Benign Airways Stenosis

Abstract

Tracheal or laryngotracheal stenosis and bronchial stenosis are non-specific terms implying the presence of airway compromise involving the larynx, trachea, or bronchi. This is usually the result of scar formation with associated morbidity depending on the location, extent, and thickness of the compromized tissue.

The most common condition is post-intubation stenosis that develops after prolonged endotracheal intubation following mechanical ventilation. The sequence of events that leads to tracheal stenosis in adults involves inflammatory reactions with associated granulation tissue and ulceration of the mucosa and the cartilage. Other etiologies are congenital, postinfectious, post lung transplant, chemical damage, radiotherapy, associated to systemic conditions or idiopathic. Symptoms vary according to the severity of the stenosis, being the most frequent different degrees of dyspnea cough and retained secretions.

Surgery is considered the treatment of choice for benign airway stenosis. However, in cases of concentric stenosis without cartilage destruction and 1 cm long, dilation with rigid bronchoscopy with or without laser obtaining a normal caliber could be definitive; in these cases surgery and thoracotomy becomes unnecessary.

Other therapeutic interventions can be offered: balloon dilatation, rigid bronchoscopy dilatation, laser resection, and placement of airway stents are the most frequently applied.

Tracheobronchial stenosis can be difficult to treat, and patients benefit from a multidisciplinary approach; every case should be discussed in a team of dedicated physicians, including the pulmonary interventionists, otorhinolaryngologists, and thoracic surgeons, in order to offer the best available solution.

We believe that effective management of tracheal stenosis requires a multidisciplinary assessment of patient’s overall clinical status and medical history in addition to etiology and morphology of the stricture.

Introduction and Definition

Tracheal or laryngotracheal stenosis and bronchial stenosis are non-specific terms implying the presence of airway compromise involving the larynx, trachea, laryngotracheal, or bronchi. It is the consequence of progressive reduction of the tracheal lumen, with multiple mechanisms depending on their etiology.

In general, there is an alteration of normal epithelium after an inflammatory reaction leading to an abnormal repair and a structural problem.

Scar formation is associated with different degrees of morbidity depending upon the location, extent, and degree of airway obstruction. The sequence of events that leads to tracheal stenosis in adults involves inflammatory reactions with associated granulation tissue, ulceration of the mucosa and cartilage, fibrous tissue formation, and contraction of fibrous scar tissue.

Clinically, tracheal or bronchial stenosis result in difficulty in breathing and is characterized by the progressive reduction of the airway diameter. Acute clinical situations can be handle by laser treatment, that solves the immediate problem in almost all cases. Although relapses are frequent, a percentage between 70 and 80% present definitive cure with the support of the endotracheal prosthesis. In our opinion, surgery must be addressed when cartilage destruction is diagnosed with rigid bronchoscopy inspection. Such compromize will not benefit from endoscopic approach.

Other causes of tracheobronchial stenosis are idiopathic, infectious, chemical damage (such as gastroesophageal reflux or toxic inhalation), radiotherapy, and associated to systemic diseases (e.g., Wegener’s granulomatosis, amyloidosis).

Patients can present with variable symptoms, depending upon the severity of the stenosis and to his/her cardiorespiratory reserve: from no symptoms at all to dyspnea on exertion, progressive dyspnea, dyspnea at rest, wheezing, stridor, and a life-threatening situation such as respiratory failure or respiratory arrest.

Management of this condition is still not standardized or unified around the world, but it is well established that treatment of benign tracheal stenosis requires a multidisciplinary approach by a team of dedicated and experienced physicians.

The initial intervention and the type of treatment depend upon location of the stenosis, wall integrity, length and severity, as well as to the presence of comorbidities and overall health status of the patient.

Traditionally, surgery has been the mainstay of treatment, with excellent results in 90% of cases [1,2,3]. However, surgery is not always definitive, and there is a percentage of recurrence that can reach 10% in some series [4]. Surgery involves some risks, and associated complications have been reported to be greater than 8–12% with a mortality rate of 5% [1, 5, 6]. Moreover, many patients are unable to undergo a surgical procedure because of underlying cardiopulmonary limitations.

Endoscopic management of tracheal stenosis provides a safe and efficient therapeutic option and is often the first-line therapy in patients who are not appropriate surgical candidates or who have failure after airway resection. Several modalities have been used to relieve endoluminal obstructions, including mechanical approaches such as dilatation with a rigid bronchoscope or with balloon; heat-related modalities such as laser, electrocautery, and argon plasma coagulation; contact probe cryotherapy; and a variety of airway stents [7, 8].

Drug therapy combined with endoscopic treatment (intralesional injection of corticosteroids or more recently topical application of mitomycin-C) is another option in the treatment of this pathology, but experience is very limited and results are variable [9, 10]. So far none of these last treatments are curative.

Etiology

Congenital Tracheal Stenosis

Congenital tracheal stenosis is a rare but underdiagnosed anomaly which can present as life-threatening respiratory insufficiency in neonates and infants. Congenital anomalies are the most common cause of airway narrowing in the pediatric population. They are rare malformation, produced by the absence of most of the membranous portion of the trachea in the affected segment, and the cartilaginous rings extend along the entire circumference of the tracheal wall. There have been described three anatomical types:

• (a) Generalized stenosis, from the cricoid to the carina with possible bronchial involvement

• (b) Infundibular stenosis, where part of the trachea, proximal or distal, has a normal caliber

• (c) Segmental stenosis, with involvement of a short portion of the trachea

These malformations can appear alone or, very often, associated with other abnormalities of the bronchovascular tree and other organ malformations, of which the most frequently seen is esophageal atresia [11, 12].

Cardiac anomalies are frequently associated and may be addressed at the time of tracheal surgery.

Management of congenital stenosis is very challenging. Children can present stridor, recurrent pneumonia, cyanosis, wheezing, and sometimes respiratory failure.

Corrective surgery is the treatment of choice; in short stenosis, resection of the compromised segment and anastomosis is the best option. When the stenosis affects long segments of the trachea, anastomosis becomes difficult for excessive pressure on the suture line, and the endoscopic approach can be an effective alternative to help these patients.

Iatrogenic

Iatrogenic airway injury after endotracheal intubation and tracheotomy continues to be a serious clinical problem. The causes of post-intubation and post tracheotomy tracheal stenosis are well established. Endotracheal tube causes pressure injury to the glottis, subglottis, and tracheal mucosa and may result in severe scarring.

Physiologically, the healing of the ulcer formed by the cuff pressure in the mucosa involves regenerating epithelium (primary healing) and repair (secondary recovery), but sometimes the regeneration of the epithelium does not occur and leads to an overgrowth of granulation tissue. Eventually, the tissue subsequently becomes avascular resulting in a fibrous scar stricture.

Post-intubation tracheal stenosis was recognized for the first time as an entity in 1880, after MacEwen instituted prolonged endotracheal intubation as a therapy in four patients with main airway obstruction [13].

Since then, many reports have been published on serious complications resulting from post-intubation stenosis (PIS) or post tracheostomy stenosis (PTS). The rate of presentation varies: among all intubated patients, 0.6–21% will develop tracheal stenosis. PTS, in turn, can present from 6 to 21% of all patients that have undergone tracheostomy [6, 14]. Only a minority of them (1–2%) will present with symptoms or severe stenosis [15].

Currently, the calculated incidence of moderate or severe stenosis resulting from endotracheal intubation or tracheostomy is estimated on 4.9 cases per million per year in the general population [16].

Prolonged tracheal intubation can produce tracheal stenosis at many tracheal levels [17], from the tip of the endotracheal tube to the glottic and subglottic area, but the most affected places are at the level of the endotracheal tube (ETT) cuff and around the stoma in tracheostomized patients.

The development of the stenosis has many stages; at the beginning there is mucosal ulceration due to decreased blood flow at the level of contact with the ETT cuff. Then, cartilages exposure and perichondritis develop, followed by granulation tissue formation, which over time becomes an established fibrous stenosis that can be more or less fixed. In the worst cases, cartilage destruction occurs, and the airway wall loses its support.

PTS usually affects the area of the stoma, where the tracheostomy tube curves down, following the same sequence mentioned above. Sometimes granulation tissue is formed above the bend of the tube and progresses toward fibrosis [18, 19]. The presence of infection, very common in ventilated patients (tracheitis, mucositis), is a contributing factor for the development of airway stenosis [20]. A common finding in post tracheostomy patients is retraction of the tracheal cartilage at the area of the tracheostomy, producing different degrees of stenosis (Fig. 12.1). Surgery is the treatment of choice in these situations. When the patient is not a surgical candidate, an airway stent may be beneficial.

Fig. 12.1

Postracheostomy tracheal stenosis

Percutaneous tracheostomy is a procedure that is increasingly indicated in the critically ill patient, and it is associated to the development of tracheal stenosis as well.

A publication on 100 patients that underwent percutaneous tracheostomy revealed that major postoperative complications presented in 2.4% of cases, and these included death, cardiac arrest, loss of the airway, pneumothorax, tracheoesophageal fistula, and injury to the posterior wall of the trachea (mucosal tear). The rate of minor complications such as bleeding or cellulitis is presented in 1.8% of cases. Tracheal stenosis was reported in 31% of patients, 20% of which were symptomatic [21].

Long-term complications of percutaneous tracheostomy are infrequently mentioned in the literature; however some published data suggests that the rate of tracheal stenosis is significantly higher than reported [22].

VanHearn et al. showed that of 80 decannulated patients after percutaneous tracheostomy, an index of stenosis greater than 10% was found in 26% of them, being moderate in 4% of the cases and severe in 2% [23].

Another study evaluating 214 of 356 patients with percutaneous tracheostomies revealed that 8 of them (3.7%) developed symptomatic tracheal stenosis [24].

Infectious

Many airway infections can cause damage to the tracheal mucosa, resulting in stenosis. Tuberculosis (TB), fungal infections, bacterial tracheitis, histoplasmosis, and diphtheria are some of them, with TB being the most frequently seen.

Tuberculosis is the most common infectious cause of airway stenosis. It usually produces distal stenosis (at the level of the bronchi), but central airway stenosis can also occur. This complication can present at the time of the active infection or long after that, up to 30 years [25]. The most important risk factor for developing airway stenosis is the presence of tuberculous bronchitis, which is found in 10–37% of patients with pulmonary tuberculosis when bronchoscopy is performed [25, 26]. In those cases, over 90% of patients will develop tracheobronchial stenosis in spite of correct TB treatment [27].

Infectious stenosis is more prevalent in underdeveloped countries, particularly in Asia and Africa. Active infection produces necrosis and ulceration of the bronchial mucosa, giving rise to granulation tissue and subsequent fibrous stenosis.

During fibrous, established stenosis, dilatation of the lesion is an option. When the stenosis occurs at bronchial level, balloon dilatation can be offered. At tracheal level, rigid bronchoscope dilatation is useful as well. Repeated dilatations or stent placement are often required, since recurrence rate is very high.

Idiopathic Tracheal Stenosis

The term idiopathic tracheal stenosis (ITS) is used to include patients with tracheal stenosis when all other etiologies have been investigated and ruled out. It is thought to be a result of an inflammatory process of unknown etiology. Since location and general characteristics are similar to inflammatory or cicatricial tracheal stenosis, the investigation of potential causes has to be exhaustive before this term is applied.

ITS is a rare condition, characterized by circumferential fibrous stenosis beginning at the subglottic area and compromising the proximal segment of the trachea. It typically affects women on their third to fifth decade and presents with months to years of symptoms such as progressive dyspnea, wheezing, stridor, or a combination of all of them. In many cases patients are misdiagnosed as difficult to treat asthmatics [28].

Grillo et al. [28] presented 49 patients with tracheal stenosis where no etiology was found after extensive evaluation. A retrospective review of records showed that radiologic studies were still available in only 15 of the 49 patients with ITS. All 15 patients had radiographs and plain tomographies, and one patient had a computerized tomography scan of the neck.

Review of the available information showed that idiopathic laryngotracheal stenosis produced focal, 2–3 cm long stenosis at the cervical trachea. The lumen was severely compromised, measuring no more than 5 mm in diameter at its narrowest portion. The stenosis was concentric or eccentric, presenting either smooth or lobulated margins.

Grillo’s report highlighted the need to pay special attention to the airway in chest radiographs or computerized tomographies when evaluating a patient with a history of prolonged dyspnea and wheezing. It is also important to consider ITS in the differential diagnosis of patients with focal narrowing of the airway.

A recent multicenter study described 23 patients, 96% of which were women aged 45 ± 16 years, endoscopically treated for ITS. Time between first symptoms and diagnosis was 19 ± 18 months. Bronchoscopy showed weblike (61%) or complex (39%) stenosis, located at the upper part of the trachea, mainly at the cricoid cartilage area.

Endoscopic treatment included mechanical dilation only (52%) or associated with laser or electrocoagulation (30%) and stent placement (18%). All procedures were efficient. Follow-up after endoscopic therapy was 41 ± 34 months, showing recurrence of ITS in 30% of patients at 6 months, 59% at 2 years, and 87% at 5 years. Treatment of recurrences (n = 13) included endoscopic management in 12 cases [29].

Bronchial Stenosis Post Lung Transplantation

Since the first lung transplant in 1963, technical advances in thoracic surgery along with new immunosuppressive agents have made lung transplantation a more common indication for those patients with terminal lung disease. However, one of the main problems of this surgical procedure is the development of stenosis at the level of the suture.

Perianastomotic stenosis occurs in 12–40% of patients and nonanastomotic distal bronchial stenosis in 2–4% of all lung transplants [30, 31].

Bronchial stenosis is related to airway inflammation, with mononuclear cell injury to the epithelium and mesenchyme that is further complicated by endothelial injury on a poorly vascularized area. The severe blood-flow impairment may lead to bronchial cartilage ossification, calcification, or fragmentation, leading to stenosis [32].

Other risk factors increase the risk for suture stenosis, such as the use of a simple suture and prolonged mechanical ventilation. There is a very high risk of suture infection also due to low blood flow and the presence of inflammation. Infection should be looked for and appropriately treated before performing any endobronchial manipulation, particularly if a stent placement is considered.

Success depends primarily on the experience of the interventional pulmonology team and the medical resources available.

Distal Bronchial Stenosis

As mentioned previously, bronchial stenosis secondary to pulmonary tuberculosis is quite common. Approximately 43% of patients with pulmonary tuberculosis will develop stenosis at the distal bronchi [33, 34] (Fig. 12.2). This number corresponds to approximately 4.1% of all bronchoscopies performed in a hospital.

Fig. 12.2

Bronchial stenosis: right upper lobe

Another cause for distal stenosis is bronchial anthracosis (called anthracostenosis) [35, 36].

As a result of bronchial stenosis, there exists difficult drainage of secretions and recurrent infections distal to the obstruction, with the development of bronchiectasis. In these situations, it is indicated to offer a dilatational therapy that can be performed via balloon dilatation with or without laser application. This treatment is simple to apply and can be easily performed during a short procedure. It has good results, improving secretions clearance which in turn prevents repeated infections. In addition to bronchoscopy, three-dimensional helical tomography of the tracheobronchial tree can be very useful in the evaluation of this condition, since it allows a better distal inspection than bronchoscopy [37].

Another less common cause of airway stenosis is radiation therapy. The incidence of bronchial stenosis has increased following treatment with brachytherapy or external beam radiotherapy of malignant lesions of the airways, with an estimated incidence of 9–12% [38].

Bronchial stenosis is established within an average of 40 weeks after initiation of radiotherapy. Bronchoscopy can show the presence of a whitish-colored membrane covering the mucosa, with important inflammatory response that ultimately results in fibrous stenosis [38]. Radiation therapy rarely compromises the tracheal mucosa.

Diagnosis Methods

Patient History

Due to the broad range of etiologies and the non-specific nature of presentation, the diagnosis of airways stenosis may be delayed in time. A careful medical history should be obtained in patients suspected of airway stenosis, since background data is very important. Prior infectious diseases, history of airway intubation, prolonged mechanical ventilation, timing and severity of dyspnea, presence of dysphonia, etc., should be recorded and evaluated.

Symptoms develop gradually as progressive dyspnea until tracheal stridor appears; this could happen in most of the cases, when the diameter is affected around 70% (diameter around 5 mm in size).

When patients present emergently, it is important to offer a therapeutic procedure to reopen the airway to avoid worsening of symptoms and serious complications such as respiratory failure or respiratory arrest. The goal of treatment is to restore and maintain patency of the airway as soon as possible, and then a multidisciplinary team can decide which is the best long-term solution for a given patient.

In clinical practice, most of the patients present with symptoms of stenosis when they are in the fibrous phase of the stenosis, with minimal evidence of inflammation. They frequently have a history of a prior airway intubation or prolonged mechanical ventilation in the past. Many patients have been diagnosed and treated for difficult to control asthma, with minimal or no response to asthma therapy.

A significantly smaller number of patients will present within days or weeks from extubation, and in those cases an important airway inflammation can be seen.

Onset of symptoms is very variable. In a work of Marquette et al. describing 58 patients with airway stenosis, 5 of them developed symptoms within 5 days, 23 patients presented symptoms from 5 to 30 days of extubation and 19 patients from 30 to 90 days, and 8 patients took more than 90 days in presenting symptoms. Half of them went to the emergency room with acute respiratory failure [39].

The auscultation of wheezes, especially a fixed one, indicates that the passage of airflow through the airway is reduced, but its location does not always correlate with the site of airflow obstruction. That means that when a fixed wheeze is heard over the trachea, it does not necessarily indicate that the source of the obstruction is the trachea [40]. When wheezing is unilateral, it often suggests an obstruction of the airway distal to the carina.

The persistence of a fixed unilateral wheezing should always warrant bronchoscopic examination, paying special attention to the distal airway (segmental or subsegmental bronchi). Stridor is always a sign of severe laryngeal or tracheal obstruction and occasionally main bronchial obstruction.

Imaging Techniques

In the study of tracheobronchial stenosis of the airway, noninvasive imaging techniques have an important role. They help not only in diagnosing but also in deciding the most appropriate treatment and assessing response to therapy during the follow-up period. These techniques have developed significantly in recent years [41] allowing a better approach to airway stenosis.

Simple chest-X rays are rarely diagnostic of central airway obstruction.

Computed tomography (CT) has been the most commonly used imaging test for diagnosis and evaluation of airway stenosis in order to have better information of the length and size of the stricture, degree of destruction of the airway wall, surrouding organ injury and also to have images control after treatments (Fig. 12.3a, b).

Fig. 12.3

(a–c) Tracheal stenosis and CT scan with reconstruction in 3D

Although very useful, CT has some limitations particularly in the evaluation of subtle airway stenosis in axial images, underestimation of the craniocaudal extent of the disease, and generation of a large number of images for review [42].

The introduction of multiplanar reformatting (MPR) CT scans with option to generate three-dimensional (3D) images and virtual endoscopy (VE) provide additional information regarding airway pathology [43] bringing visual data that closely resemble the images obtained from flexible bronchoscopy [44].

MPR CT scan allows the acquisition of thin-slice axial sections of entire body volumes during a single breath-hold, thus eliminating respiratory artifacts [45].

This technique provides information on the length and caliber of the stenosis and the degree of compromise of the laryngotracheal wall. It allows visualizing lesions in depth, showing thickening or thinning of the tracheal wall, fibrous involvement of the submucosa, or disappearance of the tracheal rings. Also, the relationship of the injury to adjacent organs can be better evaluated.

Virtual endoscopy (VE) is a reconstruction technique that exploits the natural contrast between endoluminal air and the surrounding tissue [46], allowing navigation through the tracheobronchial tree with the same endoluminal perspective as an endoscopy [44] (Fig. 12.4).

Fig. 12.4

Tracheal stenosis. Virtual bronchoscopy

Several authors have demonstrated the high diagnostic accuracy, sensitivity, and specificity of noninvasive, multirow detector CT virtual endoscopy in evaluating and grading central and segmental airway stenosis and its close correlation with flexible bronchoscopy [43, 46,47,48]. However, it is slightly more accurate at assessing central airway stenosis than segmental airway stenosis [46].

The combination of axial imaging, multiplanar reformatting, and three-dimensional rendering is useful prior to tracheal intervention, especially when there is significant anatomical distortion or airway narrowing [47].

Recently, some authors advocate the use of MRI for diagnosis localization and extension of tracheal stenosis. MRI is a noninvasive procedure without ionizing radiation and can be used to identify the relationship of the trachea to adjacent vascular structures and to determine the degree and length of tracheal stenosis in high-resolution imaging with excellent soft-tissue contrast and without applying ionizing radiation or intravenous contrast medium.

Unfortunately, standard MRI has a limited ability to show dynamic organs.

The use of real-time, dynamic, cine MRI (CMRI) can achieve better results showing the mobility of the organs identified [49].

Bronchoscopy

Flexible bronchoscopy remains the primary diagnostic technique in the study of inflammatory tracheal stenosis and is considered the gold standard procedure for this pathology, allowing direct visualization of the airway lumen and sampling (biopsies). However, when the patient is in acute sever symptoms, flexible bronchoscopy is best avoided due to the risk of precipitating acute or complete airway obstruction. In these cases, the best approach has to be rigid bronchoscopy.

Moreover, bronchoscopy offers information at different levels and can assess the mobility and morphology of the vocal cords and arytenoids in subglottic laryngeal stenosis. In tracheal stenosis, it allows location of the lesion and evaluation of the degree and length of the stenosis and notes characteristics such as the presence or absence of malacia, mucosal involvement in inflammatory disorders, granulomas, ulcerations, or established fibrosis. It also enables obtaining biopsies, a procedure that should always be performed in tracheal stenosis, to rule out other inflammatory conditions. Bronchoscopy is a minimally invasive procedure, with the additional advantage of not exposing the patient to ionizing radiation. One limitation of this technique is the inability to evaluate the distal airways in severe stenosis, since the bronchoscope cannot be further advanced from the stenotic area. In these cases, sedation during the procedures and the use of an ultrathin bronchoscope with external diameter of 2.1 mm help bronchoscopists to explore tracheobronchial tree beyond the stenosis since the bronchoscopy is better tolerated.

Figure 12.5a–c shows how bronchoscopy permits the correct evaluation of the distance from vocal cords to stricture, the length of the stricture, distance from stenosis to main carina, and the degree of compromize of the cricoid cartilage.

Fig. 12.5

Vision of flexible bronchoscopy permits the correct study of the distance from VC to stricture, length of the stricture, distance from stenosis to main carina, and affectation of the cricoid cartilage

New bronchoscopic technologies, however, permit a more accurate assessment of the airway wall structure and characterization of the stricture before, during, and after treatment, since the correct evaluation of tracheal wall structures is necessary for optimal management of tracheal stenosis.

Endobronchial ultrasound (EBUS) has been introduced as an adjunct to diagnostic bronchoscopy. Radial EBUS helps evaluating the different tracheal and bronchial wall layers, as well as parabronchial structures. Cartilage damage can be better assessed, influencing the type of treatment that will be offered [50]. Also EBUS could asses differences in central airway wall structure in patients with various forms of expiratory central airway collapse who can be identified by endobronchial ultrasound using a 20 MHz radial probe [51] (Fig. 12.6.).

Fig. 12.6

Central airway wall structures: endobronchial ultrasound (EBUS)–histology correlations. (a) The five layers of the cartilaginous wall and the three layers of the membranous area of the bronchial wall are revealed by EBUS using a 20 MHz radial probe. (b) Laminar structures of the cartilaginous wall as seen on histology and the corresponding hypo- and hyper-echoic layers seen with EBUS. [51] with permission

Optical coherence tomography (OCT) is a new bronchoscopic imaging technique that has generated considerable interest since it has a much better space resolution than computed tomography. It is capable of generating high-resolution cross-sectional images of complex tissue in real time.

Similar to ultrasound, OCT measures backscattered light intensity using coherence interferometry to construct topographical images of complex tissue. It can provide a micron level, real-time image of the airway wall structure with a resolution approaching histology [52]. It offers a unique combination of high-resolution (1–15 mm) and in-depth penetration of 2–3 mm that is adequate for imaging superficial airway anatomy and pathology. OCT has the potential to increase the sensitivity and specificity of biopsies, create 3D images of the airway to guide diagnostic procedures, and may have a future role in different areas such as the study of tracheal stenosis. Some authors hypothesize that this technology may in the future provide a noninvasive “optical biopsy” [53], helping, as we said, in diagnosis and treatment of a number of conditions (Fig. 12.7).

Fig. 12.7

OCT application of OCT image for measurement of tracheobronchial stenosis. CT scan (a) and bronchoscopic (b) image of LMB (left main bronchus) stenosis. OCT images of normal bronchial lumen before (c) and after (e) the bronchial stenosis (d). OCT allows accurate measurements pre (f) and posttreatment (g) with balloon dilatation. (Courtesy Dr. Lam and Dr. Shaipanich from BCCA)

Anatomic optical coherence tomography (aOCT) , a modification of conventional OCT, is a novel light-based imaging tool with the capacity to measure the diameter and lumen area of the central airways accurately during bronchoscopy. This technique can measure tracheal stenosis dimensions, having good correlation with chest CT scan findings and guiding the selection of a proper-sized airway stent [54]. Standard OCT also could obtain accurate measures of stenosis.

All these new technologies are very promising, and they are currently under active research to define their proper role in the study of airway conditions.

Though flexible bronchoscopy and the different imaging techniques have shown to be useful and reliable in the diagnosis of tracheobronchial strictures, they all have technical limitations that can lead to an inaccurate characterization of airway stenoses [55]. The best way to evaluate these conditions is to combine different diagnostic approaches in order to correctly define the injury and then plan the best procedure, case by case, based on clinical, endoscopic, and radiological findings.

Pulmonary Function Test

Regardless of the cause, tracheal stenosis causes increased airway resistance and decreased flows. A simple test such as spirometry can help in diagnosing and characterizing a central airway stenosis. The shape of the flow-volume curve (F/V) obtained by spirometry and flow resistance (raw) calculated by plethysmography can give important information. For instance, flattening of the inspiratory loop with preservation of expiratory flow represents variable extrathoracic obstruction of the central airway. In turn, compromise of the expiratory loop with a normal inspiratory limb indicates variable intrathoracic obstruction. In a fixed obstruction (intra- or extrathoracic), both inspiratory and expiratory curves are affected, presenting with a classic flattening in the F/V loop (Fig. 12.8).

Fig. 12.8

Pulmonary function test in tracheal stenosis

Another important information that can be obtained with spirometry concerns to the functional status, and helps deciding whether or not the patient is a surgical candidate.

Classification of Benign Tracheal Stenosis

Airway narrowing may result from intrinsic stenosis or extrinsic compression or for both. It has been classified following different parameters, in an attempt to design a useful algorithm for treatment.

Cotton et al. [56] in one of the first classifications of tracheal stenosis in 1984 used the cross-sectional area of the stenosis in a group of pediatric patients and divided this condition into four grades:

• I: 50% obstruction

• II: 51–70% obstruction

• III: 71–99% obstruction

• IV: Complete obstruction

In this classification, location and length are noted but without affecting the grading of the stenosis.

In 1992, McCaffrey [57] retrospectively reviewed the treatment of 72 cases of LTS. Although diameter and length were factors, the predominant predictor of outcome was location. Locations were confined to the glottis, subglottic area, and upper trachea.

Four stages were defined as follows:

• 1. Stage 1 in the subglottis or trachea, 1 cm in length

• 2. Stage 2 in the subglottis, .1 cm in length

• 3. Stage 3 in the subglottis and upper trachea

• 4. Stage 4 in the glottis with vocal cord fixation and paralysis

In 1999, Brichet and coworkers [8] proposed a classification based on four categories depending on bronchoscopic findings:

• Pseudoglottic stenosis: defined as typically “A”-shaped stenosis due to lateral impacted fracture of cartilages in patients with a history of tracheostomy.

• Weblike stenosis: when it involves a short segment (<1 cm).

• Membranous concentric stenosis: when there is a membrane obstructing the lumen without damage to the cartilages.

• Complex stenosis: all other stenoses, including those with an extensive scar (≥1 cm), circumferential hourglass-like contraction scarring, or malacia, were defined as such.

Moya et al. [58] reviewed 54 patients that underwent surgery for laryngotracheal stenosis and defined findings according to topographic and lesional criteria, incorporating three independent variables: stage of development (S), caliber (C), and length (L). Recently this classification has been modified. It is presented in Table 12.1.

Table 12.1 Classification criteria for inflammatory stenosis of the trachea

In 2007 Freitag et al. [59] proposed a standardized scheme, presenting descriptive images and diagrams for rapid and uniform classification of central airway stenosis. In Fig. 12.9 classification was based on the type of lesion, degree, and location. They divided airway stenosis into structural and dynamic, and they included malignant causes as well.

Fig. 12.9

Classification (Freitag et al. [56]). (With permission)

The structural group has four major types:

• Type 1: includes exophytic intraluminal malignant or benign tumors and granulation tissue.

• Type 2: stenosis is due to extrinsic compression of all causes, including nonpulmonary tumors.

• Type 3: stenosis is due to distortion, kinking, bending, or buckling of the airway wall.

• Type 4: shrinking and scarring are the predominant features.

Stenoses were further classified in dynamic when a malacic condition that varied with the respiratory cycle was found. They included two different types:

• Type 1: triangular (tent-shaped) benign stenosis in which the cartilage is damaged.

• Type 2: it is the inward bulging of a floppy posterior membrane.

In turn, the degree of stenosis was assigned a numerical code that could be applied to any site:

• Code 0: no stenosis

• Codes 1: 25% decrease in cross-sectional area

• Code 2: 50% decrease

• Code 3: 75% decrease

• Code 4: 90% decrease

They defined five locations within the central airways:

• Location I: upper third of the trachea

• Location II: middle third of the trachea

• Location III: lower third of the trachea

• Location IV: right main bronchus

• Location V: left main bronchus

In 2008, other authors [7] classified airway stenosis into two groups, according to their morphological aspect in simple and complex, similar to the Brichet’s classification. Simple stenosis included granulomas, weblike, and concentrical scarring stenosis. All these lesions were characterized by endoluminal occlusion of a short segment (<1 cm), absence of tracheomalacia, or loss of cartilaginous support (Fig. 12.10). Complex stenoses were represented by a longer lesion (greater than 1 cm) with tracheal wall involvement and subsequent scarring contraction of the latter, in some cases also associated with malacia (Fig. 12.11).

Fig. 12.10

Simple tracheal stenosis

Fig. 12.11

Complex stenosis

Almost all of these classifications quantify the degree of the stenosis as a percentage, which is a subjective observation during bronchoscopy. Sometimes we can have an approximation with images such as a CT scan, but this method is not exact either since measurements vary according to the respiratory timing of image acquisition (inspiration, expiration).

In a recent report, Murgu and Colt published a study on subjective assessment using still bronchoscopic images of benign causes of laryngotracheal stenosis containing normal and abnormal airway cross-sectional areas that were objectively analyzed using morphometric bronchoscopy and classified as mild (<50%), moderate (50–70%), or severe (>70%). These images were then subjectively assessed by 42 experienced bronchoscopists participating in an interventional bronchoscopy course. Only 47% of strictures were correctly classified by study participants (mean 16.48 ± 2.8). Of the 1447 responses included in this analysis, 755 were incorrect: 71 (9%) were overclassifications of strictures’ severity and 684 (91%) were under-classifications. There was no correlation between number of strictures correctly classified and number of lifetime bronchoscopies, or number of strictures seen by bronchoscopists in an average month. As a conclusion, the authors said that: “Experienced bronchoscopists often misclassify the degree of airway narrowing when using still bronchoscopic images to subjectively assess strictures of benign aetiology” [60].

In another paper a similar survey of 123 members of AAB (American Association for Bronchology) shows that the assessment in CAO central airways obstruction is currently performed in a visual manner (91% of the consulted clinicians). Eighty-six percent of the clinicians consulted agreed that there is an urgent need to avoid subjective visual evaluation and standardize calculations during in vivo explorations [61].

This demonstrates the importance of using systems that allow us to make a more objective measurement for conducting exploration.

Murgu and Colt proposed the morphometric bronchoscopy. They use an imaging system called Image J. During the bronchoscopic procedure, different captures are taken, in the center of the proximal airway, distal and directly into the lesion. Then after the procedure, with this manual method, it is possible to calculate the stenosis index (SI) [62] (Fig. 12.12).

Fig. 12.12

Bronchoscopic photos of the idiopathic concentric subglottic stenosis (a) and the normal distal tracheal lumen (b). The calculated stenosis index (SI) was 80%. SI improved to 30% after laser and rigid bronchoscopic dilation (c). The stenosis (d) and the normal distal tracheal lumen (e) at 12 months follow-up. The calculated SI was 50%. At 18-month follow-up, the stenosis was stable with an SI of 50% (f). [62] (with permission)

Another method to calculate the stenosis index is the one that our group is trying to validate, working with the CVC (Computer Vision Center) of the Autonomous University of Barcelona. It is a new system that allows for real-time measurements. Recording a video during bronchoscopy procedure, this imaging system analyzes different cuts at the stenotic area level as well as at the normal tracheal level and subsequently, through a mathematical algorithm, calculates the area at the level of normal and stenotic trachea. Then it compares the caliber of stenosis with normal trachea giving us the real degree of stenosis [63] (Fig. 12.13.).

Fig. 12.13

Stenosis index using the Computer Vision Center of UAB method

The ultimate aim of the various proposed classification is to define a treatment algorithm accepted and followed by all physicians dealing with this complex conditions. It is also very important to use the same definitions in order to carry out research projects designed to identify the best, type-specific, therapeutic option.

In 2015 the European Laryngological Society published a consensus paper proposing a five-step endoscopic airway assessment and a standardized reporting system to better differentiate fresh, incipient from mature, cicatricial LTSs, simple one-level from complex multilevel LTSs, and, finally, “healthy” from “severely morbid” patients [64].

Authors believe that, from the surgery point of view, this is an excellent article in order to choose the best treatment modality for each individual patient and assess post treatment outcomes accordingly.

Treatment

Most significant tracheal stenosis need interventional bronchoscopy or surgical resection.

Effective management of tracheal stenosis requires a multidisciplinary assessment of patient’s overall clinical status and medical history in addition to etiology and morphology of the stricture. When deciding the approach, the dedicated physician has to consider whether or not the patient is a surgical candidate, determine precise intraoperative technique, the extent of the resection, and an estimation of the risk for recurrence. Other treatments to consider are repeated dilatations or placement of an airway prosthesis. Symptoms of patients with an airway obstruction is variable and depend not only on location, severity of the stricture, and the speed of progression but also on underlying medical conditions.

We cannot overemphasize that when an obstruction of the tracheobronchial tree is suspected, a careful review of medical history, patient examination, and review of complementary methods such as pulmonary function testing and imaging studies (chest RX, CT scan) should be performed thoroughly. Virtual bronchoscopy can be used to have a preview of the airway, but it does not replace conventional flexible bronchoscopy as the most useful diagnostic tool to assess the extent of the stenosis as well as its severity and to determine its cause by direct inspection and biopsies. Patient clinical status is the main parameter in deciding next step, since it will determine how urgent the treatment is needed and which is the most appropriate instrument to perform the procedure.

Endoscopic Treatment

Rigid bronchoscopy under general anesthesia is an essential method in the treatment of severe symptomatic laryngotracheal stenosis. It allows a secure airway and the application of different interventional tools such as balloon dilatation, laser resection, electrocautery, placement of an airway stent, etc. It is an expedite procedure to reopen the airway, very safe and effective when applied by a well-trained team. The flexible bronchoscope has also an important role, complementary to the rigid bronchoscope during the first approach.

Our recommendation when treating a patient with severe central airway obstruction is to provide appropriate oxygenation and ventilation by intubating with the rigid bronchoscope. The rigid tube serves two purposes: first, it secures the airway, and second, it can be used to dilate the airway. Once successful intubation is achieved, the flexible bronchoscope can be used through the rigid scope to inspect the stenosis and the distal airway and to aspirate retained secretions.

The immediate therapeutic approach depends on the type and severity of the stenosis found. Many times rigid bronchoscopy will resolve the acute situation by dilating the stricture and will represent a bridge to definitive treatment to be performed electively.

According to endoscopic findings, several steps can be followed. For instance, simple severe stenosis (concentric membrane) can be immediately resolved with laser resection and dilatation with the rigid bronchoscope. In this particular situation, that may be the only procedure that the patient will need. A close endoscopic follow-up is indicated to detect and treat recurrences.

Complex stenoses represent a different situation. They may be addressed initially with endoscopic therapy to overcome the acute respiratory failure, but the definitive solution is always surgery providing that the patient has a good clinical status.

Patients that present with progressive symptoms can be inspected with both the rigid and the flexible bronchoscope, and a definitive procedure can be planned after discussing the case in a multidisciplinary team, once all information has been collected.

Some treatment algorithms have been recommended, to follow in benign tracheal stenosis, according to several defined criteria (Fig. 12.14 and Table 12.2).

Fig. 12.14

Tracheal Stenoses Treatment Algorithm. SC surgical candidate, NSC non-surgical candidate

Table 12.2 Endoscopic treatment according to morphological criteria

Dilation

As we discussed above, in urgent cases the sole use of rigid bronchoscope causes dilation and enlargement of the airway, improving both extrinsic and intrinsic obstruction. Figure 12.15 shows the result of the dilation of original tracheal stenosis (a), first time treatment dilation with rigid bronchoscopy and two more dilation after 2 and 3 months (b). Bronchoscopy control: stability after 2 months (c), 10 months (d), and 22 months (e), respectively, after last dilation with rigid bronchoscopy. No more recurrencies up to the present moment.

Fig. 12.15

(a–e) Dilation with rigid bronchoscope evolution of original tracheal stenosis (a), first time treatment dilation with rigid bronchoscopy and two more dilation after 2 and 3 months (b). Bronchoscopy control: stability after 2 months (c), 10 months (d), and 22 months (e), respectively, after last dilation with rigid bronchoscopy

When a rigid bronchoscope is not available, dilatation can be performed by using progressive diameter balloons that are introduced sequentially, thus achieving a greater diameter of the tracheal lumen (Fig. 12.16a–c).

Fig. 12.16

(a–c) Balloon dilatation (before, during, and after treatment)

Balloon dilatation does not have long-lasting effects, and it is indicated to relieve the obstruction until a more definitive treatment can be offered.

Laser Therapy

Laser treatment involves application of a laser light to the lesion. The effects of laser are determined by many factors: type of laser applied, distance and surface of application, and target tissue. The most commonly used lasers in interventional pulmonology are the Nd-YAP (neodymium, yttrium, aluminum, and phosphate) and the Nd-YAG (neodymium, yttrium, aluminum, and garnet). Diode laser can be also applied to airway lesions with similar good results. Dumon published his first large series in 1982 [65]. This author presented 111 patients treated with laser to open the airway for both benign and malignant lesions, 32 of them were benign stenosis. Cavaliere et al. [66], in turn, presented their experience on 1000 patients treated with laser for benign and malignant disease, obtaining cure in 34 of the 81 cases with benign tracheal stenosis treated with laser. We also published our series including 400 cases of benign and malignant disease treated with laser [67]. Ninety-two patients were treated for benign tracheal stenosis and received 113 laser applications. Laser resection was successful in obtaining a 50% increment on the tracheal diameter in most cases.

In another publication we report our experience with laser resection followed by airway prosthesis placement in 63 patients with benign tracheal stenosis [68]. About 79% of patients obtained definitive cure.

In order to open the airway with laser, we recommend to apply three or four radial cuts at the cardinal points of the stenotic circumference of the trachea (Fig. 12.17a–c) and then to perform careful dilation with the rigid bronchoscope. Vaporization of cartilaginous structures is strictly contraindicated because it results in weakening of the tracheal wall and potentially induces restenosis to a more severe grade.

Fig. 12.17

(a–c) Laser application in tracheal stenosis. Photoresection “in cross” and dilation with rigid bronchoscope

The flexible bronchoscope can be used to apply laser as well, but we are in favor of the rigid instrument to take advantage of simultaneous dilatation.

In case of severe subglottic stenosis, we recommend the use of a CO₂ laser to take advantage of its cutting capacities avoiding inflammation, or only dilation with the rigid bronchoscopy. Instead, Nd Yag laser can increase the stenotic area due to inflammation, and put the patient at higher risk. Sometimes tracheostomy is necessary as the first procedure in those cases.

Cryotherapy, Electrocautery, and Argon Plasma Coagulation

Cryotherapy, electrocautery (EC), and argon plasma coagulation (APC) are methods that obtain variable results in tracheal stenosis treatment.

Results on the application of these techniques in tracheobronchial stenosis of varied etiology are available. Recently, Fernando HC et al. [69] treated 35 patients with a median age of 51 years with spray cryotherapy (SC). Stricture etiology included post-intubation, post tracheostomy, radiation induced, prior surgery, other causes, or unknown etiology. Seventeen patients (49%) required additional SC therapy. Only two complications occurred (3.2%) and these included pneumothorax and intraoperative tracheostomy. Twelve patients were asymptomatic, 16 improved, 4 had no improvement or were worse, and 1 patient died from an unrelated cancer.

They concluded that initial experience with SC for benign airway strictures suggested that this could be used safely and could be effective in improving symptoms and reducing the severity of airway narrowing, but almost half of the patients required re-intervention.

Some authors agree that when applied to post-intubation tracheal stenosis EC and APC can be fibrogenetic, causing more damage and scarring of the mucosa. Cryotherapy is almost ineffective given the paucity of blood vessels in the stenotic area.

These three methods, however, are very useful in granulomas, especially APC [70,71,72]. Laser therapy still has many advantages over all of them; since it is fast, it has high coagulation power and a minimal impact on surrounding tissues.

Prosthesis

Airway prostheses are tubes of different shapes, sizes, and materials designed to stabilize or reconstruct the lumen of the airways.

In benign tracheal stenosis, tracheal prosthesis placement may be considered in the following situations:

• (a) Treatment failure after dilation of a simple stenosis

• (b) First option in cases of complex stenosis as a bridge to surgical treatment

• (c) As the only option in unresectable disease (length > 50% of the trachea)

• (d) In inoperable patients

Metal, silicon, or other materials, endobronchial prostheses may be placed in the airways to relieve the obstruction caused by endoluminal tumors or extraluminal tumors that decrease the lumen of the airways by extrinsic compression. Likewise, benign conditions that diminish airway lumen can benefit of an airway stent as well.

Application of prosthesis is most effective when the stenosis occurs in the central airways (trachea or main bronchi). Their indication in distal bronchi stenosis is questionable.

The first airway prosthesis was developed by Montgomery and placed in 1965 [73]. The so-called Montgomery T tube has an extraluminal portion and requires tracheostomy for placement (Fig. 12.18).

Fig. 12.18

Montgomery T tube

In 1990, Dumon introduced a totally endoluminal silicon-made prosthesis [74] and published his first experience on treating 118 patients with airway obstructions of different etiologies.

Since then, a large number of different airway prosthesis have been developed and are now available for medical use. However, at the moment the ideal stent has not been found yet. Many authors have listed the ideal characteristics for such a prosthesis:

• Easy to insert and remove

• Does not migrate

• Strong to support the airways

• Flexible enough to accompany the normal respiratory movements and cough and to allow adequate clearance of secretions

• Biologically inert (does not produce inflammatory response, avoiding granuloma formation)

• Available in different sizes and lengths

Published articles [68, 75, 76] reporting the application of airway stents in a variety of conditions including malignant and inoperable benign stenosis, tracheomalacia, tracheoesophageal fistula, and posttransplant stenosis showed remarkably positive results in more than 2000 patients. Stent placement was associated with significant palliative benefits, improvement of dyspnea, quality of life, and performance status. Spirometric results, when available, also demonstrated improvement after placement. Associated adverse effects and complications listed on those reports were migration, granulation tissue formation, retention of secretions, airway perforation, and fatal hemoptysis.

A combined publication from four European centers reported the 7-year experience in the application of airway prostheses. A total of 263 patients had benign conditions, and they received an average of 1.6 prosthesis per patient. Duration of stenting ranged from 14 months to 6.2 years. A follow-up demonstrated treatment success in 66% patients; 24% of them had no recurrences after one year of stent removal [77].

Both metallic and silicone stents can be used for malignant obstructions of the airway. Silicone stents are a favorite, however, since they have a low level of complications along with high efficacy and safety. They have been applied over the last 20 years with very good results.

Metallic stents have the theoretical advantage of being easy to place. In turn, they are very difficult to remove, and we discourage their generalized use based on the level of complications they produce [78].

In fact, the FDA advised against metallic stent application in benign conditions in the year 2005 [79]. In malignant diseases they are still acceptable if the expected survival period is short.

How to Proceed

Rigid bronchoscopy and laser resection have been used for more than three decades, showing excellent results on the treatment of endotracheal or endobronchial growing tissue.

Concerning treatment of benign stenosis, rigid bronchoscopy laser resection has virtually no morbidity/mortality when the technique is appropriately applied in carefully selected patients.

When implementing this treatment, we recommend to proceed as follows:

• 1. Careful intubation with the rigid bronchoscope, maintaining the rigid optic lens slightly behind the tip of the bronchoscope in order to have a broad view of the airway as you advance. It is important to perform a planned intubation and to take every possible precaution during the procedure, since these patients often have a history of difficult intubation and rush maneuvers can damage easily the upper airway, especially at the arytenoids and vocal cords area.

• 2. Once the lesion is on view, careful inspection of the area should be performed. Anatomic characteristics, extent, degree of compromise of the airway wall, and presence of inflammation should be recorded. It is important to touch the lesion with the tip of the suction catheter in order to test the nature of the stenosis, inflammation, fibrosis, cartilage affectation, etc.

• 3. When tracheal caliber is equal or greater than half the diameter of the rigid tube in use, the stenosis can be dilated by placing the bevel of the bronchoscope at the beginning of the stenosis and then surpassing the stricture dilating. During the maneuver, a slight rotation movement is applied to the scope as it is advanced through the stenotic area. In case of bleeding, use the bronchoscope to compress the bleeding area for a few minutes. If the lumen diameter obtained after dilatation is not appropriate, it will be necessary to move on to a larger diameter bronchoscope.

• 4. When the stenosis has a caliber of less than half the diameter of the bronchoscope, laser in cutting mode can be applied, performing three or four cuts at 12, 3, 6, and 9 o’clock of the stenotic circumference. Laser should always be applied parallel to the tracheal lumen, avoiding damage to the posterior tracheal wall and the esophagus that could result in a tracheoesophageal fistula. The anterior tracheal wall can also be accidentally damaged, injuring large vessels placed beyond the wall, such as the innominate artery.

  After several cuts, the stenotic tissue tends to open or is easily removed by the rigid bronchoscope, applying again a rotation pressure and resecting the stenotic membranes. Bleeding rarely occurs or is minimal. Another option is to cut the membrane stenosing the airway with endoscopic scissors, minimizing laser application to avoid burn damage to the mucosa. After the incisions, the rigid bronchoscope is used to dilate the stenotic area.

• 5. Once the stricture is surpassed, the flexible bronchoscope is passed through the rigid tube, to carefully inspect the distal airways and to aspirate retained secretions or detritus.

• 6. Finally, the rigid bronchoscope is withdrawn above the stenotic area, to check that tracheal caliber remains appropriate. Given the case the lumen remains stenotic, one can assume that there is a complex damage to the tracheal wall such as cartilage disruption or malacia. Placement of an airway prosthesis is then the safer recommendation, since it will allow solving the situation avoiding immediate recurrence of the stenosis. Also, it will give time to collect other important information and to discuss the case in a multidisciplinary fashion in order to offer a more definitive solution.

Stent Placement

When placing an airway stent, the first consideration to evaluate is whether or not the prosthesis will really improve the clinical situation or make it worse.

Once risks and benefits have been evaluated and the assessment favored a stent placement, the dedicated physician should inspect the lesion again, noting carefully the size and length of the stenotic area and the characteristics of the surrounding healthy tissue. Two distances are particularly important: vocal cords to the beginning of the stenosis and end of stenosis to carina.

A prosthesis positioned too close to the vocal cords will bring speech problems and will be prone to granuloma formation leading to more stenosis. When the distance to the vocal cords is less than two centimeters, the best results are obtained proceeding directly to tracheostomy and placing a Montgomery T tube (Figs. 12.19 and 12.20).

Fig. 12.19

(a) Tracheal stenosis less than 2 cm from the vocal cords. (b) After a Montgomery tube placement

Fig. 12.20

Rule of two algorithm

In turn, when a low stent has to be placed, less than 2 cm from the carina, it is better to offer a Y prosthesis, since a tubular stent will contact and irritate carinal mucosa leading also to granuloma formation and subsequent stenosis.

The Rule of Twos for Benign Tracheal Stenosis

For a more effective and accurate tracheal prosthesis placement and in order to avoid complications in relation to the vocal cords and carina, we have designed a scheme that may obtain better results when a stent has to be placed near these areas (Fig. 12.20).

With regard to the vocal cords:

In strictures close to the vocal cords, a placement of the prosthesis can lead to the production of granuloma due to stent movement during breathing or to frequent cough. The continuous rubbing of the prosthesis with the vocal cords will generate granulomas that almost inevitably will cause new subglottic stenosis.

With regard to the carina:

The same scenario is possible when a prosthesis has to be placed close to the main carina. Due to cough or breathing movements, continuous mucosal irritation will produce granuloma formation.

After 25 years of experience in the placement of prosthesis, we advocate that a 2 cm distance between the vocal cords and the proximal edge of the prosthesis can prevent the production of granulomas on the vocal cords.

Same with the stenosis near the main carina: we advocate that a 2 cm distance between the carina and the distal end of the prosthesis will prevent the production of granulomas at this level.

So we suggest for approaching stenting:

When considering the vocal cords, stents should:

• 1. Cover the affected area of stenosis and two additional centimeters above and below that area.

• 2. Respect the 2 cm of healthy mucosa, proximal to the vocal cords.

If (1) and (2) are not possible, then a Montgomery T tube should be placed.

Related to the carina, stents should:

• 1. Cover the affected area of stenosis and two additional centimeters above and below that area.

• 2. Respect the 2 cm of healthy tissue proximal to the carina.

If (1) and (2) are not possible, then a Y stent is should be placed.

Surgery

Surgical treatment of tracheal stenosis comprises a wide range of techniques such as tracheal resection and anastomosis or tracheal reconstruction. The choice of ideal treatment should be based on the characteristics of each patient after evaluating all the advantages and disadvantages of the procedures. A tracheal stenosis that is less than 5 cm in length can be resected with end-to-end anastomosis. Longer tracheal lesions can be treated in a palliative way by placement of a stent to secure airway lumen patency.

Primary tracheal sleeve resection is considered the treatment of choice in patients who are operable. Other complex laryngotracheal techniques are necessary when the subglottis is involved.

In our opinion, surgery must be addressed when there is cartilage destruction evident on rigid bronchoscopy examination.

In case of concentric stenosis without cartilage destruction and 1 cm long, if dilation with rigid bronchoscopy with or without laser obtains a normal caliber, surgery and thoracotomy become unnecessary. In patients with more than 1 cm long stenosis and chondritis with malacia, dilation and laser are usually not enough to achieve a permanent good result, and then surgery or stenting become necessary.

Complex tracheal stenosis affecting multiple rings with involvement at various levels and a large inflammatory component is usually an indication for surgery as a first step. Inoperable patients may benefit from a permanent airway stent.

Some surgeons recommend avoiding these procedures in all patients who are potentially candidates for surgery, stating that laser treatment or stent placement can worsen the situation. However, there is no evidence to support that, In fact, most patients are inmediately relieve in their symptoms after dilatation, laser resection or stenting of the airway. Re evaluation of these patients after the acute distress is resolved will determine next step.

Cavaliere and all published the results in 73 patients: 13 (18%) weblike and 60 (82%) complex stenoses.

Most weblike stenoses were successfully treated with laser-assisted mechanical dilation (LAMD) alone; among complex stenoses, LAMD was sufficient to treat 13 patients (22%), whereas 47 patients (78%) required stent placement: 22 had their stent removed after one year and did not require any further therapy, 13 inoperable patients required permanent stent, and 12 were referred to surgery after failure of multiple endoscopic treatments. No permanent complications secondary to endoscopic treatment were observed. Forty-eight patients (66%) obtained a stable, good result with the endoscopic procedure, 13 (18%) required a permanent stent, while 12 patients (16%) were referred to surgery. Authors concluded that endoscopic treatment of post-intubation tracheal stenoses performed in an expert setting can be considered a safe first-line therapy, leaving some selected cases and the relapsing stenoses, for surgical resection [80].

In a recent excellent article by P. Delaere and D Van Raemdonk [81], the authors update recent advances in tracheal reconstructive surgery in malignant or benign pathology involving long areas of the trachea. Animal studies have shown that a prosthetic replacement of the airway wall is not possible. In large resections, a silicon prosthesis sutured to the upper and lower margings covered by skin flaps can be useful. The authors also reviewed their experience in allotransplants and highlight the importance of vascularization in allografts since to restore blood supply it is the most difficult technical inconvenience. Regarding tracheal regeneration, they state that optimism on that matter is completely unfounded.

Summary and Recommendations

Dealing with airway stenoses can be difficult. A variety of methods can be applied in order to relieve the situation. In fact, almost any technique discussed above is useful and can be applied alone or in combination with other methods. A multidisciplinary approach will always bring the best results for patients; important considerations should be thoroughly discussed with the team:

• General status of the patient and his/her wishes

• Type of injury (acute versus chronic, extrinsic or intrinsic obstruction, fixed or dynamic stenosis, benign or malignant stenosis)

• Equipment availability

• Personal experience and expertise on a given method

After that, the “best” approach for a given patient can be offered.

As we said, frequently best results are obtained with a combination of treatments, and better outcomes for the patient are achieved in multidisciplinary, referral centers that have both extensive experience and sufficient equipment to deal with these complex clinical situations. We believe that interventional pulmonologists and thoracic surgeons must discuss thoroughly the indications, contraindications, and possible complications that can arise, case by case. We favor that the interventional team should be well trained, able to apply both the rigid and flexible bronchoscope, and has to be also knowledgeable on handling airway prostheses. The ACCP guidelines to interventional procedures provide useful recommendations including training requirements and number of suggested procedures to become competent and maintain proficiency in all the procedures described in this chapter [82].