AIRWAY DISORDERS

The study of voice, swallowing and airway disorders is referred to a laryngology, a subspecialty of otolaryngology (the study of ear, nose, and throat disorders). This includes laryngologic disorders such as hoarseness, swallowing problems, airway narrowing (subglottic or tracheal stenosis), and chronic cough.Nose obstruction, inspiratory and expiratory stridor. Sleep apnoe, allergy of upper respiratory tract.

Congenital upper airway disorders in children

Congenital upper airway abnormalities usually present as upper airway obstruction in infancy characterised by stridor, respiratory distress and failure to thrive. Poor weight gain is a hallmark of severity and occurs because of the respiratory effort required to overcome obstruction.

There are a number features of congenital upper airway abnormalities causing obstruction which are distinctive in infants, compared with older children and adults. These include:

• importance of both functional and structural causes
• airway abnormality may be isolated or be part of a multi-system disorder
• children are obligate nose breathers in the first three months of life and therefore obstruction at the level of the nose is as clinically significant as obstruction elsewhere in the airway

Congenital upper airway abnormalities may be classified according to the site of the lesion and subclassified based on whether the abnormality is structural or functional. Assessment by awake flexible laryngoscopy is often the only investigation required(1). The causes can be classified as;

Nose/nasopharynx

Nasal obstruction may occur due to inflammation of the nasal mucosa, septal deformity occurring due to traumatic delivery, or bony obstruction at the level of either the piriform aperture, mid-nose due to medial displacement of the lateral nasal wall, and choanal atresia(2). Nasal masses include naso-cranial anomalies, dermoids, haemangiomas and teratomas.

Oral/oropharynx

Oropharyngeal obstruction is most commonly due to prolapse of the tongue base (glossoptosis) which is often associated with micrognathia. This combination with cleft palate is the Pierre Robin sequence. Enlargement of the tongue is seen in Down's syndrome and Beckwith Weideman syndrome. Oral masses, particularly involving the floor of mouth, include haemangiomas and cystic hygromas.

Supraglottis

Laryngomalacia is the commonest cause of stridor in infants and is due to supraglottic inspiratory collapse. It occurs due to an imbalance between the negative inspiratory pressure which collapses the airway, and supraglottic neuromuscular control which supports the airway. Layngomalacia resolves by two years of age(3). Congenital cysts include vallecular cysts, saccular cysts and laryngoceles(4)

Glottis

Bilateral vocal cord paralysis almost exclusively involves the laryngeal abductors, and rather than being paralysed, the abductors display a loss of respiratory modulation. It may occur due to a structural CNS abnormality, (especially Arnold-Chiari malformation), generalised neuromuscular disorder, birth trauma, or be idiopathic(5). Congenital glottic webs are rare, and are thought to represent a forme fruste of laryngeal atresia.

Subglottis

Subglottic stenosis is generally acquired, and occurs following longterm endotracheal intubation. It is seen in premature neonates with lung disease who have required longterm ventilatory support, but this condition now appears to be decreasing due to improved neonatal care(6,7,8). Mucus retention cysts may develop following only brief intubation (9). Subglottic haemangiomas are benign congenital vascular tumours which enlarge with age before regressing spontaneously. Symptoms develop from 6 weeks of age.

Trachea

Tracheomalacia, weakening and collapse of the trachea, may occur due to extrinsic pressure due to a cardiovascular abnormality (most commonly from the inominate artery) or a mediastinal mass, it may be related to a focal abnormality such as a tracheo-esophageal fistula, or be a widespread primary abnormality. Tracheal stenosis may be characterised by an area of narrowing, or be due to complete tracheal rings with absence of the membranous trachea.