This study aims to determine the overall accuracy, sensitivity, and specificity of the Belun Ring device in evaluating obstructive sleep apnea by comparing the device to the attended overnight in-lab polysomnography which is the gold standard for diagnosis of obstructive sleep apnea. Our hypothesis is that the Belun-Ring, a type 4 portable monitoring device, is overall sensitive and specific for evaluation of obstructive sleep apnea when compared to the attended overnight in-lab polysomnography.

This study will include all patients who are scheduled to do an attended overnight in-lab polysomnography in 2 sleep labs owned by University Hospitals Cleveland Medical Center. These patients will receive email recruitment forms 2 weeks prior their scheduled polysomnography. Whether they are interested or not, patients are supposed to call or email the study's central contact person. Both phone number and email address of the central contact person are noted in the email recruitment form. For those patients who did not make any contact with the study's central contact person, they will be screened for eligibility by sub-investigators through chart review. List of eligible patients will be sent to the central contact backup person who is basically in-charge of making phone calls to the patients. This person will further confirm patients' eligibility over the phone and ask if they are interested. If a patient is interested, the central contact backup person will inform the sub-investigators who, in turn, will assign a unique patient identifier to the interested subject and inform the sleep lab contact person. The sleep lab contact person will, in turn, inform the sleep technicians on-call ahead of time about the list of interested subjects. On the night of the polysomnography testing of the interested subject, the latter will receive questionnaires and written informed consent form related to the study which will be explained by the sleep technician. After the subject had completed and signed the questionnaires and written informed consent form respectively, the sleep technician will apply the Belun Ring device on the patient as well as the electrodes and sensors included in a routine polysomnography. The following day, data from Belun Ring device will be uploaded to the laptop while another sleep technician will read the polysomnography. Sub-investigators will enter the data from the questionnaires, Belun Ring device, and polysomnography in the secured University Hospitals Redcap (UHRedcap). Once the target number of subjects are reached, all data will be sent to statistician for analysis.

Inclusion Criteria:

• All adult patients age 18-80 years old scheduled for overnight in-lab sleep study
• Provision of signed and dated written informed consent form

Exclusion Criteria:

• Recent hospitalization in the past 30 days
• Patients on home oxygen, non-invasive ventilator, diaphragmatic pacing, or any form of nerve stimulator
• Patients with pacemaker, defibrillator, left ventricular assist device (LVAD), or status post cardiac transplantation
• Patients with baseline heart rate under 50 bpm or over 100 bpm during last clinic visit or prior to study at the sleep lab
• Patients with unstable cardiopulmonary status judged to be unsafe for sleep study by the sleep technician and/or the on-call sleep physician in the sleep lab on the night of the study
• Patients who are unable to complete the required study
• Patients involved in another investigational study
• Pregnant women

subjects that are eligible and willing to be consented to participate in the study and whose length of data recording is sufficient for Belun Ring Analysis

2 months