Upper airway resistance syndrome

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Upper airway resistance syndrome
Other namesUARS, Non-hypoxic sleep-disordered breathing

Upper airway resistance syndrome is a sleep disorder characterized by the narrowing of the airway that can cause disruptions to sleep.[1][2] The symptoms include unrefreshing sleep, fatigue or sleepiness, chronic insomnia, orthostatic intolerance, and difficulty concentrating. UARS can be diagnosed by polysomnograms capable of detecting Respiratory Effort-related Arousals. It can be treated with lifestyle changes, orthodontics, surgery, or CPAP therapy.[3] UARS is considered a variant of sleep apnea.[4]

Signs and symptoms[edit]

Symptoms of UARS are similar to those of obstructive sleep apnea, but not inherently overlapping. Fatigue, insomnia, daytime sleepiness, unrefreshing sleep, ADHD, anxiety, and frequent awakenings during sleep are the most common symptoms. Oxygen desaturation is minimal or absent in UARS, with most having a minimum oxygen saturation >92%.[5]

Many patients experience chronic insomnia that creates both a difficulty falling asleep and staying asleep. As a result, patients typically experience frequent sleep disruptions.[6] Most patients with UARS snore, but not all.[4]

Some patients experience hypotension, which may cause lightheadedness, and patients with UARS are also more likely to experience headaches and irritable bowel syndrome.[6]

Predisposing factors include a high and narrow hard palate, an abnormally small intermolar distance, an abnormal overjet greater than or equal to 3 millimeters, and a thin soft palatal mucosa with a short uvula. In 88% of the subjects, there is a history of early extraction or absence of wisdom teeth. There is an increased prevalence of UARS in east Asians.[7]


Upper airway resistance syndrome is caused when the upper airway narrows without closing. Consequently, airflow is either reduced or compensated for through an increase in inspiratory efforts. This increased activity in inspiratory muscles leads to the arousals during sleep which patients may or may not be aware of.[1]

A typical UARS patient is not obese and possesses small jaws, which can result in a smaller amount of space in the nasal airway and behind the base of the tongue.[4] Patients may have other anatomical abnormalities that can cause UARS such as deviated septum, inferior turbinate hypertrophy, a narrow hard palate that reduces nasal volume, enlarged tonsils, or nasal valve collapse.[8][2] UARS affects equal numbers of males and females.[1]

Why some patients with airway obstruction present with UARS and not OSA is thought to be caused by alterations in nerves located in the palatal mucosa. UARS patients have largely intact and responsive nerves, while OSA patients show clear impairment and nerve damage. Functioning nerves in the palatal mucosa allow UARS patients to more effectively detect and respond to flow limitations before apneas and hypopneas can occur. Patients with intact nerves are able to dilate the genioglossus muscle, a key compensatory mechanism utilized in the presence of airway obstruction. What damages the nerves is not definitively known, but it is hypothesized to be caused by the long term effects of Gastroesophageal reflux and/or snoring.[9][10]


UARS is diagnosed using the Respiratory Disturbance Index (RDI). A patient is considered to have UARS when they have an Apnea-Hypopnea Index (AHI) less than 5, but an RDI greater than or equal to 5. Unlike the Apnea-Hypopnea Index, the Respiratory Disturbance Index includes Respiratory Effort-related Arousals (RDI = AHI + RERA Index).[11] In 2005, the definition of Sleep Apnea was changed to include patients with UARS by using RDI to determine sleep apnea severity.

Polysomnograms can be used to help diagnose UARS. On polysomnograms, a UARS patient will have very few apneas and hypopneas, but many Respiratory effort-related Arousals. RERAs are periods of increased respiratory effort lasting for more than ten seconds and ending in arousal. Whether or not an event is classified as a RERA or Hypopnea depends on the definition of Hypopnea used by the sleep technician.[11] The American Academy of Sleep Medicine currently recognizes two definitions. The scoring of Respiratory Effort-related Arousals is currently designated as "optional" by the AASM. Thus, many patients who receive sleep studies may receive a negative result, even if they have UARS.[12]

Based on symptoms, patients are commonly misdiagnosed with idiopathic insomnia, idiopathic hypersomnia, chronic fatigue syndrome, fibromyalgia, or a psychiatric disorder such as ADHD or depression.[6] Studies have found that children with UARS are frequently misdiagnosed with ADHD. One study found UARS or OSA present in up to 56% of children with ADHD.[13] Studies show that symptoms of ADHD caused by UARS significantly improve or remit with treatment in surgically treated children.[14]


Behavioral modification[edit]

Behavioral modifications include getting at least 7–8 hours of sleep and various lifestyle changes, such as positional therapy.[15] Sleeping on one's side rather than in a supine position or using positional pillows can provide relief, but these modifications may not be sufficient to treat more severe cases.[15] Avoiding sedatives including alcohol and narcotics can help prevent the relaxation of airway muscles, and thereby reduce the chance of their collapse. Avoiding sedatives may also help to reduce snoring.[15]


Nasal steroids may be prescribed in order to ease nasal allergies and other obstructive nasal conditions that could cause UARS.[15]

Positive airway pressure therapy[edit]

Positive airway pressure therapy is similar to that in obstructive sleep apnea and works by stenting the airway open with pressure, thus reducing the airway resistance. Use of a CPAP can help ease the symptoms of UARS. Therapeutic trials have shown that using a CPAP with pressure between four and eight centimeters of water can help to reduce the number of arousals and improve sleepiness.[4] CPAPs are the most promising treatment for UARS, but effectiveness is reduced by low patient compliance.[16]

Oral appliances[edit]

Oral appliances to protrude the tongue and lower jaw forward have been used to reduce sleep apnea and snoring, and hold potential for treating UARS, but this approach remains controversial.[16] Oral appliances may be a suitable alternative for patients who cannot tolerate CPAP.[15]


For nasal obstruction, options can be septoplasty, turbinate reductions, or surgical palate expansion.[2]

Orthognathic surgeries that expands the airway, such as Maxillomandibular advancement (MMA) or Surgically Assisted Rapid Palatal Expansion (SARPE) are the most effective surgeries for sleep disordered breathing. MMA is often completely curative.[11]

Though less common methods of treatment, various surgical options including uvulopalatopharyngoplasty (UPPP), hyoid suspension, and linguloplasty exist. These procedures increase the dimensions of the upper airway and reduce the collapsibility of the airway.[3] 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.[3] Palatal tissue reduction via radiofrequency ablation has also been successful in treating UARS.[16]

Maxillary Expansion[edit]

Orthodontic treatment to expand the volume of the nasal airway, such as nonsurgical Rapid Palatal expansion is common in children.[17][15] Due to the ossification of the median palatine suture, traditional tooth-born expanders cannot achieve maxillary expansion in adults as the mechanical forces instead tip the teeth and dental alveoli. Mini-implant assisted rapid palatal expansion (MARPE) has been recently developed as a minimally invasive option for the transverse expansion of the maxilla in adults.[18] This method increases the volume of the nasal cavity and nasopharynx, leading to increased airflow and reduced respiratory arousals during sleep.[19]

See also[edit]


  1. ^ a b c Shneerson, John M., ed. (2005). Sleep Medicine (Second ed.). New York: Blackwell Publishing. pp. 229-237.
  2. ^ a b c de Oliveira, Pedro Wey Barbosa; Gregorio, Luciano Lobato; Silva, Rogério Santos; Bittencourt, Lia Rita Azevedo; Tufik, Sergio; Gregório, Luis Carlos (July 2016). "Orofacial-cervical alterations in individuals with upper airway resistance syndrome" (PDF). Brazilian Journal of Otorhinolaryngology. 82 (4): 377–384. doi:10.1016/j.bjorl.2015.05.015. PMID 26671020.
  3. ^ a b c de Godoy, Luciana B.M.; Palombini, Luciana O.; Guilleminault, Christian; Poyares, Dalva; Tufik, Sergio; Togeiro, Sonia M. (2015). "Treatment of upper airway resistance syndrome in adults: Where do we stand?". Sleep Science: 42–48 – via Elsevier.
  4. ^ a b c d Cuelbras, Antonio (1996). Clinical Handbook of Sleep Disorders. New York: Butterworth-Heinemann. pp. 207.
  5. ^ Bao G, Guilleminault C (2004). "Upper airway resistance syndrome--one decade later". Curr Opin Pulm Med. 10 (6): 461–7. doi:10.1097/01.mcp.0000143689.86819.c2. PMID 15510051.
  6. ^ a b c Kushida, Clete A., ed. (2009). Handbook of Sleep Disorders (Second ed.). New York: Inform Healthcare. pp. 339–347.
  7. ^ Guilleminault, C., & Chowdhuri, S. (2000). Upper Airway Resistance Syndrome Is a Distinct Syndrome. American Journal of Respiratory and Critical Care Medicine, 161(5), 1412–1413. https://doi.org/10.1164/ajrccm.161.5.16158a
  8. ^ Garcha, Puneet S.; Aboussouan, Loutfi S.; Minai, Omar (January 2013). "Sleep-Disordered Breathing". Cleveland Clinic Disease Management. Retrieved 15 March 2017.
  9. ^ Guilleminault, C., Li, K., Chen, N.-H., & Poyares, D. (2002). Two-Point Palatal Discrimination in Patients With Upper Airway Resistance Syndrome, Obstructive Sleep Apnea Syndrome, and Normal Control Subjects. Chest, 122(3), 866–870. https://doi.org/10.1378/chest.122.3.866
  10. ^ Poothrikovil RP, Al Abri MA (2012) Snoring-induced nerve lesions in the upper airway. Sultan Qaboos Univ Med J 12 (2):161-8. DOI:10.12816/0003108 PMID: 22548134
  11. ^ a b c de Godoy, L. B. M., Palombini, L. O., Guilleminault, C., Poyares, D., Tufik, S., & Togeiro, S. M. (2015). Treatment of upper airway resistance syndrome in adults: Where do we stand? Sleep Science, 8(1), 42–48. https://doi.org/10.1016/j.slsci.2015.03.001
  12. ^ Berry, R. B., Budhiraja, R., Gottlieb, D. J., Gozal, D., Iber, C., Kapur, V. K., Marcus, C. L., Mehra, R., Parthasarathy, S., Quan, S. F., Redline, S., Strohl, K. P., Ward, S. L. D., & Tangredi, M. M. (2012). Rules for Scoring Respiratory Events in Sleep: Update of the 2007 AASM Manual for the Scoring of Sleep and Associated Events. Journal of Clinical Sleep Medicine, 8(5), 597–619. https://doi.org/10.5664/jcsm.2172
  13. ^ Huang, Y.-S., Chen, N.-H., Li, H.-Y., Wu, Y.-Y., Chao, C.-C., & Guilleminault, C. (2004). Sleep disorders in Taiwanese children with attention deficit/hyperactivity disorder. Journal of Sleep Research, 13(3), 269–277. doi:10.1111/j.1365-2869.2004.00408.x
  14. ^ Amiri, S., AbdollahiFakhim, S., Lotfi, A., Bayazian, G., Sohrabpour, M., & Hemmatjoo, T. (2015). Effect of adenotonsillectomy on ADHD symptoms of children with adenotonsillar hypertrophy and sleep disordered breathing. International Journal of Pediatric Otorhinolaryngology, 79(8), 1213–1217. doi:10.1016/j.ijporl.2015.05.015
  15. ^ a b c d e f "Upper Airway Resistance Syndrome (UARS)". Stanford Medicine. Retrieved February 28, 2017.
  16. ^ a b c Exar EN, Collop NA (Apr 1999). "The upper airway resistance syndrome". Chest. 115 (4): 1127–39. doi:10.1378/chest.115.4.1127.
  17. ^ Guilleminault, Christian and Khramtsov, Andrei. (December 2001). “Upper airway resistance syndrome in children”. Seminars in Pediatric Neurology: 207-215 - via Elsevier.
  18. ^ Brunetto DP, Sant'Anna EF, Machado AW, Moon W (2017). "Non-surgical treatment of transverse deficiency in adults using Microimplant-assisted Rapid Palatal Expansion (MARPE)". Dental Press J Orthod. 22 (1): 110–125. doi:10.1590/2177-6709.22.1.110-125.sar. PMC 5398849. PMID 28444019.CS1 maint: multiple names: authors list (link)
  19. ^ "Comparison of dimensions and volume of upper airway before and after mini-implant assisted rapid maxillary expansion". https://meridian.allenpress.com/angle-orthodontist/article/90/3/432/430028/Comparison-of-dimensions-and-volume-of-upper