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6 Tracheobronchial Tree
The trachea is located predominantly in the neck and is a continuation of the larynx, so that diseases of one organ can often affect the others. This renders the tracheobronchial system of particular interest to the otolaryngologist. In fact, endoscopic diagnosis and treatment (laryngotracheobronchoscopy) were developed by ear, nose, and throat surgeons and is still practiced by them, although other specialists in bronchial diseases, such as pulmonologists/respiratory physicians and thoracic surgeons, also practice diagnostic tracheobronchoscopy (common term: bronchoscopy). The following overview is presented from the otolaryngologist’s point of view and illustrates relationships with associated disciplines.
6.1 Applied Anatomy and Physiology
6.1.1 Basic Anatomy
The trachea is attached to the cricoid cartilage, which is the narrowest rigid element of the airway, and moves in response to movements of the floor of the mouth and the cervical muscles. It is 10 to 13 cm long in adults, and its lumen is held open by 16 to 20 horseshoe-shaped cartilaginous rings. Posteriorly the tracheal tube is formed by the membranous part, which lies in contact with the anterior esophageal wall.
The carina, i.e., the origin of the two main bronchi, lies at the level of the sixth thoracic vertebra. It has an inferiorly open angle of 55 degrees. The right main bronchus lies at an angle of about 17 degrees to the midline and the left bronchus at an angle of about 35 degrees ( ▶ Fig. 6.1a,b).
Fig. 6.1 (a–c) The tracheobronchial tree. Nomenclature of the segmental bronchi. Right. 1, Superior lobar bronchus: I, apical; II, posterior; III, anterior. 2, Middle lobar bronchus: IV, lateral; V, medial. 3, Inferior lobar bronchus: VI, superior segmental; VII, medial basal; VIII, anterior basal; IX, lateral basal; X, posterior basal. Left. 1, Superior lobar bronchus: I, apical; II, posterior; III, anterior. 4, Lingular bronchus: IV, superior; V, inferior. 3, Inferior lobar bronchus: VI, superior segmental; VII, medial basal; VIII, anterior basal; IX, lateral basal; X, posterior basal. 5, Tracheal bifurcation; 6, tracheal cartilage; 7, annular ligaments; 8, membranous wall, with tracheal glands and trachealis muscle; 9, mucosa. (a) Anterior view. (b) Posterior view, with the posterior wall partly fenestrated. (c) Cross-section of the trachea.
The bronchial tree has an extra- and an intrapulmonary course. The horseshoe-shaped cartilaginous rings of the bronchial wall gradually become complete rings to fully encircle the bronchus in its more peripheral parts. The bronchioles do not possess cartilaginous elements in their walls but only a spiral muscle. Changes in the lumen are produced by the bronchial musculature and, additionally, in the middle and small bronchi, by the bronchial veins.
The trachea and bronchi are lined by respiratory mucosa, which becomes flatter toward the periphery and passes into a single layer of cubical epithelium in the bronchioles.
Vascular supply: Blood supply to the trachea is mainly by the inferior thyroid arteries, but there are also connections with the superior thyroid arteries. The bronchi and the carina derive their blood supply directly from the aorta via bronchial arteries. Numerous anastomoses with the pulmonary arteries supply the lung tissue.
Lymphatic drainage: The trachea mainly drains to the lymphatic network of the neck, but it also connects with the thoracic lymph system, which is important for the spread of metastases.
Nerve supply: This is provided by the vagus nerve and the sympathetic trunks.
▶ Fig. 6.1a–c shows the anatomy of the central parts of the bronchial tree.
6.1.2 Basic Physiology
The self-cleaning mechanism and secretions are described on ▶ pp. 140–144. The mucociliary apparatus works in the direction of the larynx. The process of warming, humidifying, and cleaning the inspired air begins in the nose and is completed in the lower airway, so that under normal anatomic conditions intratracheal air temperature is maintained at about 36 °C when the external temperature is above 0 °C. These temperatures are considerably lower during mouth breathing. The relative humidity of the intratracheal air is also considerably lower during mouth breathing; during normal nasal breathing intratracheal humidity is 99%.
6.2 Method of Investigation: Tracheobronchoscopy
Two methods of tracheobronchoscopy are available:
Rigid endoscopy ( ▶ Fig. 6.2a–c)
Fig. 6.2 (a) Bronchoscope with 1, anesthetic attachment; 2, light carrier; 3, interchangeable window; 4, special side tubes for jet-ventilation attachment; 5, CO2 measurement device. (b) Long forceps with an attached telescope (optic forceps). (c) Specially designed microforceps for bronchoscopy.
Flexible fiberendoscopy ( ▶ Fig. 6.3)
Fig. 6.3 Flexible fiber endoscopes (Copyright XION GmbH, Berlin, Germany. Reprinted with permission).
Rigid tracheobronchoscopes (common term: bronchoscope) are tubes of different caliber with a proximal cold light source ( ▶ Fig. 6.2). Since tracheobronchoscopy is usually performed under general anesthesia, the bronchoscope has a direct connection to the anesthetic apparatus (respiration bronchoscope), so that it acts like an elongated rigid anesthetic tube. These bronchoscopes may be combined with instruments for aspiration, lavage for cytologic diagnosis, swabs for culture, aspiration biopsy, peribronchial needle biopsy, injection, curettage, biopsy, and foreign body extraction. They may also be used in combination with catheters for bronchography or catheter aspiration biopsy, and with telescopes of various angles. The simultaneous combination of bronchoscopy and radiographic screening is especially useful for aspiration biopsy, manipulation of a catheter, and foreign body extraction, which is a common indication for bronchoscopy, especially in children.
The rigid bronchoscope may also be used for photographic and video-documentation in combination with rigid telescopes. A laser-beam may be guided via a rigid endoscope for the relatively bloodless removal of benign tumors, but laser-beams guided via flexible fibers in combination with flexible endoscopy are more suitable.
Indications for the use of the rigid bronchoscope are provided in ▶ Table 6.1 .
Indication | Rigid bronchoscopy | Flexible bronchoscopy |
Emergency bronchoscopy as a temporary measure in sudden obstructive respiratory failure | + + + | + |
When intubation is difficult or impossible | + | + + + |
To remove tracheal or bronchial foreign bodies | + + | + + |
To arrest bleeding in the trachea or bronchi | + + + | + |
To remove retained secretions in obstructive disease of the lung or trachea (tracheobronchial lavage) | + | + + + |
To aspirate tuberculous lymph nodes at the carina, and lung abscesses | + + | + + |
To allow the use of laser to remove a benign endotracheal or endobronchial tumor or a cicatricial membrane | + | + + + |
To diagnose tracheal and bronchial stenoses | + + | + + |
Suspected tracheal tumor or a tumor in the surrounding tissue. The elasticity of the tracheal wall and its mobility should be assessed | + + + | + |
Suspected peripheral bronchial tumors—i.e., distal to the segmental ostia | + | + + + |
Unexplained persistent attacks of coughing and wheezing | + + | + + |
Hemoptysis of uncertain origin | + + | + + |
Suspected tracheal or bronchial trauma | + + + | + |
Transtracheal or transbronchial aspiration of a lymph node or a central tumor | + | + + + |
To control percutaneous tracheotomy | + | + + + |
Tracheobronchial stent implantation | + + | + + |
Undiagnosed disorders of the lung parenchyma, unresolved pneumonia, interstitial pneumopathy, pleural effusion of uncertain origin, middle lobe syndrome | + | + + + |
Note: + + + Method of choice; + + method of similar value; + alternative method. | ||
Site of stenosis | Type of disease | Details |
Oropharynx and hypopharynx | Inflammation | Peritonsillar or retropharyngeal abscess, infectious mononucleosis, abscess of the base of the tongue, diphtheria |
Functional disturbance | Obstructive sleep apnea, foreign body, posterior displacement of the tongue in unconscious patients, allergic reaction, angioneurotic edema | |
Tumor | Benign tumors (e.g., hyperplastic tonsils, lingual thyroid, lymphangioma, hemangioma) | |
Malignant tumors (oropharyngeal/hypopharyngeal carcinomas) | ||
Larynx | Congenital stridor | Laryngomalacia, congenital webs |
Inflammation | Epiglottitis, epiglottic abscess, laryngitis, pseudocroup (subglottic laryngitis), laryngeal diphtheria | |
Functional disturbance | Vocal cord paralysis, laryngeal spasm, glottic edema, foreign body, scars secondary to trauma or surgery | |
Posttraumatic disturbance | Larynx fracture, glottic edema, or hematoma | |
Tumor | Benign tumors (e.g., cysts, polyps, granulomas) | |
Malignant tumors (laryngeal carcinoma) | ||
Trachea and bronchial tree | Inflammation | Tracheitis and/or bronchitis |
Stenoses | Cicatricial stenosis due to long-term intubation or after tracheotomy, tracheomalacia due to compression of the trachea (e.g., goiter) or after tracheotomy or trauma | |
Functional disturbance | Foreign body, allergic reaction, asthma | |
Trauma | Tracheal subluxation, tracheal rupture, intratracheal bleeding | |
Tumor | Benign or malignant tracheal or bronchial tumors |
With diameters of 2.5 to 5 mm, flexible bronchoscopes ( ▶ Fig. 6.3) are more advantageous than rigid bronchoscopes. The movement of the distal end can be controlled externally to allow introduction into lobar bronchi, segmental bronchi, and even into the subsegmental bronchi. The instrument may be introduced via the nose or the mouth, or a tracheostomy if one is present. Fine flexible instruments can be used, guided via a working channel in the flexible bronchoscope, so procedures such as cytologic diagnostics, curettage, biopsy, and foreign body extraction are also possible in limited cases. Simultaneous fluoroscopic monitoring and laser treatments are also possible.
Flexible bronchoscopy may be carried out under local or general anesthesia. In the latter case, the endoscope is introduced through the endotracheal tube or the laryngeal mask. Indications for the diagnostic and therapeutic use of flexible tracheobronchoscopy are shown in ▶ Table 6.1 .
Mediastinoscopy is described in ▶ Fig. 8.22, see ▶ pp. 458–461.
6.3 Clinical Aspects
6.3.1 Tracheobronchial Stenoses
Acute and chronic stenoses may occur in the trachea or bronchi. In addition, stenoses can be classified as intramural (arising within the tracheal wall), extramural (compression from outside of the tracheal wall), and endoluminal (arising from the mucosal lining). Finally, there are those that affect the mucosa and the supporting elements of the wall (compression stenosis and tracheomalacia) ( ▶ Fig. 6.4a-c). A classification according to the site of the stenosis is shown in ▶ Fig. 6.5a-c.
Fig. 6.4 Different types of tracheal stenosis. (a) Scars forming webs and sails on the internal lining alone. There is a weblike scar in the subglottic space. (b) Cicatricial changes affecting all of the elements of the tracheal wall. The endoscopic view shows a stenosis in the middle part of the trachea. (c) Compression of the trachea and loss of stability lead to tracheomalacial stenosis.
Fig. 6.5 Typical locations of laryngotracheal stenosis. (a, a′) Glottis/subglottic area: 1, laryngeal stenosis; 2, laryngotracheal stenosis; 3, subglottic stenosis. Stenoses are caused by damage to the laryngeal and subglottic mucosa, the cricoid cartilage or first tracheal rings secondary to prolonged or incorrect intubation, incorrect tracheostomy, or trauma. The endoscopic image shows scars inferior to the vocal cords, narrowing the subglottic space. (b, b′) In the area of the tracheostomy: 1, suprastomal; 2, stomal; 3, infrastomal. Stenoses can occur as a result of a tracheostomy, an incorrectly performed tracheotomy, tracheomalacia, or scar tissue. The endoscopic image shows stenosis at the level of the tracheostomy. (c, c′) Retrosternal area: 1, high retrosternal stenoses are caused by prolonged intubation or excessive cuff pressure of the intubation tube; 2, low retrosternal stenoses are caused by the end of an intubation tube or tracheal cannula. The endoscopic image shows stenosis in the retrosternal area of the trachea.
Tracheal stenoses usually require urgent treatment because of the risk of asphyxia, since there are no possibilities of compensation.
6.3.1.1 Acute Stenosis
Symptoms: The main symptom is inspiratory stridor, which can be accompanied by restlessness, coughing attacks, fear of imminent death, cyanosis, and choking.
Note: Inspiratory stridor is a significant sign of obstructive respiratory failure. Retraction of the suprasternal notch and the supraclavicular and intercostal areas on inspiration is a typical sign of a high resistance in the airways.
Pathogenesis: The cause is sudden narrowing of the tracheal lumen by more than 50% secondary to blunt trauma, the aspiration of a foreign body, edema, swelling, bleeding, infection, crusts, etc.
Diagnosis: The severity of inspiratory, and often expiratory, stridor also indicates the urgency of the situation. The history usually indicates the cause. The level of the obstruction may be localized by auscultation. Endoscopy is carried out using the rigid tracheobronchoscope with insufflation. Preparations for an immediate tracheotomy should be made. Radiographs are taken only when a delay carries no risk.
Differential diagnosis: This includes laryngeal stenosis, bronchial stenosis located near the carina, pulmonary emboli and edema, and an asthmatic attack that does not cause inspiratory stridor (see ▶ Table 6.2 ). Other causes for dyspnea are:
Restrictive respiratory failure (acute respiratory distress syndrome, ARDS)
Cardiac respiratory failure
Extrathoracic respiratory failure (decreased respiratory drive due to central respiratory paralysis, diabetes, uremic coma, conditions of increased oxygen requirement, etc.)
Psychogenic respiratory distress
Treatment: Endoscopy with rigid tracheobronchoscope is used to inspect and probably dilate the stenotic airway. The integrated insufflation secures the ventilation. In cases of nonacute and fixed subglottic stenoses, which cannot be sufficiently dilated, a tracheotomy may be necessary.
Soft tissue stenosis can alternatively be dilated using a balloon technique. A short-term intubation for 24 to 48 hours may be necessary following treatment.
6.3.1.2 Chronic Stenosis
Symptoms: The typical history will be of a long period of increasing dyspnea, occasionally previous attacks of dyspnea, and a weak voice. The degree of severity of the respiratory obstruction often depends on the position of the head. Previous diagnostic measures during acute exacerbations will already have indicated the cause of the respiratory obstruction. The head is held forward with the chin downward. The patient prefers to have the body upright. The differential diagnosis of dyspnea originating from the oropharynx or the upper respiratory tract is listed in ▶ Table 6.2 .
Pathogenesis includes trauma presenting as scar formation secondary to tracheal injury or after incorrect or prolonged intubation which also causes injury to the tracheal wall, incorrect tracheotomy (see ▶ p. 390 and ▶ Fig. 6.5a), intratracheal tumors, compressing goiter, malignant thyroid conditions, bronchial and esophageal tumors, and lymphadenopathies. Other possible causes are tracheomalacia, chondro-osteoplastic tracheopathy, or specific infections like tuberculosis, syphilis, and scleroma, which can gradually destroy the structures of the tracheal wall. In addition, nonspecific infection in the neck, radiotherapy, and mediastinal causes such as dermoid cysts, emphysema, tumors, abscess, and aortic aneurysm can cause destructive local pressure on structures of the tracheal wall.
Diagnosis:
Rigid or flexible endoscopy (tracheobronchoscopy)
Chest X-ray
Magnetic resonance imaging (MRI) of the neck ( ▶ Fig. 6.6)
Fig. 6.6 Magnetic resonance image showing a lateral view of a suprastomal stenosis.
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