Tracheomalacia

Practice Essentials

Tracheomalacia is a process characterized by flaccidity of the supporting tracheal cartilage, widening of the posterior membranous wall, and reduced anterior-posterior airway caliber. These factors cause tracheal collapse, especially during times of increased airflow, such as coughing, crying, or feeding.^{[1, 2, 3, 4]} Tracheomalacia most commonly affects the distal third of the trachea and can be associated with various congenital anomalies, including cardiovascular defects, developmental delay, gastroesophageal reflux (GER), and tracheoesophageal fistula.

Tracheomalacia can be categorized into three groups on the basis of histologic, endoscopic, and clinical presentation, as follows:

• Type I presents as congenital or intrinsic tracheal abnormalities that can be associated with a tracheoesophageal fistula or esophageal atresia
• Type II presents as extrinsic defects or anomalies, such as a vascular ring causing undue pressure on the trachea
• Type III presents as acquired tracheomalacia that occurs with prolonged intubation, chronic tracheal infections, or inflammatory conditions like relapsing polychondritis

Immaturity of the tracheobronchial cartilage is thought to be the cause in type I, whereas degeneration of previously healthy cartilage is thought to produce other types. Inflammatory processes, extrinsic compression from vascular anomalies, or neoplasms may produce degeneration.

Recommendations for treatment of tracheomalacia include the following:

• Forms of milder primary tracheomalacia are best treated by nonsurgical means^[5]
• For distal tracheomalacia that is idiopathic, pulsatile, or associated with tracheoesophageal fistula or vascular anomalies, aortopexy with concomitant intraoperative bronchoscopy appears to be the procedure of choice
• For proximal or diffuse tracheomalacia, tracheostomy (despite its related high morbidity) or the use of stents is beneficial^{[3, 6]}
• With increasing experience, a direct surgical approach to treating tracheomalacia may replace tracheostomy in the management of proximal and diffuse tracheomalacia; these procedures include prosthetic stenting, tracheoplasty, and tracheal resection with end-to-end anastomosis (EEA)

For patient education resources, see Bronchoscopy.

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Anatomy

The trachea commences at the cricoid cartilage and terminates at the fifth thoracic vertebra. It lengthens and dilates during inspiration and narrows and shortens during expiration. Fifteen to 20 incomplete rings of cartilage prevent it from collapsing.

The trachea is separated from the vertebral column by the esophagus posteriorly.

In the thorax, the jugular venous arch lies anteriorly at the sternum; the brachiocephalic trunk and left common carotid artery lie at the level of the third thoracic vertebra.

The arch of the aorta is to the left and front of the distal trachea just before it bifurcates. On the right of the trachea are pleura, on the left is the aortic arch, and posterolaterally is the left subclavian artery.

The relation of the trachea to the aortic arch makes it liable to compress from aneurysm or from vascular rings, which occur with abnormal arterial development. Therefore, for distal tracheomalacia, whether associated with tracheoesophageal fistula or with vascular anomalies, aortopexy is the procedure of choice.

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Pathophysiology

Tracheomalacia is a structural abnormality of the tracheal cartilage allowing collapse of its walls and airway obstruction. A deficiency and/or malformation of the supporting cartilage exists, with a decrease in the cartilage-to-muscle ratio.

Tracheomalacia most commonly affects the distal third of the trachea. By virtue of its intrinsic flexibility, or compliance, the trachea changes caliber during the respiratory cycle. Tracheal dilatation and lengthening occurs during inspiration; narrowing and shortening occurs during expiration. Accentuation of this cyclic process may cause excessive narrowing of tracheal lumen, thus deforming the entire length or a localized segment. However, it is rarely found in combination with laryngomalacia because of the separate developmental pathways for the trachea and the larynx.

In general, abnormal collapsibility denotes a loss of structural rigidity, such as softening, better expressed as abnormally increased compliance. Any disease process affecting the integrity of the tracheal wall is apt to cause a change in tracheal compliance. The anatomic defect may be trivial or even may escape detection. The functional interference with ventilation may cause expiratory flow obstruction and interfere with clearance of secretions.^[7]

Functional impairment is proportional to the length of the involved segment and the degree of stenosis. Furthermore, kinking may occur at the transition between healthy tracheal wall and the indurated segment, as well as in the malacic segment. In diffuse tracheal disease or extensive peritracheal adhesions, the trachea usually distends unevenly during inspiration and collapses during expiration, thus interfering with the tracheal function.

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Etiology

Tracheomalacia can be associated with a variety of congenital anomalies, including cardiovascular defects, developmental delay, esophageal anomalies, and GER. It can be caused by a diffuse process of congenital origin or by a localized abnormality such as a vascular ring, anomalous innominate artery, esophageal atresia,^[2] and tracheoesophageal fistula. Internal compression by an endobronchial or tracheostomy tube also may be the culprit. Tracheal cartilage deficiency may be present in 75% of the patients with tracheoesophageal fistula. Tracheomalacia rarely is found in combination with laryngomalacia.

The entire cartilaginous structure of the upper airway is diffusely involved in congenital abnormality, or a localized area of decreased rigidity may be observed secondary to abnormal development of foregut and vasculature in embryonic life. A vascular ring around the trachea does not allow normal development in that area of trachea, and tracheomalacia is observed in the area of impingement.

The cases of acquired tracheomalacia occur with increasing frequency both in children and in adults, and the tracheomalacia often is not recognized clearly. These lesions usually cause focal tracheomalacia and may result from indwelling tracheostomy^[8] and endobronchial tube, chest trauma, chronic tracheobronchitis, and inflammation (relapsing polychondritis). They may be secondary to pulmonary resection and tracheal malignancy (cylindroma), and they may be idiopathic.

Primary (congenital) adult tracheomalacia may be classified as follows^[3] :

• Polychondritis
• Idiopathic (Mounier-Kuhn syndrome)

Secondary (acquired) adult tracheomalacia may be classified as follows^[3] :

• Posttraumatic (postintubation, posttracheotomy, external chest trauma, post-lung transplantation)
• Emphysema
• Chronic bronchitis
• Chronic inflammation (relapsing polychondritis)^[9]
• Chronic external compression of trachea (malignancy, benign tumors, cysts, abscesses, aortic aneurysm)
• Vascular rings (undiagnosed in childhood)

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Epidemiology

All types of tracheomalacia are extremely rare; no definite incidence rates are available.^[10]

In a total of 512 bronchoscopies, airway malacia was diagnosed in 160 children (94 males) at a median age of 4.0 years (range, 0-17 y).^[11] Airway malacia was classified as primary in 136 children and as secondary in 24 children. The incidence of primary airway malacia was estimated to be at least 1 in 2100.

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Prognosis

With conservative measures, the symptoms often resolve spontaneously by age 18-24 months.^[3]  Diffuse malacia of the airway of the congenital origin improves by age 6-12 months as the structural integrity of the trachea is restored gradually with resolution of the process.

Tracheostomy has been used to stent the airway until natural maturation of cartilage occurs. This often imposes a heavy penalty on the child; therefore, treatment alternatives should be explored.

Aortopexy has proven to be a safe, expedient way to relieve the problem of tracheomalacia in most patients. The success of aortopexy has been reported at about 75% in several small studies. Aortopexy has less long-term morbidity than tracheostomy. While not altering the structural characteristics of the tracheal wall, it widens the anterior-posterior tracheal dimension to maintain a patent lumen. The only treatment failures with aortopexy were patients with diffuse or proximal tracheal involvement.

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History

Infants present after a few weeks of life with expiratory stridor (also called laryngeal crow). Expiratory stridor may worsen with supine positioning, crying, and respiratory infections. Hoarseness, aphonia, breathing problems, and feeding difficulties have been described.

It is improtant to obtain a history of an acquired etiology, such as prolonged intubation, tracheostomy, chest trauma, recurrent tracheobronchitis, cartilage disorder (relapsing polychondritis), or lung resection.

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Physical Examination

Inspiratory retractions of supraclavicular and intercostal spaces may occur. Thoracic deformity may be present in cases of chronic tracheomalacia, especially in younger patients. Auscultation reveals normal inspiration but abnormal expiratory noises. Not uncommonly, infants may demonstrate signs of growth failure.

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Imaging Studies

Chest radiography

Chest radiography may demonstrate hyperinflation, excessive narrowing of the tracheal lumen during expiration, or vascular anomalies such as double aortic arch; further evaluation usually is required. (See the images below.)

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Lateral chest radiograph shows excessive tracheal narrowing.

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This shows the trachea during inspiration and expiration. Tracheal collapse of more than 50% during expiration is diagnostic of tracheomalacia.

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A 58-year-old woman with a history of polychondritis presented with inspiratory stridor and respiratory difficulties. The chest radiograph shows narro....

Cinefluoroscopy

Cinefluoroscopy performed with contrast in the esophagus using quiet respiration and coughing has proved to be an optimal means of establishing a diagnosis. During coughing, more than half to complete collapse of tracheal lumen confirms the diagnosis. In addition to showing collapse of the tracheal wall, cinefluoroscopy may identify esophageal defects, and it may reveal deformation of tracheal contour due to vascular anomaly.

Computed tomography

The dynamic airway collapse is better appreciated with ultrafast computed tomography (CT). Dynamic expiratory CT elicits a larger degree of airway collapse than standard end-expiratory CT in patients with tracheobronchomalacia.^[13]  A study that assessed airway collapse for confirmation of a diagnosis of tracheobronchomalacia (N = 14; 11 men, 3 women; age range, 19-79 y) found that dynamic expiratory CT revealed a significantly greater degree of airway collapse than end-expiratory CT did.^[14] (See the images below.)

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The CT scan of a 58-year-old woman with a history of polychondritis who presented with inspiratory stridor and respiratory difficulties shows tracheal....

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CT image showing tracheal narrowing in a 58-year-old woman with a history of polychondritis who presented with inspiratory stridor and respiratory dif....

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A 3-dimensional reconstruction of CT scan images confirms the presence of tracheomalacia in a 58-year-old woman with a history of polychondritis who p....

A study comparing dynamic airway CT (DACT) with flexible bronchoscopy for the diagnosis of tracheomalacia in children found that whereas ultralow-dose DACT was highly specific and had a positive predictive value for the detection of tracheomalacia (as well as for categorizing the severity of tracheal collapse), it was not sensitive enough to rule it out.^[15]

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Endoscopy

The definitive diagnosis of major airway depends on obtaining an accurate history combined with proper endoscopic evaluation (see the image below).^[13] The airway is directly visualized during spontaneous respiration using ventilating laryngoscope and telescoping bronchoscopy. Flexible bronchoscopy also may be employed. The findings consist of the following classic triad:

• Loss of normal semicircular shape of tracheal lumen
• Forward ballooning of the posterior membranous wall
• Anteroposterior narrowing of the tracheal lumen

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Healthy trachea is visualized endoscopically.

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Other Tests

In pulmonary function testing, the flow-volume curve, though usually performed in adults rather than children, may demonstrate a normal inspiratory curve but a truncated expiratory limb.

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Approach Considerations

Current recommendations for treatment of tracheomalacia include the following:

• Forms of milder primary tracheomalacia are best treated by nonsurgical means^[5]
• For distal tracheomalacia that is idiopathic, pulsatile, or associated with tracheoesophageal fistula or vascular anomalies, aortopexy with concomitant intraoperative bronchoscopy appears to be the procedure of choice
• For proximal or diffuse tracheomalacia, tracheostomy (despite its related high morbidity) or the use of stents is beneficial^{[3, 6]}  
• As experience continues to accumulate, a direct surgical approach to treating tracheomalacia may replace tracheostomy in the management of proximal and diffuse tracheomalacia; these procedures include prosthetic stenting, tracheoplasty, and tracheal resection with end-to-end anastomosis (EEA)

In one study, silicone stents were inserted into the trachea or left main-stem bronchus in 14 children (age range, 2-69 mo) for tracheomalacia or airway kinking (n = 7), vascular compression (n = 5), and surgically corrected congenital tracheal stenoses (n = 2). The best results were obtained in tracheomalacia. Of the 14 cases, six (43%) were considered successful, and five cases were considered failures, primarily because of stent migration.^[16]

An earlier study reviewed conservative therapy, tracheostomy, aortopexy, or tracheal reconstruction in 41 infants with tracheomalacia.^[17] Fifteen patients with mild primary tracheomalacia had resolution of symptoms by the age of 2 years; five treated with tracheostomy developed secondary tracheomalacia at the site. In nine patients with primary tracheomalacia treated with aortopexy, five were symptom-free, one was improved, and three procedures were unsuccessful.

Of the 10 patients in the acquired group treated with aortopexy, six were cured, two were improved, and treatment failed in two.^[17] Of the six patients with a tracheostomy, three eventually were extubated, one had major reconstruction, and two had tracheostomies for an extended period.

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Medical Therapy

Tracheomalacia of the milder primary variety is best treated by nonsurgical means.

Most infants who have mild-to-moderate symptoms should be offered conservative therapy because these patients improve by the age of 18-24 months.^{[8, 5]}  The majority respond to such therapy, consisting of humidified air, chest physical therapy, slow and careful feedings, and control of infection and secretions with antibiotics.

The use of continuous positive airway pressure (CPAP) has been recommended in patients having respiratory distress and may be successful in patients requiring a short-term intervention as the disorder spontaneously resolves.^[3]

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Surgical Therapy

General considerations

Tracheomalacia generally is benign; most infants outgrow the symptoms by 18-24 months of age.^[3] Surgical therapy is required when conservative measures are not adequate or when reflex apnea is present. Surgery includes correction of the underlying cause (eg, vascular ring) when present, tracheostomy, and aortopexy.^{[8, 18]}

The indications for tracheostomy are severe symptoms, failure of conservative therapy, and proximal or diffuse tracheomalacia. The indications for aortopexy are dying spells or reflex apnea, recurrent pneumonia, intermittent respiratory obstruction, and inability to extubate airway in an infant who is intubated. Surgery only is recommended for severe symptoms and failure of conservative therapy.^{[8, 3]}

During surgery, a careful search should be made for tracheoesophageal fistula, which should be treated surgically if present. Other causes of tracheal compression, such as mediastinal tumors or vascular rings, also must be corrected surgically. In patients identified as having vascular anomalies compressing the distal trachea, constricting vessels should be surgically divided and affixed to other structures to eliminate impingement on the trachea.^[19]

Tracheomalacia following long-standing tracheotomies may be helped by anterior cricoid/tracheal suspension, where muscular tissue of the overlying trachea is sutured to the fascia of strap muscles.

Acquired tracheomalacia, if severely symptomatic, can be treated by internal stenting, external stenting, or tracheostomy.

The use of various types of tubes and stents for the management of tracheomalacia is helpful.^[20] Success with Montgomery and Dumon tubes has been reported in the literature. Short-term satisfactory results also have been reported with the placement of an expandable metallic stent (Palmaz stent) in patients with intractable respiratory symptoms caused by tracheomalacia.

A report of aortopexy in 28 children with severe and localized tracheomalacia used a left lateral muscle-sparing approach. The indications included acute life-threatening events in 22 patients, failure to extubate in five, and recurrent pneumonia in one. Associated esophageal atresia was present in 15 patients, and 13 had primary tracheomalacia. Most symptoms of tracheomalacia resolved in 26 of the 28 patients after aortopexy.^[21]

Video-assisted posterior tracheopexy, with or without robotic guidance, has been suggested as a possible option for select children with severe tracheomalacia.^{[22, 23]}

Treatment of tracheomalacia in adult patients

The finding may be incidental in many adults with tracheomalacia; these patients are asymptomatic and do not require therapy.

In symptomatic patients, care is initially supportive. Tracheomalacia frequently occurs in patients who also have chronic obstructive pulmonary disease (COPD), and the obstructive disorder optimally should be treated first. If conservative measures fail, noninvasive, positive-pressure ventilation can be used in the short term to keep the airway open and to facilitate secretion drainage. In selected patients, surgery may be used. Tracheostomy alone may be effective because the tracheostomy tube might bypass the malacic segment, or the tube itself might splint the airway open. If the patient has generalized and extensive disease, a longer tube may be necessary.

Surgical placation of the posterior wall of the trachea with crystalline polypropylene and high-density polyethylene mesh has been used recently.^[24] Via a right posterolateral thoracotomy, the mesh is fashioned into a 2.5-cm-wide strip, which is sutured to the posterior membranous wall. Thereafter, 2-cm sheets of mesh can be sutured to the right and left mainstem bronchi.

A range of stents can be utilized to keep the airway open mechanically. Metal stents have been used to manage airway obstruction. Such stents can be easily placed by means of flexible bronchoscopy, are visible on plain radiographs, expand dynamically, and preserve mucociliary function. Formation of granulation tissue, which can cause severe problems including airway obstruction, airway perforation, and death, is a potential complication. Silicone stents are easy to insert, reposition, and remove; however, placing these stents requires rigid bronchoscopy and general anesthesia.

Stents have resulted in both subjective and objective improvement.^[25] Most patients report immediate improvement in their respiratory symptoms, and airflow improves, but success is not universal. Gotway et al reported long-term pulmonary function improvement with stents placed for both tracheal stenosis and tracheomalacia.^[20]

Tracheostomy

Tracheostomy helps maintain an airway while the child grows and the trachea regains structural integrity, but the problem with this procedure is that the tracheostomy tube may not support the distal trachea. The tracheostomy can be performed as an open procedure or via a percutaneous approach.

With the patient in supine position, the neck is placed in moderate hypertension. Identify cricoid cartilage and the thyroid isthmus, and aim to place the opening over the third tracheal ring. A transverse incision is made, the pretracheal fascia is divided, and the tracheal rings are counted. The third tracheal ring is identified and divided in the midline; the tracheal incision must be vertical. The second and fourth rings may need to be divided as well. No amount of tracheal tissue is removed during the procedure.

The stoma is enlarged by gently spreading the blades of the hemostat against the margins of the tracheal opening. A lubricated tracheostomy tube is inserted through this opening. Transtracheal injection of lidocaine reduces coughing and eases tube placement. The tube is secured to the neck and adjusted so that the distal end is at least 2 cm above the carina.

Percutaneous tracheostomy

The percutaneous tracheostomy can be performed in the intensive care unit (ICU) and requires specially designed introducer sets. After prepping the patient's neck, a 3-cm longitudinal incision is made over the second and third cartilaginous tracheal rings. The endotracheal tube is withdrawn somewhat, and the introducer catheter is advanced into the tracheal lumen. The intratracheal location is confirmed either under bronchoscopic guidance or though the withdrawal of air bubbles. The introducer catheter is advanced into the trachea, and the syringe and steel needle of the introducer catheter are withdrawn.

The flexible J-tipped guide wire is inserted into the trachea through the introducer catheter, and the catheter is removed. Thereafter, an introducing dilator is advanced into the trachea until the black positioning mark. The tapered sequential dilators are used successively to dilate the anterior tracheal wall to a diameter larger than the tracheostomy tube. A tracheostomy tube over the tapered dilator is advanced into the trachea, and dilator, guiding catheter, and wire guide are removed. The inner cannula is inserted, and the patient is attached to the ventilator. A chest radiograph should confirm the correct positioning.

Aortopexy

Aortopexy can provide relief of tracheal compression and relieves the external pressure on the flaccid trachea. This is not a perfect operation, because of the low but significant failure rate and the potential for complications.

The patient is positioned with the left shoulder elevated at a 30-45º angle. A bronchoscopy is performed to confirm the diagnosis of tracheal compression. Through a left anterior thoracotomy, partial thymectomy improves the exposure and increases the effective cross-sectional area of the upper mediastinum. The apex of the left upper lobe is retracted inferiorly and posteriorly. The search for the vascular ring is conducted, and the esophagus is examined.

A single row of interrupted monofilament sutures is placed from the arch of the aorta to the undersurface of the sternum and tied down to displace the arch anteriorly. The bites into the aorta must be deep enough to include media and adventitia; sometimes, the sutures are passed through the sternum to a subcutaneous pocket. Dissection around the aorta must be avoided because these attachments help to draw open the lumen of the trachea when aortopexy has been achieved.

Aortopexy attaches the aorta to the sternum, pulling the anterior wall of the trachea forward and thereby preventing its collapse.

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Postoperative Care

Postoperative care of these patients is very similar to that of patients undergoing thoracic surgery. In the immediate postoperative period, patients may need to be monitored closely in an ICU setting because several days may pass before improvement in airway function occurs. These patients require long-term follow-up for evaluating the success or failure of the surgical procedure and the development of complications.

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Complications

Long-standing tracheostomies can lead to several complications, including the following:

• Bilateral vocal cord paralysis
• Compression and erosion of the innominate artery
• Formation of secondary granulation tissue, which results in protraction of tracheomalacia
• Speech delay, in several instances

During aortopexy, as the sutures are placed through aortic wall, there is an immediate risk of hemorrhage and a later potential for postoperative aneurysm formation. Deaths have occurred as a result of operative failures, other structural anomalies, and chronic ventilatory insufficiency.

Complications of percutaneous tracheostomy include the following:

• Bleeding
• Infection
• Accidental endotracheal extubation
• Extratracheal dilator position
• Esophageal perforation
• Mucosal endobronchial flap

This approach has some advantages over the usual tracheostomy, among them that it is inexpensive and is easy to learn.

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