What role does the epiglottis play in protecting the airway from aspiration?

The Epiglottis as a Protective Airway Structure During Swallowing

The epiglottis protects the airway from aspiration by folding downward over the laryngeal entrance during the pharyngeal phase of swallowing, creating a physical barrier that directs the food bolus laterally through the pyriform sinuses and away from the trachea. 1

Mechanism of Epiglottic Protection

The epiglottis functions as one component of a three-level airway closure system during swallowing:

• Airway closure occurs at three distinct levels: true vocal fold closure, false vocal fold approximation, and arytenoid cartilage contact at the base of the epiglottis 1
• The epiglottis folds over the arytenoid cartilages during the 1-2 second pharyngeal phase, working in coordination with upward and forward movement of the hyoid bone and larynx 1
• This downfolding occurs in a two-step fashion: first from upright to transverse position (passive movement from laryngeal elevation and hyoid-thyroid approximation), then from transverse to inverted position (active contraction of the thyroepiglottic muscle) 2

Anatomical Basis for Protection

The epiglottis achieves its protective position through specific structural relationships:

• Lateral hyoepiglottic ligaments run from the lateral edge of the epiglottis to the hyoid bone near the greater horns, exerting traction on the upper third of the epiglottis as the hyoid moves anteriorly 3
• The preepiglottic space grows during the first 8 years of life to occupy areas anterior, posterolateral, and inferolateral to the epiglottic cartilage, allowing more effective retroflection during swallowing 4
• The epiglottis works with the palatopharyngeal sphincter to direct bolus flow; as this sphincter elevates, it exposes more epiglottic surface area to bolus pressure, facilitating downfolding 5

Developmental Considerations

The protective function of the epiglottis changes dramatically with maturation:

• In newborns and infants, the epiglottis does not fold backward during swallowing; instead, the bolus passes around a relatively stationary epiglottis through the piriform recesses 5
• Infants can breathe and swallow simultaneously due to the superior laryngeal position and shorter pharyngeal length, an ability lost with maturity 6
• The epiglottis lies on a somewhat horizontal axis in newborns, partially obscured behind the hyoid bone, and is composed of immature elastic cartilage 4

Clinical Significance in Aspiration Prevention

When epiglottic function fails, aspiration risk increases substantially:

• Aspiration occurs when material moves below the true vocal folds into the trachea, while penetration describes material entering only to the level of the vocal folds 1
• Aspiration pneumonia carries mortality rates of 20-65% in hospitalized adults, making effective airway protection critical 1
• The chin-down posture narrows the entrance to the laryngeal vestibule and prevents penetration into the larynx by opening the valleculae, reducing aspiration risk by approximately 50% 1

Common Pitfalls

Several factors can compromise epiglottic protection:

• Silent aspiration (aspiration without cough response) occurs commonly in patients with impaired laryngeal sensation, making epiglottic dysfunction particularly dangerous since the protective cough reflex is absent 1
• Surgical procedures involving the epiglottis (such as supracricoid partial laryngectomy with epiglottic suturing to aryepiglottic folds) result in aspiration pneumonia in 21.7% of patients 1
• Reduced tongue base retraction decreases the positive pressure needed to fold the epiglottis effectively, leading to vallecular residue and increased aspiration risk 6

The epiglottis does not function in isolation but rather as part of a coordinated sequence involving laryngeal elevation, hyoid movement, vocal fold closure, and pharyngeal constriction to achieve complete airway protection during swallowing 1.