Thyroarytenoid muscle activity in sleep apneas

Area of Science:

• Respiratory Physiology
• Sleep Medicine
• Neuroscience

Background:

• The thyroarytenoid muscle (TA), a vocal cord adductor, exhibits expiratory activity during wakefulness that ceases during non-rapid-eye-movement (NREM) sleep.
• Previous fiber-optic studies noted irregular vocal cord movements during obstructive apneas and adduction during central apneas.

Purpose of the Study:

• To investigate thyroarytenoid (TA) muscle activity during NREM sleep in individuals with sleep apnea.
• To characterize TA muscle response patterns during central and obstructive apneas.

Main Methods:

• Utilized intramuscular wire electrodes to record TA muscle activity in 14 subjects with sleep apnea during NREM sleep.
• Observed TA activity during spontaneous central and obstructive apneas.
• Assessed TA activity during nasal continuous positive airway pressure (CPAP) therapy.

Main Results:

• Continuous TA activity was observed during central apneas.
• Two patterns of TA activity emerged during obstructive apneas: complete absence or phasic activity.
• TA muscle showed marked activation during arousal and was consistently inactive during CPAP therapy.
• No correlation was found between obstructive apnea characteristics and TA activity patterns.

Conclusions:

• Persistent TA activity during central apneas may indicate prolonged neural expiratory discharge.
• Variable stimuli during obstructive apneas might activate the TA muscle, potentially contributing to glottic narrowing.
• Nasal CPAP effectively suppressed TA activity during NREM sleep.