Paul R. Lambert, MD

Professor and Chair

Obstructive sleep apnea (OSA) is a highly prevalent disorder contributing to significant medical morbidity, sleep disturbance, impaired quality of life, and an increased risk of motor vehicle accidents. Moderate or severe disease may affect greater than 7% of the adult population.¹ It results from the interaction of an anatomically smaller and more vulnerable upper airway, loss of physiologic compensation, and reduced upper airway muscle dilation during sleep. Currently, the first line therapy for moderate to severe OSA is the use of positive airway pressure which acts as an upper airway stent to maintain the patency of the upper airway during sleep. Nasal CPAP (continuous positive airway pressure) demonstrates high efficacy in treating OSA. However, the effectiveness of CPAP is limited by poor patient acceptance with long-term adherence rates of only 50-70%.² As a result, alternative therapies are required as salvage treatment for many individuals with symptomatic OSA who fail CPAP therapy.

One historical alternative to treat OSA is surgery. Surgical procedures either bypass the obstructed upper airway or attempt to reduce the structural vulnerability of the upper airway. Tracheotomy bypasses the upper airway for patients with life-threatening OSA, however long-term tracheotomy-related morbidity make it unacceptable for most routine cases of OSA. In contrast multiple surgical procedures have been developed that modify soft tissues surrounding the pharynx either by tissue reduction (ex. tonsillectomy, UPPP, partial glossectomy) or tissue stabilization and advancement (ex. maxillomandibular advancement, genioglossal advancement, hyoid suspension, tongue suspension). Acceptance is variable due to side effects and lack of high quality data on effectiveness for many procedures.³ An alternative surgical approach to treat OSA is therefore desired.

Electrical stimulation of the hypoglossal nerve has been proposed as a physiologic method to maintain upper airway patency. Whereas traditional surgical approaches irreversibly alter the tissue of the upper airway, hypoglossal nerve stimulation augments tone to the upper airway to maintain airway patency. Pre-clinical studies found that stimulation of the hypoglossal nerve reduced upper airway collapsibility in an animal model.⁴ Early feasibility studies in humans showed that stimulation could increase maximal inspiratory airflow during sleep by 100% without causing an awakening.⁵ An initial phase I trial of a first-generation device in 8 patients showed a significant decrease in the apnea-hypopnea index (AHI), however the device was prone to malfunction over time.⁶ A recent phase II trial of a second generation device (Upper Airway Stimulation (UAS) system, Inspire Medical Systems, Minneapolis, MN, USA) demonstrated a high-rate of physiologic resolution of apnea (78% of patients with a 50% reduction in AHI and overall AHI<20) with significant improvements in daytime sleepiness and sleep-related quality of life in successfully treated patients.⁷ Activation of the device during sleep prevents pharyngeal collapse and maintains airway patency throughout the respiratory cycle (Figure).

Figure: A collapsed hypopharyngeal airway (left) opens with stimulation of the hypoglossal nerve (right).

A large scale phase III study (STAR Trial, Inspire Medical Systems, Minneapolis, MN, USA ) of 124 patients completed in early 2013 demonstrated promising results and will be published in the medical literature soon. Five of the six patients (83%) surgically implanted at MUSC were considered a success and continue to use the device on a regular basis. The device is currently under consideration of approval with the FDA, and may be available to the public as a viable option for moderate-to-severe obstructive sleep apnea in CPAP failures as early as 2014.

REFERENCES:

1. Young T, Palta M, Dempsey J, Peppard PE, Nieto FJ, Hla KM. Burden of sleep apnea: rationale, design, and major findings of the Wisconsin Sleep Cohort study. WMJ. 2009;108(5):246-9.

 

2. Richard W, Venker J, den Herder C, et al. Acceptance and long-term compliance of nCPAP in obstructive sleep apnea. Eur Arch Otorhinolaryngol. 2007; 264: 1081-86. 

 

3. Caples SM, Rowley JA, Prinsell JR, et al. Surgical modification of the upper airway for obstructive sleep apnea in adults: a systematic review and meta-analysis. Sleep 2010; 33: 1396-407.

 

4. Smith PL, Eisele DW, Podszus T, et al. Electrical stimulation of the upper airway musculature. Sleep 1996; 19 (10 Suppl.): S 284-7.

6. Schwartz AR, Bennett ML, Smith PL, et al. Therapeutic electrical stimulation of the hypoglossal nerve in obstructive sleep apnea. Arch Otolaryngol Head Neck Surg. 2001; 127: 1216-23.

7. Van de Heyning PH, Badr MS, Baskin JZ, et al. Implanted upper airway stimulation device for obstructive sleep apnea. Laryngoscope 2012; 122: 1626-33.