ABSTRACT
The mucosa of each nasal passage has a separate autonomic and sensory innervation. The airflow through each nasal passage is regulated by the tumescence of the venous erectile tissue in the nasal mucosa. Engorgement of the tissue causes a constriction of the nasal passage, thus reducing airflow. This tissue exhibits cycles of constriction causing an alternation of the main airflow from one nasal passage to the other. A nasal cycle is found in about 80% of the population, yet most people are completely unaware of it since the total resistance remains relatively constant. Although the presence of the nasal cycle is well documented, its significance is still only speculated upon. One suggestion for the cycle is that each passage may rest whilst the other takes over conditioning of the inspired air.
