Pharyngeal narrowing/occlusion during central sleep apnea

Area of Science:

• Sleep Medicine
• Respiratory Physiology
• Otolaryngology

Background:

• Pharyngeal occlusion during sleep is often attributed to subatmospheric intraluminal pressure.
• Understanding the mechanisms of pharyngeal collapse during sleep is crucial for diagnosing and treating sleep-related breathing disorders.

Purpose of the Study:

• To investigate whether subatmospheric intraluminal pressure is a prerequisite for pharyngeal occlusion during sleep.
• To determine the role of inspiratory effort in pharyngeal narrowing during central sleep apnea.

Main Methods:

• Fiber-optic nasopharyngoscopy was used to assess pharyngeal patency in normal subjects and those with sleep apnea or hypopnea (SAH).
• Studies were conducted during spontaneous central sleep apnea and induced hypocapnic central apnea using nasal mechanical ventilation.
• Pharyngeal cross-sectional area was measured during non-rapid-eye-movement sleep.

Main Results:

• Complete pharyngeal occlusion occurred frequently during spontaneous central apneas in SAH patients.
• Gradual pharyngeal narrowing was observed during induced hypocapnic central apnea, more pronounced in SAH subjects and at the velopharynx.
• Pharyngeal narrowing or occlusion persisted during central apnea even without inspiratory effort, resolving only with arousal.

Conclusions:

• Subatmospheric intraluminal pressure is not required for pharyngeal occlusion during sleep.
• Pharyngeal narrowing or occlusion during central sleep apnea can result from passive collapse or active constriction.
• Velopharyngeal narrowing is a consistent finding during hypocapnic central apnea, even in healthy individuals.