Effect of Upper Airway Stimulation on Vascular Function in Obstructive Sleep Apnea

This study will evaluate the effect of hypoglossal nerve stimulation (HGNS) on different measures of cardiovascular function in patients with obstructive sleep apnea (OSA). People with OSA who have undergone implantation of the hypoglossal nerve stimulator at the study site will be told about the study at their 2-week post-operative appointment. Those who decide to participate will have blood drawn and vascular function measurements taken before HGNS activation, during treatment, and after a temporary treatment withdrawal period. Following the 30-day period of treatment withdrawal, the HGNS therapy will be reactivated.

Obstructive sleep apnea (OSA), the repetitive collapse of the upper airway during sleep, represents a growing individual and public health concern. This disease negatively impacts patients' sleep quality and daytime function, including an increased risk of motor vehicle accidents. Several large, longitudinal cohorts have consistently demonstrated deleterious effects of OSA on cardiovascular health, including elevated rates of incident hypertension, myocardial infarction and cerebrovascular accidents. The link between OSA and cardiovascular consequences can be largely explained by autonomic imbalance during repeated episodes of nocturnal airway obstruction. Compared to those without OSA, people with OSA have increased sympathetic activity when awake, with further elevation of both sympathetic activity and blood pressure during sleep. Multiple physiologic mechanisms are responsible for these autonomic changes during obstructive episodes including the interaction of baroreceptors, chemoreceptors and respiratory afferent receptors.

Positive airway pressure (PAP) serves as a pneumatic stent for the airway, maintaining airway patency and normoxia. PAP therapy has demonstrated consistent, meaningful reductions in sympathetic overactivity during wake and sleep. Although PAP therapy is highly efficacious, fewer than 50% of patients are adequately treated due to adherence difficulty. In 2014, the Federal Drug Administration approved hypoglossal nerve stimulation (HGNS) for the treatment of patients with moderate-severe OSA who are unable to adequately use PAP. This therapy has demonstrated stable, marked improvement in key polysomnography indices, sleepiness measures and functional outcomes, however, no study has examined cardiovascular endpoints of HGNS therapy in OSA patients.

The aim of this study is to evaluate the effect of HGNS therapy on autonomic and vascular function before, during and after treatment for OSA with HGNS. People who have undergone implantation of the hypoglossal nerve stimulator at the study site will be told about the study at their 2-week post-operative appointment. Those who decide to participate in the study will have blood drawn and vascular function measurements taken before the HGNS device is activated, during treatment, and after a temporary treatment withdrawal period. The researchers hypothesize that all aforementioned measurements will be significantly improved following HGNS therapy and return to baseline values following a therapy withdrawal period.

Eligibility Criteria:
Inclusion Criteria:

* English-speaking
* Able to give informed consent
* Have undergone implantation of hypoglossal nerve stimulator (HGNS) by the principal investigator of this study. HGNS inclusion criteria per FDA are as follows:

  * Apnea-hypopnea index (AHI) of 20 or more from recent sleep test
  * Unable to use positive airway pressure therapy
  * Body Mass Index (BMI) \< 32 kg/m2
  * Without circumferential collapse on drug-induced sedated endoscopy

Exclusion Criteria:

* Active smokers
* Unstable and untreated coronary or peripheral artery disease
* Use of alpha-blockers
* Severe and inadequately controlled arterial hypertension