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Implanted system to treat obstructive sleep apnea found effective in clinical trial

By Lindy Keane Carter
Illustration by Joel Nakamura

sleep apnea imagePhysicians treating patients with moderate-to-severe obstructive sleep apnea (OSA) likely will have a new treatment option at MUSC by fall 2014 when the U.S. Food and Drug Administration (FDA) is expected to give final approval of an implanted device that stimulates a tongue nerve to open the airway during sleep. MUSC sleep disorder specialists participated in the 2011/2012 Stimulation Therapy for Apnea Reduction (STAR) trial (NCT01161420), which found the device effective in treating OSA. The full STAR results were reported in the January 9, 2014 issue of the New England Journal of Medicine.1 Among the 126 people who received the device in the U.S. and Europe, the median apnea-hypopnea index (AHI) (the number of apnea or hypopnea events per hour) decreased 68%. The oxygen desaturation index (ODI) (the number of times per hour of sleep that the blood oxygen level drops by four or more percentage points from baseline) decreased 70%.

M. Boyd Gillespie, M.D., MSc, a Professor in the Department of Otolaryngology-Head and Neck Surgery, was the MUSC principal investigator. Dr. Gillespie, who is board certified in otolaryngology and sleep medicine, specializes in sleep-disordered breathing and other disorders of the upper airway. During the trial, he implanted six patients with the system, which consists of a pulse generator in the right shoulder area, a sensing lead between the internal and external intercostal muscles, and a stimulation electrode on the hypoglossal nerve. The sensing lead monitors respiration, and, when it detects an airway obstruction, sends a signal to the pulse generator, which stimulates the hypoglossal nerve. Stimulation of this nerve improves the tongue’s tone and repositions it, opening the airway. In all patients, this system decreased the AHI and ODI.

Moderate-to-severe OSA is defined as an AHI of at least 15 episodes per hour, which equates to about one episode of apnea or hypopnea every four minutes.1 During a sleep apnea episode, the upper throat muscles collapse, obstructing the airway. OSA interferes with sleep, obviously, but it also reduces the flow of oxygen to vital organs and can cause irregular heart rhythms. Aging increases the risk for OSA, as does being overweight. According to Dr. Gillespie, 24% of men in their mid-40’s and 50’s and 9% of women in that age range have at least mild OSA. But in South Carolina, because of the state’s high obesity rates, OSA is more prevalent. Dr. Gillespie estimates that of the state’s 2.5 million adults, approximately 20% overall (men and women combined) experience OSA.

OSA is associated with depression, high blood pressure, cardiovascular diseases, stroke, diabetes, workplace accidents, and auto accidents. It is as powerful a risk factor for heart disease and stroke as obesity, hypertension, a strong family history of heart disease, smoking, and high cholesterol. Moderate-to-severe OSA can even result in death in untreated patients. “We do know that cardiac arrhythmias are more likely to occur if someone has trouble with oxygenation,” Dr. Gillespie says. “Certainly sleep apnea could trigger a fatal cardiac arrhythmia. It’s not common, but there have been cases of this.”

Currently, the most effective treatment is Continuous Positive Airway Pressure (CPAP), an air pump and mask system that keeps the airway open, but 29% to 83% of patients fail to remain on this therapy long-term2 due to discomfort, nasal blockage, claustrophobia, and other factors. Other therapies include medications, oral appliances, and surgery, but these are generally found to be less effective. An analysis of the effectiveness of oral appliances in OSA showed them to be a viable alternative to CPAP in patients with moderate OSA, but in patients with severe OSA, CPAP was more effective.3 As for surgery, the procedure involves removal of the tonsils and uvula and the reshaping of the palate in conjunction with a procedure to remove tissue from the tongue or to reposition it. This treatment has high complication rates, creates scar tissue, and can change speech or swallowing. Dr. Gillespie notes that while surgery can reduce sleep apnea, it rarely eliminates it.

sleep apnea illustrationClinical Trial Methods

The STAR trial was designed by the sponsor (Inspire Medical Systems, Maple Grove, MN), the investigators, and the FDA as a multicenter, prospective, single-group trial with participants serving as their own controls. It included 126 patients, 83% of whom were men. The mean age was 54.5 years and the mean body-mass index (BMI) was 28.4. All participants had a history of nonadherence to CPAP therapy and 17% had undergone a uvulopalatopharyngoplasty for the treatment of OSA. The upper-airway stimulation device was successfully implanted in all participants with a median surgical time of 140 minutes. Ninety-five percent of the U.S. participants were discharged on the same or following day. In the study, 18% of participants experienced temporary tongue weakness, which resolved within a few days or weeks. The overall rate of serious adverse events was less than 2%.

The MUSC Upper Airway Stimulation team consisted of Dr. Gillespie and a sleep laboratory technologist who operated the device in the sleep laboratory. Follow-up visits occurred at two, six, and 12 months. Dr. Gillespie has reported that all six patients continue to use the device nightly and are pleased to finally be free of the CPAP mask.

As soon as the FDA approves the device, the MUSC team will be ready to accept patients. Good candidates will be people with moderate-to-severe OSA who have had a trial of CPAP for three to six months and have not done well with that therapy. Candidates also must have a BMI of 32 or lower. Age is a consideration, too. “There’s some evidence that sleep apnea is not as life-threatening in senior citizens as it is in younger populations,” Dr. Gillespie says. So, the best population to implant will be people in their 40’s and 50’s. Total treatment time—from preoperative evaluation to device activation—is expected to be two months. Patients should also expect another surgery on the chest wall in ten years to replace the device’s battery, which is performed under local anesthesia.

MUSC offers comprehensive treatment for all sleep-related disorders through the MUSC Snoring Clinic. The team includes Dr. Gillespie, a medical sleep specialist, a dental sleep specialist, and a facial plastic surgeon. Patients receive an assessment, a treatment strategy, and ongoing reassessment of their condition and progress.

References

1 Strollo, PJ, Soose, RJ, et al. Upper-airway stimulation for obstructive sleep apnea. N Engl J Med 2014;370:139-49.

2 Rosenberg R, Doghramji P. Optimal treatment of obstructive sleep apnea and excessive sleepiness. Adv Ther 2009 Mar;26(3):295-312.

3 Doff MH, Hoekema A, et al. Oral appliance versus continuous positive airway pressure in obstructive sleep apnea syndrome: a 2-year follow-up. Sleep 2013 Sep 1;36(9):1289-96.