Poiseuille’s law
Q=ΔPπr48ηl; r = Radius of airway
Flow (Q) is proportional to the radius to the fourth power; incremental changes in the radius cause exponential decreases in airflow
Bernoulli’s principle
Increased airflow results in a decrease in pressure
Narrowed airway → Increased airflow speed → Decreased intraluminal pressure (vacuum) → Further collapse of walls of lumen
Stridor – high-speed airflow through collapsed tissues causes vibration and a resonance, resulting in a sound
Physical obstruction of the airway is associated with noise on inspiration or expiration, depending on the site and nature of the lesion
Stridor is not only audible, but also visible
Examiner should be able to visualize site of obstruction while noise is being made
Requires adequate instrumentation techniques of the airway
Isolated tachypnea (i.e., without stridor) is not a sign of airway obstruction
Symptoms by Subsite
| Subsite | Hallmark Symptoms |
| Nasal | Mouth breathing, snoring |
| Acute respiratory distress in neonates – obligate nasal breathers | |
| Pharynx | Snoring, stertor (pharyngeal resonance, similar to snoring), retractions |
| Supraglottis | Pure inspiratory stridor, dysphagia in infants, retractions, pectus excavatum |
| Glottis | Biphasic stridor, retractions, hoarseness |
| Subglottis | Inspiratory or biphasic stridor, retractions, barking cough, recurrent croup |
| Trachea | Expiratory stridor, barking cough, poor secretion clearance |
Piriform aperture stenosis
Bony narrowing of the anterior nasal vestibule in neonates; results in airway-related respiratory distress and feeding problems
Diagnosed by computerized tomography (CT) scan showing <8 mm patency between nasal processes of maxillary bone
Can be associated with holoprosencephaly (central incisor) or choanal atresia
Treatment: sublabial approach to nasal vestibule with high-powered drill reduction of nasal process of maxillary bone
Choanal atresia/stenosis
Incomplete or uncannulated opening from the nose to the nasopharynx in neonates; results in airway-related respiratory distress
CHARGE syndrome (coloboma, heart defects, atresia choanae, growth retardation, genital abnormalities, and ear abnormalities)
May go undiagnosed if unilateral
Treatment: transnasal or transpalatal resection of posterior obstructive tissues
Adenotonsillar disease
Most common cause of obstructive sleep apnea (OSA) in children
Diagnosed by direct visualization on exam and attended nocturnal polysomnogram
Treatment: adenotonsillectomy adequately treats >80% of patients with pharyngeal airway obstruction
Pharyngomalacia
Poor pharyngeal muscle tone, results in collapse of tissues and obstruction with stertor
Treatment: noninvasive positive pressure ventilation (continuous or bilevel)
Glossoptosis/macroglossia (Figure 20-1)
Tongue and tongue base obstruction of the airway
Pierre-Robin’s sequence, Down’s syndrome, lingual tonsil hypertrophy, isolated micrognathia, Ludwig’s angina (anterior floor of mouth abscess)
Treatment: alleviate obstruction by resection, advancement, or bypass (i.e., tracheotomy)
Pharyngeal obstruction results primarily in sleep apnea symptoms
FIGURE 20-1
Glossoptosis causing upper airway obstruction. Note how the base of the tongue compresses the epiglottis against the posterior pharynx.
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