Overview
Stridor is a high pitched monophonic sound produced by irregular flow of air through a narrowed passage. It points to significant airway obstruction. It can generally be classified as inspiratory, expiratory or biphasic depending on the phase of respiration it occurs.
Types of stridor
| Classification | Occurrence |
|---|---|
| Inspiratory stridor | Extra-thoracic obstruction |
| Expiratory stridor | Intra-thoracic obstruction |
| Biphasic stridor | Lesions affecting the glottis (vocal cord paralysis), sub-glottis (sub-glottic stenosis), cervical trachea |
Description of Upper Airway sounds by site of Obstruction
| Site | Sounds |
|---|---|
| Nasopharyngeal | Stertor (snoring), no cough |
| Oropharynx | Gurgly |
| Supraglottic | Inspiratory stridor, throaty voice, feeding problems |
| Glottic | Inspiratory or biphasic stridor, hoarseness |
| Subglottic | Husky voice, biphasic stridor, wheezing, suprasternal |
| Tracheobronchial | Expiratory stridor, wheezing, suprasternal retractions indicate obstruction above the thoracic inlet |
To make understanding easier we list causes according to anatomical involvement:
Causes of stridor according to anatomical location
| Congenital | Infectious and idiopathic | Toxin and Trauma | Tumor | Endocrine | Neurologic | Systemic | |
|---|---|---|---|---|---|---|---|
| Above the larynx | Micrognathia, macroglossia, choanal atresia, lingual thyroid, nasoseptal deformity | Retropharyngeal abscess, peritonsillar abscess, mononucleosis, diphtheria | Facial fracture, retropharyngeal hematoma | Juvenile nasopharyngeal angiofibroma, neurogenic nasal tumors | Myxedema | Posteriorly displaced tongue, central sleep apnoea | Allergic rhintis, Granulomatosis with polyangiitis (Wegener’s), obesity (obstructive sleep apnoea) |
| Supraglottic | Laryngomalacia | Epiglottitis | Intubation trauma | Squamous cell carcinoma | Sarcoidosis | ||
| Glottic | Glottic web, laryngeal atresia, vocal fold immobility | TB laryngitis, laryngeal diphtheria | Laryngeal fracture, foreign body | Respiratory papillomatosis, squamous cell carcinoma | Vocal fold paralysis | Hereditary angioedema | |
| Subglottic | Vascular ring, aortic arch anomaly, tracheoesophageal fistula, subglottic stenosis | Laryngotracheobronchitis (croup) | Subglottic stenosis, thyroid or neck masses (extrinsic compression) | Subglottic hemangioma | Respiratory muscle paralysis (Guillain-Barre Syndrome) | Granulomatosis with polyangitis (Wegener’s) | |
| Tracheo-bronchial | Tracheomalacia, vascular rings | Tracheitis, bronchitis | Foreign body | Mediastinal, tracheal, or bronchial tumor | External compression (goiter), asthma |
Inhalational burns can cause swelling of all tissues in the airway
History
First we need to determine whether it is congenital or acquired stridor. This information is best gotten from the age group:
| Age | Cause of stridor |
|---|---|
| Neonate | Most like a congenital cause such as laryngomalacia |
| Infants and toddlers | Infectious causes and foreign body inhalation is common |
| School-going children and adolescents | Infectious causes and vocal cord pathologies |
- Character of upper airway sound
- Determine respiratory phase of stridor vs stertor
- Onset and duration
- Constant vs intermittent
- Contributing factors
- Infection or inflammation: Recent URTI, fever, cough, sore throat, allergy
- Trauma: recent trauma, previous tracheotomy, intubations or airway manipulations, surgery
- Medications: medicine allergies, ACE inhibitors
- Systemic diseases: sarcoidosis, connective tissue disorders, granulomatous diseases (GPA, TB), asthma, cardiac or pulmonary problems
- Associated symptoms
- Dysphagia
- Drooling
- Hoarseness
- Airway bleeding
- Weight loss
- Odynophagia
- Cough (barking cough)
- Sleep patterns (snoring, daytime somnolence)
- Chocking (laryngopharyngeal reflux, foreign body)
- Feeding difficulty (regurgitation, worse with feeding)
Causes of Acute vs Chronic Stridor
| Acute Stridor | Chronic Chronic Stridor |
|---|---|
| Croup | Congenital disorders of the larynx e.g. laryngomalacia, laryngeal webs, laryngeal cleft. |
| Tracheobronchitis | Craniofacial abnormalities such as Robin Pierre syndrome |
| Epiglottitis | Congenital disorders of the lower airway such as tracheomalacia, tracheal stenosis |
| Adenoidtonsillar hypertrophy | Neoplasms |
| Peritonsillar abscess | |
| Retropharyngeal abscess | |
| Foreign body inhalation | |
| Inhalational burns | |
| Anaphylaxis |
Stridor of laryngomalacia, micrognathia, macroglossia disappears when baby lies in prone position. Epiglottitis patients find it easier to breathe in the tripod or sniffing position. As such let the patient position themselves in the most comfortable position.
Physical Examination
- General
- Measure the child’s height and weight to determine nutritional status (poor feeding will present with failure to thrive/underweight).
- Measure vitals as fever points to an infectious cause of stridor.
- Skin
- Check for hives, rashes, swellings
- Respiratory
- Look for signs of respiratory distress such as retractions, cyanosis.
- Listen to the chest and describe the stridor.
- Nasal Exam
- Nasal endoscopy for nasoseptal deformities, nasal masses, nasal congestion (attempt to pass #6 catheter through both nares to assess patency)
- Flexible nasolaryngoscopy or mirror exam
- Airway patency
- Vocal fold mobility
- Examine tracheal stoma if it is present (retroflex to access subglottis)
Investigations
- Endoscopy
- Flexible nasolaryngoscopy (described above)
- Direct laryngoscopy: for evaluation and instrumentation of the glottis and supraglottis in theatre using direct line of site
- Bronchoscopy:
- Flexible bronchoscopy: identify the severity and location of stenosis
- Rigid bronchoscopy: instrumentation and management of an emergency airway crisis
- Imaging
- Chest X-ray and Neck X-ray: screen for laryngotracheal structural defects, intrinsic lung and mediastinal disease
- CT and MRI of the neck: evaluate location, extent, or compression of stenosis; evaluate destruction of local laryngeal structures
- Modified Barium Swallow and Esophagram: esophageal pathology, laryngopharyngeal reflux, aspiration and vascular abnormalities
- Pulmonary function tests and flow-volume loops: level of obstruction and intrinsic lung disease
- Airway fluoroscopy: dynamic evaluation of the airway, assess vocal fold motion
- Arteriography: if vascular abnormalities are suspected
- Laboratory
- Arterial Blood Gases
- Complete Blood Count
- Electrolytes
Initial Management (ABCs)
- Evaluate the airway: determine severity and stability (acute vs chronic, progressive, dyspnoea at rest vs with exercise)
- Establish airway
- Administer oxygen: masked ventilation until secure airway
- Heliox (80% helium, 20% oxygen): helium has a lower molecular weight allowing it to pass past narrow obstructions
- Consider humidification, corticosteroids, nebulized racemic epinephrine, antibiotics
Oxygen-Delivery and FiO2
| Oxygen Flow (L/min) | FiO2 | |
|---|---|---|
| Room air | – | 0.21 |
| Low flow devices | ||
| Nasal cannula | 1 – 6 | 0.24 – 0.44 |
| Simple face mask | 5 – 10 | 0.30 – 0.60 |
| Partial rebreather mask | 8 – 12 | 0.40 – 0.70 |
| Non-rebreather mask | 1 – 15 | 0.60 – 0.80 |
| High flow devices | ||
| Venturi mask | 4 – 12 | 0.24 – 0.50 |
