Stridor

Last updated: July 11, 2024

Summary

Stridor is a harsh, high-pitched vibratory breath sound produced by upper airway obstruction during inspiration and/or expiration. It is a red flag for both respiratory failure and a difficult intubation. Patients with stridor should be assessed immediately for clinical features of airway obstruction and signs of impending respiratory failure. Immediate airway management is required in patients with signs of respiratory distress. Further evaluation and diagnostic testing are done only after intubation or the exclusion of a life-threatening airway obstruction. Stridor may be caused by infection, inflammation, or structural changes in the airway. Diagnosis is clinical, but studies (e.g., airway endoscopy and neck x-rays) may be obtained to determine the etiology. Definitive treatment is based on the underlying cause.

Initial management

Stridor is a risk factor for a difficult airway.

Perform an ABCDE survey and allow the patient to assume a position of comfort.
Assess for signs of airway obstruction and impending respiratory failure.
- If present:
  - Prepare for a difficult airway.
  - Begin basic airway management.
  - Consult anesthesia and/or otolaryngology urgently.
  - Manage the difficult airway.
- If absent: Reassess the airway frequently.
Perform a focused clinical evaluation for stridor.
Obtain etiology-specific diagnostics and initiate treatment.

Avoid unnecessary procedures that may increase agitation and worsen turbulent airflow (especially in children). ^[1]

Consider transporting the patient to the operating room for intubation if the patient is stable.

Etiology

Use age to help narrow the differential diagnosis. Laryngomalacia and vocal fold immobility (e.g., vocal cord paralysis) are common in infants; foreign body aspiration and croup in young children. ^[3]

Infectious ^[1]

Allergic or inflammatory ^[1]

Structural ^[1]

Acute

Foreign body aspiration
Edema, e.g., postextubation laryngeal edema
Trauma
Laryngospasm

Chronic

Airway malacias, e.g., tracheomalacia, laryngomalacia
Laryngotracheal stenosis, e.g., after prolonged intubation or radiation therapy
Laryngeal papillomatosis
Vascular ring
Tumor, e.g., subglottic hemangioma, goiter, neoplasm
Vocal cord paralysis

Clinical evaluation

A focused history and physical examination can narrow the differential diagnosis and facilitate the choice of diagnostic testing. ^[1]^[4]

Focused history

Onset: acute or chronic
Prior events
- Choking episode
- URI or febrile illness
- Sore throat or dysphagia
- Recent trauma, intubation, and/or surgical procedure
Exacerbating factors
- Worse at night
- Worse with eating
- Worse in the supine position
- Worse with crying or strenuous activity
Associated symptoms
- Drooling
- Barking cough
- Muffled voice or cry
- Weak voice or cry

Focused physical examination

Clinical features of airway obstruction
Clinical features of respiratory failure
Type of stridor ^[4]
- Inspiratory stridor suggests obstruction above or near the glottis.
- Expiratory stridor suggests intrathoracic tracheal obstruction.
- Inspiratory and expiratory (biphasic) stridor suggests a fixed obstruction, typically glottic or subglottic.
Lung auscultation
Head and neck examination

Do not assume decreasing stridor is a reassuring sign. Respiratory failure due to decreased airflow may be imminent. ^[5]

Stridor - Lung Auscultation - Episode 6 LC Barking cough, inspiratory stridor und chest retractions in viral croup | External video

Diagnosis

Stridor is a clinical finding; the suspected etiology and the patient's clinical status guide the selection of diagnostic testing. ^[4]^[5]

Airway endoscopy

Direct visualization of the airway can provide a definitive diagnosis. Endoscopy may also be used for definitive management, e.g., removal of a foreign body or excision of an airway mass.

Fiberoptic laryngoscopy
Video laryngoscopy
Rigid bronchoscopy
Flexible bronchoscopy

Imaging ^[1]^[4]

Imaging may be helpful to assess for anatomical abnormalities, foreign bodies, or infection (e.g., abscesses).

X-ray neck and chest (lateral and AP views)
- Steeple sign (AP view of neck and chest) suggests croup.
- Thumbprint sign (enlarged epiglottis looks like a thumb on a lateral neck x-ray) suggests epiglottitis.
- Nonspecific subglottic narrowing or irregularities of the anterior trachea on neck x-ray may occur with bacterial tracheitis.
- Radiolucent foreign bodies may be seen in any view.
- Asymmetrical lung inflation suggests a foreign body in a bronchus.
CT or MRI neck and/or chest
- May confirm X-ray findings or guide surgical management.
- May demonstrate airway mass or inflammation

Ensure the airway is protected or an airway specialist is immediately available when obtaining imaging. Sedation and/or supine position may cause complete airway obstruction. ^[1]

Epiglottitis (supraglottitis) Steeple sign Thumb and vallecula signs (epiglottitis) Thumb and vallecula signs in acute infectious epiglottitis Foreign body aspiration Foreign body (button battery) ingestion Parapharyngeal inflammation with abscess

Laboratory studies ^[1]^[6]

Routine testing is not recommended for stridor, but studies may confirm the etiology and guide management.

Respiratory viral panel: may identify a causative virus
CBC: may help distinguish between bacterial and viral infections
Blood gas analysis: may show hypoxemia and/or hypercarbia

Infectious causes

Infectious causes of stridor ^[5]
Etiology	Cause	Characteristic clinical features	Diagnostics	Management
Croup ^[6]	Viral: primarily parainfluenza viruses	Onset: 12–48 hours Appearance: well-appearing Cough: barking Voice: hoarse Difficulty swallowing/drooling: absent	Clinical diagnosis X-ray neck: steeple sign	Systemic dexamethasone Consider nebulized epinephrine. See “Acute management checklist for croup.”
Epiglottitis ^[7]	Bacterial H. influenza type B or nontypeable S. pyogenes S. pneumoniae S. aureus	Onset: 4–12 hours Appearance Ill-appearing, febrile, lethargic Tripod position, sniffing position Signs of poor tissue perfusion Cough: absent Voice: muffled Difficulty swallowing/drooling: present	Clinical diagnosis X-ray neck: thumbprint sign Flexible laryngoscopy	Monitor for airway obstruction. Prepare for difficult intubation. Administer IV antibiotics. See “Acute management checklist for epiglottitis.”
Diphtheria ^[1]^[8]	Bacterial: C. diphtheriae	Onset: 4–5 days Appearance Ill-appearing Cervical lymphadenopathy Pseudomembrane on posterior pharynx Cough: barking Voice: hoarse Difficulty swallowing/drooling: present	X-ray neck: subglottic narrowing Nasal and pharyngeal cultures	Monitor for airway obstruction. Administer diphtheria antitoxin immediately. Initiate antibiotic therapy. See ”Management of diphtheria.”
Bacterial tracheitis ^[1]^[9]	Bacterial S. aureus (most common) H. influenzae S. pneumoniae S. pyogenes M. catarrhalis	Onset: 2–10 hours Prodrome: URI symptoms Appearance: ill-appearing, febrile Cough: productive Voice: hoarse Difficulty swallowing/drooling: absent	Clinical diagnosis Bronchoscopy or flexible laryngoscopy X-ray neck: subglottic narrowing and/or tracheal wall irregularities	Monitor for airway obstruction. Prepare for difficult intubation. Initiate empiric antibiotic therapy. See “Acute management checklist for bacterial tracheitis.”
Retropharyngeal abscess ^[7]	Bacterial (often polymicrobial) Streptococcus ssp. Staphylococcus ssp. Anaerobes	Appearance Ill-appearing, febrile Unilateral neck swelling Cervical lymphadenopathy Cough: absent Voice: muffled Difficulty swallowing/drooling: present	CT neck with contrast (first-line) X-ray neck: widened prevertebral space Laryngoscopy Wound/abscess culture	See “Emergency airway management of deep neck infections.” See “Acute management checklist for deep neck infections.”

Allergic or inflammatory causes

Allergic or inflammatory causes of stridor ^[5]
Etiology	Characteristic clinical features	Diagnostics	Management
Spasmodic croup ^[10]	Barking cough Hoarse voice Nightly symptoms that resolve during the day	Clinical diagnosis X-ray neck: steeple sign	Systemic dexamethasone Consider nebulized epinephrine. See “Acute management checklist for croup.”
Angioedema ^[11]	Swelling of the face, tongue, oral mucosa, extremities, or genitalia Urticaria	Clinical diagnosis	Prepare for difficult intubation. Identify and treat underlying cause Histamine-mediated angioedema treatment Bradykinin-mediated angioedema treatment See “Acute management checklist for angioedema.”
Anaphylaxis ^[12]	Exposure to a known allergen Chest or throat tightness Shortness of breath, cough, wheezing Hypotension Abdominal pain, nausea, vomiting	Clinical diagnosis	Remove inciting allergen. Administer IM epinephrine. Monitor the airway. See “Acute management checklist for anaphylaxis.”
Inhalation injury ^[13]^[14]	Exposure to smoke, irritants, and/or asphyxiants Cough, wheezing Chest pain Lacrimation, rhinorrhea Burning sensation in the eyes, nose, and throat	ABG CO-oximetry X-ray chest Flexible laryngoscopy and/or bronchoscopy	Consider early intubation. Use lung protective ventilation strategy. See “Inhalation injury.” See “Approach to asphyxiant and irritant exposure.”

Structural causes

Structural causes of stridor ^[5]
Etiology	Characteristic clinical features	Diagnostics	Management
Foreign body aspiration ^[1]^[15]	Witnessed or suspected aspiration Choking and/or cough Hemoptysis Chest pain Signs of pneumonia	X-ray chest and neck CT chest Laryngoscopy and/or bronchoscopy	Initiate maneuvers to dislodge the aspirated FB. Consider laryngoscopy-guided FB retrieval. See “Acute management checklist for foreign body aspiration.”
Postextubation laryngeal edema ^[16]^[17]	Manifests immediately after extubation Signs of acute respiratory distress	Clinical diagnosis	Signs of severe respiratory distress: Reintubate immediately. Respiratory status stable: Consider nebulized epinephrine and systemic corticosteroids.
Airway malacias ^[18]	Worse in the supine position Worse with agitation and/or crying Worse with increased respiratory effort Failure to thrive, feeding difficulty, dyspnea	Bronchoscopy or flexible laryngoscopy	See “Laryngomalacia” and “Tracheomalacia.”
Laryngotracheal stenosis ^[19]^[20]	History of prolonged tracheal intubation Wheezing, respiratory distress Dysphonia Chronic cough	Flexible laryngoscopy and/or bronchoscopy CT head and neck	Acute management: endotracheal intubation or tracheostomy Definitive management: surgical or endoscopic dilation and/or resection
Vocal cord paralysis ^[21]^[22]	Preceding iatrogenic injury, e.g., thyroid surgery ^[21] Inspiratory stridor ^[1] Change in voice quality, e.g., hoarseness ^[1]	Flexible laryngoscopy (awake)	Acute management: Monitor for signs of airway compromise Intubation may be required. Consult otolaryngology Chronic management: tracheotomy and/or laryngeal surgery See also “Vagus nerve palsy.”

Mimics

Stertor: low-pitched inspiratory noise caused by nasal or nasopharyngeal obstruction (similar to snoring) ^[5]^[23]
- Laryngomalacia
- Nasal foreign body
- Nasal congestion
- Adenoid hypertrophy
- Nasal turbinate hypertrophy
- Nasolacrimal duct cyst
- Obstructive sleep apnea
Wheezing: a prolonged musical high-pitched sound heard most commonly during expiration
- Asthma exacerbation
- COPD exacerbation
- Anaphylaxis
- Pneumonia
- Bronchiolitis
- Foreign body aspiration
- Congestive heart failure
- See also “Wheezing in children.”

Obstructive sleep apnea Sibilant Wheezing - Lung Auscultation - Episode 4 LC

Acute management checklist for stridor

Follow the ABCDE approach
Assess for signs of airway obstruction and impending respiratory failure, if present:
- Prepare for a difficult airway.
- Begin basic airway management
- Consult anesthesia and/or otolaryngology urgently.
- Consider transport to the operating room for airway management.
- Manage the difficult airway.
Perform a focused clinical evaluation for stridor.
Obtain etiology-specific diagnostics and initiate treatment.
Admit the patient for concerns of progressive airway obstruction or continued respiratory distress.

Disposition

Patient disposition varies based on the severity of symptoms and the etiology of the stridor. Consider admission for patients with: ^[1]^[5]

Ongoing respiratory distress
Concern for progressive airway obstruction
Presence of admission criteria for croup
Bacterial tracheitis
Epiglottitis
Foreign body aspiration

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