The amount of saliva in the mouth and throat plays an important role in keeping the upper airway open. Mouth breathing will cause saliva to become thicker and stickier. The increased stickiness of the upper airway contributes to collapse and makes it more difficult for the airway to reopen when breathing resumes. It is important that the areas of the throat and mouth remain moist during sleep for the muscles to function properly.
Lam JC, Kairaitis K, Verma M, Wheatley JR, Amis TC. Saliva production and surface tension: influences on patency of the passive upper airway. J Physiol. 2008 Nov 15;586(22):5537-47.
Manisha Verma, Margaret Seto-Poon, John R Wheatley, Terence C Amis, Jason P Kirkness. Influence of breathing route on upper airway lining liquid surface tension in humans. J Physiol. 2006 Aug 1; 574(Pt 3): 859–866.
