Mouth Breathing: Abnormal breathing through the mouth, usually associated with obstructive disorders of the nasal passages.Nasal Obstruction: Any hindrance to the passage of air into and out of the nose. The obstruction may be unilateral or bilateral, and may involve any part of the NASAL CAVITY.Otorhinolaryngologic Diseases: Pathological processes of the ear, the nose, and the throat, also known as the ENT diseases.Stomatognathic System: The mouth, teeth, jaws, pharynx, and related structures as they relate to mastication, deglutition, and speech.Adenoids: A collection of lymphoid nodules on the posterior wall and roof of the NASOPHARYNX.Respiration: The act of breathing with the LUNGS, consisting of INHALATION, or the taking into the lungs of the ambient air, and of EXHALATION, or the expelling of the modified air which contains more CARBON DIOXIDE than the air taken in (Blakiston's Gould Medical Dictionary, 4th ed.). This does not include tissue respiration (= OXYGEN CONSUMPTION) or cell respiration (= CELL RESPIRATION).Snoring: Rough, noisy breathing during sleep, due to vibration of the uvula and soft palate.Mouth: The oval-shaped oral cavity located at the apex of the digestive tract and consisting of two parts: the vestibule and the oral cavity proper.Cephalometry: The measurement of the dimensions of the HEAD.Work of Breathing: RESPIRATORY MUSCLE contraction during INHALATION. The work is accomplished in three phases: LUNG COMPLIANCE work, that required to expand the LUNGS against its elastic forces; tissue resistance work, that required to overcome the viscosity of the lung and chest wall structures; and AIRWAY RESISTANCE work, that required to overcome airway resistance during the movement of air into the lungs. Work of breathing does not refer to expiration, which is entirely a passive process caused by elastic recoil of the lung and chest cage. (Guyton, Textbook of Medical Physiology, 8th ed, p406)