135: Surgical Diseases of the Newborn: Diseases of the Airway, Tracheobronchial Tree, and Lungs

Intrinsic abnormalities of the airway that cause partial obstruction of the airway fall into this category. Examples include laryngomalacia, vocal cord paralysis, subglottic web, and hemangioma.

Lesions result in partial obstruction of the airway and cause stridor and respiratory distress of varying severity.

1. Laryngomalacia is due to delayed development of the supraglottic pharynx.

2. Congenital vocal cord paralysis can be congenital or acquired (birth trauma, patent ductus arteriosus ligation) and unilateral or bilateral.

3. Subglottic web is a congenital short-segment obstruction that may be partial or complete.

4. Hemangioma can occur below the glottis, engorge, and obstruct with agitation.

This can vary from mild respiratory stridor to complete airway obstruction depending on pathology.

The diagnosis is established by airway endoscopy with careful visual inspection.

Management is individualized. Some problems, such as laryngomalacia, will be outgrown and require only supportive care. Other lesions, such as subglottic webs and hemangiomas, may be amenable to endoscopic resection or laser therapy.

Choanal atresia is a congenital blockage of the posterior nares caused by a persistence of a bony septum (90%) or a soft tissue membrane (10%).

True choanal atresia is complete and bilateral, and it is one cause of respiratory distress immediately after delivery. Neonates are obligate nose breathers and do not automatically breathe through the mouth. Unilateral defects may be well tolerated and often go unnoticed.

Respiratory distress resulting from partial or total upper airway obstruction is the mode of presentation.

Diagnosis is based on the inability to pass a catheter into the nasopharynx via either side of the nose.

Making the baby cry will initiate mouth breathing and temporarily improves the respiratory status. Insertion of an oral airway maintains the ability to breathe until the atresia is surgically corrected. Definitive management requires resection of the soft tissue or bony septum in the nasopharynx.

This anomaly consists of mandibular hypoplasia (micrognathia) in association with cleft palate.

Airway obstruction is produced by posterior displacement of the tongue associated with the small size of the mandible.

Severity of symptoms varies, but most infants manifest a high degree of partial upper airway obstruction

1. Infants with mild involvement can be cared for in the prone position and fed through a special Breck nipple. Over the next few weeks to months, the mandible grows and the degree of airway obstruction subsides.

2. More severe cases require nasopharyngeal tubes, mandibular distraction, or other procedures to hold the tongue in an anterior position. Tracheostomy is generally a last resort.

A rare congenital anomaly in which there is an incomplete separation of the larynx (and sometimes the trachea) from the esophagus, resulting in a common channel of esophagus and airway. This communication may be short or may extend almost the entire length of the trachea.

The persistent communication between the larynx (and occasionally a significant portion of the trachea) and the esophagus results in recurring symptoms of aspiration and respiratory distress with feeding.

Respiratory distress during feeding is the presenting symptom.

Contrast swallow may suggest the anomaly, but endoscopy is essential to establish the diagnosis and delineate the extent of the defect.

Laryngotracheal esophageal cleft is treated by surgical correction, which is difficult and often unsuccessful.

A vascular ring denotes a variety of anomalies of the aortic arch and its branches that create a “ring” of vessels around the trachea and esophagus.

Partial obstruction of the trachea, the esophagus, or both may result from extrinsic compression by the encircling ring of vessels.

Dysphagia and/or stridor (respiratory insufficiency) are the modes of presentation. Airway compromise is rarely severe and usually presents as stridor.

Diagnosis is by barium swallow, which identifies extrinsic compression of the esophagus in the region of the aortic arch. Computed tomography (CT) and magnetic resonance imaging (MRI) are useful to further define the anatomy.

Management consists of surgically dividing a portion of the constricting vascular ring. The surgical plan must be tailored to the specific type of anomaly.

This anomaly is an uncommon type of tracheoesophageal fistula (TEF), making up 5% of cases. Esophageal continuity is intact, but there is a fistulous communication between the posterior trachea and the anterior esophagus.

When the fistula is small, “silent” aspiration with resulting pneumonitis occurs during feedings. If the fistula is unusually large, coughing and choking may accompany each feeding.

Symptoms, as noted previously, depend on the size of the fistula. This TEF subtype frequently escapes diagnosis in the newborn period.

Barium swallow is the initial diagnostic study, but it sometimes fails to identify the fistula. The test's sensitivity can be increased with a “pull back” upper gastrointestinal (UGI) series. Here, a nasogastric tube placed in the distal esophagus is pulled out slowly while instilling water-soluble contrast. The most accurate procedure is bronchoscopy (often combined with esophagoscopy). This should allow discovery and perhaps cannulation of the fistula.

Surgical correction is required. The approach (via the neck or chest) is determined by location of the fistula.

Lobar emphysema denotes hyperexpansion of the air spaces in a segment or lobe of the lung.

Inspired air is trapped in an enclosed space. As the entrapped air expands, the normal lung is increasingly compressed. Cystic problems are more common in the upper lobes.

Small cysts may cause few or no symptoms and are readily seen on radiograph. Giant cysts may cause significant respiratory distress, with mediastinal shift and compromise of the contralateral lung.

Usually, the cysts are easily seen on plain chest radiographs. However, the radiologic findings may be confused with tension pneumothorax. Chest CT is often useful.

Therapeutic options include observation for small asymptomatic cysts, repositioning of the endotracheal tube to selectively ventilate the uninvolved lung for 6–12 hours, bronchoscopy for endobronchial lavage, and operative resection of the cyst with or without the lobe from which it arises.

The term cystic adenomatoid malformation (CAM) encompasses a spectrum of congenital pulmonary malformations involving varying degrees of cyst formation. They communicate with the normal tracheobronchial tree. There are 3 types (I, II, and III) depending on the size of the cysts within the malformation.

Severity of symptoms is related to the amount of lung involved and particularly to the degree to which the normal ipsilateral and contralateral lung is compressed.

Signs of respiratory insufficiency such as tachypnea and cyanosis are modes of presentation.

The characteristic pattern on chest radiograph is multiple discrete air bubbles, occasionally with air-fluid levels, involving a region of the lung. The radiographic appearance can mimic that of congenital diaphragmatic hernia (CDH).

Treatment is surgical resection of the involved lobe of lung, allowing reexpansion of compressed normal pulmonary tissue. If small and without symptoms, the surgical management can wait until the infant is several months of age.

Pulmonary sequestration is masses of abnormal tissue with aberrant blood supply arising from a systemic and not a pulmonary source. They may be intralobar or extralobar. Intralobar sequestrations have abnormal connections to the tracheobronchial tree. Extralobar sequestrations have separate pleura and no connections to the tracheobronchial tree.

Sequestrations are usually not recognized in the neonate. Intralobar sequestrations are found after frequent recurrent infections. Extralobar sequestrations are usually not associated with infections.

Lung mass found with or without frequent recurrent infections.

Diagnosis is by chest radiograph and CT scan.

Surgical resection is warranted. Aberrant blood supply may originate from below the diaphragm.

A patent pleuroperitoneal canal through the foramen of Bochdalek is the most common defect in congenital diaphragmatic hernia (CDH) (95%). A central anterior defect of the diaphragm (Morgagni hernia) is less common and usually not associated with lung hypoplasia

1. Prenatal. Abnormal communication between the peritoneal and pleural cavities allows herniation of intestine into the pleural space as the developing gastrointestinal (GI) tract returns from its extracoelomic phase at 10–12 weeks' gestation. Depending on the degree of pulmonary compression by herniated intestine, there may be marked diminution of bronchial branching, limited multiplication of alveoli, and persistence of muscular hypertrophy in pulmonary arterioles. These lung abnormalities are most notable on the same side as the CDH (usually the left); they are also present to some degree in the contralateral lung.

2. Postnatal. After delivery, the anatomic anomaly may contribute to the following pathologic conditions:

   1. Pulmonary parenchymal insufficiency. Infants with CDH have an abnormally small functional lung mass. Some have so few conducting air passages and developed alveoli—a condition known as pulmonary parenchymal insufficiency—that survival is unlikely.

   2. Pulmonary hypertension. Infants with CDH are predisposed to persistent pulmonary hypertension of the newborn (PPHN), also known as persistent fetal circulation. In this condition, blood is shunted away from the lungs through the foramen ovale and patent ductus arteriosus (PDA). Shunting promotes acidosis and hypoxia, both of which are potent stimuli to additional pulmonary vasoconstriction. Thus, a vicious cycle of clinical deterioration is established.

Most infants with CDH exhibit significant respiratory distress within the first few hours of life.

Prenatal diagnosis can reliably be made by ultrasonography. Delivery should occur in a neonatal center with full resuscitation capability, including extracorporeal life support/extracorporeal membrane oxygenation (ECLS/ECMO). Afflicted infants tend to have scaphoid abdomens because a paucity of the GI tract is located in the abdomen. Auscultation reveals diminished breath sounds on the affected side. Diagnosis is established by a chest radiograph that reveals a bowel gas pattern in one hemithorax, with shift of mediastinal structures to the other side, and compromise of the contralateral lung

1. Indwelling arterial catheter. Blood gas levels should be monitored by an arterial catheter.

2. Supportive care. Intubation with positive-pressure ventilation should be initiated immediately. CDH lungs can be surfactant deficient, and replacement therapy may be helpful. Several different strategies for appropriate respiratory and metabolic support have been described. These include permissive hypercapnia with conventional ventilation, oscillator ventilation, and/or the addition of inhaled nitric oxide. All these therapies are aimed at providing maximal pulmonary vasodilatation with minimal secondary lung injury due to barotrauma.

3. Nasogastric tube. A nasogastric tube should be placed to lessen gaseous distention of the stomach and intestine. Care must be taken to make sure the tube remains functional and does not clog.

4. Surgical correction. This is done by reduction of intrathoracic intestine and closure of the diaphragmatic defect. Surgical intervention is an essential element of treatment, but it is not the key to survival. Most authorities favor a delayed approach, allowing the newborn to stabilize its hyperreactive pulmonary vascular bed and to improve pulmonary compliance. If indicated, ECMO/ECLS can be instituted, and repair of the hernia defect performed immediately after stabilization on ECMO/ECLS, when the infant is ready to wean from ECMO/ECLS, or after successful ECMO/ECLS decannulation.

5. Extracorporeal life support/extracorporeal membrane oxygenation (ECLS/ECMO). Used in the treatment of neonates with severe respiratory failure. Exposure of venous blood to the ECMO/ECLS circuit allows correction of Po₂ and Pco₂ abnormalities as the lungs recover from the trauma associated with positive-pressure ventilation (see Chapter 18).

Mortality rates for infants with CDH are still in the range of 50%. This high rate has prompted a search for other modes of treatment in addition to the expensive, labor-intensive modality ECLS.

1. Fetal surgery. This has been performed successfully on a case study basis, with the idea that in utero intervention will lessen the risk for development of pulmonary hypoplasia, which may be incompatible with life after delivery. However, trials of fetal tracheal occlusion and complete fetal correction have been abandoned due to high mortality.

2. Medications. Another major area of research is the attempt to develop a pharmacologic agent to decrease pulmonary vascular resistance selectively. To date, early promising data on inhaled nitric oxide have been tempered with the realization that it does not reverse pulmonary hypertension. Sildenafil (0.5–1 mg/kg every 6 hours) is reported to lower pulmonary hypertension in neonates with PPHN.