Nasal cycle

This cycle, which is controlled by the autonomic nervous system, has a mean duration of two and a half hours but varies widely with age, body-posture, and other conditions.

The nasal cycle is an alternation in both time and between left and right sides, with the total resistance in the nose remaining constant.

[2] A 1994 study suggested that breathing through alternate nostrils can affect brain hemisphere symmetry on EEG topography.

[10] A later study in 2007 showed that this cycle (as well as manipulation through forced nostril breathing on one side) has an effect on endogenous ultradian rhythms of the autonomic and central nervous system.

[11] However, more recent research has shown no statistically significant association between spontaneously (i.e., not forced) dominant nostril and active brain hemisphere.

A CT scan showing evidence of the nasal cycle: the more patent airway is on the right of the image, the swollen turbinates congesting the left