ETIOLOGY
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Idiopathic
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Primarily in women
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Short stenosis in proximal airway/subglottic larynx ( Fig. 11-1 )
Figure 11-1
Tracheal tomograms demonstrating a subglottic stenosis with the lesion and vocal cords visible.
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No history of trauma, infection, inhalation injury, or intubation
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Autoimmune workup (e.g., Wegener’s granulomatosis) negative
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Post-traumatic
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Blunt trauma
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May go unnoticed; often initially treated with tube thoracostomy for presence of pneumothorax
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Inhalation injury
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Chemical and thermal burns
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Injury often begins below vocal cords with minimal damage to the supraglottic larynx.
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Resection is difficult, and patients are often managed with silicone T-tube.
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Postintubation/post-tracheostomy
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Circumferential erosion of the trachea at the level of inflatable cuff
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Preventable with low-pressure cuffs and vigilant monitoring of pressure in tracheostomy cuff. Goal is to keep pressures lower than 20 to 25 mm Hg.
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A small leak of air around an endotracheal tube when the balloon pressure is in the appropriate range is not a problem and should be accepted when the patient is well oxygenated and well ventilated. In that situation, increasing the balloon pressure leads to tracheal damage.
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Symptoms may present within days of extubation.
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At a previous tracheostomy site, granuloma may develop.
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Subglottic injury occasionally caused by crico-thyroidotomy
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Post-therapeutic/stenosis following tracheal resection
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Following attempts at tracheal reconstruction, restenosis is most often caused by tension at the anastomosis.
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Disturbance of tracheal blood supply, postoperative radiation, and granulation tissue can also lead to restenosis.
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Extrinsic lesions
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Goiter
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Often gradual compression of airway.
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Even large goiters with tracheal deviation and/or mild stenosis are well tolerated and do not require treatment.
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Following removal of goiter, trachea may remain distorted, but significant airway obstruction rarely appears.
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Vascular
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Congential ring
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Innominate artery aneurysm
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Anomalous subclavian artery passing behind trachea and esophagus
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Mediastinal mass
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Mediastinal masses causing tracheal compression are usually malignant (thymoma, lymphoma, germ cell tumors)
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Rarely bronchogenic cyst
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Postpneumonectomy syndrome
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Following right pneumonectomy, with rotation of mediastinum, compression of remaining tracheobronchial tree
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Infectious
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Tuberculosis
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Principally appears in the lower trachea and main bronchi.
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Acute ulcerative tuberculosis leads to chronic, lengthy scarring of the airway.
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Active disease must be addressed prior to any surgical intervention.
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Histoplasmosis
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Mediastinal fibrosis leading to airway compression
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Erosion of calcified nodes into airway (broncholith)
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Inflammatory/miscellaneous
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Wegener’s granulomatosis
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Inflammatory lesions may affect larynx and trachea.
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Most commonly produces subglottic stenosis, but can affect other upper airway sites.
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With medical management, stable tracheal stenosis may result.
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Sarcoidosis
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Airway obstruction secondary to massive lymph node enlargement and fibrotic changes to airway
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Usually not amenable to surgical reconstruction
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CLINICAL FEATURES
Symptoms and Signs
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Patients often present with a long history of coughing progressing to wheezing
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Lesions often recognized late.
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Patients initially treated for adult onset asthma or chronic obstructive pulmonary disease (COPD).
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Wheezing progressing to stridor as the caliber of the airway continues to narrow.
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Chest radiographs will often demonstrate clear lung fields.
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Chest tomograms will occasionally demonstrate the tracheal lesion.
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DIAGNOSTIC WORKUP
History
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Important components of the history include
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Progressive shortness of breath
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Progressive dyspnea
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Wheezing unresponsive to bronchodilators
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Hemoptysis
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Recurrent pneumonia/pneumonitis
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Change in voice/increasing hoarseness
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Physical Examination
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Confirm airway patency.
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Ensure trachea is midline.
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Check bilateral breath sounds.
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Perform pulmonary auscultation.
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Head and neck exam including
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Thyroid examination
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Cervical lymph nodes, masses
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Palpate tracheal rings, and thyroid and cricoid cartilages
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Jugular venous distension
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Oral and pharyngeal examination
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Radiographic Evaluation
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Chest radiograph
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Clear chest radiograph in majority of cases
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Tracheal tomograms (see Fig. 11-1 )
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Plain films of the trachea demonstrate tracheal air column and location of lesion with respect to larynx
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Computed tomography CT scan
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Occasionally will demonstrate a tracheal mass. Addition of high-resolution CT images and three-dimensional and multiplanar two-dimensional reconstructions increases sensitivity and specificity
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Virtual bronchoscopy CT scan (high-resolution, rapid-sequence CT scanning with computer software to reconstruct the tracheal at inspiration and expiration) can be helpful to define the location and the extent of the tracheal pathology.
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Tracheomalacia is an underdiagnosed and underappreciated disease. This is best diagnosed by virtual bronchoscopy CT scan and can be treated with a tracheoplasty via right thoracotomy.
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Useful with goiter, vascular malformations, histoplasmosis
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Bronchoscopy
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Procedure is essential in the diagnosis and management of tracheal stenosis.
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Bronchoscopy should be performed with general anesthesia in an operating room ( Fig. 11-2 ).
Figure 11-2
Tracheal stenosis as viewed through a rigid bronchoscope before dilatation and subsequent resection.
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Potential for loss of airway in outpatient setting, so equipment for an emergent tracheostomy must be available.
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Flexible bronchoscopy is adequate
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If performed through an endotracheal tube, the tube must be pulled back and the airway examined from the level of the vocal cords
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Rigid bronchoscopy with general anesthesia superior to flexible bronchoscopy ( Fig. 11-3 )
Figure 11-3
Rigid bronchoscopes of varying sizes, which allow for better visualization of the airway and airway pathology. In addition, the rigid bronchoscope allows for dilatation of stenosis before surgical resection.
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Allows for better visualization of anatomy and tracheal measurements (distance form the vocal cords to the tracheal pathology, distance of the tracheal pathology, and distance from the distal margin of the tracheal pathology to the carina). This is a key factor for proper planning of the tracheal surgery.
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Superior biopsy specimens
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Potential for airway management and improvement through maneuvers such as dilatation
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If imaging suggests a focal lesion amenable to resection, bronchoscopy can be deferred until general anesthesia can be used when resection planned.
Pulmonary Function Tests
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Anatomic and physiologic considerations :
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The coronal diameter of the trachea is 13 to 25 mm in men and 10 to 21 mm in women, with the length 10 to 11 cm.
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With inspiration, changes in length and diameter decrease airflow resistance. At functional residual capacity (FRC), the pressure within the upper airways (extrathoracic and intrathoracic) is atmospheric (referenced as 0)
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Sensitivity of pulmonary function studies and limitations:
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The most sensitive test is the flow volume loop. The classic paper by Miller and Hyatt described three patterns: variable extrathoracic, variable intrathoracic and fixed. Abnormalities may not be appreciated until the airway is narrowed to about 8 to 10 mm.
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Variable refers to dynamic narrowing of the airway diameter during either inspiration (variable extrathoracic obstruction) or expiration (variable intrathoracic obstruction). Fixed refers to no change in airway size, despite changes in transmural pressures during the different phases of respiration, and can result from both intrathoracic or extrathoracic lesions. A plateau pattern of the expiratory loop only, is seen with variable intrathoracic obstruction, of the inspiratory loop only, with variable extrathoracic obstruction, and both phases of respiration with fixed obstruction.
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Fixed or variable intrathoracic patterns may be seen with tracheal stenosis, although fixed is much more likely. The variable intrathoracic pattern (e.g., with tracheal mass or tracheomalacia), occurs because on expiration, turbulent expiratory flow across the obstruction causes a fall in airway pressure, so that the pleural pressure at the obstructing site is greater than tracheal pressure, resulting in further narrowing of the airway. (During inspiration, the negative intrathoracic pressure, ‘tethers open’ the trachea at the site of the lesion).
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Forced expiratory flow at 50% of vital capacity (VC) (forced expiratory flow [FEF] 50% ) to FIF 50% (forced inspiratory flow at 50% of VC) ratios:
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Fixed: close or equal to 1
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Variable intrathoracic: reduced to usually 0.3
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Variable extrathoracic: less than 2
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Figure 11-4 shows an example of tracheal stenosis due to a thyroid cancer (A), with a fixed upper airway pattern noted on the flow volume loop (B).
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