Upper airway resistance syndrome: still not recognized and not treated

The upper airway resistance syndrome (UARS) is a sleep breathing disorder described by Guilleminault et al., in 1993, to identify patients that present increased respiratory effort and airflow limitation during sleep associated with an increase in the upper airway resistance. Patients usually complain of daytime sleepiness, fatigue, snoring, and difficulty to maintain sleep. Complains related to cognitive impairment, headache, anxiety, and irritability are also frequent. The physical examination shows nasal obstruction, increase in soft tissue and craniofacial abnormalities associated with decrease in the upper airway space. Nocturnal polysomnography does not show apneas or hyponeas for diagnostic criteria of obstructive sleep apnea syndrome (OSAS), and respiratory abnormalities consist on periods of increase in respiratory effort, sleep fragmentation, presence of respiratory event related arousal (RERAs) and presence of flattening of respiratory curve, which indicates airflow limitation. Controversies exist regarding the characterization of upper airway resistance syndrome as part of a continuum with other sleep breathing disorders, or as a separate entity that may not progress to obstructive sleep apnea syndrome. Treatment of upper airway resistance syndrome is more challenging than obstructive sleep apnea syndrome, since patients have lower tolerance for continuous positive airway pressure (CPAP) use. Other treatment modalities have been investigated, but they are still not established for clinical practice. Recognition of upper airway resistance syndrome is important, since it may prevent long-term consequences or progression to more severe forms of sleep-related breathing disorders.