RESUMO
Sleep is a biological mechanism essential to maintaining good health. A series of physiological changes takes place during sleep. From a ventilation point of view, during deep sleep, tidal volume increases, the inhalation and expiration phases become longer, and respiratory frequency slows, while the same volume/time ratio as in wakefulness is maintained. The concept of "sleep-related respiratory disorders" refers to a group of respiratory diseases that are aggravated during sleep. Some of these disorders are almost exclusively manifested during sleep, such as sleep apnea-hypopnea syndrome -undoubtedly the most frequent respiratory disease despite being underdiagnosed- and congenital central hypoventilation syndrome (also called Ondine's curse). However, this concept also encompasses other disorders that occur during the daytime since they worsen while patients are asleep, as seen in many obstructive or restrictive pulmonary diseases. Sleep disorders can be a manifestation of underlying diseases, some of which are highly prevalent such as obesity and gastroesophageal reflux. Likewise, abnormal sleep cycles may be a cause or a result of cognitive disorders and disturbances in children's learning processes.
