As treatments for obstructive sleep apnea (OSA) have expanded significantly over the last few years, drug-induced sleep endoscopy, or DISE, has become the main test used to determine the most effective option for patients. DISE is performed to visualize a patient's airway and airway collapse while asleep, which serves as a guide for treatment planning in adults who fail or cannot tolerate continuous positive airway pressure (CPAP) therapy. Vital as the test has proved to be, however, DISE may contain elements that could potentially bias surgical decision-making, according to a new study by members of the Penn Sleep Surgery Program.
OSA is the most common sleep-related breathing disorder. It occurs when upper airway muscles and tissues collapse and block the airway, causing people to stop breathing and desaturate many times during sleep.
CPAP, which uses continuous positive air pressure to keep upper airways open during sleep, has long been considered the gold standard of OSA treatment. However, says Julianna Grace Rodin, MD, an author of the Penn study, "many patients really struggle with CPAP. Fortunately, there's now a lot we can do to help them, from nasal surgery to improve CPAP tolerance, to hypoglossal nerve stimulators, to palate, tonsil, and skeletal surgery."
A team of researchers led by Raj C. Dedhia, MD, MSCR, Director of the Penn Division of Sleep Surgery and the CPAP Alternatives Clinic at the Penn Sleep Center, has helped standardize treatment protocols for sleep apnea based upon data collected during a DISE.
The majority of individuals referred to the CPAP Alternatives Clinic have either failed or present with intolerance to CPAP or bilevel positive airway pressure (BIPAP) therapy. Most will undergo a DISE (with the exception of a small minority who are diagnosed and treated without the test). The setup at Penn, Dr. Rodin says, is much like a home sleep study, in that physicians can see airflow, respiratory effort, and oxygen levels while the patients are sedated with propofol.
Dr. Rodin grants that most physicians administering a DISE do not have access to the advanced monitoring equipment available at Penn. However, the tabulation of a score through a system called the VOTE classification is universal during DISE. Separately or in combination, the Velum, Oropharynx, Tongue base, and Epiglottis (VOTE) have been found to collapse and contribute to OSA. At each location, a score of zero to two is assigned based on the degree of obstruction, with zero equating to no obstruction, one to a partial obstruction, and two to a total obstruction. This score is generally used to determine the appropriate course of treatment.
But Dr. Rodin and her colleagues have reason to believe that the VOTE score could be inaccurate in a significant number of cases if used at the wrong time during the DISE.
Differences in Sleep Event Types - Central vs Obstructive Sleep Apnea
Obstructive sleep apnea is different from central sleep apnea, which also causes breathing to repeatedly stop during sleep. With a central event, there's no respiratory effort when the breathing stops. It is often associated with another condition, such as heart failure or stroke. That's in contrast to OSA, where there is respiratory effort in the chest or abdomen, but partial or no airflow. "In other words, individuals are trying to breathe, but they can't because there's an obstruction from above," Dr. Rodin says.
Accurately defining the differences in these breathing events during DISE is vital to accurate diagnosis and the avoidance of scoring sentinel central events—a finding noted in a recent study for which Dr. Rodin was an investigator.
In this study of 103 OSA patients, Dr. Rodin and colleagues found that nearly half experienced a sentinel central or mixed apnea event instead of solely obstructive events.
"This could potentially mean that we, as sleep surgeons, are scoring these central events as obstructive when they're not," says Dr. Rodin, who presented the findings at the Best of Scientific Orals at the American Academy of Otolaryngology–Head and Neck Surgery 2023 Annual Meeting. The sentinel central events, or 'Scents,' also often had different VOTE scores than the obstructive events, thus possibly leading providers down the wrong treatment path.
"We saw that the central events that happened had more tongue-based collapse versus those that were obstructive," she adds. "That might lead other providers to do more Inspire implantations," a reference to Inspire Upper Airway Stimulation therapy, a Food and Drug Administration-approved alternative OSA treatment. In order for a patient to qualify for Inspire, an implantable device, they need to undergo a DISE and display a specific collapse pattern.
"If providers aren't aware of respiratory effort, or if they don't have the same airflow and respiratory metrics and monitoring that we have, they may be scoring the wrong events," Dr. Rodin says. "We think it's important for them to at least be watching the chest and abdomen as they score events."
Digging deeper into central sleep apnea
Dr. Rodin is currently completing a fellowship at Stanford University, and will return to Penn Medicine in 2024. Upon her return to Penn, Dr. Rodin is interested in further exploring central sleep apnea beyond the parameters of this study.
"We've anecdotally noticed that a fair number of clinic patients have some characteristics indicative of central sleep apnea," she says. "Maybe they don't snore as much, or they have significant cardiac history. We then order a new sleep study and often diagnose them with central sleep apnea. At which point, we have to inform them that we can't necessarily operate on them, but we can still help them and direct them in the right way."
She plans to begin by analyzing the medical records of the clinic's newest patients to determine what portion of them were diagnosed with central sleep apnea at the clinic.