following improvements allowed the reduction of hemorrhages and the prolonged palliation in central airway obstruction due to lung cancer. So, bronchoscopic mechanical resection turned into Laser Assisted Mechanical Resection (LAMR).

Indications and Contraindications

While bronchoscopic laser resection (LAMR)nds its application as a malignant and benign intraluminal tumors treatment, with relevant effectiveness especially when dealing with exophytic proximal airway lesions, it has no role when the obstruction is caused by extrinsic compression [19, 20]. Laser-assisted bronchoscopy can also be used to treat tracheo-bronchial stenosis of different etiology, such as idiopathic, vasculitis-­related (i.e., granulomatosis with poly-

angiitis subglottic localizations), pseudo-glottic, or due to either prolonged orotracheal intubation or tracheostomy.

Benign and Malignant Tumors

Although rare, benign tumors are the best indication for laser therapy due to its radicality and relative invasivity. In fact, since endoluminal benign tumors are usually polypoid with a de - nite base on bronchial mucosa, laser resection should be considered a as rst-option treatment because of its ability to remove the lesion in toto; moreover, implant base photocoagulation can be carried out to reduce to minimal levels the chance of tumor recurrence (Fig. 11.4).

While laser therapy is indicated when dealing with endoluminal tumors or cases with partial

extraluminal growth, lesions with exclusive extraluminal development should be reserved for a surgical approach.

As for malignant lesions, 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 [4, 5, 21]: although a risky maneuver due to the often-declining condition of these types of patients, the bene ts of bronchial reopening and prevention of irreversible respiratory failure (or, worse, asphyxia) are too obvious to be overlooked.

The same principle is applied when dealing with endobronchial metastases, the most frequent cases arising from gastrointestinal, kidney, melanoma, or lymphoproliferative disorders progression. Basically, every malignancy with bronchial tropism, including the group classi ed as low-­ grade malignancy (as adenoid cystic carcinoma, mucoepidermoid carcinoma, bronchial carcinoids) can be addressed by laser resection, provided it is demonstrated in previous evaluation with a fexible bronchoscope that the stenosis can be overcome and that there is patency of the downstream airway [22, 23].

In fact, while the histology of the lesion is certainly relevant in determining the prognosis of the patient, the main objective of laser-assisted resection is to restore airway patency by recanalizing the tracheobronchial tree (thus guaranteeing an adequate ventilation); therefore, the site of the lesion is the main factor to be considered in the preoperative evaluation. Moreover, it is necessary to consider the macroscopic aspect of the lesion in order to have clear relations with contiguous structures, the possible vascular pedicle, as well as a preliminary indication of the possibility of bleeding once the coring out process begins.

The greatest respiratory distress occurs when the occlusion involves large caliber airways, such as the trachea and main bronchi, since the proportion of ventilation that is lost is greater. Access to this type of lesions is easier than in the more distal airways, and intubation can be carried out

with tubes of larger diameter providing the operator not only a more comfortable route to perform the procedure, but also an easier way to manage any complication. Just think of bleeding: if the tumor is located in the more proximal airway, it is possible to localize the source of the leak, the removal of blood can occur at higher fows and the possibility of cauterizing the site is exponentially greater.

On the contrary, tumors obstructing segmental bronchi do not impair ventilation to such a degree to produce severe impairment, usually. Furthermore, the risk of perforation is also signi cantly augmented since bronchial walls begin to be thinner and laser delivery lacks direction due to reduced accessibility provided by smaller, longer tubes. Procedures on lesions localized at segmental level or further downstream are therefore reserved for conditions in which the bene t far outweighs the risk, as in the case of progressively growing benign obstructive lesions or post-obstructive pneumonia with the need for cleansing of purulent secretions (otherwise untreatable given the poor effectiveness of antibiotic therapy in cases of impeded drainage).

It is critical for the endoscopist to identify the base of the obstructing endobronchial tumor. Polypoid tumors can be easy to remove and often completely resectable (Fig. 11.3). Bronchial wall in ltration means the lesion cannot be radically treated, so the indication relies on whether ventilation is signi cantly reduced and the patient’s quality of life is impaired. If the airway lumen is not quite as compromised, laser resection may be delayed or not be necessary.

When occluding endobronchial growth tumors consist of a signi cant extraluminal or parenchymal component, or if there is mediastinal invasion (frequently with rapid growth) that results in dysventilation-related symptoms, laser-assisted resection under rigid bronchoscopy is often unsuccessful beyond the very short term. In fact, although the endoluminal growing component may be initially successfully removed, the natural progression involves recurrence of the occlusion due to continued growth of the part that cannot be treated endoscopically, to such a degree to result in compression from the outside or even

representation at the endoluminal level. Usually, the way to control this type of evolution is to place an endotracheal or endobronchial stent, safeguarding the patency of the airway for a longer period of time than a simple resection allows. Thus, laser treatment should be considered as a means to gain the minimal patency preservable by stenting or, if the extra-luminal component is merely and immediately outside the bronchi, to reduce the lesion as much as possible before approaching it by brachytherapy. Pure extrinsic compression, instead, is a major contraindication for endoscopic laser treatment.

One of the major indications for laser treatment is the development of hemoptysis due to bleeding from particularly vascularized endoluminal lesions, regardless of their histological type, location, or impact on ventilation. Resectability is not a determining factor in these cases, nor is it often possible due to the nature of the lesion and its anatomical relationships, but laser-assisted coagulation allows to control the hemoptysis leading not only to an improvement from a clinical standpoint, but also from the patient’s emotional point of view given the burden it often represents.

Furthermore, at the very least in every of the aforementioned conditions endoscopic resection allows a precise assessment of the extent of the tumor, thereby widening the treatment possibilities of previously ill-de ned lesions and possibly allowing lung-spare resections or shifting to surgery patients originally considered to be inoperable [24].

When treatments only have a palliative role, laser-assisted endoscopic resection plays a fundamental role in preparing the patient for radiotherapy or chemotherapy: in fact, it has been shown that these approaches have little effect on the endoluminal growth of a tumor, especially after airway patency has been completely compromised [9, 10]. Combining endobronchial laser therapy with other palliative therapies is therefore recommended and can be extremely advantageous. The addition of radiotherapy is particularly useful either by external beam radiation or endobronchial brachytherapy. If indicated, laser resection should be performed before radiother-

apy in order to improve the patient’s functional status by restoring and adequate airfow throughout at least the main airways. Similar therapeutic algorithms for the management of central airway neoplastic obstructions have been described by different authors [25–27].

Tumors with Uncertain Prognosis

Lung tumors of uncertain prognosis consist of numerous histologic types characterized by slow growth and rare tendency to metastasize; the most common and well-known lesions among this group include carcinoid tumors, adenoid-­ cystic carcinomas, and mucoepidermoid. Within each histological de nition tumors with different degrees of malignancy are represented, as in the case of typical and atypical carcinoids. The higher the proliferation index and therefore the degree of malignancy of the lesion, the less effective may be the endoscopic laser-assisted resection for the reasons described above. Consequently, the indications in these cases of major evolution are comparable to those of malignant tumors, including regarding combined therapies for palliative purposes or better de nition before surgical procedures.

On the contrary, tumors with a low degree of malignancy and especially lesions with well-­ de ned implantation base as target of laser therapy constitute a group comparable to benign lesions, often allowing radicality of the local treatment: in these cases laser-assisted mechanical resection may be totally curative [28, 29]. The main examples are typical carcinoid tumors, lung neoplasms with low biological aggressiveness that originate from neoplastic degeneration of Kultschitzsky cells of the bronchoalveolar Amine Precursor Uptake and Decarboxylation system (APUD) and are part of the differentiation spectrum of thoracic neuroendocrine tumors together with the faster proliferating atypical lung carcinoid, large cell carcinoma and small cell carcinoma or microcitoma. Typical carcinoid tumors can be considered somewhat benign lesions: they usually have an exclusively endoluminal growth with a narrow, well targetable base, with polyp-

oid evolution. Attention must be paid, however, to the possibility that a typical carcinoid produces serotonin or cortisol, and that its treatment can trigger symptoms such as skin fushing, watery diarrhea, heart palp, cognitive disorders (serotonergic syndrome).

Not to be confused are atypical carcinoids, which deeply in ltrate the bronchial wall and produce an appearance similar to the bronchogenic­ carcinoma: radicality should not be expected when resecting this kind of neoplasm, as reoccurrence is often an issue to deal with in the following months leading to the need for close endoscopic monitoring and possibly repeated resections.

Infammatory Disease

Finally, airway obstruction due to inhaled foreign bodies or infammatory diseases may also be an indication to endoscopic treatment with laser resection. This vast group includes airway narrowing due to granulation tissue, intubation injuries or post-radiation-, lung-transplantation-, post-resection and tracheal resection anastomosis, benign exophytic disease with either mucosal in ltration or circumferential narrowing due to granulomatosis with polyangiitis (formerly called Wegener’s granulomatosis), amyloidosis, tuberculosis, or endometriosis [30].

While patients carrying infammatory airway strictures due to causes other than infection should always be considered for open surgical resection [4, 5], the development of endobronchial treatments has changed the way we approach patients who develop dyspnea due to infammation-based airway lumen restrictions [18, 31]. Immediate laser-assisted recanalization should always be considered the rst-choice option in painfully symptomatic and progressive close stenosis which pose a risk of death to the patient: the objective is not only to restore an adequate fow within the airways, but also to avoid the execution of urgent tracheostomies with all the risks related to the surgical procedure, its management and its possible future weaning. The emergency condition therefore represents a major indication for rigid laser-assisted

bronchoscopy, regardless of the etiology of the stenosis that determines it as the endoscopic procedure constitutes the most quickly performed, symptom-relieving option. Once the emergency has been handled, then, the best therapeutic strategy can be found electively.

Oftentimes, when dealing with slow developing stenosis without acute ventilation threats, endoscopic therapy should be considered as an alternative to open surgery when the latter is contraindicated. Anyway, at the very least an endoscopic assessment of every surgically treatable stenosis should be carried out in order to identify its entity, allowing for better handling of the preoperative symptoms and for better identi cation of the surgical edges. Once surgery has been performed, complications may arise determining long-term restenosis such as granulomas or structural failure due to phlogosis of the anastomosis site, but also short-term complications such asbrin formation. Where there is no indication to repeat surgery, restenosis can be effectively treated endoscopically: in some selected simple stenoses like brin formation, web-like stenosis or stenosis without cartilage involvement stable good results can be achieved after laser-assisted mechanical resection and surgery could no longer be necessary [31–33].

Description of the Equipment

Needed

The instrumentation required to set up an endoscopy room for interventional pneumology is relatively simple. It consists of rigid tracheoscope and bronchoscope, rigid optics, forceps to mount on the optics, rigid suction tubes, laser bers, accessories for loading, and releasing endobronchial stents.

The rigid bronchoscope consists of a metal tube, the proximal end of which allows the insertion of the necessary instrumentation and the distal end of which is fute beak shaped to facilitate debulking maneuvers (Fig. 11.5).

Bronchoscopes and tracheoscopes differ mainly in length and their choice depends on the site to be treated and the type of lesion

(debulking vs. dilatation vs. prosthesis placement). Bronchoscope instruments of different calibers allow progressive dilatation. The forceps mounted on the optics, the suction probe, and the laser ber can be used in all instruments of the appropriate caliber.

The rigid optics encapsulate the light source. This made it possible to remove the light rod from the bronchoscope and improve its caliber.

The clamps load onto the optics allowing direct vision of the instrument and the site of use.

Another fundamental instrument is the rigid aspirator which, in addition to aspirating, is a true exploration and recanalization tool.

The word LASER is the acronym of Light Ampli cation of 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 refecting cylin-

drical camera with mirrors at each extremity, one of which is partially refective. When, inside the camera, an active substance is electrically or optically stimulated, it spontaneously emits photons which are refected 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) and,

––monochromatic (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 released by the laser machine and can be exclusively regulated­ through the laser equipment. It is measured in Watts (W).

––Laser Power = Watts (W)

––Laser Energy is affected by the time of exposition in a physically determined manner:

––Laser Energy (Joule) = Power (Watts) × time (sec)

––Laser Power Density is strongly dependent on the extension of the impact surface.

––Power Density (Watts/cm2) = Laser Power (Watts)/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 ber 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 infammation, 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 n e o d y m i u m - y t t r i u m - a l u m i n u m - ga r n e t (Nd:YAG) laser, neodymium-yttrium-aluminum-­ perovskite (Nd:YAP) laser, argon ion laser, excimer laser, potassium titanyl phosphate (KTP) laser, alexandrite laser, diode lasers, pulsed dye lasers, and the most recent Thulium laser.

CO2 laser was the rst laser used in bronchoscopy. It is invisible (10.600 nm in infrared range) and is transmitted to the tissue through an articu-

late arm composed of mirrors. These characteristics limit its application in bronchial endoscopy. Biologically, tissue vaporization is precise and ef cient 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 fexible quartz bers that are inserted through either a rigid or fexible 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 suf cient power to vaporize tissue, also producing a good coagulating effect. The active substance is a crystal of Yttrium-Aluminum-Garnet doped with Neodyme. 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 the tissue surface: the laser beam can be transmitted as deep as 1 cm. This radiation is differently absorbed by tissues, depending on the color of the surface and laser power density. 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 newly conceived laser exploiting a semiconductor diode technology. When electrical 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 are exclusively absorbed by hemoglobin. This laser is very useful for treating highly vascularized tissues, but absolutely indolent if red on a white surface. The 980 and 1470 nm are also well absorbed by water, so very effective when treating white tissues too.

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