Video imaging technique provides dynamic view of airway obstruction

A video imaging technique demonstrates that the soft palate, the tissue at the back of the roof of the mouth, is more elongated and angled in patients with obstructive sleep apnea both when they sleep and when they are awake, according to a report in the February issue of Archives of Otolaryngology-Head & Neck Surgery.

"Obstructive sleep apnea is a common form of sleep-disordered breathing characterized by repetitive episodes of partial or complete upper airway obstruction," the authors write as background information in the article. The condition usually causes breaks in sleeping, reduced blood oxygen levels and daytime sleepiness, and may contribute to cognitive (thinking, learning and memory) difficulties, psychosocial impairments, trouble driving, heart disease and death.

"The identification of the obstruction site of upper airway in patients with obstructive sleep apnea is essential in choosing the appropriate treatment, especially surgical intervention," the authors write. A variety of methods, including computed tomographic (CT) scanning or magnetic resonance imaging, have been used and previous studies conducted to identify changes in the upper airway of patients with this condition. However, most of the research has been performed when patients were awake or using techniques that produce static, non-moving images.

Chul Hee Lee, M.D., Ph.D., and colleagues at the Seoul National University College of Medicine, Seongnam, South Korea, used sleep videofluoroscopy-a method combining X-ray images with video recording to enable visualization of airway changes-to evaluate 63 consecutive patients. Of these, 53 were classified as having obstructive sleep apnea and 10 were diagnosed as "simple snorers." Participants underwent polysomnography at night and then sleep videofluoroscopy before and after sleep was induced by intravenous administration of the medication midazolam. Respiratory events lasting 15 seconds in which blood oxygen levels did not decrease (referred to as normoxygenation events), as well as any drop in blood oxygen levels of 4 percent or more (called desaturation sleep events), were recorded.

Desaturation sleep events were detected in all of the patients with obstructive sleep apnea but were not observed in simple snorers. When the patients were awake and breathing in, the length and angle of the soft palate increased in patients with obstructive sleep apnea but not in simple snorers; the soft palate also changed length and angle during desaturation sleep events. The sites of airway obstruction could be identified with the sleep videofluoroscopy during desaturation sleep events-the most common obstruction was mixed (soft palate plus tongue base, 43.5 percent) followed by soft palate (34 percent) and tongue base alone (22.5 percent).

"Sleep videofluoroscopy quantitatively showed that the soft palate was considerably elongated and angulated in patients with obstructive sleep apnea even in an awake state," the authors write. "It is an easy way to measure the soft palate changes and may be a useful technique to differentiate obstructive sleep apnea from simple snoring with short examination time."

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