The nasal cycle

The nasal cycle (NC) is the spontaneous congestion and decongestion of the nasal mucosa during the day, where congestion of one side is accompanied by reciprocal decongestion of the contralateral side. It is based on the dilation/constriction of the venous cavernous tissue in the submucosa of the turbinates and septum, but also of the ethmoid sinuses.It is accepted that almost 70-80% of adults experience a regular NC, but a true periodicity/reciprocity exists only in 21-39% of the Population. NC is considered an ultradian rhythm of side-toside nasal mucosal engorgement with a phase length ranging from 30 min to 6h. As first described, in an ideal cycle, the two air passages should show reciprocal changes of equal amplitude, 180° out of phase, with an identical period and similar mean airflow, with total nasal flow remaining constant.