Potential clues emerge in caring for the most complex sleep apnea cases

Researchers at the CPAP Alternatives Clinic are exploring new methods and recent records in an effort to bring greater clarity to the diagnoses and treatment protocols for sleep apnea.

Almost everyone who’s referred to the CPAP Alternatives Clinic at the Penn Sleep Center has been found to be intolerant of continuous positive airway pressure (CPAP) or bilevel positive airway pressure (BIPAP) therapy. With the exception of a small minority of individuals who are diagnosed and treated independently, all patients at the Clinic undergo a drug-induced sleep endoscopy, or DISE, test. As treatments for obstructive sleep apnea (OSA) have expanded significantly in recent years, DISE has become the main test that’s used to determine the most effective option for patients.

Julianna Grace Rodin, MD, is an Assistant Professor of Otorhinolaryngology - Head and Neck Surgery at the Hospital of the University of Pennsylvania and the Codirector of the CPAP Alternatives Clinic. Overall, she says, the Clinic's sleep medicine specialists are relatively accurate in diagnosing the clinic’s patients, whose conditions can be exceptionally complex. They also establish treatment recommendations even as key aspects of their conditions, such as what’s driving airway collapse, the principal cause of OSA, remain unknown.

However, DISE is not foolproof. In a 2023 study conducted by Dr. Rodin and Raj C. Dedhia, MD, MSCR, Director of the Penn Division of Sleep Surgery and Codirector of the CPAP Alternatives Clinic, nearly half of the 103 patients who underwent a DISE experienced a sentinel or initial central or mixed apnea event during the procedure rather than solely obstructive events. This leads Drs. Rodin and Dedhia to believe that scoring could be inaccurate in a significant number of cases if used at the wrong time.

Can DISE assessments be improved?

For these reasons, Clinic specialists continue to explore additional avenues for assessing clinic patients, including having them undergo a CT scan prior to their DISE. The imaging may help them detect predictors of where and how the airway is going to collapse. In fact, Dr. Rodin has observed that an airway whose width and depth exceed a 1:1 ratio may indicate the patient experiences complete concentric collapse at the velum or complete lateral wall collapse at the tonsil lateral wall region.

“Both have been shown to be negative predictors of certain surgical interventions, especially Inspire,” Dr. Rodin observes, referring to Inspire, an implant that delivers pulses that move the tongue out of the way with each breath during sleep.

Historically, she says, the Clinic has deferred to educating these patients on active treatments, believing that this population would not benefit from surgical interventions. However, while there are exceptions to this, there is still no reliable way to understand which patient characteristics would make them an ideal candidate for surgery.

Additionally, Dr. Rodin and her fellow researchers are using epiglottic catheters to measure airway pressure and have shown that patients with abnormal airway ratio display higher than normal pressure, or effort during breathing. The combination of the CT scan and epiglottic catheters is helping to identify which patients may need more complex treatments.

Correcting for an often-misdiagnosed form of sleep apnea

Separately, Dr. Rodin has begun an extensive review of patient records who underwent hypoglossal nerve stimulator (Inspire) implantation, spanning the last five years and multiple surgeons in the department, including herself. She is revisiting their pre- and post-op studies and rescoring their DISE data to see if any of the patients had central sleep apnea pre- or post-op or a condition called treatment-emergent central sleep apnea, or TECSA.

Central sleep apnea is different from obstructive sleep apnea, although it 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, even as there’s partial or no airflow. In other words, Dr. Rodin says, patients are trying to breathe but cannot because there is an obstruction from above.

Central sleep apnea affects less than one percent of the general population, although it accounts for about five to 10 percent of patients treated by sleep clinics. In a recent study, Dr. Rodin says she determined that 10 percent of the patients who were referred to the CPAP Alternatives Clinic at the time had undiagnosed central sleep apnea.

TECSA is a condition where central sleep apnea develops during treatment of someone with obstructive sleep apnea. It can resolve within a few months of continued treatment or after different interventions.

Dr. Rodin says the objective of this latest study is to better identify patients with central sleep apnea, which can be easy to miss and misdiagnose, and then attempt to determine whether the treatment protocol should be revised. Because it is not an upper airway phenomenon, it typically cannot be treated surgically.

She is also looking for markers among the data that indicate that patients with obstructive sleep apnea did not benefit from the Inspire implant, which could potentially enable her to refine, or expand upon, the Clinic’s assessment protocol.

Additionally, Dr. Rodin is in the early stages of yet another study to discern whether patients breathe in the same fashion during their DISE as they do during the in-lab sleep study that’s usually performed beforehand. “Basically, is what we’re seeing in the lab and during the DISE in line with what they’re experiencing at home?” Dr. Rodin says. “If their route of breathing changes, it can really affect what their airway looks like, which means we’re not making an accurate assessment.”

She anticipates gaining insight into what percentage of the population is nasal breathers versus mouth and combination breathers, another potential marker that could have bearing on treatment protocols.

“We’ve seen that, for the most part, we should be nasal breathers. But we’ve also seen that there are people who have such high nasal resistance that they truly cannot breathe well through their nose,” Dr. Rodin says. “In those patients, even just optimizing oral breathing might be the best treatment option.”

Clinical consult and patient referral

Julianna Grace Rodin, MD, and Raj C. Dedhia, MD, MSCR, see patients at Penn Medicine Otorhinolaryngology - Head and Neck Surgery in Philadelphia, PA.

For a provider-to-provider consultation with the team at the Penn Aorta Center, please call 877-937-7366, or refer a patient online.