Recognizing Upper Airway Resistance Syndrome- Prominent cause for Excessive Daytime Sleepiness and Fatigue
Upper Airway Resistance Syndrome (UARS) was first named by Guilleminault while investigating excessive daytime sleepiness with no identified cause in adults. 1 It appears that UARS is a part of the continuum between primary snoring and obstructive sleep apnea syndrome. Some researchers believe that it is a distinct syndrome from Obstructive sleep apnea-hypopnea syndrome (OSAHS). American Academy of Sleep Medicine considers UARS as a part of OSAHS.
UARS is a form of sleep-disordered breathing characterized by repeated arousals due to resistance to airflow in the upper airway that leads to excessive daytime sleepiness and fatigue. Although snoring has been noted to be present along with brief arousals, it is not necessary for the identification of the syndrome. There is no evidence of oxygen desaturation. UARS events are typically short: 1-3 breaths in duration. These events have been termed as respiratory effort-related arousals (RERA). Full polysomnography is necessary to diagnose this condition.
RERA- To identify RERA there must be a pattern of progressively increased negative oesophageal pressure that is terminated by a sudden change in the pressure to a less negative level and sleep arousal. This may be associated with change in posture in sleep. The RERA event must last for 10 seconds or longer.
Prevalence of UARS- In a study of more than 1000 volunteers in Brazil the prevalence of UARS in general adult population was 15.5 %.2 It is important to note that UARS occurs in less obese subjects, younger individuals and more commonly in women than men. (OSAHS is more common in adult men).
Pathophysiology- Guilleminault et al1 demonstrated that many non-apneic patients show a reduction in cross sectional area of the pharynx during sleep. Reduction in airway is sufficient to avoid apnea/hypopnea but enough to increase upper airway resistance. The presence of abnormal airway anatomy can also contribute to increased airway collapsibility. Increased airway resistance leads to arousals which is reflected in excessive daytime sleepiness. Nasal airway anatomical abnormalities like deviated nasal septum, inferior turbinate hypertrophy have been associated with UARS.3
Clinical Picture- The cardinal symptom of UARS is excessive daytime sleepiness and fatigue. Difficulty in concentration, morning headaches, difficulty in sleep onset, sleep maintenance and impotence are other manifestations. Sleep difficulties may present as insomnia. Administration of alcohol, hypnotics, sedatives can increase the severity of symptoms.
Diagnosis- The diagnosis of UARS requires high degree of suspicion in a clinical setting of excessive daytime sleepiness and fatigue, anatomic features consistent with upper airway narrowing and supportive polysomnographic findings. The Epworth Sleepiness Score must be greater than 10. It is now being increasingly recognized that the clinical features seen in UARS overlap with functional somatic syndromes such as chronic fatigue syndrome, chronic headache and fibromyalgia.An elevated EEG arousal index related to increased inspiratory effort is the specific measurement that distinguishes it from idiopathic hypersomnolence.4
The combination of i). clinical picture ii). increase in intensity of snoring before arousals iii). EEG arousals of more than 10 per hour of sleep associated with increased respiratory effort (usually made out by nocturnal oesophageal monitoring) iv. normal apnea-hypopnea index and clinical improvement with a short-term trial of nasal CPAP, can be regarded as supporting the diagnosis of UARS. An oesophageal pressure more negative than 10 cms H2O are abnormal. An association of alpha-delta sleep pattern (intrusion of wake alpha pattern into deep slow wave sleep) has been observed in patients with UARS.5 This phenomenon is also observed in some of the somatic syndromes mentioned but is not a feature of OSAHS.
Guilleminault and co-workers6 studied the relationship between sleep instability and subjective complaints in patients with UARS. It was observed that patients with UARS have higher electroencephalogram arousal indexes and important non-rapid eye movement sleep disturbances that correlated with subjective symptoms of sleepiness and fatigue. However, these disturbances are identifiable with sensitive measures such as cyclic alternative patterns and not with traditional diagnostic scoring systems.
Management- Patients usually respond well to nasal CPAP usage. Other options include upper airway surgery (nasal surgery, pharyngoplasty) and oral appliances. It is important to appreciate that whatever mode of therapy is employed, there must be relief in symptoms and produce normalized studies after therapy.
References
1.Guilleminault C, Stoohs R, Clerk A, Cetel M, Maistros P. A cause of excessive daytime sleepiness. The upper airway resistance syndrome Chest 1993; 104: 781-787.
2. Santos-Silva R, Tufik S, Conway SG, Taddel JA, Bittencourt LR. Sao Paulo Epidemiologic Sleep Study: rationale, design, sampling and procedures. Sleep Med 200910(6):679-685.
3.Chen W, Kushida CA. Nasal obstruction in sleep disordered breathing. Otolangol Clin North America 2003;36:437-460.
4. American Academy of Sleep Medicine Task Force. Sleep related breathing disorders in adults. Recommendations for syndrome definition and measurement techniques in clinical research. The report of American Academy of Sleep Medicine Task Force.Sleep 1999;22: 667-689.
5.Gold AR, Marcus CL,Dipalo F et al.Upper airway collapsibility during sleep in upper airway resistance syndrome. Chest 2002;121:1531-1540
6.Guilleminault C, Lopes CM, Hagen CC, Rosa A da. The cyclic alternating pattern demonstrates increased sleep instability and correlates with fatigue and sleepiness in adults with upper airway resistance syndrome. Sleep 2007;30(5): 641-7.
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