SAI YAN AU
Stridor
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Harsh, high pitched, musical sound produced by
turbulent airflow through a partially obstructed
airway.
A sign
May be inspiratory, expiratory or biphasic
Inspiratory stridor – extrathoracic lesion
(laryngeal, nasal, pharyngeal)
Expiratory stridor – intrathoracic lesion (tracheal
or bronchial)
Biphasic stridor - subglottic or glottic anomaly
Stridor: Mechanism
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Venturi principle
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Gases produce equal pressure in all direction
When gas move in a linear direction, it produces
pressure in the forward vector and decreases the
lateral pressure
When air passes through a narrowed flexible
airway in child, the lateral pressure that holds the
airway can drop and causes airway to close –
airflow obstruction – stridor
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Stridor In Infants: Causes
Laryngomalacia (congenital laryngeal
stridor)
 Subglottic stenosis
 Laryngeal webs
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Laryngomalacia (congenital
laryngeal stridor)
Most common cause of persistent stridor in
infants (first 6 weeks of life)
 Congenital abnormality of the laryngeal
cartilage
 Delay in maturation of cartilaginous support
for the supraglottic structures
 No known sex and race predilection exists
 Causes – congenital
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Laryngomalacia:
pathophysiology
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May affect the epiglottis,
arytenoid cartilages or
both
Epiglottis – elongated and
the walls fold in on
themselves ( OMEGA, Ω
shaped)
Arythenoid cartilage –
enlarged
Either cases, cartilage is
floppy; prolapsed over the
larynx during inspiration
Increase risk of GOER
Reflux laryngitis
Laryngomalacia
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History:Hx of inspiratory noises; may sound like nasal
congestion
Stridor worse in the supine position, increased
activity, URTI and during feeding but improved in
the prone position with the head up
Assoc. with pectus excavatum
On Examination:mild tachypnoea
Normal or slight drop in O2 saturation
Nasal airflow increase in supine position
Noise is purely inspiratory
Laryngomalacia
Investigations: O2 saturation
 Fluoroscopy
 Laryngoscopy and bronchoscopy
 Treatment: > 99%, no Rx is needed
 Simple tracheotomy or laryngoplasty
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Subglottic Stenosis
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Narrowing of the
subglottic which is housed
in the cricoid cartilage
no racial predilection
exists
equal sex distributions
Causes: congenital (in utero
malformation of the
cricoid cartilage)
Acquired ( infections e.g.
TB, diphtheria, typhoid
and syphilis, mechanical
trauma due to
endotracheal intubation
and GOER)
Subglottic Stenosis:
Pathophysiology
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Congenital – incomplete
canalization of the
subglottis and cricoid
rings, assoc. with trisomy
21
Acquired: Trauma causes mucosal
oedema and hyperemia;
leads to pressure necrosis
GOER – subglottis bathed
in acid, irritates and
inflames the area and
prevent from healing
Subglottic Stenosis
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History: Presence of biphasic and obstructive breathing
Hoarseness or vocal weakness
Clinical examination:Complete head and neck examination
Evaluate the child’s appearance, voice and
neurological status
Auscultate lung and neck
Identify any associated features
Subglottic stenosis
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Investigations:Direct laryngoscopy and bronchoscopy
AP and lateral neck x ray
Fluoroscopy
Dual channel pH probe testing
MRI and CT Scan
Treatment:Medical (steroids)
Surgical (tracheostomy, cricoid split and
laryngoplasty)
Laryngeal Web
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Uncommon (5% of
congenital laryngeal
abnormalities)
Incomplete canalization of
the larynx
Sporadic and equal sex
distribution
Causes – congenital
4 types – based on the
degree of occlusion
Type I, II, III, IV
Laryngeal Web
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Type I – 35% covering the anterior glottis
Type II – 35 to 50% occlusion of the lumen with vocal
cord visible
Type III – 50 to 70% occlusion of the lumen with the vocal
cord possibly visualized; most common
Type IV – 75 to 90% occlusion with vocal cords not
visualized
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Pathophysiology: -
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Developmental abnormality occurring between the 4th to
10th weeks of gestation
Epithelial fusion between 2 sides of larynx fails to dissolve
resulting in incomplete recanalization of the primitive
larynx.
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Laryngeal webs: Clinical
Features
Inspiratory and expiratory stridor +/- upper
airway obstruction with respiratory distress
 Paroxysmal dyspnoea +/- cyanosis
 Aphonia, weak cry
 Poor feeding
 Assoc with respiratory and CVS problems
(10% - 15%)
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Laryngeal Webs
Investigations: Direct laryngoscopy or bronchoscopy
 Treatment: Supportive (emergency)
 Surgery (thinner, thicker webs)
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SUMMARY
Laryngomalacia – delay in maturation of
the cartilaginous support of supraglottic
structures
 Subglottic stenosis – incomplete
canalization of subglottis and cricoid
cartilage
 Laryngeal web – fusion of the anterior
portion of true vocal cords
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