Clinical Approach to Stridor

Pediatric Comprehensive Framework

1
Symptom Overview
Overview
2
Pathophysiology
Mechanism
3
History Taking
History
4
Physical Examination
Examination
5
Differential Diagnosis
Differential
6
Investigations
Workup
7
Clinical Decision-Making
Algorithm
8
Pearls and Pitfalls
Summary

1. Symptom Overview

Understanding the clinical significance and classification of stridor in pediatric patients

Stridor is one of the most alarming sounds in pediatric medicine, representing turbulent airflow through a narrowed upper airway. It accounts for approximately 5-10% of pediatric emergency department visits related to respiratory complaints. Croup, the most common cause of acute stridor, affects approximately 3% of children annually, with peak incidence between 6 months and 3 years of age. In neonates, congenital causes such as laryngomalacia are the leading etiology, affecting approximately 1 in 2,500 live births. The pediatric airway is anatomically more vulnerable to obstruction than the adult airway, making stridor a potentially life-threatening emergency requiring prompt recognition and management.

Definition

Stridor is a high-pitched, musical sound produced by turbulent airflow through a partially obstructed upper airway, typically involving the larynx, trachea, or major bronchi. It is a symptom of airway narrowing, not a diagnosis itself. The character and timing of stridor provide critical clues to the anatomical level and severity of obstruction.

Key Epidemiological Facts

Croup: Most common cause of acute stridor; affects 3% of children per year
Peak age for croup: 6 months to 3 years
Laryngomalacia: Most common cause of chronic stridor in infants (60-70%)

Foreign body aspiration: Peak incidence 1-3 years
Epiglottitis: Now rare due to Haemophilus influenzae type b vaccination
Hospitalization rate: 1-5% of children with croup require admission

Classification by Timing (Phase of Respiration)

The timing of stridor relative to the respiratory cycle is the most important clue to localizing the level of airway obstruction. This classification guides both differential diagnosis and management decisions.

Type	Timing	Anatomical Level	Common Causes	Clinical Significance
Inspiratory Stridor	During inhalation	Supraglottic or glottic (extrathoracic)	Laryngomalacia, croup, epiglottitis, peritonsillar abscess	Most common type; suggests obstruction above the thoracic inlet
Expiratory Stridor	During exhalation	Intrathoracic trachea or bronchi	Tracheomalacia, vascular rings, intrathoracic masses	Less common; may overlap with wheeze; suggests intrathoracic obstruction
Biphasic Stridor	Both inspiration and expiration	Glottic or subglottic (fixed obstruction)	Subglottic stenosis, vocal cord paralysis, foreign body at glottis, croup (severe)	Indicates fixed or severe obstruction; often more serious

Classification by Duration (Onset)

Category	Duration	Common Causes	Clinical Approach
Acute Stridor	Minutes to days	Croup, epiglottitis, foreign body aspiration, anaphylaxis, bacterial tracheitis	Emergency evaluation; may be life-threatening; focus on airway security
Chronic Stridor	Present for weeks to months	Laryngomalacia, subglottic stenosis, vocal cord paralysis, vascular rings, hemangioma	Elective workup; may be congenital; endoscopic evaluation often required
Recurrent/Intermittent Stridor	Episodic with symptom-free intervals	Recurrent croup (“spasmodic croup”), laryngomalacia with feeding, paradoxical vocal fold motion	Investigate underlying cause; consider anatomical abnormality or atopy

Classification by Severity

Severity assessment guides the urgency of intervention. Several scoring systems exist, with the Westley Croup Score being most widely used for croup-related stridor.

Severity	Clinical Features	Oxygen Saturation	Level of Consciousness	Intervention Required
Mild	Stridor only when agitated or crying; no stridor at rest; mild or no retractions	Greater than 95%	Alert, interactive, playful	Supportive care; consider single dose of corticosteroids
Moderate	Stridor at rest; moderate retractions; mild tachypnea; decreased air entry	92-95%	Alert but anxious or irritable	Corticosteroids; consider nebulized epinephrine; observation
Severe	Loud stridor at rest; severe retractions; marked tachypnea; poor air entry; cyanosis	Less than 92%	Agitated, restless, or drowsy	Nebulized epinephrine; corticosteroids; prepare for intubation; ICU admission
Impending Respiratory Failure	Decreased or absent stridor (ominous sign); exhaustion; cyanosis; gasping respirations	Less than 90%	Decreased consciousness, lethargic	Immediate airway intervention; bag-mask ventilation; intubation

Critical Warning: The Silent Airway

Decreasing stridor in a deteriorating child is an ominous sign! As airway obstruction becomes near-complete, air movement decreases, and stridor may become quieter or absent. A child who was previously stridorous but is now quiet, exhausted, or has decreased level of consciousness requires immediate airway intervention. Never be reassured by “improving” stridor in a child who appears more unwell.

Age-Based Classification

The age of the child is one of the most valuable clues in determining the etiology of stridor. Different conditions predominate at different ages due to anatomical development and exposure risks.

Age Group	Most Common Causes	Key Considerations
Neonate (0-28 days)	Laryngomalacia, vocal cord paralysis, subglottic stenosis (if intubated), congenital webs, vascular rings	Congenital causes predominate; birth history crucial; stridor from birth suggests structural abnormality
Infant (1-12 months)	Laryngomalacia, croup, subglottic hemangioma, vascular anomalies, acquired subglottic stenosis	Laryngomalacia typically presents at 2-4 weeks; worsens until 6-8 months; subglottic hemangioma presents at 4-6 weeks
Toddler (1-3 years)	Croup (peak incidence), foreign body aspiration, bacterial tracheitis, epiglottitis (rare)	Mobile toddlers at highest risk for foreign body; croup most common in this age group
Preschool (3-5 years)	Croup, foreign body, peritonsillar abscess, retropharyngeal abscess	Deep space infections become more common; foreign body still a risk
School-age and Adolescent	Peritonsillar abscess, paradoxical vocal fold motion, anaphylaxis, trauma, recurrent respiratory papillomatosis	Infectious causes less common; consider functional causes (vocal cord dysfunction) and trauma

Classification by Sound Characteristics

High-Pitched Stridor

Characteristics: Musical, squeaky quality

Suggests: Supraglottic or glottic obstruction with smaller airway narrowing

Examples: Laryngomalacia, vocal cord paralysis, laryngeal web

Low-Pitched Stridor

Characteristics: Coarse, snoring quality (stertor)

Suggests: Nasopharyngeal or oropharyngeal obstruction

Examples: Adenotonsillar hypertrophy, retropharyngeal abscess, macroglossia

Barking Cough with Stridor

Characteristics: Seal-like, brassy cough

Suggests: Subglottic inflammation

Examples: Croup (viral laryngotracheobronchitis)

Muffled Voice with Stridor

Characteristics: “Hot potato” voice, drooling

Suggests: Supraglottic obstruction with swelling

Examples: Epiglottitis, peritonsillar abscess

Why the Pediatric Airway is Vulnerable

Understanding the anatomical differences between the pediatric and adult airway explains why children are more susceptible to clinically significant airway obstruction.

Key Anatomical Differences:

Narrowest point: Subglottic region in children (cricoid cartilage) versus glottis in adults — 1 mm of edema reduces cross-sectional area by 44% in infants versus 19% in adults
Smaller diameter: Neonatal trachea is approximately 4-5 mm diameter versus 15-20 mm in adults
Higher and more anterior larynx: C3-C4 level in infants versus C4-C6 in adults
Relatively larger tongue: More easily obstructs the airway
More compliant airway walls: Increased collapsibility, especially in dynamic lesions
Shorter trachea: Less distance for sound transmission and easier for foreign bodies to lodge
Obligate nasal breathers: Neonates cannot compensate with mouth breathing during nasal obstruction

Clinical Pearl: Poiseuille’s Law

Airway resistance is inversely proportional to the fourth power of the radius. This means a small decrease in airway caliber causes a dramatic increase in resistance and turbulent flow (stridor). In a child with a 4 mm airway, 1 mm of circumferential edema reduces the cross-sectional area by approximately 75% and increases resistance 16-fold. This explains why children deteriorate so rapidly with airway swelling.

2. Pathophysiology and Mechanisms

Understanding the underlying mechanisms of stridor in pediatric patients

Stridor results from turbulent airflow through a narrowed segment of the upper airway. Understanding the physics of airflow and the anatomical basis of obstruction is essential for localizing the lesion and guiding management. The sound of stridor is produced when laminar airflow becomes turbulent as it passes through a constricted airway segment, causing vibration of airway walls and surrounding tissues.

Physics of Stridor: Airflow Dynamics

Principle	Explanation	Clinical Relevance
Bernoulli’s Principle	As airflow velocity increases through a narrowed segment, pressure decreases laterally	Explains dynamic collapse of compliant airways during inspiration (extrathoracic) or expiration (intrathoracic)
Poiseuille’s Law	Resistance is inversely proportional to the fourth power of the radius (R ∝ 1/r⁴)	Small decreases in airway caliber cause dramatic increases in resistance; explains rapid deterioration in children
Reynolds Number	Determines transition from laminar to turbulent flow based on velocity, diameter, and viscosity	Turbulent flow produces audible sounds; occurs when airway is narrowed to approximately 50% of normal
Venturi Effect	Increased velocity through constriction creates negative pressure, drawing in surrounding tissue	Explains inspiratory collapse in laryngomalacia and dynamic lesions

Anatomical Localization by Stridor Phase

The timing of stridor during the respiratory cycle reflects the dynamic behavior of the airway at different anatomical levels in relation to intrathoracic pressure changes.

Inspiratory Stridor

Location: Extrathoracic airway (supraglottic, glottic)

Mechanism: During inspiration, negative intraluminal pressure causes dynamic collapse of compliant extrathoracic airway tissues

Examples: Laryngomalacia, croup, epiglottitis

Expiratory Stridor

Location: Intrathoracic airway (lower trachea, main bronchi)

Mechanism: During expiration, positive intrathoracic pressure compresses compliant intrathoracic airways

Examples: Tracheomalacia, bronchomalacia, vascular compression

Biphasic Stridor

Location: Fixed lesion at glottic or subglottic level

Mechanism: Obstruction is fixed and does not change with respiratory phase; narrows airway during both inspiration and expiration

Examples: Subglottic stenosis, complete vascular ring, foreign body at glottis

The Thoracic Inlet: A Critical Landmark

The thoracic inlet marks the transition between extrathoracic and intrathoracic airways. Lesions above this level (extrathoracic) tend to cause inspiratory stridor due to dynamic collapse during the negative-pressure inspiratory phase. Lesions below this level (intrathoracic) tend to cause expiratory stridor or wheeze due to compression during the positive-pressure expiratory phase. Lesions at the level of the thoracic inlet or fixed lesions cause biphasic stridor.

Mechanisms of Airway Obstruction by Condition

Condition	Mechanism of Obstruction	Type of Stridor	Treatment Implication
Laryngomalacia	Immature and flaccid supraglottic structures (epiglottis, aryepiglottic folds, arytenoids) collapse inward during inspiration due to negative pressure (Bernoulli effect)	Inspiratory	Usually self-limiting; severe cases may require supraglottoplasty to remove excess tissue
Croup (Viral Laryngotracheobronchitis)	Viral infection (usually parainfluenza) causes mucosal inflammation and edema of the subglottic region; cricoid ring is the narrowest point and cannot expand	Inspiratory (may be biphasic if severe)	Corticosteroids reduce inflammation; nebulized epinephrine causes mucosal vasoconstriction
Epiglottitis	Bacterial infection (classically Haemophilus influenzae type b, now more often Streptococcus or Staphylococcus) causes rapid supraglottic inflammation and swelling, obstructing the airway inlet	Inspiratory	Airway emergency; avoid agitation; intubation in controlled setting; intravenous antibiotics
Bacterial Tracheitis	Bacterial superinfection (usually Staphylococcus aureus) following viral illness; thick mucopurulent secretions and pseudomembranes obstruct the trachea	Inspiratory or biphasic	Airway management; intravenous antibiotics; may require bronchoscopy to remove pseudomembranes
Foreign Body Aspiration	Object lodges in airway causing mechanical obstruction; location determines clinical picture (laryngeal causes stridor; bronchial causes wheeze/atelectasis)	Variable depending on location; laryngeal foreign body causes biphasic stridor	Rigid bronchoscopy for removal; avoid blind finger sweeps
Subglottic Stenosis	Fixed narrowing of subglottic region; congenital (malformation) or acquired (prolonged intubation causing scarring)	Biphasic	Endoscopic dilation; cricoid split; laryngotracheal reconstruction in severe cases
Vocal Cord Paralysis	Unilateral or bilateral paralysis of vocal cords; unilateral causes weak cry and aspiration; bilateral causes severe stridor with airway obstruction	Inspiratory or biphasic (bilateral)	Investigate for central or peripheral nerve injury; bilateral may require tracheostomy
Vascular Ring	Anomalous great vessels encircle and compress the trachea and/or esophagus; double aortic arch and right aortic arch with aberrant subclavian are most common	Biphasic or expiratory	Surgical division of the vascular ring
Subglottic Hemangioma	Vascular tumor in subglottic region that proliferates during infancy; characteristic presentation at 4-6 weeks with progressive stridor	Biphasic	Propranolol is first-line treatment; may require surgical excision
Tracheomalacia	Weakness of tracheal cartilage allows dynamic collapse of the trachea during expiration; may be primary or secondary to vascular compression	Expiratory	Often improves with age; severe cases may require aortopexy or tracheal stenting
Anaphylaxis	Type I hypersensitivity reaction causing rapid mucosal edema and bronchospasm affecting upper and lower airways	Inspiratory (laryngeal edema) and/or expiratory (bronchospasm)	Intramuscular epinephrine is life-saving; airway management may be required
Retropharyngeal Abscess	Deep space infection causes mass effect and anterior displacement of posterior pharyngeal wall, narrowing the airway	Inspiratory; often with stertor	Intravenous antibiotics; surgical drainage if large or not responding

Developmental Changes in Airway Anatomy

The pediatric airway undergoes significant changes during growth, which explains why certain conditions present at specific ages and why some conditions resolve spontaneously.

Age	Anatomical Feature	Clinical Implication
Neonate	Obligate nasal breathing; large tongue relative to oral cavity; larynx at C3-C4; subglottic diameter approximately 4-5 mm	Nasal obstruction alone can cause respiratory distress; 1 mm edema reduces cross-sectional area by 75%
Infant (1-12 months)	Larynx begins to descend; supraglottic structures still relatively floppy; subglottic remains narrowest point	Laryngomalacia symptoms typically worsen until 6-8 months then improve; subglottic hemangioma proliferates
Toddler (1-3 years)	Airway diameter increases; subglottic cartilage becomes more rigid; still smaller than adult	Croup remains common but usually less severe than in infants; peak age for foreign body aspiration
School-age (6+ years)	Larynx descends to C4-C6; glottis becomes narrowest point (adult pattern); airway more rigid	Croup becomes rare; adult pattern of airway dynamics; less susceptible to obstruction from edema

Clinical Pearl: Why Laryngomalacia Improves

Laryngomalacia typically presents at 2-4 weeks of age, worsens until 6-8 months, and resolves by 12-18 months in 90% of cases. This natural history reflects the maturation of airway cartilage and neuromuscular control. The supraglottic structures become less compliant and less prone to inspiratory collapse as the infant grows. This explains why surgical intervention (supraglottoplasty) is reserved for severe cases with failure to thrive, apnea, or cor pulmonale.

Inflammatory and Infectious Mechanisms

Viral Croup Pathophysiology

Causative agents: Parainfluenza virus (types 1, 2, 3) causes 75% of cases; also respiratory syncytial virus, influenza, adenovirus, human metapneumovirus

Sequence of events:

Viral infection of respiratory epithelium
Mucosal inflammation and edema
Increased mucus production
Subglottic narrowing (cricoid ring cannot expand)
Turbulent airflow produces stridor

Peak inflammation: Days 2-3 of illness; typically resolves by days 5-7

Epiglottitis Pathophysiology

Causative agents: Historically Haemophilus influenzae type b (now rare due to vaccination); currently Streptococcus pneumoniae, Staphylococcus aureus, Group A Streptococcus

Sequence of events:

Bacterial invasion of supraglottic tissues
Rapid cellulitis with edema formation
Cherry-red, swollen epiglottis
Potential for complete airway obstruction within hours
Sepsis and systemic toxicity

Time course: Fulminant onset over 6-24 hours; medical emergency

Congenital Structural Mechanisms

Supraglottic Causes

Laryngomalacia: Immature cartilage; omega-shaped epiglottis; short aryepiglottic folds

Laryngeal cysts: Obstruction from cystic mass

Vallecular cyst: Cyst in vallecular space

Glottic Causes

Vocal cord paralysis: Unilateral or bilateral; central or peripheral etiology

Laryngeal web: Incomplete recanalization during development

Laryngeal cleft: Failure of posterior fusion

Subglottic Causes

Subglottic stenosis: Congenital narrowing or acquired scarring

Subglottic hemangioma: Vascular tumor; proliferates in infancy

Complete tracheal rings: Absent posterior membranous portion

Extrinsic Compression

Vascular rings: Double aortic arch, aberrant subclavian

Innominate artery compression: Anterior tracheal compression

Mediastinal masses: Lymphoma, teratoma, thymic masses

Compensatory Mechanisms and Failure

Children initially compensate for airway obstruction through increased respiratory effort. Understanding the sequence of compensation and decompensation helps identify the child in impending respiratory failure.

Stage	Physiological Response	Clinical Signs
Early Compensation	Increased respiratory rate and effort to maintain minute ventilation; use of accessory muscles; increased negative inspiratory pressure	Tachypnea; mild retractions; stridor with agitation; maintains oxygen saturation; alert and interactive
Progressive Compensation	Maximum work of breathing; negative intrathoracic pressure draws in compliant chest wall; increased oxygen consumption	Stridor at rest; moderate-severe retractions (suprasternal, intercostal, subcostal); nasal flaring; head bobbing; tachycardia; anxiety and irritability
Decompensation (Impending Failure)	Respiratory muscle fatigue; inability to generate adequate tidal volume; hypoxemia and hypercapnia develop	Decreasing stridor (ominous sign); decreasing respiratory effort; exhaustion; bradycardia; cyanosis; altered consciousness
Respiratory Failure	Complete airway obstruction or respiratory arrest; profound hypoxemia	Apnea or gasping respirations; absent breath sounds; unresponsiveness; cardiopulmonary arrest imminent

The “Quiet Child” Warning

A child with airway obstruction who becomes quiet and stops making effort is in extreme danger. The absence of stridor in a previously stridorous child who is now exhausted, pale, or cyanotic indicates critical airway compromise, not improvement. This child requires immediate airway intervention. The loudest stridor does not necessarily indicate the most severe obstruction—the child still has enough airflow to generate sound. The silent, exhausted child may have near-complete obstruction.

Clinical Pearl: Stridor Versus Stertor Versus Wheeze

These sounds are often confused but have distinct origins:

Stridor: High-pitched, musical sound from laryngeal or tracheal obstruction; primarily inspiratory (extrathoracic) or expiratory (intrathoracic)
Stertor: Low-pitched, snoring sound from nasopharyngeal or oropharyngeal obstruction (above the larynx); think adenotonsillar hypertrophy
Wheeze: Musical expiratory sound from lower airway (bronchial) obstruction; typically polyphonic in asthma; may be monophonic in focal obstruction

A child may have more than one of these sounds simultaneously (for example, stertor from adenoid hypertrophy and wheeze from reactive airways disease).

3. History Taking

A comprehensive approach to eliciting the stridor history in pediatric patients

Red Flags — Require Urgent Evaluation

Drooling with inability to swallow — Epiglottitis, severe supraglottic obstruction
Tripod positioning — Severe upper airway obstruction
Toxic appearance with high fever — Epiglottitis, bacterial tracheitis, retropharyngeal abscess
Sudden onset with choking episode — Foreign body aspiration
Rapidly progressive stridor over hours — Epiglottitis, anaphylaxis, angioedema
Cyanosis or oxygen saturation less than 92% — Severe obstruction, impending respiratory failure

Altered level of consciousness — Hypoxia, impending respiratory arrest
Severe retractions with decreasing stridor — Exhaustion, critical airway compromise
Stridor at rest in a quiet child — Significant obstruction requiring intervention
Muffled “hot potato” voice — Supraglottic pathology (epiglottitis, peritonsillar abscess)
Biphasic stridor from birth — Fixed congenital obstruction requiring workup
Failure to thrive with chronic stridor — Severe laryngomalacia, vascular ring, other structural cause

Systematic History: The “STRIDOR” Approach

Use the mnemonic “STRIDOR” to ensure comprehensive history taking in a child with noisy breathing:

S — Sound and Severity: What does it sound like? How loud? Is it getting worse? Does it occur at rest or only with activity/crying?
T — Timing and Triggers: When does it occur (inspiration, expiration, both)? What makes it better or worse? Position? Feeding? Sleep?
R — Rapidity of Onset and Recent Illness: How quickly did it start? Any preceding upper respiratory infection, fever, or choking episode?
I — Intake and Growth: How is feeding? Any choking or coughing with feeds? Weight gain? Failure to thrive?
D — Development and Duration: When did it first start? Present since birth? Developmental milestones? Any regression?
O — Other Symptoms: Voice changes? Cough character? Cyanotic episodes? Apnea? Associated skin findings?
R — Risk Factors and Relevant History: Prematurity? Intubation history? Cardiac surgery? Immunization status? Family history of atopy?

Onset and Timing: Critical Discriminators

Onset Pattern	Typical Duration	Suggests	Key Questions to Ask
Present from birth	Continuous since day 1	Congenital anomaly: laryngomalacia, vocal cord paralysis, vascular ring, subglottic stenosis	“Was the breathing noisy from the very first day of life?”
Onset at 2-4 weeks	Progressive worsening	Laryngomalacia (classic presentation), subglottic hemangioma (4-6 weeks)	“When did you first notice the noisy breathing? Has it been getting worse?”
Acute onset over hours	Hours to 1-2 days	Croup, epiglottitis, bacterial tracheitis, anaphylaxis	“When exactly did this start? Was there any fever or cold symptoms before?”
Sudden onset with choking	Seconds to minutes	Foreign body aspiration	“Was your child eating or playing with small objects when this started? Did they choke or gag?”
Recurrent episodes	Episodes lasting days, symptom-free intervals	Recurrent (spasmodic) croup, paradoxical vocal fold motion	“Has this happened before? How many times? What triggers it?”

Targeted Questions by Suspected Cause

Suspected Cause	Key Features	Ask This Question
Croup (Viral Laryngotracheobronchitis)	Barking cough, preceding coryzal symptoms, worse at night, age 6 months to 3 years	“Does your child have a cough that sounds like a seal or a dog barking? Did they have a runny nose or cold before this started?”
Epiglottitis	Toxic appearance, high fever, drooling, muffled voice, tripod position, no barking cough	“Is your child drooling? Can they swallow their saliva? Are they sitting forward with their neck extended? Did this come on very quickly?”
Laryngomalacia	Inspiratory stridor from early infancy, worse with feeding/crying/supine, improves when prone or calm	“Is the noisy breathing worse when your baby is feeding, crying, or lying on their back? Does it get better when they are calm or on their tummy?”
Foreign Body Aspiration	Sudden onset with witnessed or suspected choking, unilateral wheeze if bronchial	“Was your child eating anything or playing with small toys when this started? Did anyone see them choke or cough suddenly?”
Subglottic Hemangioma	Onset at 4-6 weeks, biphasic stridor, may have cutaneous hemangiomas (50%)	“Does your baby have any birthmarks or red spots on the skin? When exactly did the noisy breathing start?”
Vascular Ring	Stridor and feeding difficulties from early infancy, reflex apnea, respiratory infections	“Does your baby have trouble swallowing or seem to choke during feeds? Do they arch their back or extend their neck when feeding?”
Vocal Cord Paralysis	Weak or absent cry, feeding difficulties, aspiration; bilateral causes severe stridor	“How is your baby’s cry? Is it weak or different from other babies? Do they cough or choke when feeding?”
Bacterial Tracheitis	Toxic appearance, high fever, thick secretions, often following viral croup	“Did your child seem to have croup that was getting better, then suddenly got much worse with high fever?”
Retropharyngeal Abscess	Neck stiffness, limited neck extension, drooling, fever, preceding upper respiratory infection	“Is your child holding their neck stiff? Do they refuse to look up or tilt their head back? Have they had a recent sore throat?”
Anaphylaxis	Rapid onset after allergen exposure, urticaria, angioedema, hypotension	“Did your child eat anything new or get stung by an insect before this started? Do they have a rash or swelling of the lips or face?”

Pediatric-Specific History Components

Birth and Neonatal History

History Element	Relevance to Stridor	Example Questions
Gestational Age	Prematurity increases risk of subglottic stenosis (especially if intubated), laryngomalacia, tracheomalacia	“Was your baby born early? At how many weeks?”
Birth Weight	Low birth weight associated with airway abnormalities	“What was your baby’s birth weight?”
NICU Admission	Prolonged intubation is the most common cause of acquired subglottic stenosis	“Did your baby need to stay in the special care nursery? For how long?”
Intubation History	Duration of intubation correlates with risk of subglottic stenosis; multiple intubations increase risk	“Was your baby ever on a breathing machine with a tube? For how many days?”
Delivery Complications	Difficult delivery or birth trauma can cause vocal cord paralysis (especially left-sided)	“Was it a difficult delivery? Were forceps or vacuum used?”
Cardiac Surgery	Patent ductus arteriosus ligation and aortic arch surgery can injure recurrent laryngeal nerve	“Has your baby had any heart surgery?”

Feeding History

Key Feeding Questions

Feeding method: Breast or bottle? Pace and volume?
Feeding duration: How long does each feed take? (prolonged feeds suggest increased work of breathing)
Coughing or choking: Does the baby cough, choke, or turn blue during feeds?
Aspiration signs: Recurrent chest infections, wet-sounding breathing after feeds
Position preference: Does feeding improve in certain positions?
Weight gain: Is the baby gaining weight appropriately?

Feeding Clues by Condition

Laryngomalacia: Stridor worsens with feeding; may have reflux; prolonged feeds
Vascular ring: Dysphagia, choking, reflex apnea with feeds
Vocal cord paralysis: Aspiration, coughing, weak cry
Tracheoesophageal fistula: Coughing and choking with feeds, especially liquids
Severe obstruction: Inability to coordinate suck-swallow-breathe; poor weight gain

Developmental History

Why Development Matters

Developmental milestones provide important context for stridor:

Neurological conditions associated with hypotonia may cause laryngomalacia or vocal cord paralysis
Syndromes (such as Down syndrome, Pierre Robin sequence, CHARGE syndrome) are associated with airway abnormalities
Chronic hypoxia from severe airway obstruction can affect development
Failure to thrive suggests significant airway compromise affecting feeding and energy expenditure

Ask about gross motor, fine motor, language, and social milestones appropriate for age.

Immunization History

Critical Immunization to Assess:

Haemophilus influenzae type b (Hib) vaccine: Has dramatically reduced epiglottitis incidence; an unimmunized child with stridor, fever, and drooling should raise high suspicion for epiglottitis
Pertussis (DTaP/Tdap): Incomplete vaccination increases risk of whooping cough, which can present with stridor in severe cases
Diphtheria: Rare in vaccinated populations but causes membranous pharyngitis and stridor

Always ask: “Are your child’s vaccinations up to date?”

Associated Symptoms to Explore

Associated Symptom	Significance	Conditions to Consider
Barking cough	Classic for croup; “seal-like” quality	Croup, spasmodic croup, rarely subglottic stenosis
Hoarse voice or weak cry	Suggests glottic involvement	Vocal cord paralysis, laryngitis, laryngeal papillomatosis
Muffled “hot potato” voice	Supraglottic pathology	Epiglottitis, peritonsillar abscess, retropharyngeal abscess
Drooling	Inability or pain with swallowing	Epiglottitis, peritonsillar abscess, severe pharyngitis
Feeding difficulties	Competition between breathing and feeding	Laryngomalacia, vascular ring, vocal cord paralysis
Cyanotic episodes	Intermittent severe obstruction	Severe laryngomalacia, laryngeal cleft, ALTE/BRUE
Cutaneous hemangiomas	“Beard distribution” hemangiomas associated with airway hemangioma	Subglottic hemangioma (50% have skin lesions)
Recurrent pneumonia	Aspiration or immunodeficiency	Laryngeal cleft, tracheoesophageal fistula, vocal cord paralysis
Gastroesophageal reflux symptoms	Often coexists with laryngomalacia; may worsen stridor	Laryngomalacia (up to 80% have reflux), eosinophilic esophagitis

Medication and Allergy History

Allergies and Anaphylaxis Risk

Known allergies: Food allergies, medication allergies, insect stings
Previous anaphylaxis: Increases risk of severe reactions
Atopic history: Eczema, asthma, allergic rhinitis (increases risk of allergic reactions and recurrent croup)
Recent exposures: New foods, medications, or insect stings before symptom onset
Epinephrine autoinjector: Does the family have one? Was it used?

Current and Recent Medications

Inhaled corticosteroids: Chronic use can cause hoarseness, laryngeal candidiasis
ACE inhibitors: Can cause angioedema (rare in children but possible)
Recent antibiotics: May indicate treated infection; consider allergic reaction
Previous treatments for stridor: Response to steroids, epinephrine
Reflux medications: Proton pump inhibitors, H2 blockers for associated GERD

Family and Social History

Family History

Atopy: Asthma, eczema, allergies (increases risk of croup, allergic reactions)
Congenital airway abnormalities: Some conditions are familial
Recurrent croup: Family history suggests predisposition
Genetic syndromes: Associated with airway abnormalities
Immunodeficiency: Recurrent infections

Social and Environmental History

Smoke exposure: Increases respiratory infection risk and severity
Daycare attendance: Increases exposure to viral infections
Sick contacts: Others at home or school with respiratory illness
Foreign body access: Small toys, foods (nuts, grapes, popcorn)
Pets: Potential allergen exposure

Clinical Pearl: The Collateral History

In pediatric patients, always obtain history from the caregiver present during symptom onset. Key collateral history points include:

Who witnessed the onset? A witnessed choking episode is crucial for foreign body diagnosis
Video recording: Ask if the parent has recorded the stridor on their phone—this can be invaluable for intermittent symptoms
Comparison to previous episodes: For recurrent croup, is this episode similar or different?
What has already been tried? Response to humidified air, steroids, or epinephrine

4. Physical Examination

A systematic approach to examining the pediatric patient with stridor

Critical First Step: Assess Airway Stability

Before performing a detailed examination, rapidly assess for signs of impending respiratory failure:

Signs of Stability (Can Proceed with Examination):

Stridor only with agitation or crying
Alert and interactive
Normal color
Able to drink or speak

Signs of Instability (Minimize Intervention, Prepare for Airway):

Stridor at rest with severe retractions
Drooling, unable to swallow
Cyanosis or oxygen saturation less than 92%
Altered consciousness, exhaustion
Tripod positioning

Do NOT examine the pharynx of a child with suspected epiglottitis! Agitation can precipitate complete airway obstruction. Keep the child calm, allow them to remain in their position of comfort, and prepare for controlled airway management.

Systematic Framework: Use the “Look, Listen, Feel” approach, starting with observation from a distance before any hands-on examination. In a child with stridor, much information can be gathered simply by watching and listening before touching the patient.

Vital Signs: Age-Appropriate Normal Values

Vital sign interpretation must account for age-specific normal ranges. Tachypnea and tachycardia are early compensatory signs of respiratory distress.

Age Group	Heart Rate (bpm)	Respiratory Rate (/min)	Systolic Blood Pressure (mmHg)	Oxygen Saturation
Neonate (0-28 days)	100-160	30-60	60-90	Greater than 95%
Infant (1-12 months)	100-150	25-40	80-100	Greater than 95%
Toddler (1-3 years)	90-140	20-30	90-105	Greater than 95%
Preschool (3-5 years)	80-120	20-25	95-110	Greater than 95%
School-age (6-12 years)	70-110	18-22	100-120	Greater than 95%
Adolescent (13+ years)	60-100	12-20	100-130	Greater than 95%

Vital Sign	What to Look For	Clinical Significance
Temperature	Fever (greater than 38°C) or high fever (greater than 39°C)	Fever with stridor suggests infection: croup (low-grade), epiglottitis (high), bacterial tracheitis (high), retropharyngeal abscess (high)
Heart Rate	Tachycardia above normal for age; bradycardia is late sign	Tachycardia indicates stress, fever, or hypoxia; bradycardia suggests impending arrest
Respiratory Rate	Tachypnea; very high rates with shallow breathing	Compensatory tachypnea; decreasing rate with exhaustion is ominous
Oxygen Saturation	Less than 92% indicates significant hypoxemia	Hypoxemia is a late sign in upper airway obstruction; indicates severe disease
Blood Pressure	Hypotension is a very late sign	May indicate sepsis (epiglottitis, bacterial tracheitis) or anaphylaxis

General Inspection (From a Distance)

Begin by observing the child from the doorway or across the room. This initial assessment provides crucial information while keeping the child calm.

Observation	What to Look For	Clinical Significance
Level of Consciousness	Alert and interactive versus anxious, irritable, lethargic, or obtunded	Lethargy or decreased consciousness indicates severe hypoxia or exhaustion—critical warning sign
Position of Comfort	Sitting forward, neck extended (“tripod” or “sniffing” position); refuses to lie down	Tripod position optimizes airway patency; classic for epiglottitis but seen in any severe upper airway obstruction
Color	Pink, pale, mottled, or cyanotic (especially perioral or central)	Cyanosis indicates severe hypoxemia; pallor suggests poor perfusion or anemia
Work of Breathing	Retractions (suprasternal, intercostal, subcostal), nasal flaring, head bobbing (infants)	Increased work of breathing indicates significant obstruction; decreasing effort with altered consciousness is ominous
Drooling	Unable to swallow secretions; saliva dripping from mouth	Suggests severe pain or inability to swallow—highly concerning for epiglottitis or peritonsillar abscess
Stridor Character	Inspiratory, expiratory, or biphasic; loud or quiet; high-pitched or low-pitched	Localizes level of obstruction; decreasing stridor in a worsening child indicates critical obstruction
Voice and Cry	Normal, hoarse, weak, muffled (“hot potato” voice), or absent	Hoarse voice suggests glottic involvement; muffled voice suggests supraglottic pathology
Cough	Barking (“seal-like”), brassy, weak, or absent	Barking cough is classic for croup; absent cough in epiglottitis (too painful)

Clinical Pearl: The “4 Ds” of Epiglottitis

Remember the classic presentation of epiglottitis with the “4 Ds”:

Drooling
Dysphagia (difficulty swallowing)
Dysphonia (muffled voice)
Distress (respiratory)

Note: Patients with epiglottitis typically do NOT have the barking cough seen in croup. If these features are present, do not examine the pharynx—prepare for controlled airway management.

Assessment of Respiratory Distress Severity

Sign	Mild	Moderate	Severe
Stridor	Only with agitation or crying	At rest, easily audible	At rest; may become quieter as obstruction worsens
Retractions	Mild or none	Moderate (suprasternal, intercostal)	Severe (suprasternal, intercostal, subcostal, sternal)
Air Entry	Normal	Mildly decreased	Markedly decreased or absent
Color	Normal (pink)	Normal or pale	Cyanotic or dusky
Level of Consciousness	Alert, playful	Anxious, irritable, but responsive	Lethargic, exhausted, decreased responsiveness
Oxygen Saturation	Greater than 95%	92-95%	Less than 92%

Head and Neck Examination

General Head and Face

Dysmorphic features: Syndromes associated with airway abnormalities (Pierre Robin sequence, Down syndrome, Treacher Collins syndrome)
Micrognathia: Small jaw associated with glossoptosis and airway obstruction
Facial swelling: Angioedema, allergic reaction
Cutaneous hemangiomas: Especially in “beard distribution” (chin, lower lip, anterior neck)—associated with subglottic hemangioma

Nose

Nasal patency: Choanal atresia (neonates), nasal congestion, nasal polyps
Nasal flaring: Sign of respiratory distress
Discharge: Purulent (sinusitis), clear (viral upper respiratory infection, allergic rhinitis)

Oropharynx (Only If Safe to Examine)

Caution: When NOT to Examine the Oropharynx

Do NOT perform oropharyngeal examination if the child has:

Drooling with inability to swallow
Tripod positioning
Toxic appearance with high fever
Muffled “hot potato” voice
Severe respiratory distress

These features suggest epiglottitis or severe supraglottic pathology. Examination may precipitate complete airway obstruction.

If safe to examine:

Tonsillar size and symmetry: Peritonsillar abscess causes asymmetric tonsillar enlargement with uvular deviation
Posterior pharyngeal wall: Bulging suggests retropharyngeal abscess
Oral lesions: Vesicles (herpangina), pseudomembranes (diphtheria)
Airway secretions: Thick, purulent secretions suggest bacterial infection

Neck

Lymphadenopathy: Tender anterior cervical nodes in infectious causes
Neck swelling: Cellulitis, abscess, angioedema
Neck position: Extended (optimizing airway), stiff (retropharyngeal abscess, meningitis)
Tracheal position: Deviation suggests mass effect or tension pneumothorax
Scars: Previous tracheostomy, thyroid surgery, cardiac surgery (risk of recurrent laryngeal nerve injury)

Respiratory Examination

Inspection

Chest shape: Pectus excavatum, barrel chest (chronic air trapping), Harrison’s sulcus (chronic respiratory disease)
Respiratory pattern: Rate, depth, regularity, use of accessory muscles
Retractions: Suprasternal, intercostal, subcostal—indicate increased work of breathing
Paradoxical breathing: Chest retracts while abdomen rises—indicates severe obstruction
Scars: Previous thoracotomy, tracheostomy

Auscultation

Finding	Description	Conditions
Inspiratory stridor	High-pitched sound during inspiration, best heard over neck	Extrathoracic obstruction: laryngomalacia, croup, epiglottitis
Expiratory stridor	Sound during expiration, may overlap with wheeze	Intrathoracic obstruction: tracheomalacia, vascular compression
Biphasic stridor	Present during both inspiration and expiration	Fixed obstruction: subglottic stenosis, complete vascular ring, glottic foreign body
Stertor	Low-pitched, snoring sound	Nasopharyngeal/oropharyngeal obstruction: adenotonsillar hypertrophy, retropharyngeal abscess
Wheeze	Musical expiratory sound from lower airways	Lower airway disease: asthma, bronchiolitis; bronchial foreign body
Unilateral decreased breath sounds	Asymmetric air entry	Foreign body (bronchial), pneumothorax, large pleural effusion
Transmitted upper airway sounds	Sounds that clear with coughing or change with position	Secretions in upper airway; may mimic lower airway disease

Clinical Pearl: Localizing Stridor by Auscultation

Auscultate with the stethoscope at multiple locations to help localize the source:

Over the nose/mouth: Stertor from nasopharyngeal obstruction
Over the neck (larynx): Stridor loudest here suggests laryngeal pathology
Over the trachea (suprasternal): Tracheal lesions may be loudest here
Over the chest: Compare stridor to breath sounds; stridor transmitted equally suggests upper airway; focal findings suggest lower airway

Cardiovascular Examination

Heart sounds: Murmur may indicate congenital heart disease (associated with vascular rings, airway abnormalities)
Capillary refill: Prolonged (greater than 2 seconds) suggests poor perfusion
Peripheral pulses: Quality and symmetry
Signs of heart failure: Hepatomegaly, edema (may be seen with severe airway obstruction causing cor pulmonale)

Skin Examination

Hemangiomas: Cutaneous hemangiomas, especially in beard distribution, associated with subglottic hemangioma
Urticaria: Suggests allergic reaction or anaphylaxis
Eczema: Atopic child at increased risk of allergic reactions and recurrent croup
Rash: Viral exanthem, scarlet fever rash
Cyanosis: Central (tongue, mucous membranes) versus peripheral

Growth Parameters

In chronic stridor, assess growth as an indicator of severity:

Weight: Failure to thrive suggests significant airway compromise affecting feeding
Length/height: Plot on appropriate growth chart
Head circumference: Important in infants; may be abnormal in syndromic conditions
Weight-for-length: Particularly useful in assessing nutritional status

Expected Findings by Etiology

Condition	General Appearance	Stridor Character	Other Key Findings
Croup	Mild-moderate distress; not toxic	Inspiratory; barking cough; hoarse voice	Low-grade fever; coryzal symptoms; worse at night
Epiglottitis	Toxic; tripod position; drooling; severe distress	Inspiratory; muffled voice; NO barking cough	High fever; dysphagia; refuses to lie down; “4 Ds”
Bacterial Tracheitis	Toxic; high fever; thick secretions	Inspiratory or biphasic	Often follows viral croup; does not respond to usual croup treatment
Laryngomalacia	Well-appearing; thriving (mild) or failure to thrive (severe)	Inspiratory; worse with feeds, crying, supine	Present from early infancy; improves with prone positioning
Foreign Body (Laryngeal)	Sudden onset; may be in distress or stable	Variable; often biphasic if at glottis	History of choking; unwitnessed in some cases
Subglottic Stenosis	Variable; depends on severity	Biphasic	History of intubation; recurrent “croup-like” episodes
Vocal Cord Paralysis (Bilateral)	May have severe distress	Inspiratory or biphasic; weak or absent cry	Birth trauma; cardiac surgery; may have aspiration
Subglottic Hemangioma	Progressive symptoms; onset at 4-6 weeks	Biphasic	50% have cutaneous hemangiomas (beard distribution)
Vascular Ring	Chronic symptoms; feeding difficulties	Biphasic or expiratory	Dysphagia; reflex apnea; hyperextends neck with feeds
Retropharyngeal Abscess	Toxic; fever; neck stiffness	Inspiratory; often with stertor	Limited neck extension; torticollis; drooling
Anaphylaxis	Rapid deterioration; may have urticaria, angioedema	Inspiratory (laryngeal edema); may also wheeze	Allergen exposure; skin findings; hypotension

Important Teaching Point: Findings May Be Minimal

In early or mild cases of stridor, especially in chronic conditions like mild laryngomalacia or early croup, physical examination findings may be subtle or absent at the time of evaluation. Key points:

Stridor may only be present when the child is feeding, crying, or agitated
A calm, sleeping child may have minimal or no audible stridor
Intermittent conditions (such as recurrent croup) may have completely normal examination between episodes
The severity of symptoms often fluctuates—assess the worst episode, not just the current state
Parent-recorded videos can be invaluable for capturing intermittent symptoms

The Westley Croup Score

For children with suspected croup, the Westley Croup Score helps quantify severity and guide management:

Feature	0 Points	1 Point	2 Points	3-5 Points
Stridor	None	When agitated	At rest	—
Retractions	None	Mild	Moderate	Severe (3 pts)
Air Entry	Normal	Mildly decreased	Markedly decreased	—
Cyanosis	None	—	—	With agitation (4 pts) / At rest (5 pts)
Level of Consciousness	Normal	—	—	Altered (5 pts)

Westley Score Interpretation:

0-2: Mild croup — Outpatient management with single dose of corticosteroid
3-5: Moderate croup — Corticosteroid; consider nebulized epinephrine; observation
6-11: Severe croup — Nebulized epinephrine; corticosteroid; close monitoring; admission likely
≥12: Impending respiratory failure — Prepare for intubation; ICU admission

5. Differential Diagnosis

Systematic approach organized by probability, acuity, and anatomical location

The differential diagnosis of stridor in children is broad and varies significantly by age and acuity of presentation. A systematic approach considering the timing of onset, phase of stridor, and associated features helps narrow the differential efficiently. Always consider life-threatening causes first.

Life-Threatening Causes: Rule Out First

Before proceeding with a systematic differential, always consider these emergencies:

Foreign body aspiration — Sudden onset, choking history
Epiglottitis — Toxic, drooling, tripod position
Bacterial tracheitis — Toxic, high fever, thick secretions

Anaphylaxis — Allergen exposure, urticaria, rapid onset
Retropharyngeal abscess — Neck stiffness, fever, drooling
Severe croup — Stridor at rest with respiratory distress

Acute Stridor (Onset: Minutes to Days)

Probability	Condition	Key Features	Red Flags
COMMON (approximately 80%)	Viral croup (laryngotracheobronchitis)	Age 6 months to 3 years; barking cough; hoarse voice; preceding upper respiratory infection; worse at night; low-grade fever	Stridor at rest; severe retractions; cyanosis; altered consciousness
COMMON	Spasmodic (recurrent) croup	Recurrent episodes; sudden onset at night; often no prodrome; resolves quickly; atopic history common	Frequent severe episodes; poor response to treatment
LESS COMMON (approximately 15%)	Foreign body aspiration	Sudden onset; witnessed or unwitnessed choking; age 1-3 years peak; may have asymmetric findings if bronchial	Complete obstruction; inability to phonate; cyanosis
LESS COMMON	Bacterial tracheitis	Toxic appearance; high fever; thick purulent secretions; often follows viral croup; does not respond to epinephrine	Rapidly progressive; respiratory failure; sepsis
LESS COMMON	Retropharyngeal abscess	Fever; neck stiffness; limited neck extension; drooling; preceding pharyngitis; age typically less than 6 years	Airway compromise; mediastinal extension; sepsis
LESS COMMON	Peritonsillar abscess	Older children and adolescents; severe sore throat; muffled voice; trismus; uvular deviation	Airway obstruction; extension to parapharyngeal space
UNCOMMON BUT SERIOUS (approximately 5%)	Epiglottitis	Rare post-Hib vaccine; toxic; high fever; drooling; tripod position; muffled voice; NO barking cough; rapid progression	Complete airway obstruction; may occur within hours
UNCOMMON BUT SERIOUS	Anaphylaxis	Allergen exposure; rapid onset; urticaria; angioedema; may have wheeze and hypotension	Cardiovascular collapse; refractory bronchospasm
UNCOMMON BUT SERIOUS	Angioedema (hereditary or acquired)	Recurrent episodes of swelling; may have family history; ACE inhibitor-induced in older children	Laryngeal involvement; does not respond to epinephrine (hereditary type)
UNCOMMON BUT SERIOUS	Diphtheria	Unvaccinated; pharyngeal pseudomembrane; bull neck; systemic toxicity	Airway obstruction from membrane; myocarditis; neurotoxicity
UNCOMMON BUT SERIOUS	Thermal or caustic injury	History of smoke inhalation, hot liquid ingestion, or caustic ingestion; oropharyngeal burns	Progressive airway edema over hours; may need early intubation

Chronic Stridor (Present for Weeks to Months)

Step-by-Step Approach to Chronic Stridor:

Step 1: Determine age of onset — Stridor from birth suggests congenital cause; onset at 2-6 weeks suggests laryngomalacia or subglottic hemangioma
Step 2: Characterize the stridor — Inspiratory (supraglottic/glottic), expiratory (intrathoracic), or biphasic (fixed obstruction)
Step 3: Assess for red flags — Failure to thrive, cyanotic episodes, apnea, feeding difficulties indicate severe disease requiring urgent workup
Step 4: Review history for acquired causes — Intubation history (subglottic stenosis), cardiac surgery (vocal cord paralysis)
Step 5: Proceed to endoscopic evaluation if diagnosis unclear or symptoms severe

Probability	Condition	Typical Onset	Stridor Type	Key Distinguishing Features
COMMON (60-70%)	Laryngomalacia	2-4 weeks of age	Inspiratory	Worsens with feeding, crying, supine position; improves prone; usually self-limiting by 12-18 months
LESS COMMON (10-20%)	Vocal cord paralysis	From birth or post-surgery	Inspiratory (bilateral causes biphasic)	Weak or absent cry; aspiration; unilateral may be asymptomatic; bilateral causes severe stridor
LESS COMMON	Subglottic stenosis	From birth (congenital) or post-intubation	Biphasic	Recurrent “croup” episodes; history of prolonged intubation; fixed obstruction
LESS COMMON	Tracheomalacia	Infancy	Expiratory (or biphasic)	Barking cough; worsens with respiratory infections; may be associated with tracheoesophageal fistula repair
LESS COMMON	Vascular ring/sling	From birth or early infancy	Biphasic or expiratory	Feeding difficulties; dysphagia; reflex apnea; hyperextends neck; associated cardiac anomalies
UNCOMMON (less than 5%)	Subglottic hemangioma	4-6 weeks of age	Biphasic	Progressive; 50% have cutaneous hemangiomas (beard distribution); proliferates until 12 months
UNCOMMON	Laryngeal web	From birth	Variable	Weak cry; associated with 22q11 deletion syndrome; may present later if partial
UNCOMMON	Laryngeal cleft	From birth	Variable; often with stridor and aspiration	Aspiration; coughing and choking with feeds; recurrent pneumonia; may be associated with syndromes
UNCOMMON	Recurrent respiratory papillomatosis	2-4 years typical	Inspiratory	Progressive hoarseness then stridor; history of maternal genital warts (HPV); multiple surgeries required
UNCOMMON	Laryngeal cyst (saccular cyst, vallecular cyst)	From birth or early infancy	Inspiratory	May cause feeding difficulties; can present acutely if cyst enlarges
UNCOMMON	Complete tracheal rings	From birth	Biphasic; fixed narrowing	Associated with pulmonary artery sling; presents with severe respiratory distress

Age-Based Differential Approach

The age of the child is one of the most helpful discriminating factors in the differential diagnosis of stridor.

Age Group	Most Likely Causes	Less Common Causes	Key Considerations
Neonate (0-28 days)	Laryngomalacia; vocal cord paralysis; congenital subglottic stenosis	Laryngeal web; vascular ring; choanal atresia; Pierre Robin sequence	Congenital causes predominate; birth and intubation history critical; stridor from day 1 suggests structural abnormality
Infant 1-6 months	Laryngomalacia (peak symptoms); croup (after 6 months)	Subglottic hemangioma (onset 4-6 weeks); acquired subglottic stenosis; vascular anomalies	Laryngomalacia typically worsens until 6-8 months; look for cutaneous hemangiomas
Infant 6-12 months	Croup; laryngomalacia (improving)	Foreign body (as mobility increases); subglottic stenosis	Croup becomes more common; laryngomalacia should be improving
Toddler (1-3 years)	Croup (peak incidence); foreign body aspiration (peak)	Bacterial tracheitis; epiglottitis; retropharyngeal abscess	Peak age for both croup and foreign body; high index of suspicion needed
Preschool (3-5 years)	Croup (decreasing); foreign body	Retropharyngeal abscess; peritonsillar abscess; recurrent respiratory papillomatosis	Deep space infections become more common; croup should be less severe
School-age (6-12 years)	Peritonsillar abscess; anaphylaxis	Paradoxical vocal fold motion; trauma; recurrent respiratory papillomatosis	Croup rare after age 6; consider functional causes; trauma history important
Adolescent	Peritonsillar abscess; paradoxical vocal fold motion; anaphylaxis	Trauma; angioedema; neoplasm (rare)	Functional stridor (paradoxical vocal fold motion) common; often misdiagnosed as asthma

Anatomical Approach to Stridor

Organizing the differential by anatomical level helps correlate clinical findings with the site of obstruction.

Supraglottic (Above Vocal Cords)

Stridor: Inspiratory

Voice: Muffled “hot potato” voice

Causes:

• Laryngomalacia

• Epiglottitis

• Peritonsillar abscess

• Retropharyngeal abscess

• Vallecular cyst

• Lingual thyroid

• Macroglossia

Glottic (Vocal Cord Level)

Stridor: Inspiratory or biphasic

Voice: Hoarse or weak cry

Causes:

• Vocal cord paralysis

• Laryngeal web

• Laryngeal papillomatosis

• Laryngeal foreign body

• Paradoxical vocal fold motion

• Laryngeal trauma

Subglottic (Below Vocal Cords)

Stridor: Biphasic

Voice: Normal or slightly hoarse

Causes:

• Croup

• Subglottic stenosis

• Subglottic hemangioma

• Bacterial tracheitis

• Complete tracheal rings

• Subglottic cyst

Tracheal (Intrathoracic)

Stridor: Expiratory or biphasic

Voice: Normal

Causes:

• Tracheomalacia

• Vascular ring

• Innominate artery compression

• Mediastinal mass

• Tracheal foreign body

• External compression (lymph nodes, thyroid)

Stridor Phase as Diagnostic Clue

Stridor Phase	Anatomical Level	Common Causes	Less Common Causes
Inspiratory	Supraglottic or glottic (extrathoracic)	Laryngomalacia, croup, epiglottitis	Vocal cord paralysis (unilateral), peritonsillar abscess, laryngeal papillomatosis
Expiratory	Intrathoracic trachea or bronchi	Tracheomalacia, bronchomalacia	Vascular ring, mediastinal mass, intrathoracic foreign body
Biphasic	Glottic, subglottic, or fixed lesion	Subglottic stenosis, severe croup, vocal cord paralysis (bilateral)	Subglottic hemangioma, complete vascular ring, glottic foreign body, laryngeal web

Conditions Associated with Stridor

Certain syndromes and conditions are associated with airway abnormalities. Recognition of associated features can guide diagnosis.

Syndrome or Condition	Associated Airway Abnormality	Other Features
Down syndrome (Trisomy 21)	Subglottic stenosis, laryngomalacia, tracheal stenosis	Hypotonia, characteristic facies, congenital heart disease
Pierre Robin sequence	Glossoptosis, micrognathia causing upper airway obstruction	Cleft palate, small mandible, feeding difficulties
22q11 deletion syndrome (DiGeorge)	Laryngeal web, vascular anomalies	Cardiac anomalies, hypocalcemia, immune deficiency
CHARGE syndrome	Laryngomalacia, choanal atresia, laryngeal cleft	Coloboma, heart defects, growth retardation, ear anomalies
Treacher Collins syndrome	Micrognathia, choanal atresia	Malar hypoplasia, downslanting palpebral fissures, ear anomalies
PHACE syndrome	Subglottic hemangioma	Large facial hemangioma, posterior fossa anomalies, arterial anomalies, cardiac defects, eye anomalies
Tracheoesophageal fistula (post-repair)	Tracheomalacia, recurrent fistula	History of esophageal atresia repair, VACTERL association

Quick Reference: “If You See This, Think This”

Clinical Clue	Think This First	Next Step
Barking cough + hoarse voice + low-grade fever in toddler	Croup	Assess severity; corticosteroid; consider nebulized epinephrine if moderate-severe
Toxic child + high fever + drooling + tripod position	Epiglottitis	Do NOT examine pharynx; prepare for controlled airway management; call anesthesia/ENT
Sudden onset during eating or playing with small objects	Foreign body aspiration	Chest radiograph; rigid bronchoscopy if high suspicion
Stridor from 2-4 weeks, worse with feeding, improves prone	Laryngomalacia	Assess feeding and growth; flexible laryngoscopy if severe
Progressive stridor at 4-6 weeks + cutaneous hemangioma	Subglottic hemangioma	Direct laryngoscopy/bronchoscopy; start propranolol
Weak or absent cry + stridor from birth	Vocal cord paralysis	Flexible laryngoscopy; investigate cause (birth trauma, cardiac surgery, central)
Recurrent “croup” episodes + history of intubation	Subglottic stenosis	Direct laryngoscopy/bronchoscopy to assess and grade stenosis
Biphasic stridor + feeding difficulties + reflex apnea from birth	Vascular ring	CT angiography or MR angiography; echocardiogram; bronchoscopy
Croup not responding to treatment + high fever + thick secretions	Bacterial tracheitis	Intravenous antibiotics; airway management; may need bronchoscopy
Neck stiffness + fever + refuses to extend neck	Retropharyngeal abscess	Lateral neck radiograph or CT neck; intravenous antibiotics; surgical drainage if needed
Progressive hoarseness then stridor in preschool child	Recurrent respiratory papillomatosis	Direct laryngoscopy; surgical debulking; HPV testing
Stridor only during wakefulness, disappears during sleep	Paradoxical vocal fold motion (functional)	Flexible laryngoscopy during episode; speech therapy; psychology referral

Clinical Pearl: The “Rule of Twos” for Croup

Classic croup follows a predictable pattern that can help distinguish it from other causes:

2 days of prodromal upper respiratory symptoms before stridor onset
2 am is the typical time of worst symptoms (nocturnal worsening)
2 years is the peak age (6 months to 3 years range)
2 hours is how long symptoms typically improve after treatment with nebulized epinephrine
2 days of barking cough typically followed by gradual resolution over 5-7 days

Deviation from this pattern should raise suspicion for an alternative diagnosis or complication.

6. Diagnostic Investigations

A stepwise, clinically-guided approach to investigating stridor in children

Key Principle: In many cases of pediatric stridor, particularly typical croup, the diagnosis is clinical and no investigations are required. Investigations are guided by clinical suspicion and should not delay treatment of airway compromise. The priority is always to secure the airway first if the child is unstable.

When Are Investigations Needed?

Clinical Scenario	Investigations Needed?	Rationale
Typical mild-moderate croup	NO — clinical diagnosis	Classic presentation with barking cough, hoarse voice, low-grade fever; treat empirically
Severe or atypical croup	Consider chest radiograph	Rule out foreign body, bacterial tracheitis, or other pathology
Suspected foreign body	YES — chest radiograph; bronchoscopy	Most foreign bodies are radiolucent; bronchoscopy is diagnostic and therapeutic
Suspected epiglottitis	NO imaging before airway secured	Lateral neck radiograph may show “thumbprint sign” but should not delay airway management
Suspected retropharyngeal abscess	YES — lateral neck radiograph or CT	Widened prevertebral space; CT defines extent and guides drainage
Chronic stridor from infancy	YES — flexible laryngoscopy	Required to diagnose laryngomalacia and other congenital causes
Recurrent croup or treatment failure	YES — direct laryngoscopy/bronchoscopy	Assess for subglottic stenosis or other structural abnormality

Baseline Investigations

These investigations may be considered for children with moderate-severe stridor or atypical presentations:

Investigation	Purpose	What to Look For	Practical Points
Pulse Oximetry	Assess oxygenation; continuous monitoring in moderate-severe cases	Oxygen saturation less than 92% indicates significant hypoxemia	Hypoxemia is a late sign in upper airway obstruction; do not be falsely reassured by normal saturation in a child with severe retractions
Chest Radiograph (AP and lateral)	Exclude foreign body, assess subglottic narrowing, evaluate lung parenchyma	“Steeple sign” in croup; foreign body; hyperinflation; infiltrates	Not required for typical croup; obtain if diagnosis uncertain, foreign body suspected, or poor response to treatment
Lateral Neck Radiograph	Evaluate supraglottic and retropharyngeal space	“Thumbprint sign” (epiglottitis); widened prevertebral space (retropharyngeal abscess)	Should not delay airway management in suspected epiglottitis; must be taken during inspiration for accurate prevertebral measurement
Blood Gas (Capillary or Arterial)	Assess ventilation in severe cases	Hypercapnia (rising PaCO2) indicates respiratory failure	Do not agitate a child with severe obstruction for blood draws; clinical assessment takes priority
Complete Blood Count	Assess for bacterial infection	Leukocytosis with left shift suggests bacterial infection (bacterial tracheitis, epiglottitis, abscess)	Not required for viral croup; obtain if toxic appearance or suspected bacterial cause
Blood Culture	Identify causative organism in bacteremia	Positive in epiglottitis, bacterial tracheitis, deep space infections	Obtain before antibiotics in suspected bacterial infection if feasible

Radiographic Findings in Stridor

Chest and Airway Radiograph Findings

Steeple sign: Subglottic narrowing on AP view; classic for croup but not always present
Thumbprint sign: Swollen epiglottis on lateral view; classic for epiglottitis
Widened prevertebral space: Greater than 7 mm at C2 or greater than 14 mm at C6 suggests retropharyngeal abscess (must be taken in inspiration with neck extended)
Radiopaque foreign body: Directly visible (coins, button batteries)
Unilateral hyperinflation: Air trapping distal to bronchial foreign body (ball-valve effect)
Atelectasis: Complete bronchial obstruction by foreign body

Limitations of Plain Radiographs

False negatives: Most aspirated foreign bodies are radiolucent (food, plastic)
Steeple sign: Only present in approximately 50% of croup cases
Normal radiograph: Does not exclude significant pathology
Prevertebral space: Can appear falsely widened during expiration or flexion
Agitation: Imaging should not worsen respiratory distress; defer if child unstable

Targeted Investigations by Suspected Etiology

If Suspecting Croup (Viral Laryngotracheobronchitis)

First-Line (Usually Not Needed)

Clinical diagnosis: No investigations required for typical mild-moderate croup
Pulse oximetry: Monitor in moderate-severe cases

Second-Line (If Atypical or Severe)

AP neck radiograph: “Steeple sign” (subglottic narrowing)
Viral testing: Nasopharyngeal swab if epidemiological interest; does not change management
Direct laryngoscopy: If recurrent episodes to exclude structural cause

If Suspecting Epiglottitis

Critical: Do Not Delay Airway Management for Imaging

If epiglottitis is suspected, the priority is controlled airway management. Do not send the child for radiographs or attempt to visualize the pharynx. Prepare for intubation in the operating room with anesthesia and ENT support.

After Airway is Secured

Blood culture: Often positive; guides antibiotic therapy
Complete blood count: Leukocytosis with left shift typical
Epiglottic culture: Obtained during intubation if feasible

Imaging (If Diagnosis Uncertain and Child Stable)

Lateral neck radiograph: “Thumbprint sign” — swollen epiglottis; loss of vallecular air space
Must accompany child: Physician capable of emergency airway management must be present

If Suspecting Foreign Body Aspiration

First-Line Tests

Chest radiograph (inspiratory and expiratory): May show radiopaque foreign body, unilateral hyperinflation, or atelectasis; expiratory film accentuates air trapping
Lateral decubitus films: Alternative to expiratory films in young children; affected side fails to deflate when dependent

Definitive Investigation

Rigid bronchoscopy: Gold standard; both diagnostic and therapeutic; proceed if high clinical suspicion even with normal radiograph
Flexible bronchoscopy: May be used for diagnosis, but rigid bronchoscopy preferred for removal
CT chest: May be used if diagnosis uncertain; can detect radiolucent foreign bodies

If Suspecting Chronic Congenital Stridor

Suspected Condition	First-Line Investigation	Additional Investigations
Laryngomalacia	Flexible nasolaryngoscopy (awake); shows omega-shaped epiglottis, prolapsing arytenoids	pH/impedance study or trial of acid suppression (if reflux suspected); polysomnography (if apnea); swallow study (if aspiration)
Vocal Cord Paralysis	Flexible nasolaryngoscopy (awake); visualize vocal cord movement	MRI brain and neck (central cause); CT/MRI chest (mediastinal mass); echocardiogram (cardiac anomaly); video fluoroscopic swallow study
Subglottic Stenosis	Direct laryngoscopy and bronchoscopy under anesthesia; assess and grade stenosis	CT airway if complex anatomy suspected; MRI if associated vascular anomaly
Subglottic Hemangioma	Direct laryngoscopy and bronchoscopy; characteristic subglottic mass	MRI neck (if deep extension suspected); skin examination for cutaneous hemangiomas; PHACE workup if facial hemangioma present
Vascular Ring	CT angiography or MR angiography; defines vascular anatomy	Echocardiogram; barium swallow (posterior esophageal indentation); bronchoscopy (external tracheal compression)
Tracheomalacia	Flexible bronchoscopy (awake, spontaneous breathing); shows dynamic collapse greater than 50%	Dynamic CT airway (if available); echocardiogram (associated cardiac anomalies)
Complete Tracheal Rings	Bronchoscopy; shows fixed circumferential narrowing	CT angiography (associated pulmonary artery sling); echocardiogram

If Suspecting Deep Space Neck Infection

Retropharyngeal Abscess

Lateral neck radiograph: Widened prevertebral space (greater than 7 mm at C2 or greater than one vertebral body width at C6)
CT neck with contrast: Gold standard; defines abscess versus cellulitis; guides surgical drainage
Blood cultures and complete blood count: Before antibiotics

Peritonsillar Abscess

Clinical diagnosis: Asymmetric tonsillar enlargement, uvular deviation, trismus
CT neck with contrast: If diagnosis uncertain or to assess extent
Needle aspiration: Both diagnostic and therapeutic
Intraoral ultrasound: Emerging tool to confirm abscess

Endoscopic Evaluation

Endoscopy is the gold standard for diagnosing many causes of stridor and is essential for chronic or recurrent cases.

Type	Technique	Advantages	Indications
Flexible Nasolaryngoscopy	Awake; passed through nose; visualizes supraglottis, glottis, and dynamic movement	Assesses dynamic airway (laryngomalacia, vocal cord paralysis); no anesthesia required; can be done at bedside	First-line for chronic stridor; suspected laryngomalacia or vocal cord paralysis; paradoxical vocal fold motion
Direct Laryngoscopy	Under general anesthesia; provides direct view of larynx with magnification	Superior visualization; allows palpation and biopsy; can assess subglottis	Detailed assessment of laryngeal pathology; biopsy; therapeutic intervention
Rigid Bronchoscopy	Under general anesthesia; rigid scope through larynx into trachea and bronchi	Allows foreign body removal; provides airway during procedure; superior suctioning	Foreign body removal; subglottic evaluation; tracheal pathology; therapeutic procedures
Flexible Bronchoscopy	Can be awake or sedated; flexible scope through nose or via laryngeal mask	Assesses dynamic airway collapse (tracheomalacia); can reach distal airways	Tracheomalacia evaluation; distal airway assessment; when rigid bronchoscopy is not needed for intervention

Pediatric Considerations for Endoscopy

Flexible laryngoscopy: Can often be performed awake in infants with minimal distress; parental presence helpful
Anesthesia: Spontaneous ventilation preferred for dynamic airway assessment (tracheomalacia, laryngomalacia); paralysis may mask dynamic collapse
Airway size: Use age-appropriate equipment; smaller scopes for neonates and infants
Synchronous airway lesions: Up to 20% of children with one airway abnormality have a second lesion; complete airway evaluation recommended

Advanced Imaging

Imaging Modality	Indications	What It Shows	Pediatric Considerations
CT Neck with Contrast	Deep space infections (retropharyngeal abscess); neck masses; complex anatomy	Abscess versus cellulitis; extent of infection; airway narrowing; vascular involvement	Radiation exposure; may require sedation; rapid acquisition minimizes motion artifact
CT Angiography	Vascular ring; vascular sling; aortic arch anomalies	Detailed vascular anatomy; relationship to airway and esophagus	Contrast required; radiation exposure; excellent for surgical planning
MRI Neck and Chest	Soft tissue masses; hemangioma extent; mediastinal pathology; vascular anatomy	Superior soft tissue contrast; no radiation; vascular anatomy without contrast (MRA)	Usually requires sedation or general anesthesia in young children; longer acquisition time
Dynamic CT Airway	Tracheomalacia; dynamic airway collapse	Airway caliber during respiratory phases; identifies collapsing segments	Higher radiation than standard CT; requires respiratory gating or coaching
Barium Swallow/Esophagram	Vascular ring (posterior esophageal compression); tracheoesophageal fistula; aspiration	Esophageal indentation from vascular ring; fistula tract; aspiration during swallow	Minimal radiation; readily available; complementary to other imaging

Empiric Treatment as Diagnostic Tool

In some cases, response to empiric treatment helps confirm the diagnosis, particularly when the cause is uncertain.

Therapeutic Trials in Stridor

Nebulized epinephrine: Rapid improvement supports croup; lack of response suggests alternative diagnosis (bacterial tracheitis, foreign body, structural abnormality)
Corticosteroids: Sustained improvement over 24-48 hours supports inflammatory cause (croup, subglottic edema); may have modest effect on subglottic hemangioma
Heliox (helium-oxygen mixture): Reduces turbulent flow; temporizing measure; improvement supports significant upper airway narrowing
Propranolol trial: In suspected subglottic hemangioma, response to propranolol supports diagnosis (though usually confirmed endoscopically first)
Proton pump inhibitor trial: In laryngomalacia with suspected reflux, improvement with acid suppression supports gastroesophageal reflux disease as contributing factor

Investigation Algorithm Summary

Stepwise Approach to Investigating Stridor:

Assess stability: Is immediate airway intervention needed? If unstable, secure airway first.
Clinical diagnosis: Can the diagnosis be made clinically? (Typical croup usually needs no investigations)
Pulse oximetry: Continuous monitoring for moderate-severe stridor
Plain radiographs: If diagnosis uncertain, foreign body suspected, or atypical features
- Chest radiograph (AP and lateral) — foreign body, pneumonia, cardiomegaly
- Lateral neck radiograph — epiglottitis, retropharyngeal abscess
Laboratory tests: If bacterial infection suspected (complete blood count, blood culture)
CT imaging: For deep space infections, complex anatomy, vascular anomalies
Endoscopy: For chronic stridor, recurrent episodes, treatment failure, or when structural cause suspected

7. Clinical Decision-Making

Practical algorithms and decision pathways for pediatric stridor

Clinical decision-making in pediatric stridor requires rapid assessment of severity, identification of life-threatening causes, and initiation of appropriate treatment. This section provides practical algorithms to guide management from initial assessment through disposition.

Step 1: Is This an Airway Emergency?

The first priority is to identify children who require immediate airway intervention. Use the “30-second assessment” to triage urgency.

Clinical Scenario	Urgency Level	Immediate Action
Complete airway obstruction (no air movement, silent, cyanotic)	IMMEDIATE	Back blows/chest thrusts (infant) or Heimlich maneuver (child); prepare for emergency airway; call for help
Impending respiratory failure (decreasing stridor, exhaustion, altered consciousness)	EMERGENT	Bag-mask ventilation; prepare for intubation; call anesthesia/ENT; 100% oxygen
Suspected epiglottitis (toxic, drooling, tripod position, high fever)	EMERGENT	Do NOT examine pharynx; keep child calm with parent; call anesthesia/ENT for controlled airway in operating room
Anaphylaxis with stridor	EMERGENT	Intramuscular epinephrine (0.01 mg/kg, max 0.5 mg); prepare for airway intervention; IV access; fluids
Severe stridor at rest with cyanosis or oxygen saturation less than 92%	URGENT	Nebulized epinephrine; corticosteroids; continuous monitoring; prepare for escalation
Moderate stridor at rest with retractions	URGENT	Corticosteroids; consider nebulized epinephrine; observation; reassess frequently
Mild stridor only with agitation, otherwise well	ROUTINE	Corticosteroids; comfort measures; observation; discharge if improving
Chronic stridor, well-appearing, normal growth	ELECTIVE	Outpatient referral to ENT; flexible laryngoscopy; reassurance if likely laryngomalacia

The “Hands-Off” Approach for Suspected Epiglottitis

If epiglottitis is suspected, take a “hands-off” approach:

Do NOT examine the pharynx or attempt to visualize the epiglottis
Do NOT lay the child flat or attempt IV access if it causes distress
Do NOT send for radiographs if it delays definitive airway management
DO allow the child to remain in their position of comfort (usually sitting forward)
DO keep the parent present to minimize distress
DO call for anesthesia, ENT, and prepare the operating room for controlled intubation
DO have emergency airway equipment immediately available

Step 2: Classify by Acuity and Duration

Acute Stridor (Hours to Days)

Proceed to Algorithm A

Most common: Croup

Must exclude: Epiglottitis, foreign body, bacterial tracheitis

Recurrent Stridor

Proceed to Algorithm B

Consider: Recurrent croup, underlying structural abnormality

Requires: Endoscopic evaluation if more than 3 episodes

Chronic Stridor (Weeks to Months)

Proceed to Algorithm C

Most common: Laryngomalacia

Requires: ENT referral and flexible laryngoscopy

Algorithm A: Acute Stridor Management

Clinical Scenario	Most Likely Diagnosis	Immediate Action	Disposition
Barking cough, hoarse voice, low-grade fever, preceding upper respiratory infection, age 6 months to 3 years, mild stridor only when agitated	Mild Croup	Single dose dexamethasone (0.6 mg/kg PO/IM, max 10 mg); comfort measures	Home with safety-net advice; return if stridor at rest or worsening
As above but stridor at rest, moderate retractions, normal oxygen saturation	Moderate Croup	Dexamethasone; nebulized epinephrine (0.5 mL/kg of 1:1000, max 5 mL); observation for 2-4 hours post-epinephrine	Observe in emergency department; discharge if no stridor at rest after epinephrine wears off (2-4 hours)
Severe stridor at rest, marked retractions, decreased air entry, oxygen saturation less than 92%	Severe Croup	Dexamethasone; nebulized epinephrine (may repeat); high-flow oxygen; continuous monitoring	Admit to monitored bed or ICU; may need repeated epinephrine; prepare for possible intubation
Toxic appearance, high fever (greater than 39°C), drooling, muffled voice, tripod position, NO barking cough	Epiglottitis	Hands-off approach; call anesthesia/ENT; controlled intubation in operating room; IV antibiotics after airway secured	ICU admission; IV antibiotics (ceftriaxone); typically extubate in 24-48 hours when air leak present
Sudden onset during eating/playing, witnessed or possible choking, age 1-3 years	Foreign Body Aspiration	If complete obstruction: back blows/chest thrusts. If partial obstruction and stable: chest radiograph, then rigid bronchoscopy	ENT/pulmonology for bronchoscopy; admission if foreign body removed or suspected but not visualized
Initially croup-like then worsening with high fever, thick secretions, not responding to epinephrine	Bacterial Tracheitis	IV antibiotics (ceftriaxone + clindamycin or vancomycin); may need intubation; consider bronchoscopy for secretion clearance	ICU admission; airway management; prolonged IV antibiotics
Fever, neck stiffness, refuses to extend neck, drooling, recent pharyngitis	Retropharyngeal Abscess	CT neck with contrast; IV antibiotics (ampicillin-sulbactam or clindamycin); ENT for possible drainage	Admission; surgical drainage if large abscess or no improvement; IV antibiotics
Rapid onset after allergen exposure, urticaria, angioedema, may have wheeze and hypotension	Anaphylaxis	Intramuscular epinephrine (0.01 mg/kg, max 0.5 mg); repeat every 5-15 minutes if needed; IV fluids; corticosteroids; antihistamines	Observation minimum 4-6 hours (longer if biphasic reaction risk); discharge with epinephrine autoinjector and allergy follow-up

Algorithm B: Recurrent Stridor Management

Key Questions for Recurrent Stridor:

How many episodes? (More than 3 episodes warrants endoscopic evaluation)
Is each episode typical for croup? (Atypical features suggest structural cause)
Is there complete resolution between episodes? (Persistent symptoms suggest fixed obstruction)
Is there a history of intubation? (Risk of subglottic stenosis)
Is there a family history of recurrent croup? (Familial predisposition; also consider atopy)

Clinical Scenario	Likely Diagnosis	Action
2-3 typical croup episodes, complete resolution between, responds to standard treatment	Recurrent viral croup or spasmodic croup	Treat each episode as croup; consider atopy workup; endoscopy not yet required
More than 3 croup-like episodes	Possible underlying structural abnormality	ENT referral for direct laryngoscopy and bronchoscopy to rule out subglottic stenosis, hemangioma, or other lesion
Recurrent croup with history of neonatal intubation	Acquired subglottic stenosis	ENT referral for endoscopy; Cotton-Myer grading if stenosis confirmed; may need surgical intervention
Recurrent episodes, atypical features (biphasic stridor, poor response to treatment)	Structural abnormality (subglottic stenosis, hemangioma, web)	Expedited ENT referral; direct laryngoscopy and bronchoscopy
Recurrent nocturnal episodes with rapid onset and resolution, no prodrome, often atopic child	Spasmodic croup	Treat episodes as croup; consider reflux workup; lower threshold for endoscopy if frequent

Algorithm C: Chronic Stridor Management

Clinical Scenario	Likely Diagnosis	Action	Urgency
Onset 2-4 weeks; inspiratory stridor; worse with feeding, crying, supine; improves prone; normal growth	Mild laryngomalacia	Reassurance; feeding modifications; anti-reflux measures; flexible laryngoscopy to confirm; follow growth	Routine ENT referral; expect improvement by 12-18 months
As above but poor weight gain, cyanotic episodes, apnea, or severe feeding difficulties	Severe laryngomalacia	Urgent ENT referral; flexible laryngoscopy; consider polysomnography; may need supraglottoplasty	Urgent—surgical intervention may be required
Stridor from birth; weak or absent cry; feeding difficulties with aspiration	Vocal cord paralysis	Flexible laryngoscopy to confirm; investigate cause (MRI brain/neck, cardiac echo); swallow study; may need tracheostomy if bilateral	Urgent if bilateral with severe stridor
Biphasic stridor; onset 4-6 weeks; progressive; cutaneous hemangiomas present	Subglottic hemangioma	Direct laryngoscopy to confirm; start propranolol (2-3 mg/kg/day); monitor closely during proliferative phase	Urgent—proliferates rapidly in first year
Biphasic stridor; feeding difficulties; dysphagia; reflex apnea from infancy	Vascular ring	CT or MR angiography; echocardiogram; bronchoscopy; surgical division	Semi-urgent—surgical repair needed
Biphasic stridor; history of prolonged intubation; recurrent “croup” episodes	Acquired subglottic stenosis	Direct laryngoscopy and bronchoscopy; grade stenosis (Cotton-Myer); may need dilation or laryngotracheal reconstruction	Semi-urgent—depends on severity
Progressive hoarseness then stridor; age 2-4 years; history of maternal genital warts	Recurrent respiratory papillomatosis	Direct laryngoscopy; surgical debulking (often multiple procedures); adjuvant therapy in severe cases	Semi-urgent—can progress to airway obstruction

“What Do I Do If…” Decision Reference

Clinical Situation	Immediate Action	Next Step
Child with croup not improving after dexamethasone and nebulized epinephrine?	Repeat nebulized epinephrine; reassess; consider alternative diagnosis	Think bacterial tracheitis, foreign body, or structural cause; consider chest radiograph, lateral neck radiograph; prepare for possible intubation
Child with croup improves after epinephrine then worsens again?	Repeat epinephrine; continue monitoring	Expected—epinephrine effect lasts 1-2 hours; this is why 2-4 hour observation is required post-epinephrine; admit if requires more than 2 doses
Parents want to take mild croup child home but I’m worried?	Ensure dexamethasone given; provide clear safety-net instructions	Return immediately if: stridor at rest, increased work of breathing, unable to drink, drooling, or any concern. Consider observation if gut feeling is wrong
Suspected foreign body but chest radiograph is normal?	Normal radiograph does NOT exclude foreign body (most are radiolucent)	If high clinical suspicion (witnessed choking, sudden onset), proceed to rigid bronchoscopy; do not delay based on imaging
Cannot determine if stridor is from croup or epiglottitis?	Treat as potential epiglottitis if any doubt (toxic, drooling, muffled voice, no cough)	Do NOT examine pharynx; involve anesthesia/ENT; lateral neck radiograph only if stable and does not delay airway management
Infant with chronic stridor—parents asking if it’s serious?	Assess for red flags: failure to thrive, cyanotic episodes, apnea, severe feeding difficulties	If no red flags and likely laryngomalacia: reassure, routine ENT referral; if red flags present: urgent referral for flexible laryngoscopy
Stridor in a child with known subglottic stenosis who presents with “croup”?	Treat as croup with dexamethasone and epinephrine; lower threshold for admission	These children are at higher risk for severe symptoms; may need more aggressive treatment and longer observation; involve ENT if not improving
Child with stridor and suspected anaphylaxis—epinephrine not working?	Repeat epinephrine every 5-15 minutes; IV fluids for hypotension	Consider epinephrine infusion; prepare for intubation (may be difficult due to edema); involve anesthesia; consider surgical airway

Croup Medication Dosing Quick Reference

Medication	Dose	Route	Notes
Dexamethasone	0.6 mg/kg (max 10 mg)	PO preferred; IM if vomiting	Single dose; onset 2-3 hours; duration 24-48 hours; first-line for all severities
Prednisolone	1-2 mg/kg (max 60 mg)	PO	Alternative if dexamethasone unavailable; may need 2-3 day course
Nebulized Epinephrine	0.5 mL/kg of 1:1000 (max 5 mL)	Nebulized	Onset 10-30 minutes; duration 1-2 hours; observe 2-4 hours post-dose; may repeat
Racemic Epinephrine	0.05 mL/kg of 2.25% (max 0.5 mL) diluted to 3 mL	Nebulized	Equivalent efficacy to L-epinephrine; less commonly available

Disposition Decision Framework

Safe Discharge Criteria for Croup

No stridor at rest after treatment and observation
Normal oxygen saturation on room air
Good oral intake; able to drink fluids
No or minimal retractions
Alert and interactive
At least 2-4 hours post-nebulized epinephrine (if given)
Corticosteroid administered
Reliable caregivers who understand safety-net instructions
Ability to return promptly if worsening

Admission Criteria

Persistent stridor at rest after treatment
Oxygen requirement
More than 2 doses of nebulized epinephrine required
Poor oral intake or signs of dehydration
Toxic appearance or suspected bacterial infection
Uncertain diagnosis requiring observation
Social concerns or inability to return if worsening
Known airway abnormality (such as subglottic stenosis)
Very young infant (less than 6 months) with moderate-severe symptoms

When to Involve Subspecialists

Subspecialist	When to Involve	How Urgently
Anesthesiology	Suspected epiglottitis; impending respiratory failure; anticipated difficult airway	Immediate
ENT (Otolaryngology)	Suspected epiglottitis; deep space neck infection; chronic stridor requiring endoscopy; airway foreign body	Immediate for emergencies; urgent for infections; routine for chronic stridor
Pediatric Surgery/Thoracic Surgery	Vascular ring; mediastinal mass; complex airway reconstruction	Semi-urgent to elective depending on severity
Pulmonology	Complex airway disease; tracheomalacia; bronchoscopy for foreign body	Urgent for foreign body; routine for chronic conditions
PICU (Pediatric Intensive Care)	Severe stridor requiring repeated interventions; post-intubation; impending respiratory failure	Immediate
Allergy/Immunology	Anaphylaxis requiring follow-up; recurrent angioedema; suspected hereditary angioedema	Outpatient follow-up post-acute episode

8. Clinical Pearls and Pitfalls

Practical wisdom — learn from successes and avoid common mistakes

Must-Know Clinical Pearls

Stridor phase localizes the lesion: Inspiratory stridor indicates extrathoracic (supraglottic/glottic) obstruction; expiratory stridor suggests intrathoracic obstruction; biphasic stridor indicates a fixed lesion at the glottic or subglottic level.

The pediatric airway is vulnerable: Due to Poiseuille’s law, 1 mm of circumferential edema in a 4 mm infant airway reduces cross-sectional area by 75% and increases resistance 16-fold. This explains why children deteriorate rapidly.

Croup is a clinical diagnosis: In a child aged 6 months to 3 years with barking cough, hoarse voice, and inspiratory stridor following viral upper respiratory symptoms, croup is diagnosed clinically. No investigations are needed for typical mild-moderate cases.

All children with croup get corticosteroids: A single dose of dexamethasone (0.6 mg/kg) benefits all severities of croup—mild, moderate, and severe. It reduces return visits, intubation rates, and length of stay.

Observe after nebulized epinephrine: The effect of nebulized epinephrine wears off in 1-2 hours. Children must be observed for at least 2-4 hours after administration to ensure they do not deteriorate when the effect wanes.

The “4 Ds” identify epiglottitis: Drooling, Dysphagia, Dysphonia (muffled voice), and Distress. Notably absent is the barking cough of croup. If these features are present, do NOT examine the pharynx—prepare for controlled airway management.

Laryngomalacia is the most common cause of chronic infant stridor: It accounts for 60-70% of chronic stridor in infants. Classic features are inspiratory stridor starting at 2-4 weeks, worsening with feeding and supine position, and improving when prone or calm.

Ask about cutaneous hemangiomas: In an infant with progressive stridor starting at 4-6 weeks, look for cutaneous hemangiomas, especially in the “beard distribution” (chin, lower lip, anterior neck). This finding is present in 50% of cases of subglottic hemangioma.

Recurrent croup warrants endoscopy: If a child has more than 3 episodes of croup-like illness, consider direct laryngoscopy and bronchoscopy to rule out an underlying structural abnormality such as subglottic stenosis or hemangioma.

Normal chest radiograph does NOT exclude foreign body: Most aspirated foreign bodies (food, plastic) are radiolucent. If clinical suspicion is high (witnessed choking, sudden onset), proceed to rigid bronchoscopy regardless of radiograph findings.

Critical Pitfalls to Avoid

Being reassured by “quiet” stridor in a deteriorating child: Decreasing stridor in a child who is becoming exhausted, lethargic, or cyanotic is an OMINOUS sign indicating near-complete obstruction. This child needs immediate airway intervention, not reassurance.

Examining the pharynx in suspected epiglottitis: Attempting to visualize the pharynx or using a tongue depressor in a child with suspected epiglottitis can precipitate complete airway obstruction. Keep the child calm and prepare for controlled airway management.

Discharging a child immediately after nebulized epinephrine: The effect of epinephrine lasts only 1-2 hours. Discharging a child before observing for rebound can result in return with severe symptoms. Always observe for 2-4 hours post-epinephrine.

Excluding foreign body based on negative radiograph: Most aspirated foreign bodies are radiolucent. A normal chest radiograph in a child with a convincing history of choking should not delay bronchoscopy. Clinical suspicion trumps imaging.

Attributing recurrent croup episodes to “just another infection”: Multiple episodes of croup, especially with atypical features or poor treatment response, may indicate an underlying structural abnormality. These children need endoscopic evaluation.

Forgetting intubation history in children with croup: A child with a history of neonatal intubation presenting with croup-like symptoms may have acquired subglottic stenosis. These children are at higher risk and have a lower threshold for investigation.

Delaying treatment to obtain investigations: In acute stridor, treatment should not be delayed for radiographs or other investigations. Administer corticosteroids and nebulized epinephrine based on clinical assessment; investigations can wait until the child is stabilized.

Assuming chronic stridor is always benign: While laryngomalacia is common and usually benign, failure to thrive, cyanotic episodes, apnea, or severe feeding difficulties are red flags indicating severe disease requiring urgent evaluation and possible intervention.

Misdiagnosing bacterial tracheitis as croup: Bacterial tracheitis often follows viral croup but presents with toxic appearance, high fever, and thick purulent secretions. It does not respond to nebulized epinephrine and requires IV antibiotics and airway management.

Forgetting to assess immunization status: An unvaccinated child with stridor, high fever, drooling, and toxic appearance should raise high suspicion for epiglottitis. Haemophilus influenzae type b vaccination has dramatically reduced but not eliminated this disease.

Key Takeaways

Stridor is a symptom of upper airway obstruction, not a diagnosis—always determine the underlying cause.
The timing of stridor (inspiratory, expiratory, biphasic) localizes the anatomical level of obstruction.
Decreasing stridor in a worsening child is a critical warning sign of impending respiratory failure.
Croup is the most common cause of acute stridor in children aged 6 months to 3 years; it is a clinical diagnosis.
All children with croup should receive corticosteroids (dexamethasone 0.6 mg/kg) regardless of severity.
Children receiving nebulized epinephrine must be observed for at least 2-4 hours due to rebound effect.
Suspected epiglottitis requires a “hands-off” approach—do not examine the pharynx; prepare for controlled airway management.
Laryngomalacia is the most common cause of chronic stridor in infants; most cases are mild and self-limiting by 12-18 months.
Red flags in chronic stridor (failure to thrive, cyanotic episodes, apnea) indicate severe disease requiring urgent intervention.
A normal chest radiograph does not exclude foreign body aspiration—proceed to bronchoscopy if clinical suspicion is high.
Recurrent croup (more than 3 episodes) warrants endoscopic evaluation to exclude structural abnormality.
Age is a key discriminator: croup peaks at 6 months to 3 years; foreign body at 1-3 years; laryngomalacia presents at 2-4 weeks; subglottic hemangioma at 4-6 weeks.

Quick Reference Algorithm

Systematic Approach to Pediatric Stridor:

Assess airway stability: Is this an emergency? Look for signs of impending respiratory failure (decreasing stridor, exhaustion, altered consciousness, cyanosis).
Determine acuity: Is this acute (hours-days), recurrent, or chronic (weeks-months)?
Characterize the stridor: Inspiratory (extrathoracic), expiratory (intrathoracic), or biphasic (fixed obstruction)?
Consider the age: Croup in toddlers; laryngomalacia in infants; foreign body in 1-3 year olds; congenital causes in neonates.
Look for red flags: Toxic appearance, drooling, tripod position, sudden onset with choking, failure to thrive, cyanotic episodes.
Treat empirically if appropriate: Corticosteroids for all croup; nebulized epinephrine for moderate-severe; IM epinephrine for anaphylaxis.
Investigate if needed: Chest radiograph for atypical or severe cases; lateral neck radiograph for suspected epiglottitis or abscess (only if stable); endoscopy for chronic or recurrent stridor.
Involve subspecialists early: Anesthesia and ENT for suspected epiglottitis or impending respiratory failure; ENT for chronic stridor requiring endoscopy.
Determine disposition: Safe discharge requires no stridor at rest, normal oxygen saturation, adequate oral intake, reliable caregivers, and completion of post-epinephrine observation period.
Provide safety-net advice: Clear instructions to return immediately if stridor at rest, increased work of breathing, inability to drink, drooling, or any parental concern.

Emergency Contact Numbers Template

Safety-Net Advice for Parents

Provide written discharge instructions including:

Expected course: Symptoms typically worst on nights 2-3, then gradually improve over 5-7 days
Comfort measures: Cool mist, calm environment, adequate fluids, upright positioning
Return immediately if: Stridor at rest when calm; difficulty breathing worsening; unable to drink; drooling or unable to swallow; blue lips or fingertips; very sleepy or difficult to wake; any parental concern
Contact numbers: Emergency department, primary care physician, nurse helpline