Similar Central hypoventilation syndrome, Obesity hypoventilation syndrome, Respiratory disturbance index, Sleep apnea | ||
Upper airway resistance syndrome or UARS is a sleep disorder characterized by airway resistance to breathing during sleep. The primary symptoms include daytime sleepiness and excessive fatigue.
Contents
Diagnosis
Polysomnography (sleep study) with the use of a probe to measure Pes (esophageal pressure) is the gold standard diagnostic test for UARS. Apneas and hypopneas are absent or present in low numbers. Multiple snore arousals may be seen, and if an esophageal probe (Pes) is used, progressive elevation of esophageal pressure fluctuations terminating in arousals is noted. UARS can also be diagnosed using a nasal cannula/pressure transducer to measure the inspiratory airflow v. time signal.
Explanation
During sleep the muscles of the airway become relaxed. The relaxation of these muscles in turn reduces the diameter of the airway. Typically, the airway of a person with UARS is already restricted or reduced in size, and this natural relaxation reduces the airway further. Therefore, breathing becomes labored. It can be likened to breathing through a straw.
Pathophysiology
Pathophysiology of UARS is similar to obstructive sleep apnea / hypopnea syndrome in that abnormal airway resistance in the upper airway during sleep leads to unwanted physiologic consequences. Increased upper airway resistance in this disorder does not lead to cessation of airflow (apnea) or decrease in airflow (hypopnea), but instead leads to an arousal secondary to increased work of breathing to overcome the resistance. Repeated and multiple arousals (of which the person is usually unaware) result in an abnormal sleep architecture and daytime somnolence (sleepiness). Arousals result in sympathetic activation, and UARS is therefore likely to cause hypertension similar to obstructive sleep apnea syndrome (This has not been verified in large clinical populations because of the relatively small number of people with UARS in the larger epidemiologic studies so far. However, repeated arousals in individuals have clearly been shown to be related to sympathetic activation and elevation in blood pressure).
Clinical presentation
People with UARS present with snoring and excessive daytime somnolence. Hypotension is likely to be present. Also, fatigue, cognitive impairment, unrefreshing sleep, frequent awakenings, and chronic pain may be present.
UARS is often misdiagnosed as fibromyalgia or similar disorders. Guilleminault et al. write that up to 75% of adults with sleepwalking have UARS.
Treatment
Treatment for UARS is essentially the same as that for obstructive sleep apnea.
Behavioral modification
Behavioral modification includes getting at least 7–8 hours of sleep, avoiding sleeping in supine position (on the back), sleeping with head end of bed elevated and avoiding sedatives, alcohol and narcotics.
Positive airway pressure therapy
Positive airway pressure therapy is similar to that in obstructive sleep apnea and works by stenting the airway open from the pressure, thus reducing the airway resistance. Reimbursement for the positive airway pressure device (CPAP etc.) may be a concern in certain healthcare models.
Oral appliances
Oral appliances to protrude the tongue and mandible (lower jaw) forward have been used to reduce/eliminate sleep apnea/snoring but have uncertain performance in treating excessive daytime sleepiness.
Surgery
Various surgical options including uvulopalatopharyngoplasty (UPPP), hyoid suspension, and linguloplasty to increase the dimensions of the upper airway and to reduce the collapsibility of the airway are viable treatment modalities for UARS. One should also be screened for the presence of a hiatal hernia, which may result in abnormal pressure differentials in the esophagus, and in turn, constricted airways during sleep.
Prognosis
People with UARS usually respond to treatment with no long term sequelae.