Fig. 8.1
(a–d) Extrinsic/intrinsic stenosis before and after treatment
Management of critical central airway obstruction requires initial stabilization of the patient with secure access to the airways to permit ventilation. Further interventions can then be considered. In a stable patient, imaging studies and pulmonary function tests should be obtained as mentioned above. In patients with severe tracheal or bronchial obstruction and limited lung function, flexible bronchoscopy can be performed only after the airway has been secured (orotracheal tube/deep sedation or general anesthesia) and appropriate gas exchange documented. During the bronchoscopic examination, the airway is inspected, lesions are assessed, distal secretions are suctioned, and diagnostic samples are obtained if needed. This information is used to plan further interventions aimed at opening the airways and maintaining patency. After the patient has been stabilized, he should be transferred to an interventional pulmonary department where a dedicated team is available.
In case of severe tracheal obstruction, the use of the open ventilating rigid bronchoscope is the preferred method of airway control. The rigid bronchoscope not only provides a secure airway during visualization but is also a therapeutic tool. It is the preferred instrument for unstable patients especially when significant bleeding can be expected. The airway can be dilated with the barrel of the scope [2]. During this procedure, the patient is intubated with the instrument under general anesthesia. The optical telescope is advanced through the stenotic airway opening and the barrel then pushed through the obstruction in a rotating motion. Bleeding is usually minimal due to compression of the lesion by the rigid scope (Fig. 8.2). In one session, using the rigid bronchoscope under general anesthesia, immediate good results can be achieved: bronchial recanalization with improvement of ventilation and drainage of post-stenotic secretions. Dilation is immediately effective for intrinsic and extrinsic lesions, but the results are usually not lasting. For this reason, multimodality approaches featuring a combination of several interventions are preferred for their mucosal sparing effects and long-term success over dilation alone [1–3]. The number and scope of therapeutic options have increased dramatically, and a given intervention must be chosen carefully in the context of an individual patient’s situation. They can be divided into “slow methods” such as photodynamic therapy, cryotherapy, and brachytherapy or fast methods: laser, argon plasma coagulation (APC), and electrocautery (EC). Fast methods will be the topic of this chapter whereas slow methods are described elsewhere in this book. Laser therapy more often integrates rigid bronchoscopic resection; this procedure is worldwide known as laser-assisted mechanical resection (LAMR) and represents the safest and more effective way to obtain all potential effects of laser in bronchoscopy. Some authors use laser with the flexible bronchoscope with limited safety and efficacy if compared to LAMR [14]. Different operating modalities allow tissue-light interaction with diverse thermal tissue modifications such as vaporization, coagulation, resection, or incision of obstructing lesions [15]. Laser therapy was originally indicated for short endobronchial central airway lesions with a visible distal lumen. Bronchoscopists who become familiar with the technique will use it even in complete stenoses where the distal bronchial tree can only be reached using the suction tube and the rigid bronchoscope basing upon precise knowledge of the anatomy and preferably with support from CT scan images. In these cases the combination of rigid bronchoscopy and laser firing is crucial. The technique is most commonly applied in cases of malignant intrinsic airway obstruction or in post-intubation tracheal stenosis. The effects upon airway lumen size are usually immediate and accompanied by excellent control of bleeding.
Fig. 8.2
Tumor resection with the rigid bronchoscope
EC and APC also rely on thermal tissue destruction. With EC, a high-frequency current is applied to the lesion with bipolar probes. When the current is directly applied to the tissue, heat develops and leads to tissue necrosis. EC is traditionally defined “the poor man’s laser” since it can mimic the effects of laser firing when vaporization and resection are needed with a less expensive equipment. APC is a related therapeutic intervention. Argon gas is emitted through a flexible Teflon tube. This gas is ionized because of exposure to high-frequency current and an electric arc is formed which allows for desiccation and tissue destruction. It is a valuable tool in treating superficial bleeding and debulking granulation tissue and tumors. Indications, equipment, application, and outcomes of these techniques will be extensively discussed hereafter.
Laser-Assisted Mechanical Resection
History and Historical Perspectives
1897—Gustav Killian performed the first rigid bronchoscopy to remove a pork bone from the right main bronchus of a young man [16].
1907—Few years later, in the USA, Chevalier Jackson published his landmark book Tracheobronchoscopy, Esophagology and Bronchoscopy [17].
1987—Dumon designed a flexible, multisized, studded silicone stent that gained worldwide popularity in the field of operative rigid bronchoscopy [18].
Nonetheless, until the early 1980s, the endoscopic treatment of central airway obstructions was hazardous and often inadequate. Mechanical resection was performed using the rigid bronchoscope and rigid biopsy forceps with high risk of bleeding. Even when successfully managed, it provided only short-term results. Endoscopic electrosurgery and cryotherapy were then introduced to reduce the risk of bleeding and prolong palliation. These methods though provided only delayed recanalization also carrying an unpredictable risk of damage to the adjacent healthy tissue.
1982—The advent of laser immediately proved very useful in reducing hemorrhages. Once an appropriate technique for the treatment of the implantation base was developed, laser coagulation in depth proved also quite effective in prolonging palliation in central airway obstruction due to lung cancer.
Bronchoscopic mechanical resection turned then into laser-assisted mechanical resection (LAMR). Nowadays, LAMR through rigid bronchoscopy remains the best tool for the safest management of airway obstructions.
Indications and Contraindications
Bronchoscopic laser resection (LAMR) can relieve malignant and benign intraluminal tumors, particularly exophytic proximal airway lesions, but it has no role when the obstruction is caused by pure extrinsic compression [19, 20]. Laser is also useful in the treatment of benign diseases such as cicatricial tracheobronchial stenoses.
Malignant and Benign Tumors
Airway obstruction from bronchogenic carcinoma is the most frequent indication for laser resection. It is typically employed in patients who have exhausted their therapeutic options, although some may be eligible for salvage chemotherapy, brachytherapy, or surgical resection [2, 3, 21].
Other malignant causes of central airway obstruction that have been managed by laser resection include the so-called low-grade malignancy such as adenoid cystic carcinoma, mucoepidermoid carcinoma, and bronchial carcinoids. Finally, common indications for LAMR are endobronchial metastases from melanoma, colon, kidney, and breast cancer [22, 23].
The major aim of laser therapy in malignant central airway obstruction is to recanalize the tracheobronchial tree and restore adequate ventilation with subsequent drainage of post-stenotic secretions. It is the location and macroscopic appearance of a tumor, rather than its histological type, which determine whether or not laser therapy can be useful. Because of their immediate accessibility and severe impact on ventilation, the best results are obtained in tumors located in the trachea or main bronchi, which is in fact where obstruction causes the greatest respiratory distress. On the contrary, tumors obstructing segmental bronchi do not impair ventilation to the degree that severe symptoms are produced. Furthermore reduced accessibility with the laser fiber and the thin walls of these bronchi increases the difficulty of laser delivery and the risk of perforation. The sole indications for laser disobstruction of segmental bronchi are prevention of bleeding in case of highly vascularized lesions, drainage of distal purulent secretions (postobstructive pneumonia), and cure of benign tumors.
It is very important for the endoscopist to identify the base of the obstructing endobronchial tumor. Polypoid tumors are easy to remove and often completely resectable (Fig. 8.3a, b). Intraluminal tumors with infiltration of the airway wall cannot be treated completely. Though, if the airway lumen is not seriously reduced by tumor infiltration, ventilation is usually not impaired appreciably, and laser resection may not be necessary.
Fig. 8.3
(a, b) Polypoid lesions
For occluding endobronchial tumors with significant extraluminal (even mediastinal) growth, laser treatment alone is frequently unsuccessful. Although the endoluminal component may be initially successfully removed, the airway is quickly re-obstructed as a result of further growth, extrinsic compression, and/or endobronchial migration of the tumor. In these cases, laser treatment is to be considered as preliminary to stenting, or, if the extraluminal component is only limited in depth and not compressing, brachytherapy might prove useful. Pure extrinsic compression is a major contraindication for endoscopic laser treatment, being it amenable to immediate stenting.
Regardless of impact on ventilation, location, or macroscopic appearance, vascular tumors producing hemoptysis represent a good indication for laser bronchoscopy. Although the tumor is often not completely resected, short-term reduction or ceasing of bleeding occurs systematically after laser coagulation.
In all of the previous conditions, endoscopic resection allows a precise assessment of the extent of the tumor, shifting to surgery patients originally considered to have inoperable disease or allowing lung-sparing resections [24].
The combination of endobronchial laser therapy with other palliative therapies is possible and can be extremely advantageous. The addition of radiotherapy is particular useful either by external beam radiation or endobronchial brachytherapy, with extension of the palliation. When indicated, laser resection will be performed before radiotherapy, because preventive laser recanalization of obstructed airways allows improved functional status. Furthermore, it is well known that radiotherapy and chemotherapy are poorly effective on the endoluminal component of the tumor [7, 8]. Similar therapeutic algorithms for the management of central airway neoplastic obstructions have been described by different authors [25, 26]. Figure 8.4 is an example [27].
Fig. 8.4
Algorithm for the management of malignant central airway obstruction
Tumors with Uncertain Prognosis
Tumors with uncertain prognosis lump together several tumors characterized by slow growth and rare tendency to metastasize; among these, carcinoid tumors, adenoid cystic carcinomas, and mucoepidermoid carcinomas are the most common in the airways. The same histological type can present with different grades of malignancy. As for malignant tumors, laser therapy is mainly palliative or in some cases useful for a better surgical assessment.
Local cure may exceptionally be achieved when the tumor has a small and localized base and a low-grade malignancy. This different therapeutic approach in relation to the different tumoral characteristics is to be considered only for typical carcinoid tumors. Atypical carcinoids, i.e., well-differentiated neuroendocrine carcinomas, can deeply infiltrate the bronchial wall and produce an appearance similar to the bronchogenic carcinoma. In most cases the tumor cannot be removed completely and recurrence after laser resection is expected. On the contrary, typical carcinoids can be considered as more benign lesions; their macroscopic and microscopic aspect is similar to benign neoplasms. They are defined as well-differentiated neuroendocrine tumors, normally growing exclusively inside the bronchial lumen as polyps with a narrow base. In these cases, laser-assisted mechanical resection (see further) can be curative [28, 29] (Fig. 8.5).
Fig. 8.5
Carcinoid tumor
Although rare, benign tumors are the best indication for laser therapy. If exclusively endoluminal, endoscopic laser resection should be the first therapeutic choice for such tumors, as they are usually polypoid and rarely recur if the tumor base can be well photocoagulated with the laser. Surgery should be limited to those cases with partial or exclusive extra bronchial growth.
Benign Conditions
Airway obstruction due to benign conditions may also be amenable to LAMR. Such lesions include inhaled foreign bodies, stenoses due to granulation tissue, intubation injuries, postradiation strictures, lung transplantation, tracheal or bronchial resection and anastomosis, or weblike strictures from inhalation injury; other possible conditions affecting the airway lumen are represented by benign exophytic disease with either mucosal infiltration or circumferential narrowing due to granulomatosis with polyangiitis (formerly called Wegener’s granulomatosis), amyloidosis, tuberculosis, or endometriosis [30].
Generally speaking, patients who have benign airway strictures due to causes other than infection should always be considered for open surgical resection [2, 3].
Candidates for bronchoscopic LAMR include those who are not candidates for open resection because of age, overall medical status, fear of surgery, severity of other underlying disease, or the extent, location, and degree of the stricture.
The advent of endoscopic therapy has deeply modified the approach to the management of iatrogenic tracheobronchial strictures [31, 32].
In particular immediate laser recanalization must be considered as the first choice treatment in severely symptomatic and progressive stenoses, putting the patient at risk of death. In such conditions, bronchoscopic recanalization could avoid urgent tracheotomy, which could be responsible for further damage to the trachea. It is almost always possible to obtain rapid and immediate good results, independently of the type of stenosis. Once the emergency has been handled, there will be more time to consider the best treatment strategy (Fig. 8.6a, b). In case of relatively indolent stenoses without severe ventilation impairment, endoscopic therapy should be considered as an alternative to open surgery when the latter is temporarily nonfeasible or contraindicated. Even, patients eligible for resection could benefit from a preliminary endoscopic treatment to allow stenosis stabilization and precise delimitation. Complications to open surgery such as granulomas or restenosis can be effectively treated endoscopically. In some selected simple stenoses (e.g., weblike stenoses or stenoses without cartilage involvement), stable good results can be achieved after laser-assisted mechanical resection, and surgery could no longer be necessary [33–38].
Fig. 8.6
(a, b) Severe tracheal stenosis
For the treatment of inflammatory strictures of the trachea, it has been recently proposed a combined technique using real-time bronchial endosonography to evaluate and limit the possible laser-induced damage during resection, but this procedure is affected by elevated costs and unavailability in most endoscopic centers [39, 40].
Also, cold instruments such as hand scissors have been proposed occasionally as an alternative to laser for cutting the stenosis radially. Compared with laser, the main advantages are the user-(more)friendly technology and low costs and the absence of thermal damage.
This method is apparently easy to perform and safe and facilitates the resection of simple stenotic scars. It should be considered cautiously though considering the small number of cases reported and should be corroborated by larger studies [41].
Description of the Equipment Needed
The word LASER is the acronym of light amplification by stimulated emission of radiation. The main components of a laser are the laser cavity, the pumped material, and the pumping system. The cavity is a reflecting cylindrical camera with mirrors at each extremity, one of which is partially reflective. When, inside the camera, an active substance is electrically or optically stimulated, it spontaneously emits photons, which are reflected by the mirrors through the active substance itself producing new photons with the same wavelength (and energy) and direction. The result of this stimulated radiation is a laser beam. The wavelength depends on the nature of the active material that is stimulated. For example, Nd:YAG laser emits in the infrared range at 1.064 nm.
The main characteristics of a laser beam are:
Coherence (the waves emitted are in phase)
Collimation (the waves are parallel to each other)
Monochromaticity (the waves are all of the same length)
These properties allow concentration, without loss of power, of the laser beam on a small target. When using laser, one should always have a precise knowledge of a few physical aspects:
Laser power is the power erogated by the laser and can be exclusively regulated through the leaser equipment. It is measured in watts (W).
Laser energy is affected by the time of exposition in a physically determined manner:
Laser Energy (Joule) = Power (Watt) × time (s)
Laser power density is strongly dependent on the extension of the impact surface:
Power Density (Watt/cm2) = Laser Power (Watt)/surface (cm2)
Releasing high power density can cut and vaporize living tissue. A lower power density laser can rather coagulate tissue determining necrosis or hemostasis without loss of substance.
The interaction between laser and living tissues also depends on many other factors, such as wavelength, distance from fiber to target, angle of incidence, color of impact surface, exposure time, absorption, and penetration in depth of the radiation. The thermal effects are the best known and the most used.
With regard to temperature, below 50 °C, we obtain tissue necrosis and inflammation, at a higher temperature vaporization is observed. Power density is inversely proportional to square distance. Penetration, which is inversely proportional to absorption, depends on the frequency of the radiation, tissue color, and its vascularization.
There are many types of biomedical lasers, including the carbon dioxide (CO2) laser, the neodymium-yttrium-aluminum-garnet (Nd:YAG) laser, neodymium-yttrium-aluminum-perovskite (Nd:YAP) laser, argon ion laser, excimer laser, potassium titanyl phosphate (KTP) laser, alexandrite laser, diode lasers, pulse dye lasers, and the most recent thulium laser.
CO2 laser was the first laser used in bronchoscopy. It is invisible (10,600 nm in infrared range) and is transmitted to the tissue through an articulate arm composed of mirrors. These characteristics limit its application in bronchial endoscopy. Biologically, tissue vaporization is precise and efficient because of low penetration in depth; yet low penetration determines poor hemostasis.
The laser that is most commonly used for bronchoscopic laser resection is the Nd:YAG laser. Its energy is delivered through flexible quartz fibers that are inserted through either a rigid or flexible bronchoscope. The wavelength of this laser (1064 nm) is invisible; thus, a red helium-neon beam is used to indicate where the laser energy will be applied.
It delivers sufficient power to vaporize tissue, also producing a good coagulating effect. The active substance is a crystal of yttrium-aluminum-garnet doped with neodymium.
A 1320 nm Nd:YAG laser is also available with greater cutting and vaporization effects, especially in low vascularized tissues with high water content.
Coagulation and vaporization are produced by a thermal effect, which is not limited to tissue surface: the laser beam can be transmitted as deep as 1 cm. Tissues, depending on the color of the surface and laser power density, differently absorb this radiation. The beam can pass through a pale and low vascularized tissue without a visible effect, but it will be absorbed by a dark surface limiting penetration in depth.
Diode laser is a differently conceived laser exploiting a semiconductor diode technology. When electric current passes through a diode, it emits a laser radiation. Diode technology reduces problems related to the laser cavity complexity, allowing the design of portable, compact, and high-power air-cooled lasers. It is available in different wavelengths (808, 940, 980, and 1470 nm). The 808 and 940 nm is exclusively absorbed by hemoglobin, making this laser very useful for treating highly vascularized tissues, but absolutely indolent if fired on a white surface. The 980 and 1470 nm is also well absorbed by water and so very effective when treating white tissues too.
In Nd:YAP laser , the active substance is yttrium-aluminum-perovskite, with a wavelength of 1.340 nm, which is absorbed by water 20 times more than the 1.064 nm of the Nd:YAG, thus providing a better effectiveness-power ratio. Coagulation is particularly good.
Thulium laser has more recently been considered for endobronchial application. The 2-μm wavelength emitted by Cyber TM (thulium) laser is strongly absorbed by water resulting in an outstanding coagulation and aero-hemostatic effects with preservation of the surrounding tissue. Since 2-μm laser wavelength is strongly absorbed by water, which is ubiquitous in all tissues, the speed of cutting and vaporizing will remain relatively constant regardless of tissue vascularization. Energy from the thulium laser penetrates only fraction of millimeter in the tissue, with a high degree of control and substantially reduced risk of inadvertent injury.
In practice, the ideal laser in bronchoscopy should be transmissible by fiber, safe, easy to set up and use, cheap, and portable. It should produce many and sometimes opposite specific effects: excellent coagulation so as to control bleeding and different resecting modes according to clinical occurrence. For cicatricial stenosis, mainly post-intubation tracheal stenosis, lasers should be as precise as a scalpel to spare the surrounding tissues; on the contrary, for endoluminal neoplastic masses, a vaporizing effect on large volumes is needed. More importantly, high penetration of energy without loss of substance, producing deep thermal damage and consequently a cytocidal effect, is required to treat the tumor base in depth and delay (malignant tumors) or even prevent recurrences. This is the principle for cure in benign, strictly endoluminal tumors, typical carcinoids, carcinoma in situ, and early cancers. All these characteristics do not perfectly coexist in the same laser, so the interventional pulmonologist has to choose the best compromise or use more than one tool.
Rigid Bronchoscopy
The rigid bronchoscope is a straight hollow stainless steel tube ∼40–45 cm long. Its caliber varies from 6.5 to 13.5 mm. The distal end of the rigid bronchoscope is beveled, allowing mechanical resection of obstructing lesions. The proximal end is conceived with several side ports where instruments can be placed or ventilation tubes can be connected. Zero-degree telescopes are the devices most commonly used to visualize the airway through the rigid scope. Angled telescopes are uncommon; more frequently a flexible bronchoscope can be used in combination with the rigid scope for lobar and segmental bronchi visualization.
The Efer-Dumon bronchoscope consists of a “universal head” to which multiple bronchoscope barrels of varying lengths and diameters can be attached (Fig. 8.7a). This bronchoscope is also designed to deploy endoluminal silicone stents using custom-made stent introducers (Fig. 8.7b).
Fig. 8.7
(a) An Efer-Dumon rigid bronchoscope set with the “universal head,” several bronchoscope barrels of varying lengths and diameters, a rigid 0° telescope, a pair of optic forceps, and a light wire. (b) A set of silicone stent delivery systems of different diameters
Application of the Technique
Most bronchoscopic laser resection will be performed via rigid bronchoscopy in the operating room with general anesthesia [28–30]. In fact laser therapy normally integrates rigid bronchoscopic resection; this procedure is worldwide known as laser-assisted mechanical resection (LAMR) and represents the safest and more effective way to obtain all potential effects of laser in bronchoscopy. Some authors use laser with the flexible bronchoscope with limited safety and efficacy if compared to LAMR. It is performed in a specially equipped bronchoscopy suite with topical anesthesia and conscious sedation [14]. During LAMR patient’s oxygenation and ventilation can be supported through the rigid bronchoscope by spontaneous-assisted ventilation or jet ventilation. Intermittent negative pressure ventilation (poncho) is another ventilation modality associated with lower incidence of complications such as acidosis due to hypercapnia [8]. Muscle relaxants and paralytic agents can be helpful during general anesthesia because they prevent the patient from coughing during the endoscopic maneuvers and they facilitate insertion of the rigid bronchoscope.
Ventilation System and Anesthesia
Originally, rigid bronchoscopy was performed during spontaneous-assisted ventilation with general intravenous anesthesia, which maintains spontaneous breathing [7]. Low levels of respiratory acidosis are virtually unavoidable with this method particularly during complex long-lasting procedures [8].
Positive pressure ventilation and jet ventilation are popular ventilation modalities but neither guarantees effective ventilation and safety, and both can limit surgical options. In addition, they carry the risk of intraoperative pneumothorax or pneumomediastinum [42].
Negative pressure ventilation (NPV) can safely be used as an alternative [43]. This procedure allows opioid sparing and a shorter recovery time, prevents respiratory acidosis, and avoids manually assisted ventilation while maintaining optimal surgical conditions [44] (Fig. 8.8).
Fig. 8.8
Intermittent negative-pressure ventilation (poncho)
Both external high-frequency oscillation (EHFO) and NPV ensure effective ventilation and comfortable operating conditions in the majority of patients. Some patients may receive inadequate ventilation with EHFO, developing respiratory acidosis and requiring manually assisted ventilation. In comparison with NPV, EHFO requires a higher fraction of inspired oxygen [8].
Effects of Laser and Laser-Assisted Mechanical Resection
The four main effects laser can provide are coagulation and resection, vaporization, and incision (Table 8.1).
Table 8.1
Laser techniques
Techniques | ||
|---|---|---|
Laser vaporization | Flexible bronchoscope | Up to 90% of cases. Time consuming but can be effective |
Rigid bronchoscope | Rare; for control of bleeding and vaporization of tumor remnants after mechanical resection | |
Laser resection | Rigid bronchoscope (LAMR) | To reduce risk of bleeding during tumor debulking |
Laser coagulation | Rigid bronchoscope | To prevent bleeding before mechanical resection |
To treat implant base in depth (up to 5 mm) and delay recurrence | ||
Radial incision | Flexible/rigid | Performed to reduce tension of cicatricial stenoses (before dilation if rigid scope is used) |
Laser resection is generally facilitated by the use of the rigid scope in the so-called laser-assisted mechanical resection already mentioned before.
Laser coagulation involves directing the laser at the target lesion, devitalizing the lesion via photocoagulation of the feeding blood vessels, so that the devitalized tissue can be more easily removed with the beveled edge of the bronchoscope, forceps, or suction minimizing the risk of bleeding. Coagulation is possible because the laser penetrates tissue to a depth of up to 10 mm in an inverted cone fashion and provides reliable photocoagulation at this depth. Moving the laser closer to or farther from the target tissue can alter its power density.
Vaporization is possible because energy from the laser is relatively well absorbed by water. It involves aligning the laser parallel to the bronchial wall and aiming at the edge of the intraluminal lesion (the laser should never be discharged perpendicular to the airway wall because of an increased risk of perforation). It can also be performed through the flexible scope; in this setting laser pulses of only 1 s or less are used to vaporize the tissue to prevent thermal injury to the scope and airways. On the contrary, when performed in rigid bronchoscopy, laser can be used for longer periods of time reaching higher temperatures with higher power densities. This is possible because the suction tube inserted through the scope minimizing the risk of injury can effectively suction laser debris and smokes.
Laser vaporization applied using a fiber-optic bronchoscope should be limited to small non-bleeding lesions, to refine and complete treatments previously performed with the rigid scope and, through a tracheal tube, for treating neoplasms in the upper lobe bronchi, in distal locations, and for distal tracheobronchial toilette.
The channel of the rigid bronchoscope is wide enough to ensure ventilation and passage of telescopes, suction tubes, and the laser fiber. Simultaneous laser coagulation of a bleeding site and suction of blood and clots is very important when dealing with airway hemorrhages. In addition, the rigid bronchoscope allows mechanical resection of polypoid tumors, previously coagulated with laser, which saves considerable time over laser vaporization. For all these reasons, most bronchoscopists prefer rigid bronchoscopy, although a flexible bronchoscope is to be available if the airway abnormality is within a distal segmental bronchus and also to remove the blood and debris from the distal airways.
A proposed technique [24] for laser treatment of endobronchial tumors consists of initial low power Nd:YAG laser firing (<30 W) to coagulate the tumor (Fig. 8.9a) followed by removal of the endoluminal portion of the lesion with the tip of the rigid bronchoscope, the biopsy forceps, and the suction tube (Fig. 8.9b).
Fig. 8.9
(a) Laser coagulation. (b) Mechanical resection. (c) Treatment of the implantation base
High power settings (50–60 W) are then employed to vaporize the residual endoluminal tumor. At the end of the procedure, the base of the lesion is exposed to low power settings with long pulses (20–30 W for 4–5 s; 2000 J/cm2) to obtain a cytocidal effect deeply within the airway wall. To avoid perforation and explosion, the light is directed tangentially to the wall of the airway and moved continuously (Fig. 8.9c).
Dark colored tissues (e.g., charred or hemorrhagic tissue) and large lesions require special consideration. With respect to dark tissues, laser coagulation in depth is limited because the dark color enhances tissue absorption, limits deep tissue penetration, and reduces deep photocoagulation, leading to poor devascularization of the target lesion. With respect to large lesions, firing with laser in full tumor is not advisable. It is time-consuming and uselessly risky to reduce the whole endoluminal mass by charring and vaporizing it with laser. The laser must be used exploiting its various characteristics in association with the mechanical resection in the so-called laser-assisted mechanical resection. To avoid charring and vaporization due to radiation absorption on the surface and to obtain coagulation in depth, the laser fiber must be kept at a sufficient distance from the tumor surface and directed a little bit more tangentially to the bronchial wall, thus obtaining, because of the divergence of the beam, an increase of the diameter of the spot and therefore a reduction of the power density [45–47].
In the treatment of cicatricial tracheal stenosis (e.g., post-intubation weblike stenoses), laser is used in contact mode to perform radial incisions before a mechanical dilation is obtained with rigid bronchoscopes of progressive caliber. The radial incisions permit to reduce tension with minimum heating of the adjoining tissue thus limiting recurrence [48–50].
Other authors [39] described a different technique with repeated small radial incisions in contact mode through the flexible bronchoscope.
The Setting
Most interventional pulmonary teams include a bronchoscopist, an anesthesiologist experienced with interventional pulmonology techniques and airway management, an endoscopy nurse familiar with the equipment, and a second endoscopy nurse who assists the bronchoscopist and controls the laser settings.
General anesthesia is usually more comfortable for both the patient and the operator; it allows maximal control of ventilation and immediate management of complications.
Anesthetic agents that are rapidly eliminated or readily reversed should be used so that the patient can be rapidly reawakened and postoperative mechanical ventilation can be avoided. Regardless of the type of anesthesia, the laser endoscopist and the anesthesiologist need to work in close agreement throughout the procedure, adapting to mutual needs.
For endobronchial tumors, which represent the most common indication for laser treatments, the use of a rigid bronchoscope is determining since the most evident part of the maneuver, i.e., the removal of the obstructing mass, is mechanically performed. Laser is more efficiently used to coagulate the endoluminal mass before the mechanical resection to avoid or reduce bleeding and to treat in depth the implantation base of the tumor as discussed before.
Bronchoscopists who have advanced training and experience should only perform bronchoscopic laser resection. Bronchoscopists and team members should remain familiar with the technique and be aware of its potential complications and necessary precautions [40].
To minimize the risk of combustion:
The fraction of inspired oxygen should be kept below 40% during laser firing [51].
Power settings should not exceed the maximum recommended for the laser being used (e.g., 60 W for the Nd:YAG laser).
Flammable materials (including silicone stents) should be kept far away from the operating field [52].
Adequate suction must be available to remove the combustible laser plume (the smoke caused by vaporization of tissues).
If a flexible bronchoscope is employed, the laser must be kept a sufficient distance beyond the tip of the bronchoscope.
Video systems allow all personnel to observe the procedure, which makes it easier for assistants to anticipate the needs of the bronchoscopist and patient. Most bronchoscopic laser resection procedures are performed in less than 1 h.
Evidence-Based Review
Outcome data regarding bronchoscopic laser resection are sparse. However, it appears to be a rapid and safe method to relieve airway obstruction. In 1988, a first series of patients treated with Nd:YAG laser was published [53]. Another case series from the same authors that included 2610 laser resections in 2008 patients with malignant airway obstruction proved that airway patency was restored and symptoms were palliated in over 90% of patients [24]. In this series the rigid bronchoscope was used in 92% of the treatments that were performed almost always under general anesthesia. The fiber-optic bronchoscope—alone—was used in less than 10%. In 93% of the patients with endobronchial malignant obstruction, Nd:YAG laser therapy allowed the patency of the central airways and avoided the most distressing symptoms of the disease, enhancing the patient quality of life. According to the authors, the location and macroscopic appearance of the lesion play the greatest role in determining the success of the procedure: for tumors involving the trachea and main bronchi, immediate results were almost always excellent (>95%). The median time between the first and second palliative treatment was 102 days. Mortality was less than 1% within 7 days of the procedure. Smaller series have reported similar results [11], while a larger series reported that death occurred in only 15 out of 5049 patients (0.3%) and serious complications occurred in only 119 out of 5049 patients (2.4%). In 38 typical carcinoids and in more than 150 benign tumors, in which the base of the lesion was reached, laser therapy was curative. These results were achieved in exclusively endoluminal polypoid tumors in which coagulation of the lesion and mechanical resection were followed by a systematic treatment of the base of the tumor with low power setting and long exposure time, avoiding tissue loss while still obtaining a cytocidal effect in depth. Overall mortality rate was 0.25% [42]. In benign stenoses and particularly in post-intubation tracheal stenoses, laser-assisted mechanical dilation can guarantee cure in up to 66% of cases and 100% when only cicatricial weblike stenoses are considered [9]. A more recent report of a series of 124 patients confirms that operative rigid bronchoscopy represents an excellent tool for the endoscopic treatment of locally advanced lung tumors, especially when patients have exhausted the conventional therapeutic resources [54].
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