A study published in the Journal of Applied Physiology examined the folding of the pharyngeal mucosal wall in patients with obstructive sleep apnea.

Mechanical processes underlying pharyngeal closure have not been examined. We hypothesised the pharyngeal mucosal surface would fold during closure and lowering the upper airway lining liquid surface tension would unfold areas of mucosal apposition, i.e. folds. We compared baseline pharyngeal fold numbers and response to reduction in upper airway liquid surface tension in healthy and obstructive sleep apnea (OSA) subjects.