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CHAPTER 40  Structure and Development of the Upper Respiratory System • Fig 40.1  ​Bronchoscopy 455 • Fig 40.2  ​Laryngeal web with trachea above with tracheoesophageal fistula below Epiglottis Epiglottis Arytenoid swelling Primitive glottis A weeks B weeks Epiglottis Epiglottis Glottis Glottis Arytenoid swelling Cartilages C weeks D 10 weeks • Fig 40.3  ​Embryologic development of the larynx  (Modified from Arvedson JC, Brodsky L, Lefton-Greif MA Pediatric Swallowing and Feeding: Assessment and Management 3rd ed San Diego: Plural Publishing; 2020.) cartilage in the airway to form a complete ring Because of its inflexibility, edema from intubation and inflammation can result in serious injury that should be avoidable in most cases Laryngeal web or subglottic stenosis can present with stridor, likely biphasic, and respiratory distress in a newborn infant (Fig. 40.5) While medical treatment—such as steroids, racemic epinephrine, heliox, or intubation—may manage these infants in the acute setting, many infants with congenital webs or stenosis will need surgical intervention Laryngeal atresia that is not diagnosed prenatally will lead to often fatal respiratory distress at birth (Fig 40.6) The infants’ mothers will likely present with severe polyhydramnios and fetal hyperinflation of the lungs Fetal MRI 456 S E C T I O N V   Pediatric Critical Care: Pulmonary assists in the diagnosis A tracheostomy in the newborn period is necessary, in coordination with an ex utero intrapartum treatment procedure for airway management Abnormalities of the lower airway can lead to critical airway distress Although the only normal complete tracheal ring is the cricoid cartilage, complete tracheal rings or tracheal stenosis can lead to difficult intubations and respiratory distress Depending on the severity of distress and tracheal stenosis, surgical management is needed in the majority of cases (Figs 40.7 and 40.8) Children with Down syndrome can present with multilevel airway • Fig 40.4  ​Laryngeal cleft during repair • Fig 40.7  ​Bronchoscopy demonstrating distal complete tracheal rings • Fig 40.5  ​Subglottic stenosis • Fig 40.6  ​Laryngeal atresia • Fig 40.8  ​Congenital tracheal stenosis CHAPTER 40  Structure and Development of the Upper Respiratory System problems as a result of midface hypoplasia, a small nasopharynx, a relatively large tongue, and a congenitally narrowed subglottic space If a child with Down syndrome requires intubation, a smaller endotracheal tube that is one-half size to one full size lower than that used for a child with a normal airway should be employed tube and oxygen delivered by mask rather than by nasal cannula to avoid obstruction and injury to this area The nasal cavity courses posteriorly to reach the nasopharynx The adenoid pad is located in the nasopharynx and sits against the muscles covering the cervical spine at the base of the skull During the first several years of life, the adenoid may enlarge In most instances the adenoids involute between age years and puberty unless ongoing inflammation occurs as a result of allergies, infection, or gastrointestinal reflux In the newborn infant, abnormal development of the nasal cavity can lead to airway obstruction Pyriform aperture stenosis is an overgrowth of the maxillary crest leading to anterior nasal obstruction Choanal atresia is a failure of recanalization of the posterior nasopharynx, leading to obstruction that may be unilateral or bilateral (Fig 40.11) An oral airway or intubation can bypass these airway obstructions in an acute setting Choanal atresia is part of CHARGE syndrome (which includes coloboma, heart defects, and retarded growth and development, among other anomalies) Pyriform aperture stenosis is associated with holoprosencephaly, pituitary abnormalities, and central mega incisor syndrome Therefore, comprehensive genetic and systemic evaluations are critical The nasal passage is divided by the nasal septum, which is cartilaginous anteriorly and bony posteriorly Injury to the anterior nasal septum is not uncommon with the use of nasal tubes, nasal cannula, or nonhumidified oxygen because of the thin epithelium overlying the cartilage anteriorly Bacterial colonization frequently occurs when the nasal passages become dry and stasis of secretions occurs In the critically ill patient, injury to this anterior mucosa can lead to epistaxis This can be treated with pressure, oxymetazoline, and packing if needed Anatomy and Physiology of the Upper Airway Nasal Passages The upper airway begins at the tip of the nose and the vermilion border of the lips Both the nasal and oral passages allow air to stream from the environment through the larynx into the lungs, where oxygen and carbon dioxide are exchanged in alveolar-capillary units Oral passages (oral cavity, oropharynx, and hypopharynx) are conduits for the ingestion of the food and liquid needed to support growth and development The structures of the upper airways of the infant (Fig 40.9) gradually change in the first few years of life to assume their adult configuration (Fig 40.10) Preferential nasal breathing is present in typical term neonates and persists until months of age because of the high position of the larynx in the neck with the soft palate and valleculae in close anatomic approximation Nasal breathing is a necessary underpinning for nipple feeding at the breast or bottle in order for infants to coordinate sucking, swallowing, and breathing sequencing Infants with upper airway obstruction who require enteral feedings are served better with an orogastric tube than a nasogastric INFANT Hard palate Soft palate Vallecula Maxilla Nasopharynx Tongue Mandible Hypopharynx Epiglottis Hyoid Larynx 457 Esophagus Trachea • Fig 40.9  ​Lateral view of the infant’s upper airway The soft palate and valleculae form a tongue-and- groove relationship that effectively separates the oral cavity from the nasal cavity during the first months of infancy when most children are primarily nasal breathers This anatomic proximity effectively separates the oral route for ingestion from the nasal route for respiration Anterior placement of the larynx has implications for intubation technique (Modified from Arvedson JC, Brodsky L, Lefton-Greif ML Pediatric Swallowing and Feeding: Assessment and Management, 3rd ed San Diego: Plural Publishing; 2020.) 458 S E C T I O N V   Pediatric Critical Care: Pulmonary OLDER CHILD Nasopharynx Tongue Oropharynx Soft palate Vallecula Hypopharynx Hyoid Epiglottis Trachea Larynx Esophagus • Fig 40.10  ​Lateral view of the older child’s upper airway Note the development of the oropharynx, a shared passage for eating and breathing The tongue occupies less of the oral cavity The larynx sits lower in the neck, which is unique to humans and has allowed for the development of human speech production However, the shared passageway with the digestive system creates challenges in airway protection, particularly during intubation (Modified from Arvedson JC, Brodsky L, Lefton-Greif ML Pediatric Swallowing and Feeding: Assessment and Management, 3rd ed San Diego: Plural Publishing; 2020.) The ostia of the paranasal sinuses drain into the nasal cavity Any obstruction secondary to tubes or inflammation can lead to poor mucus clearance, bacterial overgrowth, and sinusitis In the critically ill and immunocompromised patient, invasive fungal sinusitis can be a rare but fatal source for fever of unknown origin Nasal endoscopy and possible biopsy and debridement are needed for evaluation of this disease (Fig 40.12) Mouth (Oral Cavity) and Pharynx • Fig 40.11  ​Unilateral choanal atresia undergoing repair posterior view The structures of the oral cavity include the lips, teeth, tongue, palate, and palatine tonsils The anterior structures are primarily involved in speech and bolus preparation of food and liquid The tongue in young infants fills the oral cavity Children with BeckwithWiedemann syndrome have macroglossia The tongue often protrudes out of the mouth In some instances, tongue reduction may be necessary, or the airway may need to be bypassed Some craniofacial anomalies are characterized by micrognathia or retrognathia, when even a normal- or smaller-sized tongue may be posteriorly placed, causing upper airway obstruction Glossoptosis can produce airway obstruction that prevents ventilation by natural or mechanical means In the critical care setting, an endotracheal tube may be required to bypass the obstruction Infants with Pierre Robin sequence (micrognathia, glossoptosis, posterior CHAPTER 40  Structure and Development of the Upper Respiratory System • Fig 40.12  ​Invasive fungal sinusitis of right necrotic middle turbinate U-shaped cleft palate) may present with severe airway obstruction, especially in supine positioning Nasal trumpets, oxygen, prone positioning, and intubation may be necessary in the critical setting for airway management Intubation is difficult with usually a grade to (Cormack and Lehane) laryngeal view Fiberoptic intubation may be helpful The oropharynx that is not seen in young infants begins posterior to the posterior tonsillar pillars, with its superior border at the edge of the soft palate and its inferior border at the superior tip of the epiglottis With growth and development, the pharynx elongates so that an oropharynx can be noted between ages and 3 years The lateral walls of the pharynx consist of the three pairs of constrictor muscles, which are innervated by cranial nerves V, IX, and X These cranial nerves provide innervation to muscles that are important for the protection of the lower airways The muscle tone 459 of the pharyngeal constrictors is often compromised in children with neurologic impairment, which may result in airway collapse and obstruction even in the absence of enlarged tonsils and adenoid or glossoptosis Palatine tonsils are found laterally; when chronically or severely inflamed, they may enlarge and cause upper airway obstruction similar to that found with an enlarged adenoid at the nasopharyngeal level Often, but not always, enlargement of the tonsils and adenoid occurs together Hypertrophied palatine tonsils can be noted deep in the pharynx with lateral view VFSS in some children even when the tonsils did not appear markedly enlarged upon visual oral inspection Hypertrophied tonsils may interfere with bolus transit of solid foods in some children The oropharynx is the crossroads for the nasopharynx from above and the hypopharynx from below Infants have no distinct oropharynx because the nasopharynx is contiguous to the hypopharynx Lingual tonsil hypertrophy in older children occurs less frequently than hypertrophy of palatine tonsils Hypertrophy of lingual tonsils may result in airway obstruction or feelings of food getting stuck in the pharynx When enlarged, they can cause airway obstruction that prevents visualization of the glottis Vallecular cysts may present in the newborn infant with dysphagia and upper airway obstruction In some instances, vallecular cysts are associated with acute life-threatening events (Fig 40.13) The hypopharynx is the most inferior of the shared passageways for respiration and deglutition Superiorly, it is defined by the tip of the epiglottis, which is at the level of the hyoid bone in the neck of an adult, a relationship that is variable in an infant and child The inferior border of the hypopharynx is at the level of the cricopharyngeus muscle, which is the primary muscle unit in the upper esophageal sphincter, located directly posterior to the cricoid cartilage Protection of the airway occurs in this area, particularly during deglutition The anterior boundary of the hypopharynx is the larynx Although immunization has nearly eradicated epiglottitis, it should still be considered in the differential diagnosis in toxic-appearing children with stertor, respiratory difficulty, and drooling (Fig 40.14) The critical treatment is operative airway management with the possibility of tracheotomy • Fig 40.13  ​Vallecular cyst at the base of tongue  ... dry and stasis of secretions occurs In the critically ill patient, injury to this anterior mucosa can lead to epistaxis This can be treated with pressure, oxymetazoline, and packing if needed Anatomy... anatomic approximation Nasal breathing is a necessary underpinning for nipple feeding at the breast or bottle in order for infants to coordinate sucking, swallowing, and breathing sequencing Infants... airway may need to be bypassed Some craniofacial anomalies are characterized by micrognathia or retrognathia, when even a normal- or smaller-sized tongue may be posteriorly placed, causing upper