Superior pharyngeal constrictor activation in obstructive sleep apnea

Area of Science:

• Otorhinolaryngology
• Sleep Medicine
• Respiratory Physiology

Background:

• Obstructive sleep apnea (OSA) is characterized by recurrent upper airway collapse during sleep.
• The role of the superior pharyngeal constrictor (SPC) muscle in maintaining airway patency in OSA is not fully understood.

Purpose of the Study:

• To investigate the respiratory-related activity of the SPC muscle in patients with OSA during wakefulness and sleep.
• To determine the involvement of SPC muscle activation in airway closure and reopening during apneic events and with positive airway pressure support.

Main Methods:

• 18 patients with OSA underwent nasopharyngeal implantation of hooked-wire electrodes into the SPC muscle.
• SPC muscle activity was recorded during wakefulness, spontaneous non-rapid-eye-movement (NREM) sleep apneas, and during nasal continuous positive airway pressure (CPAP) administration and withdrawal.

Main Results:

• During wakefulness, SPC muscle showed expiratory activity, often after swallowing.
• In NREM sleep, SPC muscle activated during airway reopening in 13 patients and was inactive in 5 during apneas.
• Nasal CPAP abolished SPC activity in most patients; CPAP withdrawal induced airway closure without altering SPC activity.

Conclusions:

• SPC muscle activation patterns in OSA patients resemble those of other pharyngeal dilator muscles.
• SPC muscle activation is not required for upper airway closure during NREM sleep in OSA.
• These findings suggest that the SPC muscle's role in OSA may be more related to airway reopening than to preventing collapse.