Understanding Sleep Architecture Can Aid Diagnosis

The patients had a mean age of 47.5 years, 70% were male, and the population had a mean body mass index (BMI) of 30.2. The sleep study showed the patients had a mean Epworth score of 10.6; a mean apnea-hypopnea index (AHI) of 21.4, and a mean respiratory disturbance index (RDI) of 33.4. The mean snoring severity score was 4.9.

Of this cohort, 70 percent went on to receive a diagnosis of obstructive sleep apnea, Kleinberger said. Sleep architecture was impaired in this group, too. Compared to normative data from the Sleep Heart Health Study, our cohort experienced significantly more light sleep, less slow-wave sleep, and less REM sleep. These differences were highly significant, he said.

In brief, age, Epworth score, and snoring score were the most significant predictors of impaired sleep architecture. Not surprisingly, AHI and RDI also correlated with impaired sleep architecture.

If a clinician encounters a patient in the office with vague sleep complaints, he or she should consider ordering a sleep study if [any of] the following is present: older age, high Epworth score, or high snoring severity score. It’s these patients who will be more likely to display impaired sleep architecture, he said.

Mr. Kleinberger noted (this was not part of the study), Seventy-two patients with obstructive sleep apnea underwent UPPP [uvulopalatoplasty], and sleep studies before and after that. And they were found to have improved sleep architecture after UPPP.

Real-Time MRI Shows Obstruction in Action

When it comes to knowing just how severe a patient’s apnea is and what happens during an event, it is always good to be able to see the anatomy. Even better is being able to measure arousals and relating that to what is happening at the site of obstruction. Combining real-time (RT) MRI (which is excellent at showing soft tissue dynamic obstruction) with peripheral arterial tone (PAT) may be the answer. Watch-PAT detects and records arousals from sleep, and RT-MRI is a real-time imaging acquisition program using MRI to acquire up to 33 frames per second.

Jose Barrera, MD, an instructor of sleep surgery and facial plastic surgery at Stanford University, presented findings from a preliminary study to determine just how well RT-MRI combined with autonomic measures during natural sleep could predict the precise site of obstruction in OSA patients.

A prospective study of 17 OSA patients was performed to demonstrate the feasibility of this technique. They were all OSA patients with a mean BMI of 27.5, and had a mean AHI of 36.8 events per hour. For the study, patients underwent continuous RT-MRI monitoring during a 90-minute nap without sedation, their upper airways were visualized in real-time, and Watch-PAT measurements were attained at the same time.