Medical and Surgical Interventions for Respiratory Distress and Airway Management




Introduction


The advent of the specialty of neonatology has promoted the care and survival of ever-increasing numbers of extremely small newborns. These patients have a whole host of complex anatomic problems. Consequently, neonatologists and pediatric surgeons face vast challenges in the management of problems with the airway and lungs. In this chapter, we look first at medical management of the neonatal airway and then progress to the supporting role of pediatric surgeons and otolaryngologists in the diagnosis and management of complex airway problems.




Medical Management of the Neonatal Airway


Maintenance of the airway in sick neonates is critical for ensuring their survival. A compromised airway such as a partial obstruction could potentially lead to gas trapping and ventilatory problems. This in turn can lead to hypoxia, hypercarbia, and serious hemodynamic disturbances. Successful airway management in neonates involves accurate and continuous assessment of the patient by a team of skilled care providers. Adequate preparation prior to performing airway securing procedures is vital to avoid complications associated with artificial airway maintenance. Adequate preparation includes checking all required equipment for availability and full functionality, utilization of resources available in the neonatal intensive care unit (NICU) such as nurses and respiratory therapists, and last, but not least, due diligence on the part of the neonatologist to anticipate and prepare for complications (see Chapter 27 , Pulmonary Care).


Typically, the neonatal airway is managed by a team of physicians, respiratory therapists, and nurses in the NICU. The NICU has developed into a unit that provides care not only for premature infants but also for infants with surgical or cardiac problems. Airway needs and indications for interventions may be completely different in such situations and may require the intervention of airway experts such as otolaryngologists and pediatric surgeons. In this section we will discuss the challenges involved in management of the neonatal airway and the medical interventions performed for airway maintenance prior to seeking surgical support.




Anatomic Disadvantages of the Neonatal Airway


The neonatal airway is distinctly different from the adult airway. The anatomic disadvantages begin with the shape of the head in neonates, who have a larger occiput. The large occiput in a supine posture naturally places the infant’s neck in a flexed position that may cause kinking of the airway and potentially lead to obstruction. This may also obscure visualization of the larynx during intubation, which may require a shoulder roll to reduce neck flexion. A “sniffing posture” with slight extension of the neck when the infant is supine is often required to align the airway axis to achieve unobstructed air entry.


Neonates are obligate nasal breathers, which makes their nasopharynx a vital conduit for ventilation. Secretions and mucosal edema causing impediment to airflow at the level of the nasopharynx can significantly compromise the neonate’s airway. Therefore care providers managing the airway of neonates should not only be proactive about clearing secretions but also use extreme caution during airway toileting procedures to avoid iatrogenic nasal mucosal edema.


Hypopharyngeal structures such as the vallecula, the epiglottis, and the laryngeal structures such as arytenoids that commonly serve as landmarks during laryngoscopy and intubation also differ in neonates. The epiglottis is omega-shaped and is generally longer, larger, and less flexible in infants, making this structure more susceptible to injury during intubation and suctioning. Abnormalities of the epiglottis or swelling associated with certain conditions in newborns, such as trauma, and in infants and older children, such as epiglottitis, may make endotracheal intubation extremely challenging. The soft tissue structures of the hypopharynx and larynx follow the physical principles of Bernoulli and the Venturi effect and collapse easily. Bernoulli’s principle states that, when these structures are subjected to fast airflow, a low pressure is exerted on the walls of the tube. The Venturi effect is seen during inspiration when these low-pressure walls collapse. Conditions such as laryngomalacia may exaggerate these effects and compromise the airway further.


The lower airway in the premature infant is significantly smaller compared to that of older children and adults. In 1982 Wailoo and Emery described the normal development of the trachea from 28 weeks to 14 years of age based on quantitative assessment of the trachea obtained postmortem. It was observed that the trachea is funnel-shaped, with the upper end wider than the lower end in the neonatal period. It becomes cylindrical with increasing age. This discrepancy was found to be inversely proportional to the gestational age of the infant. The narrowest part of the infant’s trachea is considered to be at the level of the cricoid cartilage, whereas in an adult it is at the level of the epiglottis. The unique funnel-shaped trachea with a natural subglottic narrowing places neonates at a certain disadvantage and at higher risk for further airway compromise, especially with development of mucosal edema following prolonged intubations. The cricoid cartilage is composed of two parts: a posterior plate-like portion that forms the posterior wall of the larynx and an inferior ring. In neonates, the plate is inclined posteriorly, with the narrowest part of the funneled trachea at the level of the cricoid ring.


As the infant grows the cricoid plate becomes vertical, the ring enlarges, and the point of narrowing at the funnel spout disappears. In addition to the anatomic orientation of the trachea, the susceptibility of the subglottic area to mucosal edema is related to the difference in cellular lining. The lining above the cords is resilient squamous epithelium, whereas below the cords it is ciliated columnar epithelium that is loosely attached to the submucosal tissue and can be easily infiltrated by fluid to form edema. This alters the internal diameter of the already narrow subglottic trachea. As explained by Poiseuille’s law, the resistance to airflow is inversely proportional to the fourth power of the radius of the airway during laminar airflow and to the fifth power during turbulent flow. When the internal diameter of the neonatal airway is decreased to 50% in conditions such as mucosal edema, the resistance to airflow is increased 16-fold. This highlights the importance of timely assessments of airway status and suitable interventions to prevent obstruction to airflow.


Infants with airway narrowing or obstruction may require immediate airway assistance. Interventions are aimed at splinting the airway open for unobstructed airflow. Use of nasal continuous positive airway pressure (CPAP) has gained popularity among neonatologists because of its noninvasiveness and ability to splint the airway effectively, especially in premature infants. However, tracheal intubation with an endotracheal tube (ETT) is sometimes essential to quickly resuscitate an infant.




Medical Management of Neonates with Common Respiratory Disorders Requiring Surgical Intervention


With increasing emphasis on prenatal care and availability of fetal ultrasonography, a large number of congenital respiratory disorders are being detected during fetal life. Availability of early diagnosis provides ample opportunity to plan the early neonatal and preoperative management to reduce the risk of surgical complications and improve postoperative outcomes. Planning often involves availability of medical personnel, which includes neonatologists, respiratory therapists, skilled nurses, pediatric surgeons, otolaryngologists, and bronchoscopists; availability of all required equipment and infrastructure, which includes operating rooms, bronchoscope, and tertiary-level NICU; and ability to perform extracorporeal membrane oxygenation (ECMO) or rapidly transfer the baby to a center with such capabilities. However, a lack of prenatal diagnosis may result in quick decompensation of the neonate, which in turn might create challenges in the surgical management and long-term outcomes of the infant. Most of these neonatal conditions may require specific corrective or palliative interventions. However, the overall management of the infant prior to surgery often follows common principles.


Congenital Airway Disorders


Congenital respiratory or airway disorders such as laryngomalacia, macroglossia, retrognathia or micrognathia, neck masses, hydrops fetalis with neck swelling, congenital diaphragmatic hernia, cystic adenomatoid malformation, congenital lobar emphysema, and similar anomalies can lead to rapid respiratory failure and hemodynamic instability in infants. Stabilization of the infant in the delivery room and a well-planned and well-executed initial management in the NICU may minimize further complications. The airway should be assessed immediately upon delivery for patency. Secretions should be cleared using bulb suction or other suction devices if needed. Studies by Velaphi et al. have shown that wiping could be as effective as suctioning in certain cases. In many circumstances, infants with congenital respiratory disorders will require assisted forms of ventilation, and each infant should be individually assessed and managed. In less severe cases, noninvasive ventilation such as nasal CPAP or nasal intermittent mandatory ventilation may be adequate to achieve target oxygenation and ventilation parameters. However, in more severe cases, tracheal intubation through oral or sometimes even nasal routes may be necessary. Difficult intubations may require the use of fiber-optic laryngoscopes.


Persistent hypoxemia or hypercarbia as a result of inadequate ventilation can result in failure of the infant to transition from the fetal to the neonatal circulation, resulting in persistent pulmonary hypertension of the newborn (PPHN). It is important to closely monitor blood gases and chest X-ray to optimize ventilation. Certain airway disorders lead to persistent hypoxia that in turn can activate various pathways in the lung that result in airway and pulmonary vascular remodeling. These infants may require alternate modes of tissue oxygenation such as ECMO. Ideally, infants should be adequately ventilated and oxygenated (although with caution in premature infants to minimize risks of oxygen toxicity) to avoid complications such as persistent hypoxia, acidosis, or PPHN. At the same time, extreme caution should be taken to avoid volutrauma, oxytrauma, and barotrauma, which are commonly associated with assisted invasive ventilation. This can be achieved by adopting gentle ventilation strategies and permissive hypercarbia.


Once the infant is stabilized, a formal consultation with the surgical specialty should be arranged and appropriate imaging studies ordered to confirm the diagnosis. Frequently, chest X-ray is the initial study of choice to assess lung expansion and extent of abnormality. Other studies that are commonly used are chest ultrasonography, computed tomography (CT), or magnetic resonance imaging (MRI). Infants should always be accompanied to these studies by a provider capable of intubation and resuscitation. Sedation for long procedures is commonly done by the neonatologist or anesthesiologist. In recent times, infant immobilizing devices have been used as a safer alternative to sedation for imaging procedures.


Nutrition plays a major role in preparing these infants for surgery. Although the caloric requirement is better met with enteral feeding, in some infants with respiratory disorders requiring ventilatory support, enteral feeding may not be feasible. Parenteral forms of nutrition are preferred in such infants and instituted early, typically within 24 hours of birth, to provide necessary proteins and lipids that could contribute to growth and body building. Lower total body fat mass and acute and chronic malnourishment are associated with worse clinical outcomes in children undergoing major surgeries.


Acquired Airway Disorders


Acquired airway disorders commonly seen in neonates are often secondary to traumatic laryngoscopic procedures, prolonged intubation, and chronic irritation from a hard nasal cannula. The most vulnerable site for problems in the neonatal airway appears to be the subglottic portion of the trachea at the level of the cricoid ring because of the above-mentioned anatomy and physiologic mechanisms. These complications can be avoided by using gentle techniques during naso-oropharyngeal suctioning and endotracheal intubation. Longer length of intubation time and multiple reintubations frequently result in subglottic stenosis, which makes it more challenging to extubate. Infants who require prolonged ventilation should be intubated only with uncuffed ETTs. This could potentially minimize an inflammatory response in the surrounding walls of the subglottic trachea. However, with prolonged duration of intubation these changes might become inevitable. These neonates should be evaluated at regular intervals for signs of obstruction or airway edema. Currently used ventilators provide information on expiratory flow leak and tidal volume. Infants with significant airway edema tend to have low airflow leak estimations. In some cases altered breath sounds such as stridor, crowing, or dysphonic or raspy cry in association with respiratory distress, which are signs of airway edema, are identified only post extubation. The goal, however, should be to identify infants at risk for development of airway edema prior to extubation. Cautiously planned and timely efforts to extubate infants to a noninvasive form of ventilation are needed. The provision of positive end-expiratory pressure in some form (CPAP, high-flow nasal cannula, noninvasive ventilation) is often helpful in avoiding extubation failure. Use of a short course of dexamethasone in high-risk cases is frequently recommended prior to extubation to reduce airway edema and risk of reintubation. Also racemic epinephrine may be used with caution to decrease the vascular congestion in the trachea and improve stridor post extubation. Reflux precautions in these infants can also be helpful in preventing caustic damage to the airway by stomach acid. However, use of antireflux medications generally should be avoided and reserved for infants with unique anatomic problems such as tracheoesophageal fistula. Unfortunately, some infants are exceedingly dependent on artificial airways and may eventually require surgical interventions such as a tracheostomy as a long-term solution.




Surgical Management of the Neonatal Airway


Respiratory distress in the neonate has a variety of causes ( Box 36-1 ), and pediatric surgeons and otolaryngologists are increasingly becoming involved in the care of these patients. The ability to intubate, mechanically ventilate, and thereby prolong the lives of children with neonatal asphyxia, congenital anomalies, or other causes of respiratory distress redefines the role of the surgeon as part of the neonatal management team.



BOX 36-1





  • Prolonged intubation (6 to 8 weeks)



  • Repetitive failure of extubations



  • Inability to aerate all lobes of the lung (persistent atelectasis)



  • Clinical need for cultures or bronchial washings



  • Suspicion of necrotizing tracheobronchitis



  • Evaluation of stridor



Indications for Neonatal Bronchoscopy


The role of the surgeon is twofold: (1) as a diagnostician and therapist for those infants who manifest respiratory distress from an anatomic problem or who present with congenital airway obstruction (i.e., congenital stridor [ Box 36-2 ]) and (2) as a consultant for neonates undergoing medical treatment requiring long-term intubation of their airways.



BOX 36-2


Nasopharynx





  • Choanal atresia



Tongue





  • Idiopathic



  • Beckwith-Wiedemann syndrome



  • Metabolic disorders




    • Hypothyroidism/lingual thyroid



    • Glycogen storage disease




  • Down syndrome



Oropharynx (Micrognathia and Glossoptosis)





  • Pierre Robin sequence



  • Treacher Collins syndrome



  • Hallermann-Streiff syndrome



  • Möbius syndrome



  • Freeman-Sheldon syndrome



  • Nager syndrome



Larynx





  • Laryngeal atresia



  • Laryngeal web



  • Vocal cord paralysis



  • Laryngomalacia



  • Subglottic stenosis




    • Congenital/traumatic




  • Laryngocele



  • Laryngeal cleft



  • Subglottic hemangioma



Trachea





  • Intrinsic compression




    • Tracheomalacia



    • Tracheal stenosis



    • Necrotizing tracheobronchitis




  • Extrinsic compression




    • Cystic hygroma



    • Vascular rings




Differential Diagnosis of Neonatal Stridor (Anatomic Approach)




The Pediatric Surgeon/Otolaryngologist as Diagnostician and Therapist


The role of the pediatric surgeon/otolaryngologist is often defined by the anatomic abnormalities present in any given infant. For purposes of organization, material presented here is divided into developmental abnormalities of (1) the airway, (2) the lung, (3) the diaphragm, and (4) the skeleton.


Developmental Abnormalities of the Airway


Tracheal Obstruction


Nasopharyngeal Obstruction


The presence of stridor signals a need for urgent diagnosis and possible intervention due to the narrow size of the infant airway and the ease at which it can reach critical narrowing. The severity of neonatal stridor can vary. Some cases may be managed medically, whereas other cases may represent impending total obstruction; therefore, the approach to diagnosis is deliberate ( Fig. 36-1 ).




FIG 36-1


Composite diagram of some of the lesions that result in neonatal stridor (proceeding downward through the respiratory passages).


A differential diagnosis for neonatal upper airway obstruction can be formulated by approaching the subject anatomically, beginning in the nasopharynx and oropharynx and progressing down through the respiratory tract.


Choanal Atresia


Choanal atresia, a rare anomaly, with a reported incidence of 1 in 8000 births, involves occlusion of the posterior nares by a membranous (10%) or bony (90%) septum ( Fig. 36-2 ). Unilateral lesions typically can be asymptomatic, but bilateral lesions may cause total airway obstruction because neonates are preferential nasal breathers. Symptoms are most evident when a baby is at rest, because when agitated and crying, the infant breathes via the oropharynx. Associated anomalies include esophageal atresia, congenital cardiac lesions, colobomata, and Treacher Collins syndrome, among a large number of rarer associations. Diagnosis can be made by the inability to pass a catheter through the nostrils into the oropharynx. Management ranges from simple placement of an oropharyngeal airway to operative opening of the occlusion with placement of stents. Rarely, tracheostomy may be needed if definitive surgical correction cannot be performed in the neonatal period.




FIG 36-2


Choanal atresia. A, Endoscopic view. B, Nasopharyngeal view.


Oropharyngeal Obstruction


Macroglossia


The tongue is often a site of obstruction. Stridor in a neonate can occur if the tongue is disproportionately larger than the infant’s oropharynx. Physical examination confirms the diagnosis. Insertion of an oral airway is usually successful in treating this type of airway obstruction. Several well-known syndromes include macroglossia as a component.


Beckwith-Wiedemann Syndrome


Severe hypoglycemia, in many cases secondary to hyperinsulinemia, initially brought these examples of infantile gigantism to medical attention. Macroglossia secondary to muscular hypertrophy, visceromegaly, microcephaly, and a series of umbilical abnormalities ranging from congenital umbilical hernia to omphalocele also compose this syndrome. Affected infants may also demonstrate a facial nevus flammeus, renal medullary dysplasia, and a characteristic pit on the tragus of the ear. These babies are typically large for gestational age. The congenital stridor resulting from the enlarged tongue usually resolves rapidly with the insertion of an oropharyngeal airway. Little further diagnostic workup of the airway is necessary if the child is identified as having this syndrome.


Metabolic Disorders


Several neonatal metabolic disorders cause macroglossia and result in congenital stridor, the best known of which are hypothyroidism and glycogen storage disease. The large tongue, high nature of the airway obstruction, and findings consistent with the underlying condition should suggest the diagnosis and appropriate workup early in the course of the disease. The stridor in these babies is generally mild, usually successfully treated with an oropharyngeal airway, and disappears shortly after birth as the underlying condition is successfully treated. Diagnostic evaluation in these patients should be directed at the underlying metabolic disorder; little additional diagnostic work is needed for the tracheobronchial tree.


Down Syndrome (Trisomy 21)


Children affected by Down syndrome are easily identified by their constellation of abnormalities. Their relative macroglossia may result in a mild congenital stridor. Because of the reported association between Down syndrome and congenital subglottic stenosis, endoscopy may be necessary to establish the cause of the stridor.


Lingual Thyroid


Lingual thyroid can be a rare cause of oropharyngeal obstruction. Stertor in the presence of hypothyroidism, detected by persistent elevation of thyroid-stimulating hormone on routine neonatal screening, raises the suspicion of lingual thyroid, although other lesions are more commonly responsible. This condition occurs in just over 1 in 10,000 births.


Laryngoscopy is used to confirm a mass at the base of the tongue. Further characterization by CT scan and thyroid scintigraphy should be performed. Of note, the thyroid may continue to hypertrophy during early infancy and childhood. Respiratory complications associated with hypothyroidism, such as respiratory depression, may not occur until later.


Severe Bronchopulmonary Dysplasia


Although not generally reported and not often appreciated, macroglossia can develop in infants with severe bronchopulmonary dysplasia and worsen the chronic pulmonary compromise. The obstruction caused by this condition is the result of chronic hypoxia (similar to clubbing of the fingernails) and often heralds a poor outcome. The condition often contributes to compensated respiratory acidosis and is best treated by tracheostomy as opposed to surgical reduction of the tongue.


Craniofacial Dysmorphology Syndromes


The craniofacial dysmorphology syndromes range from unusual to extremely rare. All result in an obstruction located in the oropharynx. This is secondary to micrognathia with glossoptosis. Stridor varies from mild to severe, and it is important to identify the underlying problem, which is often genetic. More complete descriptions of these conditions can be found in texts on congenital malformations.


Pierre Robin Syndrome


Pierre Robin syndrome represents the most common craniofacial dysmorphology with micrognathia and glossoptosis. In addition to the aforementioned characteristics, approximately half of these babies also have cleft palates/cleft lip anomalies, perhaps attributable to protrusion of the tongue between the posterior palatine plates during embryologic development. This protrusion results in failure of normal midline fusion. Furthermore, the tongue often prolapses posteriorly, resulting in partial obstruction of the upper airway. During inspiration, negative pressure in the pharynx retrodisplaces the already enlarged tongue and this increases the degree of pharyngeal obstruction. Stridor consequently results in children with Pierre Robin syndrome, and they have particular difficulty with inspiration. The airway obstruction is usually resolved with insertion of an oropharyngeal airway, and these patients tend to breathe more comfortably in a prone position. Feeding may create further problems for these babies and necessitate special nipples or gavage nutrition.


Tracheostomies are rarely necessary in these cases and are to be avoided if at all possible because of the risks of airway occlusion and death. Surgical procedures such as glossopexy or creation of a lingual flap have been described as alternatives but are also seldom needed except in the most severe cases. The first few months of life are critical in determining the severity of a particular infant’s anomaly and its importance in the overall prognosis.


Treacher Collins Syndrome


Treacher Collins syndrome, also known as mandibulofacial dysostosis , is a variable and diffuse group of craniofacial anomalies. This syndrome is characterized by downward-sloping palpebral fissures, colobomata of the lower lids, sunken cheek bones, and blind fistulae on an angle between the mouth and the ears ( Fig. 36-3 ). Pinnae may be deformed, deafness is common, and micrognathia is part of the syndrome (usually less severe than that seen in Pierre Robin syndrome). The presumed genetic defect is autosomal dominant, with mutation in the TCOF1 gene at chromosome 5q32-q33.1.




FIG 36-3


Example of a child with Treacher Collins syndrome demonstrating sunken cheek bones, downward sloping palpebral fissures, and micrognathia.


The hypopharynx is the location of the obstruction in these children (as in children with Pierre Robin syndrome), owing to the disproportionate relationship between the small jaw and the large tongue. These cases of stridor can most often be managed medically, often with simple insertion of an oropharyngeal airway, and tracheostomy is seldom necessary. Rarely, bronchoscopy may be indicated if associated tracheobronchial tree anomalies are a concern, but these are quite unusual.


Hallermann-Streiff Syndrome


The Hallermann-Streiff syndrome is a rare syndrome that consists of microphthalmia, cataracts, blue sclerae, and nystagmus. Associated anomalies include a pinched nose, micrognathia, and hypertrichosis of the scalp, eyebrows, and eyelashes ( Fig. 36-4 ). Transmission is presumed to be autosomal dominant, although most cases are thought to represent de novo mutations. Congenital stridor in these infants arises from micrognathia with relative glossoptosis, and treatment is similar to that outlined for Pierre Robin or Treacher Collins syndrome.




FIG 36-4


Example of an infant with Hallermann-Streiff syndrome demonstrating microphthalmia, pinched nose, micrognathia, and hypertrichosis of the scalp.


Möbius Syndrome


Infants with the Möbius syndrome have a characteristic absence or maldevelopment of various cranial nerve nuclei. Cranial nerve VII (facial nerve) is the most commonly involved, but other cranial nerves such as cranial nerves V, VI, and VIII may also be affected. Common findings include facial paralysis, ptosis, ophthalmoplegia, clubbed feet, and syndactyly. It is presumed that this condition is inherited in an autosomal dominant manner.


Paralysis of the facial nerve is the cause of upper airway obstruction as well as difficulties with mastication and deglutition. Both inspiratory and expiratory components of stridor result from the relatively fixed nature of the obstruction. Tracheostomy may be required in severe cases. Many children, however, can be successfully treated by parental instruction in very careful feeding techniques.


Freeman-Sheldon Syndrome


Infants with Freeman-Sheldon syndrome are often called “whistling-faced” children. They have hypoplastic alae nasi, clubbed feet, and masklike whistling facies. Their eyes are deep set with blepharophimosis, ptosis, and strabismus. Transmission is autosomal dominant with some variations that transmit as autosomal recessive. Chromosomal abnormalities have been reported at both 11p15.5 and 17p13.1. These children are classified as having a type of distal arthrogryposis.


Stridor in these children is the result of air passage through a narrow channel. Although the sound may be alarming, it usually does not require intervention.


Nager Syndrome


Nager syndrome is a rare acrofacial dysostosis that presents with upper limb malformation, mandibular and malar hypoplasia, downward-slanting palpebral fissures, absent eyelashes in the medial third of the lower lids, dysplastic ears with conductive deafness, and variable degrees of palatal clefting. This syndrome is associated with chromosome 9 defects. Airway obstruction in these patients is related to posterior tongue displacement due to hypoplasia of the mandible. Acute management often requires early tracheostomy, and subsequent mandibular distraction is eventually needed to correct the defect.


Laryngeal Anomalies


An infant’s larynx is the next site of possible obstruction, and laryngeal anomalies account for the majority of cases of stridor in newborns.


Laryngeal Atresia


The most extreme form of obstruction at this level, laryngeal atresia, results in a desperate emergency during the first few moments of life. This lesion was originally described in 1826, but only 51 cases were reported in the subsequent 160 years. Very few of these patients survive because surgical intervention to secure a definitive airway must occur within 2 to 5 minutes of clamping of the umbilical cord.


The most dramatic physical finding is that the child is aphonic, with absence of any cry or gasp at birth. If the lesion is immediately recognized on direct laryngoscopy, an emergency cricothyroidotomy should be performed. Diagnosis of laryngeal atresia has now been reported prenatally, and in the future, clinicians may be able to prepare for emergent airway management at birth or schedule the child for an ex utero intrapartum treatment procedure followed by emergent airway opening.


Laryngeal Web


Laryngeal webs account for approximately 5% of laryngeal anomalies ( Fig. 36-5 ). These lesions arise about the 10th week of intrauterine life and probably represent an arrest of the development of the larynx in the area near the vocal cords. Seventy-five percent of these lesions occur at the level of the cords; the rest are subglottic or supraglottic in about equal numbers. The web generally occurs anteriorly, and the lesions are often asymptomatic if they extend less than halfway back along the cords. Because the glottic area is triangular, these anteriorly placed webs reduce the glottic area by only 15% to 20% and are usually not sufficient to cause stridor.




FIG 36-5


Endoscopic view of neonatal larynx with partial laryngeal atresia and a laryngeal web partially obstructing the laryngeal orifice.


If the web extends posteriorly, the symptoms may be marked. The stridor is primarily inspiratory but often has an expiratory component. The affected infant’s cry is hoarse and weak; the child is rarely aphonic and often is dyspneic at rest.


Laryngoscopy and bronchoscopy should be performed as soon as possible. If a thin, transparent web is encountered at the level of the cords, it may be easily swept away with the bronchoscope, completely correcting the problem. Completion of the bronchoscopy should be performed to rule out associated anomalies beneath the area of the web.


If the web is thick and fibrous, no attempt should be made to force the bronchoscope through the area. This kind of web is often encountered in the subglottic region. Tracheostomy is the treatment of choice if the child is dyspneic and unable to tolerate the web. If aeration of the child is satisfactory despite the stridor, as evidenced by arterial blood gas determinations, simple observation may be sufficient management until the baby is able to undergo surgical repair. This is usually deferred until the child is 18 to 24 months of age. The best results to date have been achieved in those children who undergo a meticulous removal of the thick fibrotic web. Depending on the thickness of the web, laser therapy is an alternative and may yield superior results in the future.


Congenital Vocal Cord Paralysis


Congenital vocal cord paralysis is the second most common cause of congenital stridor. In the past, birth trauma was frequently implicated in the etiology of the paralysis but now appears to be a declining cause. Intracranial lesions and the possibility of congenital cardiac lesions, especially one impinging on the recurrent laryngeal nerve, must be considered.


Fortunately, paralysis is unilateral in 70% to 80% of cases. Some studies report that both sides are equally involved, but left-sided paralysis is typically associated with underlying congenital cardiac anomalies. These infants have a hoarse and weak cry, and if the paralysis is bilateral, these children may be truly aphonic. The inspiratory stridor is obviously worse in bilateral paralysis. Marked suprasternal and intercostal retractions may be present in these children.


Diagnosis is rapidly made by laryngoscopy, and treatment depends on the severity of the problem. In a unilateral paralysis with minimal or no dyspnea, simple observation is appropriate. Bilateral paralysis, generally associated with severe symptoms, necessitates tracheostomy. Once the airway is adequately secured, the cause of the paralysis can be explored. If the causal lesion can be identified and corrected, the stridor may improve. If no lesion can be found or if it cannot be safely corrected, later fixation of the arytenoids with the vocal cord in abduction may result in satisfactory control of the stridor and decannulation.


Laryngomalacia


Laryngomalacia is the most common cause of congenital stridor, accounting for 60% to 75% of cases of stridor in newborns. It also accounts for three-fourths of the congenital laryngeal abnormalities. The pathophysiology of this condition involves an immature, floppy larynx that collapses during each inspiration ( Fig. 36-6 ), producing an inspiratory stridor of varying severity that is often much worse when the baby is agitated or screaming. Some infants improve at night, but others experience a worsening of their respiratory sounds.




FIG 36-6


Endoscopic view of immature floppy glottis characteristic of laryngomalacia. Dynamic examination demonstrates downward placement of glottis into larynx with inspiration.


Laryngomalacia occurs with a 2:1 male-to-female predominance and is usually present at birth. Despite most cases being present at birth, for up to a quarter of patients, the first symptoms appear during the first or second week of life. Many cases are reported to have micrognathia, and some may be confused with Pierre Robin syndrome.


Diagnosis is made easily by laryngoscopy, which shows a soft, enfolded epiglottis. The larynx is often difficult to expose and is found high under the tongue. Bronchoscopy should accompany laryngoscopy to rule out associated anomalies or extensive malacia, such as tracheomalacia and/or bronchomalacia.


Maturation of the epiglottis by the age of 18 to 24 months usually results in resolution of the stridor. Accordingly, tracheostomy is not typically necessary in the final treatment of this disorder.


Congenital Subglottic Stenosis


The overall incidence of congenital subglottic stenosis is unknown because many such cases remain undiagnosed. It has been estimated that 39% of all subglottic stenoses are congenital (the remaining group being acquired). The stenotic area is typically found 2 to 3 mm below the vocal cords and may reduce the subglottic area to 3 to 3.5 mm. The proposed cause of the congenital group is arrested development of the conus elasticus or the cricoid.


The stridor, if present at all, is usually biphasic and sometimes arises during the first or second month of life. Respiratory distress after an upper respiratory tract infection is typically the presenting symptom. These patients are generally unable to clear the resultant increased secretions found in association with infection. Affected children are often treated for recurrent pneumonias or prolonged tracheobronchitis. Many cases are not discovered until a severe episode of croup or epiglottitis results in emergency intubation or tracheostomy.


Mild lesions should be observed, and antibiotic therapy should be added during periods of upper respiratory tract infection. Tracheostomy is necessary in more than half the cases of children with severe stenosis and marked symptoms. Once the tracheostomy is in place, dilation during monthly serial laryngoscopy under general anesthesia often results in improvement. The dilation must be gentle to prevent further damage or fibrosis of the subglottic region. For more severe degrees of stenosis, open surgical intervention may be necessary. The outcome in this congenital group of subglottic stenosis is quite good, with 82% of patients in one large series successfully decannulated after one procedure.


Acquired Subglottic Stenosis


Acquired subglottic stenosis is most often caused by prolonged endotracheal intubation. Because of the increased survival of neonates with respiratory difficulties requiring intubation (especially extremely low birth-weight infants), this lesion is increasing in frequency as a cause of stridor. A protracted form of acquired subglottic stenosis was found to occur in 8.3% of neonates surviving a period of endotracheal intubation in one study. In its mildest form, the stenosis consists of laryngeal edema and has been reported in 30% of infants immediately after intubation. Stridor in these patients is inspiratory and presents with the first breaths after tube removal. This usually resolves within 72 hours. During this 3-day period, head elevation, humidified air, racemic epinephrine, nasal CPAP or noninvasive nasal ventilation, and occasionally systemic steroids are used to treat the mild form of this disorder.


In its most severe form, acquired stenosis is a dense scar of well-organized fibrous tissue. This lesion may require tracheostomy before the actual stenosis can safely be manipulated. Initial treatment includes graded, gentle dilation with or without intralesional steroids. As many as half of the stenotic scars will improve and often stabilize after four to six treatments. Failure to achieve significant improvement by then indicates the need for more aggressive treatment such as cryosurgery, laser ablation, cricoid split procedure, or resection and reconstruction with stents. There have been reasonable results with the cricoid split procedure and intubation during healing rather than recourse to tracheostomy, and this alternative should always be considered.


Laryngeal Cleft


Although laryngeal clefts were once considered extremely rare lesions, they have frequently been reported since 1990. This is probably a result of enhanced endoscopy techniques and improved ability to make the diagnosis in the antemortem period. The lesion forms owing to a failure of dorsal fusion during the chondrification of the cricoid cartilage. A midline cleft thus remains posteriorly and extends down between the arytenoids into the upper portion of the esophagus and trachea. Affected children are often very stridorous at birth, and many have died in the past because of inadequate resuscitation. In addition to their respiratory difficulties, aspiration and pneumonitis occur if these patients are fed without regard for their clefts. Consequently, they require recognition, intubation, and stabilization. A feeding gastrostomy and possible fundoplication are often necessary until definitive repair can be performed. Once extubation is accomplished, close observation is necessary to ensure that upper airway secretions do not continuously pass into the lungs. If this proves to be a severe and ongoing problem that precipitates recurrent pneumonia and respiratory distress, it may be necessary to place a tracheostomy until surgical closure of the cleft can be achieved.


Subglottic Hemangioma


Hemangiomas are another cause of congenital subglottic obstruction. The onset of symptoms is variable, as symptomatology is related to the growth and development of these lesions. The lesions are at first quite small and may have a period of rather rapid growth, followed by a long plateau and slow involution. Time to presentation for patients with subglottic hemangiomas depends upon the age at which the hemangioma develops. If the hemangioma develops early in fetal life, then the patient will become symptomatic earlier in life. On the other hand, if the subglottic hemangioma develops after birth, there may be several months’ lag in the time to presentation of symptoms. Hemangiomas on other areas of the body suggest the possibility of subglottic hemangioma; definitive diagnosis is made by laryngoscopic and bronchoscopic examination.


A bronchoscopic finding of a red or purple mass just beneath the cords is generally considered diagnostic. Most pediatric surgeons believe that biopsy is contraindicated when such findings are seen, because hemorrhage necessitating emergent surgery is a distinct possibility after biopsy. Once the diagnosis is established, appropriate therapy is chosen according to the severity of symptoms. If the child is stable and has normal blood gas values at rest, observation is sufficient. If the obstruction is significant enough to result in dyspnea, severe stridor, and possibly abnormal blood gas values, tracheostomy below the lesion should be considered. One must also be aware of the possibility of platelet trapping (Kasabach-Merritt syndrome) before surgical intervention.


It is questionable whether radiation should be used in the treatment of these children today because of the risk of thyroid malignancy. Prednisone, 2 to 4 mg/kg per day, and β-blockers, such as propranolol, are quite beneficial if the hemangioma is growing quickly and causing thrombocytopenia. The side effects of interferon-α are so substantial as to preclude use in most cases as of this writing. Dramatic regression of the hemangioma and prompt correction of the thrombocytopenia with the use of these agents have been reported, although both have also been associated with significant side effects.


Tracheal Anomalies


Intrinsic Tracheal Compression


Tracheomalacia


Tracheomalacia results from a failure of the cartilaginous rings to fully support the round shape of the normal trachea. The cartilages are hypoplastic and allow the trachea to collapse, especially during expiration ( Fig. 36-7 ). This condition is commonly seen in babies and children undergoing bronchoscopic evaluation but is only incidentally responsible for stridor in a moderate number of them. Because obstruction of the airway tends to occur as the trachea collapses with expiration, stridor occurs at that time. The condition is diffuse and usually occurs throughout the length of the trachea.


Jan 30, 2019 | Posted by in PEDIATRICS | Comments Off on Medical and Surgical Interventions for Respiratory Distress and Airway Management
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