaler (four to eight puffs) [24].

Maintaining adequate analgesia and proper sedation during BT is necessary because each procedure lasts for up to 1 h. At our institution sedation is accomplished with the combination of a short-acting benzodiazepine and a short-acting narcotic, specifically midazolam (Versed) and fentanyl (Sublimaze). Midazolam (1–2 mg IV initial bolus followed by repeated 1–2 mg IV doses) and fentanyl (50–100 mcg IV initial bolus followed by repeated 25–50 mcg IV doses) are administered alternately throughout the procedure. Sedation level is frequently reassessed during the procedure, and additional sedation is administered as needed. Benefits of this specific drug combination include familiarity with the drugs, rapid onset of action of both agents and their additive effects, convenient dose titration, and the ability to rapidly reverse either agent if needed [18]. Other agents including propofol have been utilized for sedation. Some centers have utilized general anesthesia administered with anesthesiologist assistance. Ultimately, the final decision on sedation is dependent on the physician performing the procedure and institution-specific guidelines.

In order to suppress the cough reflex during bronchoscopy, topical anesthetics are administered prior to and during the procedure. At our institution, anesthetization of the upper airway is achieved using 4 mL of 2% lidocaine nebulized through a mask prior to the procedure. Next, the posterior pharynx and laryngeal area are anesthetized with 5 mL of 1% lidocaine using a syringe with blunt-tip catheter directed over the back of the tongue. The bronchoscopy is initiated, and the bronchoscope is advanced to the level of the vocal cords, which are directly anesthetized with two to three 2 mL aliquots of 1% lidocaine delivered through the working channel of the bronchoscope. Finally, the trachea, carina, and each of the main stem bronchi are anesthetized with 2 mL aliquots of 1% lidocaine until the patient appears comfortable and exhibits minimal coughing. When the bronchoscope is advanced into the airway segments targeted for treatment, additional 2 mL aliquots of 1% lidocaine can be administered. During the procedure it may be necessary to administer additional targeted doses of lidocaine utilizing the intervals when the catheter is removed from the bronchoscope for suctioning. In our experience, the use of 1% lidocaine limits the potential for toxicity. While elevated levels of lidocaine have occurred, toxicity is rare. Lidocaine doses in the range of 400–600 mg (9 mg/kg) appear to be safe in asthmatic patients undergoing bronchoscopy as long as patients are monitored continuously for evidence of toxicity [25, 26]. Signs and symptoms of toxicity include lightheadedness, dizziness, headache, visual disturbances, metallic taste, muscular twitching, tremors, perioral tingling, auditory disturbances, seizures, or loss of consciousness [27].

Due to the length of the procedure and the level of sedation required, the use of an airway device may become necessary. An endotracheal tube (ET) can be used to maintain a patent airway and minimize the number of desaturations but runs the risk of irritating the asthmatic airways, potentially triggering bronchospasm. At our institution, a laryngeal mask airway (LMA) is used when performing BT. It does not enter the trachea, protects the upper airway, and provides comparable benefits to an ET tube. Ultimately the discretion of the bronchoscopist and their level of comfort with the various airway devices will determine which device is optimal.

Pathway planning is performed at the beginning of each BT procedure. This is essential and guarantees that no targeted bronchopulmonary segments are missed during each procedure. It also ensures that each targeted segment is treated once, and only once, and that no overlapping ablations are performed. Pathway planning is accomplished by inspecting, identifying, and mapping out the segments targeted for treatment. A systematic, methodical, and consistent approach is key, working from distal airways to proximal and from airway to airway across the lobe being treated to ensure that all accessible airways are identified and treated only once [17, 18]. Within each segment, subsegmental airways should also be identified and treated. We recommend moving from superior airways to those that are more inferior or from airways to the right of the field of view toward those to the left. Diagrams of the tracheobronchial tree can assist in both planning BT and documenting treated airway segments (Fig. 33.3).

Once planning is complete, RF ablation may be initiated. The bronchoscope is directed into the desired segment or subsegment of the lobe under visualization. The Alair catheter is deployed through the working channel of the bronchoscope into the targeted area under direct bronchoscopic visualization until the desired location is reached. The diameter of the non-expanded catheter is 1.5 mm and is used to determine the diameter of the targeted airways. Once the catheter tip is at the desired location, the actuator is gripped allowing the arms of the catheter array to expand into contact with the airway wall. The degree of pressure applied to the actuator is determined by visualization of the expanding array in more proximal airways, while resistance guides the bronchoscopist in more distal segments where visualization is not possible. Once all four electrode wires are firmly in contact with the airway wall (Fig. 33.4), the footswitch is depressed (activated) and released and RF energy is delivered automatically for approximately 10 s [17, 23]. The actuator is then released, partially collapsing the electrode array, and the catheter is retracted 5 mm proximally. This distance corresponds to a set of black markings present on the distal end of the catheter just proximal to the electrode array. These markings guide withdrawal of the catheter during the BT ensuring that the electrode array is positioned adjacent to, but does not overlap, the previous activation site (Fig. 33.5). If contact with the airway walls is not adequate during an attempted activation, a different audible signal will be emitted from the RF controller notifying the bronchoscopist. In these instances, the array will need to be collapsed and the catheter will need to be repositioned prior to retreating that particular area. The airways are always treated from the smaller more distal subsegments all the way to the most proximal main lobar bronchi. The usual number of activations per treatment session varies, and the usual range for successful activations is between 50 and 100 per lobe.

In our experience, and based on the manufacturer’s recommendations, the following may assist when performing BT:

The technique for the second and third treatments is identical to the first with one important addition. Prior to initiating the second and third treatments, the lobe treated at the previous session must be inspected before starting pathway planning to evaluate for airway secretions or inflammation that may require suctioning or postponement of the current treatment.

After BT is completed, normal post-bronchoscopy monitoring is performed, often in conjunction with institution-specific practice guidelines. Because of the increased doses of sedation required for the prolonged bronchoscopy, patients should be monitored for the presence of an intact gag reflex and tolerance for oral liquids on recovery from sedation. In addition, patients undergoing BT must have serial post-procedure FEV₁ tests performed after bronchodilator administration. In order to be discharged home, the post-procedure FEV₁ should be ≥80% of the pre-procedure post-bronchodilator value. Upon discharge, patients need to be advised of potential adverse events and reminded to take their remaining prophylactic steroid doses. Since patients undergoing BT have severe asthma, worsening of respiratory-related symptoms, including wheezing, dyspnea, chest discomfort, and cough, is not uncommon following the procedure [20, 28]. These typically occur within 1–2 days of treatment and resolve over 1 week with standard treatment with bronchodilators and systemic steroids. As a result, patients should be contacted at 24 h, 48 h, and 1 week post procedure to assess their respiratory status. Alternatively, very severe or labile asthmatics may be admitted overnight to the hospital for observation. Lastly, the patient should be assessed at a clinic visit 2–3 weeks after the procedure to determine whether they are stable for the next BT [23].