Upper Airway Resistance Syndrome (UARS) - by Eric Falcon, MD
As you may know, if you've already been diagnosed with this condition, UARS mimics 'sleep apnea' (otherwise known as obstructive sleep apnea), because the symptoms are nearly identical, namely excessive daytime drowsiness and difficulty with early morning arising. Snoring is also a very common symptom that is often present in both UARS as well as sleep apnea.
Sleep apnea differs from UARS however, in that it is characterized by periods of 'apnea' or 'hypopnea' which happen frequently throughout the night, as demonstrated in the standard polysomnogram (also commonly referred to as a sleep study). ‘Apnea' means that the sufferer experiences episodes where little or no air exchange occurs when attempting to breath while asleep, typically due to the tongue and other soft tissues relaxing and collapsing down into the back of throat and restricting air movement. This is the "obstructive" part of the term "obstructive sleep apnea." Poor oxygenation during sleep causes the body and brain to experience fatigue the next day.
Although the symptoms among sleep apnea and UARS patients are similar, UARS does not entail significant findings of apnea or hypopnea, as demonstrated in a standard sleep study. Nor does UARS typically involve the tongue causing obstruction by collapsing down into the back of the throat, as happens with sleep apnea. Nonetheless, the impaired breathing of UARS, the cause of which up until now has not been fully understood in the medical community, involves decreased ventilation and oxygenation during the night which leads to a disrupted sleep pattern.
These sleep disruptions come in the form of mini-arousals (or mini waking periods) which may be observed and measured on an electroencephalogram (or EEG), which is an instrument that is used during conventional sleep studies. Again like sleep apnea, the result of the sleep disruptions and poor oxygenation during UARS is that the body and brain experience fatigue the following day.
When a patient who undergoes a sleep study is diagnosed with UARS instead of sleep apnea, many doctors will suggest that the patient consider a trial of the typical treatments for sleep apnea anyway, such as CPAP, palate surgery, or oral appliances. These treatments are not always effective for UARS however, and there are often reimbursement challenges with these treatments for UARS when dealing with many insurance companies, due to the absence of the actual diagnosis of sleep apnea.
The discovery and history of UARS: A physician and researcher at the prestigious Stanford University Sleep Medicine Program, Dr Christian Guilleminault, who is also a French citizen, is credited with bringing UARS to light within the medical community. Dr Guilleminault has been a researcher in the field of sleep medicine from the 1970's until the present day. He was the first to recognize the 'sleep-disordered breathing' condition which he termed 'UARS', in a series of medical journal articles that he wrote and published with his co-authors in the early 1990's. The phrase sleep-disordered breathing refers to a group of related conditions that includes snoring, UARS, and sleep apnea, among others.
A seminal article on UARS is "A cause of excessive daytime sleepiness: The upper airway resistance syndrome", which Dr Guilleminault co-published in the journal Chest. This is the official journal of the American College of Chest Physicians, and the article may be found in the 1993; 104 volume of Chest, on pages 781-787. A link where you can read this online if you're interested is located at: http://www.chestjournal.org/cgi/reprint/104/3/781 .
Prior to Dr Guilleminault's published findings, patients who suffered from symptoms of UARS were commonly labeled by their physicians as "idiopathic hyersomniacs", which is a medical term for patients who are excessively tired during the daytime, but for which the underlying cause is unknown. A common treatment for such patients had been the use of "stimulants," such as amphetamines.
Dr Guilleminault admitted that stimulants had a role in the temporary treatment of tiredness that was truly "idiopathic," and not due to any discernable underlying causes. However, he advocated that the use of stimulants was not ideal for the long-term treatment of patients diagnosed with sleep-disordered breathing conditions.
Early in his research on UARS, Dr Guilleminault performed studies on a group of patients who had been labeled as "idiopathic hypersomniacs" by their doctors. Dr G. found that a sub group of these patients displayed numerous very short arousal periods during the sleep studies which he performed on them. He found that these arousal periods correlated with an abnormal increase in respiratory efforts during sleep. In other words, he noticed that this sub group of patients labored to take deeper breaths shortly before their mini waking periods. He determined this through the use of a device which measures the esophageal pressures of his patients. The esophagus is the tube which carries your food from the back of your throat down to your stomach, when you swallow food. Dr G. found that the mini arousals were preceded by a peak in the inspiratory esophageal pressure.
To this day, many sleep specialists, when they discuss UARS with their patients, will mention that "esophageal pressure monitoring" (abbreviated Pes), combined with a sleep study, is necessary for definitively diagnosing UARS. This comes from Dr G.'s work and his discoveries regarding the characteristic rises in esophageal pressure which precede the transient night-time arousals in patient with UARS.
Nonetheless, esophageal pressure monitoring is not commonly used in sleep studies, and this measuring modality is rarely available, except perhaps for research studies like those which Dr G. conducted. Therefore, UARS is generally a "diagnosis of exclusion." The diagnosis is usually arrived at "presumptively" when a patient has symptoms of sleep apnea, but the sleep study reveals that no apnea episodes are actually present at night.
Regarding treatment, Dr G. suggested that some patients suffering from UARS might be successfully treated with nasal CPAP on a temporary basis, and that in some cases palate surgery might provide relief, as well. Ultimately though, he conceded that a universal, long-term cure for UARS had yet to be discovered.