Topic map

1. Definition, anatomy, and mechanism
   • Relevant upper-airway anatomy: nose, nasopharynx, oropharynx, supraglottis, glottis, subglottis, trachea
   • Dynamic airway narrowing and turbulent airflow
   • Relation of sound timing to anatomical level
2. Types of stridor and site of origin
   • Inspiratory stridor: usually supraglottic or glottic obstruction
   • Biphasic stridor: often glottic, subglottic, or upper-tracheal obstruction
   • Expiratory stridor/wheeze: intrathoracic tracheal or lower-airway obstruction
   • Acute versus chronic stridor
3. Aetiology
   • Paediatric causes: laryngomalacia, croup, epiglottitis, foreign body, subglottic stenosis, vocal-cord paralysis, vascular compression, and others
   • Adult causes: tumour, laryngeal oedema, infection, bilateral vocal-cord palsy, post-intubation stenosis, foreign body, and extrinsic compression
4. Clinical assessment
   • Recognition of severity and impending respiratory failure
   • Key history, examination, and differentiation from wheeze/stertor
   • Red flags: cyanosis, altered consciousness, exhaustion, silent airway, drooling, inability to speak/feed, severe retractions
5. Investigations
   • When not to investigate immediately
   • Flexible nasoendoscopy/laryngoscopy, bronchoscopy, radiographs, CT/MRI, and relevant laboratory tests
   • Special precautions in suspected epiglottitis or severe obstruction
6. Management and emergency airway
   • Initial ABC approach and minimal handling
   • Oxygen, monitoring, positioning, cause-specific treatment
   • Indications and principles of intubation, rigid bronchoscopy, surgical airway, tracheostomy/cricothyrotomy
   • Paediatric versus adult airway considerations

High-level textbook approach

Stridor - Textbook-Style Note

1. Definition

2. Relevant anatomy

1. Nasal cavity and nasopharynx
2. Oropharynx and hypopharynx
3. Supraglottis
   • Epiglottis
   • Aryepiglottic folds
   • Arytenoids
4. Glottis
   • True vocal folds
   • Vocal-fold aperture
5. Subglottis
   • Region below the vocal folds to the lower border of cricoid cartilage
6. Cervical trachea
7. Intrathoracic trachea and main bronchi

Stridor versus stertor versus wheeze

3. Mechanism and pathophysiology

A. Turbulent flow

B. Bernoulli principle

C. Poiseuille relationship

D. Fixed versus dynamic obstruction

• Dynamic extrathoracic obstruction: worsens on inspiration because the airway tends to narrow under negative inspiratory pressure.
• Intrathoracic obstruction: tends to worsen on expiration because intrathoracic pressure compresses the airway.
• Fixed obstruction: causes obstruction in both phases and often produces biphasic stridor.

4. Types of stridor and site of origin

A. Inspiratory stridor

Site

• Pharynx
• Supraglottis
• Glottis
• Sometimes immediate subglottis

Typical causes

• Laryngomalacia
• Epiglottitis/supraglottitis
• Laryngeal oedema
• Foreign body at laryngeal inlet
• Supraglottic tumour or cyst
• Unilateral vocal-fold paralysis
• Upper-airway angio-oedema

Mechanism

B. Biphasic stridor

Site

• Glottis
• Subglottis
• Upper trachea

Typical causes

• Bilateral vocal-fold paralysis
• Subglottic stenosis
• Laryngeal web
• Subglottic haemangioma
• Fixed foreign body
• Post-intubation laryngeal or subglottic stenosis
• Upper-tracheal stenosis
• Laryngeal tumour

Mechanism

C. Expiratory stridor

Site

• Intrathoracic trachea
• Main bronchi
• Tracheobronchial tree

Typical causes

• Tracheomalacia
• Intrathoracic foreign body
• Lower tracheal compression
• Tracheobronchitis
• Bronchial obstruction

D. Acute and chronic stridor

Acute stridor

• Croup
• Epiglottitis
• Bacterial tracheitis
• Foreign body
• Anaphylaxis or angio-oedema
• Laryngeal trauma
• Retropharyngeal abscess
• Peritonsillar abscess
• Acute vocal-fold dysfunction or paralysis

Chronic or recurrent stridor

• Laryngomalacia
• Tracheomalacia
• Vocal-fold paralysis
• Laryngeal web
• Subglottic stenosis
• Subglottic haemangioma
• Vascular ring or sling
• Recurrent respiratory papillomatosis
• Laryngeal/tracheal tumour
• Goitre or mediastinal compression

5. Aetiology

A. Causes by anatomical level

B. Important paediatric causes

1. Laryngomalacia

• Most common cause of congenital stridor in infancy.
• Usually presents soon after birth or in the first weeks of life.
• Classically causes inspiratory stridor.
• Often worsens with crying, agitation, feeding, and upper respiratory infection.
• May improve with prone positioning or neck extension.
• Caused by inspiratory collapse of immature supraglottic structures, including the epiglottis, aryepiglottic folds, and arytenoids.
• Most children improve spontaneously, but severe disease may cause feeding difficulty, failure to thrive, apnoea, cyanosis, or pulmonary hypertension.

2. Vocal-fold paralysis

• Unilateral paralysis may cause weak cry, hoarseness, aspiration/feeding difficulty, and stridor.
• Bilateral paralysis may cause severe airway obstruction, stridor, cyanotic episodes, and apnoea.
• Diagnosis is by flexible laryngoscopy.

3. Subglottic stenosis

• Congenital or acquired.
• Acquired disease often follows prolonged endotracheal intubation, particularly in premature infants.
• May present with persistent biphasic stridor or recurrent “croup.”

4. Croup

• Viral laryngotracheobronchitis, commonly due to parainfluenza virus.
• The commonest cause of acute upper-airway obstruction/stridor in children.
• Gradual onset of low-grade fever, coryza, hoarse voice, barking cough, and inspiratory stridor.
• Drooling is generally absent.

5. Epiglottitis

• Acute potentially life-threatening infection/inflammation of epiglottis and adjacent supraglottic structures.
• Classical findings: fever, toxic appearance, severe sore throat, muffled voice, dysphagia, drooling, tripod posture, and inspiratory stridor.
• Cough is usually absent or minimal.
• Do not upset the patient or attempt unnecessary oropharyngeal examination before an airway plan is in place.

6. Bacterial tracheitis

• Child is often toxic, febrile, and has rapidly worsening stridor.
• May resemble croup but responds poorly to usual croup therapy.
• May require airway control and antimicrobial treatment.

7. Inhaled foreign body

• Sudden onset after choking, coughing, gagging, or playing/eating.
• May cause stridor, wheeze, diminished breath sounds, or an asymmetrical chest examination.
• Marked variation in the stridor pattern should raise suspicion of a foreign body.

8. Retropharyngeal abscess

• Fever, neck stiffness/torticollis, dysphagia, drooling, muffled voice, and inspiratory stridor.

9. Vascular rings and slings

• Congenital anomalous vessels compress trachea and/or oesophagus.
• May produce stridor from early infancy, recurrent respiratory symptoms, and feeding difficulty.
• CT angiography, echocardiography, and bronchoscopy may be required.

C. Important adult causes

1. Laryngeal or hypopharyngeal tumour
   • Particularly in a smoker or a patient with heavy alcohol use.
   • Associated hoarseness, dysphagia, odynophagia, weight loss, neck mass, or progressive symptoms should raise suspicion.
2. Bilateral vocal-fold paralysis
   • May follow thyroid, neck, mediastinal, or cardiothoracic surgery.
   • Can present with biphasic stridor and a relatively preserved voice.
3. Laryngeal oedema
   • Anaphylaxis/angio-oedema
   • Thermal or inhalational injury
   • Post-extubation oedema
   • Trauma
   • Infection
4. Laryngeal stenosis
   • Post-intubation, post-traumatic, inflammatory, autoimmune, or idiopathic.
5. Goitre or mediastinal mass
   • May cause extrinsic tracheal compression.
6. Deep-neck infection
   • Ludwig angina, retropharyngeal or parapharyngeal infection.
7. Foreign body
   • Especially with abrupt onset during eating.

6. Clinical assessment

Principle

A. Immediate assessment

1. Observe before touching the patient

• General appearance and posture
• Level of consciousness
• Ability to speak, cry, or feed
• Colour: pallor, cyanosis, mottling
• Respiratory rate and pattern
• Phase and character of stridor
• Work of breathing
• Chest movement and breath sounds
• Presence of drooling

2. Signs of severe obstruction or impending respiratory failure

• Stridor at rest, especially if increasing
• Severe suprasternal, intercostal, or subcostal recession
• Nasal flaring
• Tachypnoea followed by exhaustion or reduced respiratory effort
• Cyanosis
• Altered mental state, agitation, confusion, drowsiness, or hypotonia
• Silent chest or markedly reduced air entry
• Inability to speak, cry, swallow, or handle secretions
• Drooling with distress
• Tachycardia progressing to bradycardia
• Apnoea or recurrent cyanotic episodes

B. History

1. Time course

• Sudden onset: foreign body, anaphylaxis, trauma, acute laryngeal oedema.
• Hours to days: croup, epiglottitis, bacterial tracheitis, deep-neck infection.
• Since birth or early infancy: congenital anomaly.
• Chronic progressive symptoms: stenosis, tumour, papillomatosis, extrinsic compression.

2. Precipitating event

• Choking, coughing, gagging, eating, or a witnessed aspiration event.
• Allergy, drug exposure, insect sting, or food exposure.
• Recent upper respiratory infection.
• Recent intubation, airway instrumentation, surgery, neck trauma, or inhalational injury.

3. Associated symptoms

• Fever and toxic appearance
• Barking cough and hoarseness
• Drooling and dysphagia
• Voice change, weak cry, hoarseness, or muffled “hot-potato” voice
• Feeding difficulty, choking, aspiration, or failure to thrive
• Apnoea or cyanotic episodes
• Positional variation
• Neck swelling, neck stiffness, or torticollis

4. Paediatric-specific history

• Age at onset
• Birth history and prematurity
• Previous neonatal intensive care admission
• Previous intubation
• Congenital cardiac disease
• Feeding and growth
• Immunisation history, particularly Hib vaccination

C. Examination

General approach

• Vital signs and pulse oximetry
• Phase of stridor
• Severity of recession
• Chest expansion and air entry
• Voice and cry
• Hydration and ability to swallow
• Nasal patency
• Oral cavity and neck, only if safe
• Neck masses, tracheal position, and surgical emphysema
• Cutaneous haemangiomas in infants, especially beard-distribution lesions

Dangerous situation: drooling child with stridor

7. Investigations

General rule

A. Pulse oximetry and monitoring

• Continuous oxygen saturation monitoring in significant stridor.
• Continuous cardiorespiratory observation in moderate to severe disease.
• Normal oxygen saturation does not exclude significant upper-airway obstruction early in the course.

B. Flexible fibre-optic nasopharyngolaryngoscopy

• Nasal cavity and nasopharynx
• Supraglottis
• Epiglottis
• Arytenoids and aryepiglottic folds
• Vocal-fold movement
• Glottis
• Some subglottic pathology

• Laryngomalacia
• Vocal-fold palsy
• Laryngeal lesion
• Persistent unexplained stridor
• Adult stridor with voice or throat symptoms

C. Direct laryngoscopy and bronchoscopy

• Flexible laryngoscopy is non-diagnostic
• Subglottic, tracheal, or bronchial disease is suspected
• A foreign body is suspected
• Intervention may be required
• There is severe, persistent, recurrent, or unexplained stridor

D. Plain radiography

Neck radiographs

• Subglottic narrowing in croup
• Enlarged epiglottis in epiglottitis
• Retropharyngeal soft-tissue widening
• Tracheal narrowing or displacement
• Radio-opaque foreign body

Chest radiograph

• Foreign-body aspiration, including unilateral hyperinflation or collapse
• Tracheal deviation/compression
• Cardiac enlargement
• Pulmonary pathology
• Aortic arch anomaly

E. CT and MRI

• Neck mass
• Laryngeal/tracheal stenosis
• Deep-neck infection
• Retropharyngeal/parapharyngeal abscess
• Tumour
• Vascular rings/slings
• Mediastinal compression

F. Other targeted investigations

• Echocardiography/CT angiography: suspected vascular ring or sling.
• Barium swallow/esophagography: may demonstrate oesophageal compression from vascular anomalies.
• Microbiology: blood culture, tracheal aspirate, or operative specimen in suspected bacterial infection, but only after airway priorities are addressed.
• Blood gas: severe distress, fatigue, hypoxaemia, hypercapnia, or impending respiratory failure. Do not delay airway action to obtain it.

8. Management

A. Initial management of every patient with stridor

1. Call for help early
   • Anaesthesia/airway team
   • ENT surgeon
   • Paediatric team in children
   • Emergency/critical-care support as appropriate
2. Use an ABC approach
   • Airway
   • Breathing
   • Circulation
3. Keep the patient calm
   • Avoid unnecessary procedures.
   • Do not separate a distressed child from the parent unnecessarily.
   • Allow a position of comfort, often sitting upright or in the parent’s arms.
4. Give oxygen
   • Use the least distressing effective technique.
   • High-flow oxygen may be needed in severe illness.
5. Continuous monitoring
   • Pulse oximetry, cardiorespiratory monitoring, frequent reassessment.
6. Keep the patient nil by mouth if significant obstruction is suspected and airway intervention may be required.
7. Prepare for a difficult airway
   • Appropriate airway equipment
   • Smaller endotracheal tubes
   • Suction
   • Video/fibre-optic equipment when appropriate
   • A clear failed-airway plan
   • ENT support for surgical airway
8. Treat the cause after stabilisation.

B. Supportive measures

Heliox

Nebulised adrenaline/epinephrine

Corticosteroids

Antibiotics

Antihistamine/adrenaline and cause-specific treatment

9. Cause-specific management

A. Croup

• Keep child calm and minimise handling.
• Corticosteroid therapy.
• Nebulised adrenaline/epinephrine for moderate or severe obstruction.
• Observe for deterioration or recurrence after nebulised treatment.
• Intubation is required if progressive exhaustion, hypoxaemia, worsening obstruction, reduced consciousness, or impending respiratory failure occurs.

B. Epiglottitis/supraglottitis

• Treat as an airway emergency.
• Do not force a throat examination in a distressed patient.
• Keep patient upright and calm.
• Arrange controlled airway management by experienced anaesthetic and ENT personnel, ideally where immediate surgical airway support is available.
• Administer intravenous antimicrobial therapy after cultures if appropriate and without delaying airway protection.

C. Bacterial tracheitis

• Admission, close monitoring, and early airway assessment.
• Intravenous broad-spectrum antimicrobial therapy.
• Intubation may be difficult because of secretions, oedema, and pseudomembranes; experienced airway support is needed.

D. Foreign body

• If complete airway obstruction: perform age-appropriate basic life-support manoeuvres.
• If partial obstruction with effective ventilation: avoid blind finger sweeps and arrange urgent definitive assessment.
• Bronchoscopy is used for diagnosis and removal of an aspirated airway foreign body.

E. Laryngomalacia

• Most cases are managed conservatively with monitoring of breathing, feeding, and growth.
• Flexible laryngoscopy confirms diagnosis.
• Severe disease with apnoea, failure to thrive, hypoxaemia, or pulmonary hypertension may require supraglottoplasty.

F. Vocal-fold paralysis

• Identify cause and assess aspiration risk.
• Flexible laryngoscopy confirms impaired movement.
• Severe bilateral paralysis with airway compromise may require intubation or tracheostomy, followed by definitive specialist management.

G. Subglottic stenosis

• Assess severity endoscopically.
• Treatment may include endoscopic dilation, laser procedures, reconstructive surgery, or tracheostomy depending on severity and cause.

H. Angio-oedema/anaphylaxis

• Immediate treatment according to anaphylaxis protocol where appropriate.
• Early airway planning is essential because swelling may progress rapidly and intubation becomes increasingly difficult.

10. Emergency airway management

A. Indications for urgent definitive airway control

• Progressive stridor with severe work of breathing
• Stridor at rest with worsening distress
• Hypoxaemia or cyanosis
• Hypercapnia, exhaustion, or deteriorating consciousness
• Inability to handle secretions/drooling with significant obstruction
• Recurrent apnoea
• Diminishing breath sounds or silent airway
• Anticipated rapid progression, such as epiglottitis, anaphylaxis, severe deep-neck infection, or expanding neck haematoma

B. Principles of airway management

1. Use the most experienced available operator.
2. Call ENT and anaesthesia early.
3. Maintain spontaneous ventilation whenever possible until the airway is secured in selected critical upper-airway lesions.
4. Avoid repeated traumatic attempts at intubation.
5. Have an explicit rescue plan before the first attempt.
6. Use smaller-than-usual tracheal tubes if subglottic narrowing or oedema is likely.
7. Secure the airway before transfer when obstruction is unstable or rapidly worsening.

C. Endotracheal intubation

• Oedema
• Altered anatomy
• Secretions/blood
• Laryngeal mass
• Subglottic stenosis
• Limited mouth opening in deep-neck infection
• Rapid desaturation, especially in small children

D. Surgical airway

Adults

Children

Tracheostomy

• Intubation is impossible or unsuitable
• Prolonged airway protection is needed
• Upper airway obstruction is not rapidly reversible
• There is fixed laryngeal or subglottic obstruction

11. Practical approach to stridor

Step 1: Is there immediate airway danger?

• Cyanosis
• Altered consciousness
• Exhaustion
• Severe recession
• Silent or poorly ventilated airway
• Drooling with distress
• Progressive obstruction

Step 2: Localise from timing

• Inspiratory: supraglottic/glottic or extrathoracic lesion
• Biphasic: glottic, subglottic, or fixed upper-tracheal lesion
• Expiratory: intrathoracic tracheal/tracheobronchial lesion

Step 3: Use age and onset

• Neonate/young infant: congenital anomaly likely
• Toddler with barky cough: croup likely
• Toxic drooling child: epiglottitis/deep-neck infection until proved otherwise
• Sudden onset after choking: foreign body until proved otherwise
• Adult with progressive symptoms/hoarseness: tumour, paralysis, oedema, stenosis, or extrinsic compression

Step 4: Investigate only when stable

• Flexible laryngoscopy for stable upper-airway assessment
• Bronchoscopy for distal lesion or foreign body
• Imaging for deep-neck disease, compression, or vascular anomaly
• Do not delay airway protection in a threatened airway.

12. Key textbook points

• Stridor is a sign of partial airway obstruction and may be life-threatening.
• Severity is judged by work of breathing, oxygenation, consciousness, air entry, ability to speak/swallow, and trajectory, not by loudness alone.
• A quieter stridor in a deteriorating patient can indicate less airflow and impending respiratory arrest.
• In children, minor oedema can cause major obstruction because resistance rises sharply as airway radius decreases.
• Inspiratory stridor usually suggests an extrathoracic/supraglottic or glottic lesion.
• Biphasic stridor suggests fixed glottic, subglottic, or upper-tracheal obstruction.
• Stridor with drooling is a major warning sign. Avoid upsetting the patient or performing an unprepared throat examination.
• Persistent, severe, or unexplained stridor requires visualisation of the larynx and airway.
• In acute airway compromise, definitive airway management takes precedence over diagnostic testing.

Textbook sources

• Textbook of Family Medicine, 9th ed., pp. 435-436.
• Bailey and Love's Short Practice of Surgery, 28th ed., pp. 814-815.
• Tintinalli's Emergency Medicine, pp. 830-832.
• Rosen's Emergency Medicine: Concepts and Clinical Practice, p. 3165.
• Murray & Nadel's Textbook of Respiratory Medicine, pp. 1645-1653, 1674-1678.
• Scott-Brown's Otorhinolaryngology and Head & Neck Surgery, Vol. 1, p. 6051.