Question 8

a)    List six possible causes of stridor at rest in a previously well 3-year-old child. ( 30% marks)

b)    What features elicited on history, examination and imaging would help in refining the diagnosis?
(40% marks)

c)    What are the indications for intubation in this situation? (30% marks)

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College answer

  1. List the possible causes of stridor at rest in a previously well 3 year old child
  • viral croup
  • epiglottitis
  • inhaled foreign body
  • severe bilateral tonsillitis, meeting in the midline (e.g.: infectious mononucleosis)
  • tonsillar abscess
  • retropharyngeal infection/abscess
  • spasmodic (recurrent allergic) croup
  • allergic reaction/angio-oedema
  • bacterial tracheitis
  • intra-thoracic obstruction vascular rings (less likely in prev. well), peri-tracheal tumours
  • diphtheria
  • other congenital causes (laryngomalacia, tracheomalacia, tracheal webs etc) unlikely in this setting, no marks for these responses
  1. What features elicited on history, examination and imaging would help in refining the diagnosis
  1. History:
  • past history including neonatal problems, previous intubation
  • vaccination especially HiB
  • prodrome, URTI symptoms
  • choking episodes (FB)
  • febrile symptoms
  • cough (implies epiglottitis unlikely)
  1. Examination
  • (minimise disturbance to child, examine in parent’s lap)
  • toxicity & fever
  • swallowing / drooling
  • petechial rash in HiB sepsis
  • inspect the throat (without instrumentation and if child cooperative), looking for tonsillar hyperplasia, uvula swelling, FB
  1. Radiology:
  • very limited utility, may be unsafe to transfer
  • possibly if radio-opaque FB suspected
  • lateral soft tissue neck of no/little value
  1. What are the indications for intubation in this situation?
  • Complete or imminent airway obstruction
  • Worsening airway obstruction despite appropriate therapy (e.g. steroids + nebulised adrenaline in croup)
  • Dangerous reduction in conscious state
  • Uncorrectable hypoxaemia


Causes of stridor are potentially numerous:

Causes of stridor in children, according to timing of onset
Acute Subacute Chronic
  • Foreign body
  • Airway burns
  • Thermal epiglottitis
  • Caustic burns (ingestion)
  • Anaphylaxis
  • Epiglottitis
  • Laryngotracheitis (croup)
  • Retropharyngeal abscess
  • Peritonsillar abscess
  • Laryngomalacia
  • Tracheomalacia
  • Subglottic stenosis
  • Vocal cord dysfunction, Paradoxical vocal cord motion
  • Vocal cord paralysis
  • Vascular ring
  • Bronchogenic cyst
  • Laryngeal malformation
  • Infantile haemangioma
  • Tumour
  • Hypocalcemic laryngeal spasm
  • Recurrent respiratory papillomatosis

So, given that this is a "previously well 3-year-old child",  one can probably forget about all the chronic causes. Thus:

  • Foreign body
  • Airway burns
  • Thermal epiglottitis
  • Caustic burns (ingestion)
  • Anaphylaxis
  • Epiglottitis
  • Laryngotracheitis (croup)
  • Retropharyngeal abscess
  • Peritonsillar abscess

For 40% of the marks, one would not be expected to reproduce the table offered below, but occasionally the author feels the need to list every possible permutation of answer content:

Assessment of stridor: history, examination, labs and imaging
  • Neonates and young infants: congential problems
  • Infants and toddlers: croup and foreign body
  • School-aged: abscesses and vocal cord dysfunction
  • All ages: anaphylaxis and tracheitis
  • Hyperacute: anaphylaxis, angioedema
  • Acute: bacterial tracheitis or epiglottitis
  • Subacute: laryngotracheitis
  • Chronic: anatomical problem, eg. stenosis or neoplasm
Associated symptoms
  • Fever (infectious causes)
  • Drooling (supraglottic obstruction)
  • Muffled voice (supraglottic obstruction)
  • Cough (barking = croup)
  • Voice quality (vocal cord lesion)
  • Stridor during feeding (tracheo-oesophageal fistula)
  • Onset during activity (vocal cord dysfunction)
  • Urticaria (anaphylaxis)
  • Onset during sleep (spasmodic croup, tonsillar enlagement)
  • Altered mental state (cause of stridor, or consequence of hypoxia)
General inspection
  • Failure to thrive (poor feeding, weight loss)
  • Congential abnormalities
  • "Funnel Chest" - pectus excavatum suggestive of chronic airway obstruction
  • Urticaria (anaphylaxis)
  • Haemangiomas (one may be in the airway
  • Cafe au lait spots (neurofibromatosis of the airway)
  • "tripid position" of epiglottitis
  • Cyanosis, hypoxia
Timing of stridor
  • Inspiratory: supraglottic onstruction
  • Expiratory: intrathoracic obstruction
  • Biphasic: fixed obstruction, or something in the glottis itself
  • "Stertor" - low pitched snoring sound, coming from an obstruction in the nasopharynx or oropharynx
Infectious testing
  • FBC for WCC
  • Cultures
  • Nasal swabs for viral PCR (especially for parainfluenza types 1, 2, and 3)
  • FBC for eosinophil count
  • Mast cell tryptase for anaphyalxis
  • Allergen testing
  • CMP: for calcium level
  • Vitamin D for rickets
Plain radiographs of the airway
  • Foreign body
CT of the neck and chest
  • Abscesses
  • Tumours
  • Fistulae
  • Vocal cord dysfunction
  • Laryngomalacia
  • Foreign body retrieval

Indications for intubation: one might benefit from bringing up the Croup Score at this stage:

Score 0 1 2
Breath sounds  Normal  Harsh, wheeze  Delayed 
Stridor  None  Inspiratory  Inspiratory and expiratory 
Cough  None  Hoarse cry  Bark 
Recession/flaring  None  Flaring, suprasternal recession  Flaring, suprasternal and intercostal recession 
Cyanosis  None  In air  In oxygen 40% 

By this scoring system, intubation should be considered in anybody who scores 7-10. Though this is a directive which comes from a truly ancient manuscript (Downes et al, 1975), it still gets quoted in modern literature. Also, this might not be croup. 

Alternatively, one might turn to more modern non-croup related literature, such as an authoritative article by Gray et al (2017). It appears to have been written by an anaesthetic registrar for the purpose of increasing the CME point score of his co-authors. However unglamorous, it contains an excellent list of very sensible indications for intubation, which is plagiarised here:

Situations where immediate intubation should be considered include:

  • Suspected epiglottitis
  • Inhalational injury
  • Falling conscious level
  • Increasing respiratory failure, indicated by:
    • Rising PaCO2
    • Exhaustion
    • Hypoxia (SpO2 <92% despite high flow oxygen administered via mask)


Cavanagh, Florence. "Stridor in children." Proceedings of the Royal Society of Medicine 58.4 (1965): 272.

Pfleger, Andreas, and Ernst Eber. "Assessment and causes of stridor." Paediatric respiratory reviews 18 (2016): 64-72.

Downes, John J., and Russell C. Raphaely. "Pediatric intensive care." Anesthesiology: The Journal of the American Society of Anesthesiologists 43.2 (1975): 238-250.