[Physiopathology of mouth breathing. Snoring and apnea].

Oral breathing causes changes in pulmonary mechanics as well as in the pressure of arterial blood gases. In response to increased nasal obstruction oro-nasal breathing occurs. The level of oro-nasal partitioning maintains an adequate level of respiratory resistance. Sleep disordered breathing, although not only related to oral breathing, is a common disorder. When upper airway resistance is increased limitation of flow occurs. Snoring indicates a mild degree of reduced airflow. Sleep apnea occurs when upstream pressure falls below a critical pressure (Pcrit). The mechanisms are reviewed.