When nasal breathing becomes obstructed the lips must separate to allow air to enter the mouth. The tongue lowers itself to the floor of the mouth to allow air to enter the pharynx. The hyoid bone which is attached to the tongue is also pulled lower and the mandible becomes retrognathic. The head position on the spinal column also assumes a more forward posture to facilitate oral breathing.
The respiratory central pathway of the brain can induce oral respiration when nasal breathing is obstructed. Once learned, the low tongue position of oral breathers becomes the predominant reflex, the child’s swallowing and breathing mode both become dysfunctional, and permanent structural and postural changes occur. It is the lower tongue position, the narrowing of the airway and subsequent increased collapsibility during sleep that predispose to pediatric OSA and snoring. In fact OSA has become recognized as the most extreme variety of mouth breathing and snoring.
Environmental challenges that cause obstruction of nasal breathing result in a dysequilibrium between structure and function. If the accommodative changes become habitual, the posture and structure will permanently change. Anything that contributes to oral breathing, such as enlarged tonsils and adenoids and swollen nasal membranes, alters rest position of the tongue. Habitual oral breathing results in skeletal changes, postural changes and alterations of normal function.