Rapid ablative techniques refer to various thermal therapies used to treat endobronchial diseases which have their effect almost immediately. They include laser, electrocautery, and argon plasma coagulation (APC). They are most appropriate for lesions within the airway lumen causing obstruction or hemoptysis. Rapid ablative techniques can be used alone or in combination with delayed ablative techniques and mechanical debridement. This chapter will briefly discuss general indications and technical considerations for the rapid ablative techniques and then provide more detailed information about each of the three commonly used rapid ablative methods. Mechanical debridement and delayed ablative techniques will be reviewed elsewhere in this book.
General Considerations for Rapid Ablative Techniques
Rapid ablative techniques are primarily indicated for palliative treatment of endoluminal lesions of the central airways. They are effective for obstruction caused by both malignant and benign lesions as long as the obstruction is caused by endoluminal disease. Rapid ablative techniques are not indicated to treat central airway obstruction (CAO) caused primarily by extrinsic compression. Complex lesions with both extrinsic compression and endoluminal obstruction are optimally treated with multimodality therapy including rapid ablative techniques for the endoluminal component followed by mechanical dilation or stenting for residual obstruction after the endoluminal portion of the lesion has been ablated. Rapid ablative techniques are also very effective for hemoptysis arising from a central endoluminal source. Rapid ablative techniques have also been used for local control of minimally invasive endobronchial tumors when more established and definitive therapies such as surgery or radiotherapy are contraindicated.
General Technical Considerations
Several anatomic characteristics of endobronchial lesions predict their suitability for treatment with rapid ablative techniques. The most important of these is a predominant endoluminal component. The presence of normal lung distal to the obstructing lesion with an intact distal blood supply is also important. Pedunculated or polypoid lesions are better candidates for rapid ablative techniques than sessile ones. It should also be recognized that lesions of the central airways are most amenable to rapid ablation, and conversely lesions present in the upper lobes are more difficult to treat with these methods.
Rapid ablative techniques can be used with both rigid and flexible bronchoscopes. Advantages of ablation through the rigid bronchoscope include better control of the airway, availability of additional therapeutic options, better suction, and the ability to isolate a bleeding area while ventilating the contralateral lung. Advantages of ablation with the flexible bronchoscope include familiarity to most pulmonologists, ease of use, better access to distal airways and the upper lobes, and the ability to intervene through an endotracheal tube when required. In practice introducing the flexible bronchoscope through the rigid instrument allows the interventional bronchoscopist to enjoy the advantages of both techniques when rigid bronchoscopic intubation is utilized as the initial therapeutic modality.
Because all of the rapid ablative therapies discussed here use thermal energy to destroy endobronchial lesions and achieve hemostasis, the fraction of inspired oxygen (F io 2 ) must be reduced to 40% or less to reduce the risk of airway fire. In addition to reducing the F io 2 , frequent venting or suctioning of the gases produced by thermal destruction of tissue is recommended as the gases may be volatile and ignite if allowed to persist in high concentrations. Additionally the electric current utilized for ablation with electrocautery and APC requires grounding and may affect the function of implanted medical devices. Laser may be preferred in patients with such devices if feasible. Staffing for therapeutic bronchoscopy requiring ablative techniques should include at minimum a nurse, a technician, and the bronchoscopist. It is usually prudent to perform complex cases with anesthesia support if the need for ablation is recognized beforehand. Therapeutic bronchoscopy for malignant CAO using moderate sedation is associated with a higher complication rate than therapeutic bronchoscopy using general anesthesia.
General Principles of Laser Bronchoscopy
Laser is an acronym for light amplification by stimulated emission of radiation. There are three properties of laser light that make it useful in medicine. First, it is monochromatic—of a single wavelength and color. Laser is also coherent, indicating a tightly focused beam. Finally, laser is collimated, meaning that the beam stays narrow over distance. Laser light may interact with tissue in a variety of ways. These include conversion into thermal energy, the stimulation of biochemical reactions within tissue, and being reflected or scattered at the surface of the tissue. The wavelength of the laser determines which of these effects is predominant, and most lasers used in bronchoscopy are those which produce a thermal effect on tissue resulting in cutting, coagulation, and vaporization.
For a laser to be useful in bronchoscopy a delivery system that allows it to be used within the airway is needed. Most of the lasers used in bronchoscopy can be delivered via optical fibers, and both rigid and flexible probes are available. The ratio of absorption and scattering coefficients in soft tissue also determines the effect of a given laser. Increased absorption relative to scattering produces cutting effects, while increased scattering leads to more coagulation. The tissue effect is also determined by the power, duration of exposure, and distance from the tissue of the laser fiber. The CO 2 laser was the first used in medicine and remains popular in otolaryngology due to its ability to cut with great precision. However, its utility in bronchoscopy is limited since it is not suitable for transmission by optical fibers and requires a rigid delivery system and it is also poor at achieving hemostasis because of its very shallow depth of penetration. The neodymium:yttrium aluminum garnet (Nd:YAG) laser is the most commonly used and studied in bronchoscopy. It is able to achieve excellent coagulation and even vaporization of tissue, and its shorter wavelength is suitable for transmission through flexible optical fibers. Other lasers used in bronchoscopy include neodymium:yttrium aluminum perovskite (Nd:YAP), holmium:yttrium aluminum garnet (Ho:YAG), argon, thulium, and diode lasers. Each has distinct tissue effects determined by the wavelength of light used and the way it interacts with tissues. Characteristics of some commonly used medical lasers are summarized in Table 8.1 .
|Type of Laser||Wavelength (nm)||Coagulation||Cutting and Vaporization||Depth of Penetration (mm)||Typical Power Settings (W)|
|CO 2||10, 600||+||+++||<1||4–8|
As discussed earlier, selection of patients for bronchoscopic laser ablation should begin with an assessment of the lesion. Raised endoluminal lesions of the central airways are ideal. The respiratory status of the patient should also be assessed to determine whether or not the patient can tolerate hypoxemia since the safe use of laser requires that the F io 2 be reduced to 40% or less. Because lasers deliver thermal energy by light and not electricity, laser is safe for use in patients with pacemakers or other implanted cardiac devices.
Laser console with foot pedal to activate the laser
Reusable or disposable optical fiber to carry the beam (both rigid and flexible fibers are available, as are contact and noncontact probes)
Safety glasses for the specific wavelength of light used by the laser.
Technique of Laser Bronchoscopy
When planning a laser procedure it is of critical importance for the bronchoscopist to know the patient’s anatomy and maintain good orientation in the airway at all times. The F io 2 should be reduced to 40% or less before activating the laser. All personnel present in the procedure suite must wear safety glasses prior to activating the laser. Typical settings for laser bronchoscopy include power of 20–40 W and a pulse time of 0.4–1 s for the Nd:YAG laser, but exact setting varies based on the type of laser. The bronchoscope is advanced until the target lesion is visualized, and then the fiber is extended beyond the tip of the scope by at least 4 mm. Only then should the assistant arm the laser.
The bronchoscopist should orient the axis of the laser fiber parallel to the long axis of the airway to reduce the risk of perforation. Treatment should begin with the fiber at least 0.4–1 cm away from the target and start with short-duration pulses. The effect of laser on the tissue is then evaluated, and if more effect is desired the fiber can be moved closer to the target lesion or longer pulses can be used. Large obstructing lesions can be coagulated using a lower power setting prior to mechanical debulking (see Fig. 8.1 ). This method of coagulation using thermal ablation followed by mechanical debulking is repeated in an iterative manner to progressively resect larger tumors. The bronchoscopist is essentially shaving the tumor down by coagulating, then resecting the tumor, and then repeating the process until the airway is open. Smaller or friable tumors can be vaporized using higher power settings. Prolonged firing or firing in an axis other than parallel to the airway increases the risk of perforation with attendant bleeding and respiratory failure and should be avoided.
Complications of Laser
Hemorrhage (immediate and delayed)
Precautions and Pearls
Laser can cause airway fire when used in an oxygen-rich environment. The F io 2 must be decreased to 40% or less when using laser. Clear verbal communication with the procedure assistant or anesthetist is critical to confirm that the F io 2 is at an acceptable level before activating the laser. Closed-loop communication is recommended, meaning that the bronchoscopist should give an order specifying the F io 2 desired and the anesthesiologist should repeat and confirm the message once the F io 2 is adjusted prior to any thermal ablation.
Laser is best for pedunculated or protruding lesions. Because it delivers energy as light the beam travels straight ahead in the axial plane, so radial firing is not possible. This makes treating sessile mucosal lesions difficult.
Laser is good for deeper tissue penetration when compared to APC, but this increases the risk of perforation relative to APC. Treatment of the posterior tracheal and mainstem bronchial walls imparts increased risk of perforation and should be considered with caution.
Laser is preferred over electrocautery and APC in patients with implanted cardiac devices because the light beam transmitting thermal energy does not affect them in the way that electric current does.
Different lasers have different effects based on the wavelength of their light. Be familiar with the device you are using and its characteristic tissue interactions.
Numerous case series demonstrate the effectiveness of laser for CAO and bleeding, although few of these studies have been randomized or controlled. It is also important to remember that most recent studies report data on procedures that are multimodality, using a combinations of thermal techniques (e.g., laser plus electrocautery) with combinations of mechanical debridement techniques (e.g., coring out and forceps) with or without stenting. Effectiveness measures and complications reported are really a reflection of the multimodality approach, and it is difficult to dissect how different parts of the multimodality approach impact outcomes. Given these limitations, Cavaliere and colleagues reported the results of almost 1400 laser procedures in 1000 patients, with 64% having malignant CAO. Significant improvement in airway lumen size or ventilation was seen in over 90% of patients with malignant bronchial tumors, but symptoms were not measured with validated instruments in these early studies. Performance status in similar patients with malignant CAO was also significantly improved by laser treatment. Treatment with Nd:YAG laser followed by radiotherapy in 15 patients with inoperable lung cancer and CAO requiring emergent treatment led to increased survival compared to radiotherapy alone in 11 historical controls. However, when assessing efficacy and complication rates, it is important to recognize that complication rates for therapeutic bronchoscopy vary by indication. Patients with malignant CAO have higher complication rates than those with benign airway disease undergoing therapeutic bronchoscopy. The AQuIRE multicenter registry evaluated 1115 procedures in 947 patients with malignant CAO undergoing therapeutic bronchoscopy using multimodality approaches. Laser bronchoscopy was utilized in 24% of cases. They found that 93% of procedures resulted in technical success, defined as significant anatomic improvement in airway obstruction (<50% residual obstruction). Clinically significant improvement in symptoms occurred in 48%. The overall complication rate was 3.9%, but there was significant variation between centers (range 0.9%–11.7%). Risk factors for complications included use of moderate sedation, urgent or emergent procedures, American Society of Anesthesiology score >3, and redo therapeutic bronchoscopy cases. Limited data are available on the impact of therapeutic bronchoscopy on quality adjusted survival. In a prospective observational study of 102 patients with malignant airway obstruction, anatomic technical success was achieved in 90% of cases, resulting in decreased dyspnea at 7 days (mean change in Borg score −1.7) and improved health-related quality of life (HRQOL) (change in utility at 7 days + 0.047 utiles, P = 0.0002). Improvements in dyspnea and HRQOL were maintained long term. Data on impact of therapeutic bronchoscopy using laser on quality adjusted survival in benign disease are currently lacking. Overall, the data suggest that the efficacy and safety profile of bronchoscopic laser treatment as part of a multimodality airway approach is acceptable in experienced hands, with overall complication rates ranging from 2.3% to 8.4% in the largest series.
Laser is a safe and effective method for relieving CAO and treating bleeding in the airways. It is expensive and requires special eyewear, but does not affect implanted medical devices and has a long track record of safety.
General Principles of Bronchoscopic Electrocautery
Electrocautery uses high-frequency electrical current to generate heat which then coagulates and destroys tissue. Contact between the cautery instrument and the tissue is required for the thermal effect. Because the heat is generated by an electrical current the patient must be grounded to avoid shock and allow the current a safe way to exit the body. The tissue effect is determined by voltage, duration, area of contact, tissue density, and the water content of the tissue.
Different electrocautery devices are used for different purposes. Common instruments used for electrocautery include a blunt probe, hot forceps, cautery knife, and cautery snare. The flexible blunt probe is used to coagulate and destroy tissue with direct contact. Rigid electrocautery blunt probes function similarly. In addition, there are rigid electrocautery-suction probes that provide the additional benefit of providing electrocautery coagulation and destruction while simultaneously suctioning the airway of blood. The hot forceps are able to deliver heat while a transbronchial or endobronchial biopsy is being taken (see Fig. 8.2 ). The cautery knife is used to precisely cut through tissue and is particularly good at disrupting benign webs causing airway stenosis (see Fig. 8.3 ). The cautery snare is used to grasp pedunculated lesions at the base to facilitate rapid removal.