[Why you should know the "nose cycle" as a pneumologist and sleep medicine specialist].

The nasal cycle refers to the anticyclic swelling and decongestion of the two nasal cavities that occur during the day and during sleep, while the overall nasal flow remains constant. The nasal cycle was first described by R. Kayser in 1895. Each cycle consists of a working phase and a subsequent resting phase, the purpose of which is the rehydration and regeneration of the mucosa. A nasal cycle occurs in about 70-90% of people. The duration of the phase is affected by age, body position, physical activity, mucociliary clearance and time of day. Typically, the cycle lengthens during sleep. Long-term rhinoflowmetry enables assessment of the circadian course of the alternating cyclic changes of the nasal mucosa.