Anatomic Disorders of the Chest and Airways

Pierre Robin Syndrome (Robin Sequence)

Although this pattern of upper airway problems was first described by Pierre Robin in 1923, characterization of Pierre Robin syndrome remains difficult and controversial. A constellation of anomalies within the spectrum of cleft palate, micrognathia, and glossoptosis that results in airway obstruction, the Pierre Robin syndrome been linked to mutations in the SOX9 and KCNJ2 genes. Given the varying definitions published, the incidence of Pierre Robin syndrome is difficult to pinpoint; it has been reported to occur in anywhere from 1 in 8500 to 1 in 30,000 births. The hypoplastic development of the mandible is of clinical significance as the micrognathia can lead to airway obstruction and cyanosis. Obstruction is common when the infant is in the supine position, during feeding, and in active sleep, when pharyngeal muscle tone is absent. Excessive air swallowing, followed by gastric distention, vomiting, and tracheal aspiration, is a frequent problem. The pharyngeal obstruction is maintained by the generation of large negative pressures in the lower pharynx during inspiration and swallowing. Chronic obstruction leads to carbon dioxide retention, failure to thrive, and development of pulmonary hypertension with right ventricular failure.

As with the imprecise diagnosis of Pierre Robin syndrome, the severity of respiratory obstruction and the management indicated are varied. Mild cases may present with only mild glossoptosis, and because oral feeds are tolerated without respiratory obstruction, these cases can be managed by side-to-side nursing and prone positioning. In the event of respiratory symptoms with feedings or failure to thrive, a nasogastric tube for feedings may be required. In severe cases of respiratory distress, nasopharyngeal intubation should be performed, typically by passing a 3.5-mm tube through the nose and into the hypopharynx. This prevents the generation of negative pressure and greatly relieves the respiratory difficulty. The nasopharyngeal tube may be left in place for weeks or even months with proper management. Other treatments include tongue–lip adhesion surgery (glossopexy) to hold the tongue forward and tracheostomy if a nasopharyngeal tube does not adequately relieve the obstruction. Mandibular distraction and velar extension appliances can be performed in attempts to avoid tracheostomy. Nutrition can be maintained with a hypercaloric formula fed by nasogastric or gastrostomy tube. With adequate airway management and the passage of time, the problem becomes less threatening, especially after a few months, when the infant gains better control of the tongue. Oral feedings can then be introduced, usually with a long lamb’s nipple to help hold the tongue forward. With adequate nutrition and growth of the mandible, the problem usually resolves by 3 to 12 months of age, when cleft palate repair can safely take place.

Glossoptosis–Apnea Syndrome

Pierre Robin syndrome is not the only condition characterized by mechanical obstruction by the tongue. Infants with Beckwith–Wiedemann syndrome may have considerable breathing difficulties and apnea due to the associated macroglossia. Infants with a normal-sized tongue who also have conditions such as unilateral choanal atresia, choanal stenosis, or swelling of the nasal mucosa may generate considerable negative pressure in the pharynx; this, combined with inadequate muscular control over the tongue, may lead to pharyngeal obstruction with respiratory distress, cyanosis, and severe episodes of apnea.

Pharyngeal Incoordination

While the tongue provides the majority of force to move a food bolus into the esophagus, weakness and incoordination of the pharyngeal musculature can lead to disordered swallowing. This incoordination causes choking and cyanosis with feedings and may be complicated by aspiration pneumonia. Affected infants have difficulties in swallowing their own secretions. The condition may be seen in infants with severe hypoxic–ischemic encephalopathy and pseudobulbar palsy, Arnold–Chiari malformation, Möbius syndrome, and other facial malformations. Electromyography of the facial and pharyngeal muscles during rest, crying, and eating can aid in diagnosis. Specifically, it can be used to assess the sucking and swallowing coordination in infants during bottle feeding. Drugs with antimuscarinic effects, such as atropine, can decrease secretions and may produce some relief. Although some infants may gradually improve, long-term management may require initiation of tube feedings or even gastrostomy in children who fail to improve.

Laryngomalacia (Congenital Laryngeal Stridor)

A relatively common condition, congenital laryngeal stridor or laryngomalacia is the most frequent cause of stridor in infants. Laryngomalacia is characterized by the prolapse of poorly supported supraglottic structures—the arytenoids, the aryepiglottic folds, and the epiglottis—into the airway during inspiration, causing respiratory obstruction and difficulty with feeding. Despite loud, high-pitched inspiratory stridor and significant chest retractions that typically present during the first month of life, the infant seldom has cyanosis, hypercarbia, notable feeding difficulty, failure to thrive, or an abnormal cry. Laryngomalacia is worse in the supine position, with the neck flexed, and subsides in the prone position, with the neck extended. Obstruction is worse during episodes of agitation and lessens when the infant is calmed. Severe forms of laryngomalacia may cause apneic events, pulmonary hypertension, or difficulties with feeding and/or weight gain.

Although a CT scan is effective at demonstrating the abnormal prolapse of the aryepiglottic folds supporting the diagnosis, confirmation should be obtained with flexible fiberoptic laryngoscopy. Laryngeal ultrasound is an adjunctive tool for diagnosis that is non-invasive, and dynamic. In some cases, gastroesophageal reflux or episodes of obstructive apnea may be associated with this condition. Synchronous airway abnormalities are found in up to 30% of infants, including vocal cord paralysis, tracheomalacia, and subglottic stenosis. Thus, the evaluation of stridor must include the examination of the entire upper airway and upper digestive tract. Stridor associated with laryngomalacia is usually loudest at 4 to 8 months, and most cases resolve with conservative management around 12 to 24 months. Conservative therapy entails prone positioning, feeding and weight monitoring, and acid suppression therapy and most demonstrate improvement over roughly 18 months. Approximately 20%, however, will have severe obstructive apnea, cor pulmonale, and/or failure to thrive and require a surgical intervention. In these cases, supraglottoplasty may be indicated, with 71% having complete resolution of symptoms and 94% having symptom improvement postoperatively. Tracheostomy is reserved for supraglottoplasty failures.

Vocal Cord Paralysis

Unilateral cord paralysis is usually left sided and typically presents without marked stridor or retractions manifesting as aspiration. The infant may cough and choke during feedings, as laryngeal closure with swallowing is impaired. The condition is most frequently secondary to iatrogenic injury, usually caused by excessive stretching of the neck during delivery or injury during surgery; however, it can also be due to neurologic disorders. Right-sided vocal cord paralysis has been reported as a complication of cervical extracorporeal membrane oxygenation (ECMO) cannulation. Ligation of a patent ductus arteriosus (PDA) has also been associated with a high rate of left-sided vocal cord paralysis, probably secondary to recurrent laryngeal nerve injury during dissection. A recent systematic review reported that 32% of low birth weight infants who undergo PDA ligation have left vocal cord paralysis demonstrated on laryngoscopy. This increases their risk of developing bronchopulmonary dysplasia (BPD), reactive airway disease, and feeding problems requiring a gastrostomy tube. Laying the infant on the paralyzed side may decrease the amount of stridor, as the affected cord falls away from the midline. Diagnosis can be confirmed with flexible nasolaryngoscopy but may require direct laryngoscopy in the operating room ( Fig. 44.1 ). The condition tends to improve over a period of several weeks or months, and speech and swallow therapy can be used in cases where improvement is not seen. Generally, medialization of the vocal cord (including injection laryngoplasty and thyroplasty) is not recommended in neonates less than 6 months of age; however, in children with gross aspiration and severe phonotory difficulty, it may be required. Tracheostomy is preferred in severe cases of respiratory obstruction.

Bilateral cord paralysis is a much more serious condition, accompanied by high-pitched inspiratory stridor; frequently, however, the cry is normal. Usually, severe central nervous system problems are to blame, such as hypoxic–ischemic encephalopathy, cerebral hemorrhage, Arnold–Chiari malformation, hydrocephalus, or brainstem dysgenesis. Associated problems may include pharyngeal incoordination with swallowing difficulty and esophageal dysfunction, recurrent apnea episodes, and tracheal aspiration of mucous secretions and formula. The stridor may resolve slowly if brain swelling subsides after birth, as is the case with ventriculoperitoneal shunt placement. The diagnosis may be suspected at laryngoscopy but should be confirmed by flexible fiberoptic bronchoscopy, rigid bronchoscopy, or ultrafast cine CT scan. Tracheostomy is frequently required in about 50% to 60% of patients, and the prognosis usually is poor secondary to the underlying problems.

Laryngeal Atresia

Laryngeal atresia is the result of failed recanalization of the larynx during embryologic development, resulting in a newborn with complete laryngeal obstruction presenting with severe respiratory distress. In some cases, the larynx may be completely obstructed by a laryngeal web seen in the delivery room during attempts to intubate the cyanotic infant. An endotracheal tube sometimes can be forced beyond the obstruction into the trachea. Otherwise, a large-bore needle should be inserted percutaneously into the trachea to maintain marginal gas exchange while preparations for emergency tracheostomy are made. Most infants with laryngeal atresia have other lethal malformations. Most cases are now diagnosed prenatally from ultrasound findings consistent with congenital high airway obstruction syndrome (CHAOS), such as polyhydramnios and enlarged hyperechoic lungs with an associated flattened or inverted diaphragm. The mother may be evaluated for ascites or hydrops fetalis due to impaired venous return to the heart, and the amniotic fluid lecithin level may be very low in such cases. In the absence of other lethal malformations, the characteristic ultrasound diagnosis may permit preparations for emergency tracheostomy after delivery of the infant or an ex utero intrapartum treatment (EXIT)-to-airway procedure, discussed later. Intrapartum fetoscopic tracheal decompression is being investigated.

Laryngotracheoesophageal Cleft (Congenital Laryngeal Cleft)

In laryngotracheoesophageal cleft, a longitudinal communication is present between the airway and the esophagus, stretching from the larynx into the upper trachea or sometimes as far as the carina. This rare condition is reported in 1 in 10,000 to 1 in 20,000 births and is caused by failed fusion of the two lateral growth centers of the posterior cricoid cartilage, preventing proper fusion of the posterior cricoid lamina. Affected infants have respiratory distress with inspiratory stridor and cyanosis, associated with tracheal aspiration of saliva and feedings. Chest radiographs may show evidence of aspiration pneumonia, and the cine esophagogram shows contrast material spilling into the trachea. The diagnosis can be established with direct laryngoscopy and bronchoscopy. Given the high association with other congenital anomalies and syndromes, such as tracheal atresia, tracheoesophageal fistula, and Opitz–Frias syndrome, a thorough evaluation of all organ systems and genetic karyotype are recommended.

Laryngotracheoesophageal clefts are classified, by severity of symptoms, into four groups (types I to IV), which are used to determine the management strategy and the need for surgical intervention. For all types, initial management involves adequately securing the airway, including with an endotracheal tube or tracheostomy if necessary. Mild cases can sometimes be managed by conservative therapy, including swallow rehabilitation and anti-reflux medication. In those who fail conservative management, endoscopic therapy including injection augmentation of the cleft may be attempted. More severe cases require extensive reconstruction employing an anterior translaryngotracheal approach or even a partial upper sternotomy. Despite these reconstruction attempts, mortality remains high, up to 25% among all types of clefts and higher in cases with associated congenital anomalies and type IV clefts.

Tracheal Agenesis

Tracheal agenesis is a rare condition that occurs in less than 1 in 50,000 births. The trachea can be atretic just below the vocal cords but is most often absent all the way down to the carina. Clinical manifestations include severe distress, absence of vocal sound, and severe cyanosis. Affected infants usually have additional congenital anomalies within the VACTERL association, including tracheoesophageal fistulas, severe cardiac malformations, and sometimes renal and anal anomalies. Prenatal diagnosis is difficult, but prenatal presentation may manifest as CHAOS. If diagnosed prenatally, delivery via EXIT should be arranged to maximize the chances for survival. Postnatal diagnosis should be suspected in cases of respiratory distress with immediate hypoxia, no audible cry, and a mechanical inability to intubate. Despite the presence of a larynx, intubation cannot be accomplished at delivery; however, if the tracheal tube is positioned in the esophagus and connected to a mechanical ventilator, reasonable gas exchange can be obtained via the tracheoesophageal fistula. When the tracheal atresia is high, a tracheostomy can be performed in the remnant tracheal tissue. If survival seems possible, gastric division and a gastrostomy for feeding should be performed. Reconstructive surgery is not likely to be successful, however, and the prognosis is extremely poor, if not because of poor ventilation, then because of the underlying malformations.

Congenital Tracheal Stenosis

In congenital tracheal stenosis, a segment of the trachea is narrowed, usually starting in the subglottic region. The affected segment may be short or long; occasionally, the entire trachea is hypoplastic, and the bronchi may be involved. This disorder affects 1 in 64,500 live births and is usually caused by complete or nearly complete cartilage rings that narrow the trachea. Affected patients may have inspiratory stridor, expiratory wheezing, feeding difficulties, and experience cyanotic episodes. Mild inflammation and small mucous plugs may cause life-threatening deterioration. In up to 60% of cases, other congenital malformations are also present, such as vascular ring anomalies, congenital heart defects, tracheoesophageal fistula (especially the H type), and hemivertebrae. There also is an association with pulmonary agenesis.

Patients with this deformity usually can be intubated, but the endotracheal tube cannot be advanced and should not be forced. Mechanical ventilation with generous levels of positive end-expiratory pressure (PEEP) may help stabilize the infant. Tracheostomy is not indicated and interferes with making the diagnosis. Sometimes the diagnosis can be made by inspiration and expiration chest radiographs, using air as the contrast medium. However flexible fiberoptic bronchoscopy in the neonatal intensive care unit (NICU) or rigid bronchoscopy in the operating room is usually required for diagnosis. Because it is important to examine the lower limits of the stenosis, it may be necessary to proceed with tracheobronchography, but this may sometimes cause acute decompensation and is controversial. Ultrafast cine CT scan and MRI have become useful diagnostic techniques to define the lower limits of the stenosis. In addition, three-dimensional (3D) CT reformats provide valuable information on the trachea–cardiovascular relationship and can allow for 3D printing of models to rehearse complex surgical interventions.

In most cases, the stenosis requires treatment of some kind in the operating room. Balloon dilation alone is not likely to be successful in the case of a complete tracheal cartilage ring, because cartilage cannot be stretched. For short-segment stenosis, balloon tracheoplasty may be sufficient, where serial dilations during rigid bronchoscopy split the complete tracheal rings. Some groups have used metallic stents to prevent restenosis with long-term success; however, granulation tissue over the stent can make removal difficult. For longer-segment stenosis, slide tracheoplasty has become standard of care. Backer et al. described the successful use of free autografts of resected trachea. Additionally, rib cartilage and pericardial patch have been used for tracheoplasty. Tissue bioengineering as future treatment with decellularization of trachea and recellularization with stem cells is currently being studied.

The use of cardiopulmonary bypass has improved treatment and is advocated by some as averting the need for complex anesthesiology techniques. Premature infants with congenital tracheal stenosis cannot undergo tracheal resection and tracheoplasty with cardiopulmonary bypass procedures. For these patients, aggressive balloon dilations are recommended, with splitting of the weaker posterior aspect of the tracheal rings. With improvements in surgical techniques and the addition of ECMO to complex repairs, survival rates have improved to greater than 80%. Those patients undergoing slide tracheoplasty who have concurrent distal bronchomalacia is predicted to have more adverse outcomes.

Tracheobronchomalacia (Tracheomalacia)

Tracheobronchomalacia is characterized by dynamic collapse of the trachea during breathing secondary to delayed development of tracheal cartilage. This condition may be primary or associated with tracheoesophageal fistula, BPD, extrinsic tracheal compression, or prolonged intubation. Tracheobronchomalacia should be suspected in infants presenting with respiratory distress, cyanotic spells, or persistent respiratory symptoms including expiratory stridor, recurrent respiratory infections, or persistent or recurrent wet cough. Chest radiographs are usually normal, with only a 62% sensitivity in diagnosing trachebronchomalacia. With improvements in multidetector CT scanners and ultrafast cine CT scanners, diagnosis can be made with improved accuracy. Bronchoscopy remains the gold standard for diagnosis, which shows approximation of the anterior and posterior walls of the trachea during expiration. The bronchoscope may support the walls of the trachea, alleviating the respiratory distress by passage of the bronchoscope to the carina, while potentially disguising the extent of the abnormalities.

Factors associated with the development of tracheomalacia include immaturity, higher mean airway pressure, and prolonged mechanical ventilation. Affected infants may have significant dynamic compression of the trachea. Because the trachea of premature infants is very compliant and may be excessively stretched and injured during mechanical ventilation, very immature infants are particularly prone to tracheomalacia. Some premature infants have greatly enlarged tracheas or tracheomegaly after prolonged mechanical ventilation.

Many infants with tracheomalacia spontaneously improve by 1 to 2 years of age, when the cartilage has become strong enough to support tracheal patency and airway caliber increases. Severe cases with life-threatening episodes of airway obstruction necessitate tracheostomy with an elongated tracheostomy tube. However, current treatments for milder cases include tracheal intubation with continuous positive airway pressure (CPAP) or PEEP, which prevents tracheal collapse, and anterior aortopexy (fixation of the aorta to the sternum), which has the effect of supporting the attached trachea. When aortopexy is performed, the majority occur via a left anterior thoracotomy, however there are reports of right anterior and muscle sparing approaches as well as thoracoscopic aortopexies. Many of the most severely affected patients respond well to aortopexy. Posterior tracheopexy has also been performed for severe tracheomalacia with posterior membranous tracheal intrusions, and can be performed in conjunction with aortopexy. Both thoracoscopic and muscle sparing thoracotomy approaches for posterior tracheopexy have been employed. Tracheal stents have been limited due to higher failure rate than aortopexies and serious long-term complications including migration and erosion of stents. 3D printed bioresorbable external splinting for airway support is currently being investigated.

Tracheal Compression by Vascular Rings

Tracheal compression can be caused by several factors: (1) a double aortic arch, (2) a right aortic arch, (3) a left-sided origin of the (right) innominate artery, (4) a right-sided origin of the left common carotid artery, or (5) an anomalous origin of the left pulmonary artery from the right pulmonary artery. With a right aortic arch, the trachea is compressed by the main pulmonary trunk, aortic arch, and ligamentum arteriosus. The anomalous innominate or common carotid arteries form a tight crotch, which impinges on the anterior trachea. The anomalous left pulmonary artery returns to the left by passing between the esophagus and the trachea, compressing the trachea between the right and the left pulmonary arteries. Infants with tracheal compression have inspiratory stridor and expiratory wheezing, with symptoms usually appearing later in the neonatal period. Affected infants often lie with the head and neck hyperextended to stretch the trachea and make it less compressible. If the esophagus is compressed, feeding is associated with regurgitation.

There are several methods of diagnosis. The chest radiograph may show mild overinflation, a right-sided aorta, and, with appropriate technique, evidence of tracheal narrowing. A barium swallow examination may show indentation of the esophagus. Bronchoscopy should reveal a pulsatile mass with narrowing near the carina ( Fig. 44.2A,B ). Cross-sectional imaging with CT and MRI has proven to be accurate in defining most vascular malformations and can give detailed imaging of the surrounding anatomy ( Fig. 44.2C ). While echocardiography is less reliable in making the diagnosis of a vascular ring, it has been demonstrated that prenatal diagnosis by ultrasound avoided unnecessary delays in the repair of symptomatic vascular rings and that repair on identification of symptoms prevented the development of secondary tracheobronchomalacia. Treatment involves surgical division of the vascular ring. Recently, minimally invasive techniques including a video-assisted thoracoscopic approach and endoscopic robotic-assisted techniques have been employed. After surgical division of the vascular ring, the respiratory distress may persist for weeks or longer because of localized tracheal deformity (either stenosis or tracheomalacia), emphasizing the need for immediate repair on diagnosis. In cases of isolated vascular rings, repair provides treatment with minimal mortality and limited postoperative complications.

Tracheal Compression by Extrinsic Masses

The trachea may also be compressed by a bronchogenic cyst, an enteric duplication cyst, a thoracic neurogenic tumor, or a mediastinal teratoma. These may be demonstrated by anteroposterior and lateral chest films and are especially apparent on CT scan. Such masses may also compress the esophagus and can be demonstrated with a barium swallow.