Phasic volume-related feedback on upper airway muscle activity

Area of Science:

• Respiratory Physiology
• Neuroscience

Background:

• Upper airway muscles are crucial for maintaining airway patency during breathing.
• Vagal feedback, related to lung volume, is known to influence respiratory control.

Purpose of the Study:

• To investigate the role of vagally mediated volume-related feedback on upper airway muscle activity.
• To compare the modulation of upper airway muscles versus respiratory muscles (diaphragm, phrenic nerve) by this feedback.

Main Methods:

• Electromyography of genioglossus, posterior cricoarytenoid, and alae nasi muscles in anesthetized dogs.
• Recording of tidal volume and electrical activity of phrenic nerve or diaphragm.
• Analysis of muscle activity during normal breaths and single-breath airway occlusions before and after vagotomy.

Main Results:

• Airway occlusion delayed peak activity in upper airway muscles, shifting it to late inspiration.
• Inspiratory muscle depression occurred earlier and at lower volumes for upper airway muscles compared to diaphragm/phrenic nerve.
• Depressive effects were most pronounced in genioglossus, followed by posterior cricoarytenoid and alae nasi.
• Vagotomy abolished these depressive effects, confirming vagal mediation.

Conclusions:

• Vagally mediated volume feedback significantly modulates upper airway muscle activity.
• This feedback plays a more prominent role in regulating upper airway muscles than the diaphragm or phrenic nerve.
• Findings highlight the importance of vagal afferents in controlling airway muscle tone during respiration.