Stridor - upper airway obstruction in neonates
- All newborns with stridor need evaluation of their airway because of the risk of significant airway obstruction.
- The small size and underdevelopment of the neonatal airway make it more vulnerable to the effects of either extrinsic compression or intrinsic obstruction.
- The causes of upper airway obstruction are best considered according to their location.
Stridor is a loud, high pitched respiratory sound usually heard on inspiration but it can occur on expiration in severe upper airway obstruction.
The upper airway
The upper airway can be divided into 3 segments:
- Supraglottic area:
- Glottic (laryngeal) and subglottic region:
- vocal cords
- immediate subglottic area
- extrathoracic trachea
- Intrathoracic portion:
- thoracic trachea
Characteristics of the newborn airway
Characteristics of the newborn airway:
- The newborn airway is of a smaller calibre than that of a child or adult.
- It has less well developed cartilaginous structures which contribute to flaccidity of the airway.
Both of these characteristics make the newborn airway more vulnerable to the effects of either extrinsic compression or intrinsic obstruction.
Obstruction of the upper airway
- Obstruction of the upper airway produces turbulent airflow which produces stridor.
- If the obstruction is severe or complete there may be little or no airflow and stridor may be absent.
Signs and symptoms of obstruction
Associated signs and symptoms of obstruction include:
- increased work of breathing (suprasternal, intercostal, subcostal retractions),
- poor feeding
- cyanosis and decreased conscious state are late signs
The causes of upper airway obstruction are best considered according to their location.
Obstruction in this segment produces an inspiratory stridor.
Choanal atresia, a narrowing or blockage of the nasal area, is the most common congenital anomaly of the nose. Issues to note:
- When unilateral there are usually no symptoms unless the other side of the nose becomes obstructed.
- Bilateral choanal atresia can be life-threatening.
Micrognathia is a small lower jaw (eg Pierre-Robin sequence, Treacher-Collins syndrome). Issues to note:
- Results in posterior displacement of the tongue which obstructs the hypopharynx.
- It is more often seen in the supine position.
Macroglossia is an abnormally large tongue. Issues to note:
- It can cause obstruction of the hypopharynx if the tongue is large enough.
- Down syndrome
- glycogen storage diseases
- congenital hypothyroidism
A lingual thyroid results from failure of descent of the thyroid gland from its embryological origin at the base of the tongue via the thyroglossal duct. Issues to note:
- Thyroglossal duct cysts arise from remnants of the thyroglossal duct.
- On examination there will be a smooth discrete mass in the midline anywhere from just above hyoid bone to the thyroid gland which moves up when the tongue is poked out.
2. Glottic (laryngeal) and subglottic
A biphasic stridor is typically associated with obstruction in this region.
Laryngomalacia is the most common cause of chronic stridor. Issues to note:
- It results from prolapse of the epiglottis/arytenoids/aryepiglottic folds during inspiration due to a developmental delay in maturation of these supporting structures of the larynx.
- It is worse with crying, upper respiratory tract infections, after feeding and when supine.
- It usually resolves by 1-2 years of age.
Vocal cord paralysis
Vocal cord paralysis is the second most common cause of stridor in infants. Issues to note:
- When due to a central nervous system lesion (eg Arnold-Chiari malformation, raised intracranial pressure, hypoxic ischaemic encephalopathy (HIE), cerebral haemorrhage) it is usually bilateral and associated with marked respiratory distress but a normal cry.
- After trauma during birth (usually traction) or at intubation it is usually unilateral with a hoarse cry and little or no respiratory distress.
Subglottic (or tracheal) stenosis
Issues to note about subglottic (or tracheal) stenosis:
- It can be congenital or acquired.
- When acquired it is most often due to endotracheal intubation.
A laryngeal web
A laryngeal web is failure of the embryonic airway to recanalise. Issues to note:
- It is usually at the level of the vocal cords.
- A laryngeal cyst is found in the aryepiglottic fold of the epiglottis and contains mucus from minor salivary glands.
- Both present soon after birth.
Issues to note about cystic hygroma:
- It is a collection of abnormal lymphatic vessels which may cause external compression of the airway.
Issues to note about subglottic haemangiomata:
- Usually submucosal and associated with others elsewhere on the body.
- The stridor produced is worse with crying or straining as the lesion becomes engorged with blood.
Issues to note about laryngotracheo-oesophageal cleft:
- It is a defect in the party wall that separates the posterior larynx and trachea from the oesophagus.
- It can be asymptomatic or present with stridor, cyanosis or aspiration.
Obstruction in this part of the airway produces an expiratory stridor.
Tracheomalacia is a weakness in the walls of the trachea. Issues to note:
- Inadequate cartilaginous support of the trachea leads to collapse in expiration.
- Tracheomalacia usually appears after the first few weeks of life but can be a problem in the neonatal period.
- Vascular rings and slings can cause external compression of the airway.
- Some examples are:
- double aortic arch
- anomalous inominate artery
- anomalous left common carotid artery
- The stridor is often worse with feeding.
Mediastinal masses may be caused by:
- lymphadenopathy which can also compress the airway.
Management of stridor
All newborns with stridor need evaluation of their airway because of the risk of significant airway obstruction.
When performing the initial history and examination, bear the list of differentials in mind.
A review of the history should include:
- pregnancy (fetal movements, distress)
- birth (trauma, HIE)
- feeding problems
- presence, nature and any progression of stridor
- age of onset of stridor
- precipitating factors (crying, feeding)
- is stridor positional
- cyanotic episodes
When examining the infant check for:
- degree of respiratory distress
- nature of stridor
- ability to feed
- choanal patency
- jaw and tongue size
- auscultation (transmission of breath sounds)
Initial management of stridor involves:
- cardiorespiratory and O2 saturation monitoring
- maintenance of airway
- position prone
- nil by mouth
- intravenous fluids if significant respiratory distress or feeding problems (choking/aspiration)
- oral or nasal airway
- CPAP, intubation and mechanical ventilation
- consider referral to tertiary centre for ENT evaluation
- management dependent on cause
Further investigations for stridor include:
- AP and lateral neck/chest
- Look for soft tissue masses and delineate the airway.
- Barium swallow:
- Extrinsic compressors of the trachea will probably also compress the oesophagus.
- to exclude vascular rings or slings
- Flexible fibre-optic nasopharyngoscopy and laryngoscopy:
- performed by ENT with patient awake can visualise supraglottic and laryngeal lesions, observe laryngomalacia and vocal cord movement
- Operative laryngoscopy/bronchoscopy: performed under GA
- Can see better views of the subglottic area and can biopsy lesions or drain cysts
- US and CT are rarely helpful
- Cohen LF. Stridor and upper airway obstruction in children. Pediatrics in Review 2000; 21:4-5
- Leung AKC, Cho H. Diagnosis of stridor in children. American Family Physician 1999; 60:2289-96
- Tunkel DE, Zalzal GH. Stridor in infants and children: ambulatory evaluation and operative diagnosis. Clinical Pediatrics 1992; 31;48-55
- Simon NP. Evaluation and management of stridor in the newborn. Clinical Pediatrics 1991; 30:211-6
- Mancuso RF. Stridor in neonates. Pediatric Clinics of North America 1996; 43:1339-1356
- Chapter 14: Airway obstruction. In: Meyer CM, Cotton RT.A Practical Approach to Pediatric Otolaryngology. Year Book Medical Publishers Inc., 1988:169-205.