Introduction

Central airway obstruction is a problem that faces both medical and surgical physicians treating chest diseases and requires a comprehensive multidisciplinary approach.

Central airway obstruction can occur secondary to a variety of lung primary, adjacent, or metastatic malignancies and benign processes. It can be either intrinsic or extrinsic [1, 2].

Considering the epidemiology of lung cancer, an increasing number of patients will develop complications related to proximal bronchial involvement. Moreover, considering the ef cacy of cancer treatment, the number of long-term cancer survivors is increasing. Furthermore, with increased use of arti cial airways such as endotracheal intubation in the aging population and in patients with severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection, the incidence of both benign and iatrogenic complications is also likely going to increase.

The most common cause of malignant central airway obstruction is direct extension from an adjacent lung tumor (most commonly bronchogenic carcinoma) followed by esophageal and thyroid carcinoma. Primary tumors of the airway are not common and mainly represented by squa-

M. Bezzi (*)

SC Pneumologia - SS Pneumologia Interventistica ASST Spedali Civili di Brescia, Brescia, Italy

mous cell carcinoma and adenoid cystic carcinoma for trachea, and carcinoid tumors distal to the carina. Metastases may also localize to the airways, most frequently from renal cell, breast, and thyroid carcinoma.

Benign disease can be congenital or acquired. The most common histologically benign strictures are postintubation tracheal stenosis and post-tracheostomy tracheal stenosis, followed by idiopathic and autoimmune causes (granulomatosis with polyangiitis, sarcoidosis, ulcerative colitis), airway foreign bodies, tracheal, or bronchomalacia. Strictures can also occur as a brotic evolution of endobronchial tuberculosis or lung transplantation. All these conditions must be excluded before considering the stricture as idiopathic. This is relevant for treatment, as idiopathic laryngotracheal stenosis is characterized by hypertrophy of the mucosa and submucosa with intact cartilaginous structures, for which stent insertion should not be used [1–3].

Interventional options for central airway obstruction require experienced personnel and equipment. The choice of intervention is based on the degree of obstruction and severity of symptoms, the nature of the underlying problem, and the patient’s overall prognosis and quality of life. In case of airway tumors, surgical resection is the treatment of choice. However, most patients with an endobronchial mass have an advanced stage of disease, poor performance status, com-

plete or partial atelectasis of the affected lung, and thus are not suitable for surgery [1–7].

Thirty percent of patients with lung cancer will develop obstruction of trachea and main bronchi [8] with consequent dyspnea, bleeding, and infection. The technique of endobronchial coagulation and disobstruction plays a pivotal role in all these situations, since conventional treatment with chemoand radiotherapy is often performed with unsatisfactory results with regard to the endobronchial component of the tumor [9, 10]. Endoscopic coagulation and debulking allow restoring of airway patency, palliation of symptoms, and improvement of quality of life. However, palliation with endoscopic techniques should be reserved to inoperable obstructive central tumors in symptomatic patients.

Airway obstruction due to a benign lesion may also be amenable to laser resection. If exclusively endoluminal, endoscopic laser resection should be the rst therapeutic choice for central benign tumors. Surgery should be limited to those cases with partial or exclusive extra bronchial growth or in case of recurrence.

The advent of endoscopic therapy has also deeply modi ed the approach to the management of infammatory tracheo-bronchial strictures. Candidates for bronchoscopic laser resection include those who are not eligible 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), but also severe, dreadfully symptomatic stenosis. Interestingly, most simple stenosis (e.g., web-like stenosis or stenosis without cartilage involvement) can be successfully dilated through laser-assisted mechanical dilation and surgery may no longer be necessary [11].

Clinical Presentation

CAO may cause a variety of symptoms, from shortness of breath to respiratory failure and death. The entity of symptoms does not only rely on the etiology but is mainly affected by the location (tracheal vs. bronchial) and the rate of progression of the obstruction: patients may develop symptoms

suddenly, as can happen with foreign body aspiration, or more gradually, as is often the case with slowly growing malignant obstructions. Symptoms and signs develop when airfow impairment reaches a critical threshold. Patients complain of shortness of breath, which is often constant and unresponsive to bronchodilators. Monophonic wheezing may be present, and can be unilateral if the lesion is distal to the carina. Stridor is a sign of severe subglottic or tracheal obstruction. Breathing becomes labored in advanced phases and heralds impending respiratory failure. In the decompensated patient, immediate restoration of ventilation and oxygenation is of vital importance. Patients with minor obstruction are often asymptomatic or may present with other nonspeci c symptoms such as exertional dyspnea and positional wheezing, since airfow limitation is mild. However, rapid deterioration may occur if swelling or secretions increase the degree of luminal impingement during a respiratory tract infection. It is not uncommon for patients with subcritical lesions to be misdiagnosed as suffering from an exacerbation of asthma or chronic obstructive pulmonary disease unresponsive to bronchodilators. Patients with airway obstruction also frequently present with pneumonia [1–3].

Diagnosis

A number of studies are employed to con rm the presence of central airway obstruction and estimate its magnitude. Conventional chest radiographs are rarely diagnostic, yet are often obtained as the initial radiologic test. Obvious pathology, such as tracheal deviation, can be identi ed; however, chest X-ray is unable to determine airway invasion or aid in procedure planning. If an airway lesion is suspected and time permits, a high-resolution chest computed tomography (CT) should be performed. CT scans give better characterization as to whether the lesion is intraluminal or extrinsic to the airway and whether the airway distal to the obstruction is patent. In addition, it allows us to de ne its relationship to other structures such as vessels [1–3] (Fig. 11.1).

In a stable patient spirometry can show the characteristic fattening of the curve on fow-­ volume loops, frequently before abnormalities in the spirometric volumes are noted.

Bronchoscopy is always necessary in assessing airway obstructions. Direct visualization allows to determine the nature, length, diameter of the obstruction and precise location in relation to the vocal cords and main carina, and provides useful information for treatment planning, such as the relative amount of intraluminal and extraluminal disease and patency of distal airways (Fig. 11.2) [1–3].

Treatment

Several techniques are available to manage central airway obstruction and include airway dilatation, ablation techniques, tracheo-bronchial stenting, and surgery [12]. In each case, management requires initial stabilization of the patient with secure access to the airways to guarantee ventilation.

In a stable patient, imaging studies and pulmonary function tests should be obtained as mentioned above. A patient with severe tracheal or bronchial obstruction and marginal lung function

Fig. 11.2  CT scan shows left main bronchus stenosis due to vegetation. Flexible bronchoscopy shows neoplastic vegetation with a small implant base and a patent distal lumen. These conditions are an optimal indication for

laser-assisted mechanical resection. The procedure restored the left main bronchus lumen. Low power laser allowed implant base treatment to postpone endobronchial recurrence

requires initial stabilization to secure ventilation and oxygenation. Flexible bronchoscopy can be performed 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 tissue is obtained if needed. This information is used to plan further interventions aimed at opening an airway and maintaining patency. After the patient has been stabilized, he should be transferred to a specialized center where a dedicated airway team is available. In case of severe tracheal obstruction, 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. In emergent cases, the rigid bronchoscope is the preferred instrument for unstable patients and when signi cant bleeding is expected. The airway can be dilated with the barrel of the scope [4]. 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 instrument. In one session, using the rigid bronchoscope under general anesthesia, immediate good results can be achieved: bronchial

recanalization with improvement of ventilation and/or drainage of post-stenotic secretions (Fig. 11.3). Dilation is immediately effective for intrinsic and extrinsic lesions, but the results are usually not sustained. For this reason, multimodality approaches featuring a combination of sev-

eral interventions are preferred for their mucosal sparing effects and long-term success over dilation alone [4, 5]. The number and scope of therapeutic options has increased dramatically, and a given intervention must be chosen carefully in the context of an individual patient’s situation.

Fig. 11.3  Endoluminal obstruction caused by malignant vegetation. Laser-assisted mechanical resection allowed safe removal, avoiding bleeding, and restoring airway

patency. Implant base photocoagulation will delay potential reoccurrence