Tracheomalacia, Vascular Rings and Slings, and Bronchomalacia
Maria Teresa Santiago, MD
Tracheomalacia
Introduction/Etiology/Epidemiology
•Tracheomalacia is characterized by tracheal collapse during forced expiration. It may be congenital (primary) or acquired (secondary).
•Congenital tracheomalacia
—It may be isolated but also occurs with airway abnormalities, including laryngomalacia, bronchomalacia, and laryngeal clefts.
—The incidence rate is 1 in 2,100 children.
—Proximal esophageal atresia with distal tracheoesophageal fistula is the most common associated congenital anomaly.
—Tracheomalacia is seen with craniofacial anomalies, chromosomal defects, mucopolysaccharidoses, and inherited connective tissue disorders.
•Acquired tracheomalacia
—Tracheotomy is the most common cause.
—This condition affects 10% of patients who previously underwent tracheotomy and 16% of premature infants with bronchopulmonary dysplasia.
Pathophysiology
•Congenital tracheomalacia
—This occurs when reduction and/or atrophy of cartilage rings causes softening of cartilage and/or decreased tone of the trachealis muscle.
—Increased intrathoracic pressures during expiration cause airway collapse.
•Secondary tracheomalacia
—This may occur after trauma, external compression, positive pressure ventilation, infection, and inflammation.
—Premature infants are at increased risk, since airways are prone to deformation and injury when exposed to positive pressure.
•Patients present with croupy, barklike or brassy cough, and shortness of breath with exercise.
•Recurrent pneumonia and/or atelectasis occurs because of impaired mucociliary clearance.
•Severe malacia causes apnea and cyanotic spells (particularly those that occur with feeding or reflex apnea).
•A monophonic wheeze or expiratory stridor can be observed in patients with intrathoracic tracheomalacia and biphasic stridor with extrathoracic tracheomalacia.
Differential Diagnosis
Differential diagnosis includes conditions associated with recurrent or persistent wheezing and airway obstruction.
•Bronchiolitis
•Asthma
•Bronchopulmonary dysplasia
•Cystic fibrosis
•Gastroesophageal reflux
•Bronchomalacia and/or stenosis
•Subglottic stenosis
•Bronchogenic cyst
•Vascular rings or slings
•In children ≥5 years of age, spirometry may demonstrate expiratory flow limitation consistent with a variable intrathoracic obstruction.
•Tracheography, bronchography, and fluoroscopy may demonstrate expiratory airway narrowing.
•Multidetector computed tomography (CT) allows 3-dimensional (3D) reconstruction of the tracheobronchial tree (virtual bronchoscopy) and provides static images of tracheal narrowing.
•Dynamic magnetic resonance (MR) images show vascular compression of main airways but require patient cooperation and cannot be obtained in preschool-aged children.
•Direct airway visualization with flexible and/or rigid bronchoscopy demonstrates that >50% tracheal wall narrowing is the standard for diagnosis. Flexible bronchoscopy more effectively demonstrates airway dynamics, while rigid bronchoscopy can be used to evaluate associated anomalies. Widening of the posterior membrane with anterior collapse during expiration or “fish-mouthing” of the trachea is most commonly seen with congenital tracheomalacia associated with tracheoesophageal fistula and esophageal atresia (Figure 14-1). Malacia from external compression also results in flattening of the anterior cartilage. The ratio of the cartilage ring to the posterior membranous wall decreases from 4:1 or 5:1 to 2:1 or 3:1.
•The severity of tracheomalacia can be underappreciated if a child is given deep anesthesia during bronchoscopy.
Treatment
•Symptoms associated with mild tracheomalacia usually resolve by 18 months to 2 years of age without treatment.
•Pharmacotherapy, positive pressure ventilation, and surgery may be considered for symptomatic patients.
•Pharmacotherapy treatment
includes the following.
—Bethanechol, a cholinergic agent delivered at doses of 0.1 to 0.2 mg per kilogram of body weight per dose 3–4 times daily, directly stimulates airway smooth muscle and improves airway mechanics.
—In low doses, inhaled ipratropium bromide blocks presynaptic muscarinic receptors (M2), prolongs acetylcholine release at the neuromuscular junction, and stimulates smooth muscle contraction.
—β-agonists such as albuterol may decrease airway smooth muscle tone, resulting in central airway collapse, and should therefore be used cautiously.
•Continuous positive airway pressure, introduced noninvasively or via endotracheal tube or tracheotomy, maintains central airway patency, decreases expiratory resistance, and increases lung volumes and maximal expiratory flow rates. Although tracheotomy can facilitate positive pressure ventilation and maintains patency of malacic segments, it will not bypass distal compression or obstruction.
•Surgical treatment includes the following.
—An aortopexy is a procedure where peritracheal soft tissue, typically the aorta, is lifted anteriorly and sutured to the sternum. Occasionally, the innominate artery, pericardium, and/or trachea itself (anterior tracheopexy) may be sutured to the sternum. This remains the mainstay of surgical treatment for patients with severe malacia who have clinically significant respiratory distress or “death spells” or are failing to thrive.
—Slide tracheoplasty has been used in severe malacia associated with tracheoesophageal fistula.
Figure 14-1. Tracheomalacia. Bronchoscopic image shows “fish-mouthing” of the trachea and anterior bowing of the trachealis muscle during expiration.
Prognosis
•Symptoms of isolated congenital tracheomalacia and malacia from positive pressure ventilation improve markedly by 2 years of age, while malacia related to foregut abnormalities or external compression tends to persist into late childhood.
When to Refer
•Evaluation by a subspecialist for underlying anatomic tracheobronchial abnormalities should be considered in patients with recurrent croup and/ or wheezing who are unresponsive to medications used to treat bronchospasm, such as bronchodilators, steroids, and/or leukotriene antagonists.
•Patients with “resistant asthma” and recurrent pneumonias or atelectasis, particularly if they are not thriving, should also be referred to a subspecialist for further evaluation.
When to Admit
•Admission should be considered for patients with respiratory distress and hypoxemia associated with viral illnesses.
Vascular Rings and Slings
Introduction/Etiology/Epidemiology
•Rare malformations occurring during embryonic aortic arch development represent approximately 1% of cardiovascular congenital anomalies.
•The spectrum and relative frequency of aortic arch abnormalities in children are listed in Table 14-1.
•“Vascular rings” are complete circumferential vascular anomalies.
—Double aortic arch
▪This is the most common symptomatic vascular ring.
▪Persistent right and left fourth embryonic aortic arches encircle and compress the trachea and esophagus, producing respiratory distress and feeding difficulty in early infancy.
▪Ninety percent of patients are symptomatic and require surgical correction. The right arch is dominant in 70%–90% of cases. Determination of dominance is critical for deciding which side to ligate without causing cerebrovascular ischemia.
▪A double aortic arch may be associated with congenital heart defects such as transposition of the great arteries, ventricular septal defect, persistent truncus arteriosus, tetralogy of Fallot, and coarctation of the aorta.
| Table 14-1. Classification and Relative Frequency of Aortic Arch Abnormalities That Cause Tracheoesophageal Compression in Children | |
| Abnormality Type | Frequency |
| Complete vascular rings | |
| Double aortic arch | 48%–55% |
| Right aortic arch | 12%–15% |
| Incomplete vascular rings or slings | |
| Innominate artery compression syndrome | 15% |
| Pulmonary artery sling | 7% |
| Left aortic arch and aberrant subclavian artery | 5% |
—Right-sided aortic arch
▪Two common variations are a concomitant aberrant retroesoph-ageal left subclavian artery (65%) and mirror image branching (35%).
▪Ten percent to 50% of patients have associated congenital heart defects. Mirror image branching carries a 90% risk of congenital heart defects.
•“Slings” are incomplete or noncircumferential anomalies.
—Aberrant right subclavian artery
▪Occurs in 0.5% of the population.
▪Presentation is variable, and most patients are asymptomatic.
▪Older children and adults may experience dysphagia due to esophageal compression.
▪There is increased incidence in patients who have Down syndrome with congenital heart defects (38%).
—Pulmonary artery sling
▪The aberrant left pulmonary artery arises from the main pulmonary artery, dorsally encircles the right bronchus, and passes between the trachea and the esophagus before it enters the hilum of the left lung.
▪Although not a complete vascular ring, respiratory symptoms and feeding difficulties occur in infancy. Forty percent to 50% of patients have a “ring-sling complex” (a pulmonary artery sling with complete tracheal rings, causing tracheal stenosis).
▪These anomalies account for most fatalities associated with ring or sling defects.
▪Tracheobronchial abnormalities such as tracheomalacia, hypoplasia, and long-segment tracheal stenosis may be associated.
▪More than 50% of cases are associated with CHD.
— Innominate artery compression syndrome
▪This is usually an incidental bronchoscopic finding.
▪Symptoms relate to tracheomalacia from anterior tracheal compression and/or an associated esophageal atresia.
Pathophysiology
•The embryonic dorsal and ventral aortas are connected by 6 bilateral arches.
•During the fourth week of development, aortas fuse to form a single aorta with 6 adjoining arches that encircle the primitive trachea and esophagus.
•Normally the first, second, fifth, and right fourth arches involute, freeing the esophagus and trachea.
•Failure of embryonic arches to fuse or regress normally results in vascular anomalies.
•Errors in fourth arch development result in anomalies that form complete rings encircling and/or compressing the intrathoracic trachea and/or esophagus.
•Sixth arch anomalies usually do not form circumferential anomalies.
Clinical Manifestations
•Symptoms depend on the anatomic site of the ring, the degree of “tightness,” and the site of compression.
•Children with complete rings often present early in infancy with progressive stridor, cyanosis, and dysphagia.
•At physical examination, biphasic stridor, monophonic wheezing, a croupy or brassy cough, and/or noisy breathing may be observed.
•Feeding difficulties such as dysphagia, slow feeding, and neck hyperextension may occur with introduction of solid foods. Dysphagia in association with respiratory symptoms is reported in 30% of patients at initial presentation but is an isolated symptom in 5%–15% of cases. Apnea or cyanosis may be precipitated by swallowing a solid food bolus that presses against a collapsible posterior trachea at the site of the anomaly.
Diagnostic Considerations
•Anteroposterior and lateral chest radiographs demonstrate tracheal deviation from a right-sided aortic arch. Lateral views demonstrate anterior bowing of the trachea and a retrotracheal density.
•More than 90% of vascular ring anomalies can be seen on esophagrams obtained with barium. Extrinsic posterior esophageal indentations from an aberrant subclavian artery, bilateral indentations from a double aortic arch, and anterior indentation from a pulmonary artery sling are readily demonstrable (Figure 14-2).
•Changes in the upper axial “3-vessel and trachea” view, along with color Doppler findings, may be seen at prenatal ultrasonography.
•Flexible bronchoscopy allows dynamic evaluation of the tracheobronchial tree and is used
to assess the level and extent of tracheal narrowing and compression pre- and postoperatively (Figure 14-3).
•Echocardiography is not
a dominant diagnostic
tool for vascular anom-
alies but is essential for
detecting associated
CHDs, which occur in 12%–30% of cases.
•Definitive diagnosis and exact anatomy of an aortic arch malformation and relationship to adjacent structures require cross-sectional imaging with CT or MR imaging with angiography. Both techniques have equal diagnostic sensitivity.
—CT scans may not require sedation and allow 3D reconstruction (virtual bronchoscopy) but expose patients to higher levels of ionizing radiation and potentially nephrotoxic iodinated contrast material.
—MR imaging has the advantage of demonstrating intracardiac abnormalities, ventricular function, and intracardiac blood flow, as well as vascular anomalies and their relationship to the trachea and esophagus, without ionizing radiation or iodinated contrast material. However, it requires deep sedation, which could further compromise patients in respiratory distress.
Figure 14-2. Esophagogram with arrow demonstrating posterior indentation of the esophagus in a patient with a right-sided aorta and ligamentum arteriosum.
Treatment and Prognosis
•Many patients will be treated for airway obstruction but will receive minimal or no relief from bronchodilators or steroids.
•Patients with feeding difficulties benefit from feeding therapy and require intervention, depending on their aspiration risk and weight gain.
•Most patients with mild anomalies improve with airway growth.
•Symptomatic vascular rings require early surgical intervention to avoid prolonged airway vascular compression and decrease morbidity and mortality associated with hypoxic or apneic spells.
—The surgical approach depends on the specific anomaly and usually requires open thoracotomy or video-assisted thoracic surgery.
—Surgery has low mortality and morbidity rates and effectively relieves tracheoesophageal compression in >95% of infants.
When to Refer
•Pediatric subspecialty referral should be considered for patients with evidence of lower airway obstruction that is unresponsive to asthma therapy and for those with difficulty feeding and failure to thrive.
When to Admit
•Admission and inpatient workup should be pursued in infants with severe symptoms such as apnea, cyanosis, and “death spells.”
Bronchial Wall Disorders
Congenital Tracheobronchomegaly (Mounier-Kuhn Syndrome)
•Tracheomalacia and bronchiectasis with markedly dilated major airways
•Types
—The trachea and bronchi demonstrate symmetrical, diffuse enlargement.
—The most common type is eccentric enlargement of the saccular diverticula between cartilages, with pronounced change to normal bronchial size.
—The diverticula extend to the distal bronchi.
•Strong male predilection, with a ratio of 8:1; usually symptomatic in the third decade of life
•Associated with Ehlers-Danlos syndrome, Marfan syndrome, and cutis laxa, as well as rheumatologic disorders
•Signs and symptoms
—Symptoms include chronic respiratory infections with dry cough, purulent sputum, dyspnea, and hemoptysis.
—Crackles, wheezing, and digital clubbing are observed.
—Bullous emphysema and pneumothoraces may be seen on radiographs.
•Gastroesophageal reflux may contribute to or exacerbate sleep apnea.
•Anesthesia and surgery may be complicated by large and weak airways, leading to endotracheal tube dislodgement, large air leaks, and postoperative tracheal collapse.
•Diagnosis
—The diagnostic features may be missed on plain chest radiographs until the tracheal size exceeds the width of the vertebral column.
—Increased tracheal diameter and expiratory collapse from tracheomalacia may be seen during flexible bronchoscopy.
—Varying degrees of obstruction and increased residual capacity may be noted at pulmonary function testing.
•Therapy
—Chest physiotherapy and antibiotics are the mainstays of therapy.
—Successful airway stent placement and surgical tracheobronchoplasty procedures have been reported.
—Endoscopic laser surgery causes submucosal tissue retraction, which can lead to increased rigidity of the membranous trachea.
—Some patients have undergone lung transplantation.
Bronchomalacia
•Congenital bronchomalacia is often isolated and has a good prognosis.
•Bronchomalacia may be associated with connective tissue disorders and with Larsen syndrome and Fryns syndrome.
•Premature infants who require intubation and positive pressure ventilation are at increased risk.
•Clinical features
—Patients present with persistent expiratory wheezing and cough.
—Premature infants with chronic lung disease and severe malacia may fail extubation and weaning from ventilator support, have persistent infiltrates from atelectasis, and/or develop hypercapnic respiratory failure.
•Diagnosis is assigned by performing flexible bronchoscopy with the patient under light sedation, with spontaneous ventilation.
•Mild malacia improves with airway growth.
•Patients with more severe involvement may require long-term treatment with noninvasive positive pressure or tracheotomy and mechanical ventilation.
•A resorbable, extraluminal, custom-printed 3D stent has been used to treat an adult with severe bronchomalacia.
Williams-Campbell Syndrome
•This rare congenital syndrome is characterized by diffuse bronchomalacia secondary to defective or absent wall cartilage, usually in fourth- to sixth-generation bronchi.
•Patients have recurrent pneumonias, coughing, wheezing, bronchiectasis, and digital clubbing.
•Differential diagnosis includes more common causes of bronchiectasis, including aspiration, immune deficiency, cystic fibrosis, ciliary dyskinesia, postinfectious bronchiectasis, and allergic bronchopulmonary aspergillosis.
•Therapy
—Patients are treated with antibiotics for acute infections.
—Exercise and inspiratory muscle training may improve quality of life and exercise tolerance.
—Inhaled steroids may reduce sputum volume but do not reduce exacerbations.
—No large randomized trials have been performed to demonstrate benefit with bronchodilators, anticholinergics, mucolytics, and/or chest physiotherapy.
—Noninvasive positive pressure ventilation may be beneficial for patients with chronic respiratory failure.
Resources for Families
•Croup and Your Young Child (American Academy of Pediatrics). www.healthychildren.org/English/health-issues/conditions/chest-lungs/Pages/Croup-Treatment.aspx
•Tracheomalacia—Congenital (U.S. National Library of Medicine). www.nlm.nih.gov/medlineplus/ency/article/001084.htm
Clinical Pearls
•Primary or congenital tracheomalacia is most often associated with tracheoesophageal fistula.
•Most patients with congenital tracheomalacia usually improve by 2 years of age.
•Tracheal collapse during expiration is best demonstrated with bronchoscopy (flexible and/or rigid) but could be missed if the patient is deeply sedated.
•Surgical treatment may be considered for patients with severe symptoms from tracheomalacia, such as respiratory distress and “death spells.”
•The pediatrician needs to maintain a strong index of suspicion for tracheobronchial abnormalities or tracheal compression from vascular abnormalities in patients with airway obstruction that does not improve with therapy for bronchospasm.
•Congenital abnormalities, such as tracheomegaly or congenital absence of bronchial cartilage, are rare and manifest with recurrent infections and bronchiectasis. They are diagnosed by obtaining chest CT scans.
Stay updated, free articles. Join our Telegram channel
Full access? Get Clinical Tree
