By the nasal cycle, medicine understands an ultradian rhythm that causes the nasal mucous membranes to alternately swell and decongest. This alternation of working and resting phases serves to regenerate the mucous membranes. An exaggerated nasal cycle is also known as specific or nonspecific nasal hyperreactivity.
What is the nasal cycle?
The nasal cycle is the alternating waxing and waning of the mucosal areas in both turbinates. The nasal cycle is the reciprocal swelling and decongestion of the mucosal areas in the two turbinates. This process takes place permanently and independently of external stimuli. A cycle lasts between about 30 minutes and 14 hours. On average, about 2.5 hours are estimated for a nasal cycle. However, the interindividual differences are serious. Because its periods are less than 24 hours, the nasal cycle is classified as an ulradian rhythm. In the case of the swollen state of the mucous membranes, the ultradian nasal cycle is also referred to as the working phase. The swollen state, on the other hand, is called the resting phase. The nasal cycle persists during the day as well as during the night. However, the day and night cycles differ in the amount of air. Thus, the proportional flow of air between the resting and working phases is greater during the night than during the day. Kayser, a physician from Wroclaw, first described the nasal cycle at the end of the 19th century. Today, the phenomenon is mainly associated with regenerative effects.
Function and task
The nasal cycle is controlled by the brain region of the sympathetic nervous system. This area of the brain performs important functions in the autonomic nervous system. The sympathetic and parasympathetic nervous systems complement each other, regulating organ activity with extreme precision. The action of the sympathetic nervous system is described as ergotropic, since the regulatory center increases the ability to act externally. The nerve impulses and bodily functions controlled from here are independent of voluntary control and thus take place permanently and unconsciously. The hypothalamus is the supreme regulatory center for all vegetative processes, such as circulation or body temperature. This part of the diencephalon takes over the neuronal coordination in the nasal cycle. During the nasal cycle, the mucous membrane of one side of the nasal concha is always swollen, while that of the other side is in the working phase. During this working phase, a much higher airflow enters the nose than during the turbulence-free resting phase. The swollen state in the resting phase minimizes the air reaching the mucosa. Therefore, the mucosa releases much less moisture to the nose during the resting phase. Since air enters the nose unimpeded in the working phase due to the swollen state, this results in an all the greater humidification effort for the mucosa in this phase. The resting phase therefore serves to relax and regenerate the nasal mucosa. In this phase of regeneration, the mucous membrane not only saves moisture, but also energy. During the night phase, the body’s own regeneration processes reach their peak. The nasal mucous membranes play a role primarily as protective devices against inhaled foreign bodies and pathogens. Their cilia beat up to 900 times per minute and thus remove foreign substances from the body. The regeneration processes ensure that the mucous membranes remain functional. Especially after colds or infections, the ability to regenerate is important for restoring protective functions. Although the mucous membranes could recover even without the nasal cycle, regeneration would probably be less effective if the cycle did not exist.
Diseases and ailments
One of the most well-known ailments associated with the nasal cycle is nasal hyperreactivity. In this phenomenon, the natural nasal cycle is disturbed by contact with external stimuli. Naturally, the mucous membrane of the nose reacts to certain stimuli with nasal breathing obstruction, sneezing or similar phenomena. Nasal obstruction or nasal obstruction in response to chemical, physical or pharmacological stimuli is called nasal hyperreactivity. In this context, medicine distinguishes between specific and non-specific hyperreactivity. In specific hyperreactivity, the patient reacts excessively to allergens.If, on the other hand, he reacts with nasal obstruction to a change in his own body position, to exertion, or to environmental stimuli such as smoke, fumes, or cold air, we are talking about nonspecific hyperreactivity. Both inflammation and disturbances in nerve control play a role in hyperreactivity. The production and release of endogenous substances such as neurotransmitters changes and the receiving receptors of the vessels and nerves or glands overreact. Allergic rhinitis sets in. About 15 percent of the population suffers from such rhinitis. The nasal cycle has also been observed in the field of sleep medicine. Particularly for patients with sleep apnea syndrome, abnormalities in the nasal cycle have been documented. Those affected by sleep apnea syndrome suffer from small respiratory arrests during the sleep phase. According to sleep medicine studies, there is an indisputable connection between their nasal cycle and their body position during sleep. Thus, in patients, the nasal concha swells on the side on which the patient lies during sleep. The increased tone of the sympathetic nervous system is thought to be the cause of this observation in sleep apnea syndrome sufferers. The nasal cycle also plays a role in the context of colds or other infections. Consequently, colds and flu can temporarily throw the natural rhythm out of balance.
