Screening Moderate to Severe Obstructive Sleep Apnea With Wearable Device

The goal of this study is to find the best method to use Wellue O2 ring to screen for moderate to severe obstructive sleep apnea. The method that investigators use to screen for moderate to severe obstructive sleep apnea is oxygen desaturation index(ODI). The main questions of this study are 1. What is the best ODI to screen for moderate to severe obstructive sleep apnea? 2. What are the sensitivity, specificity and AUC of the study? In this study, participants are recruited from Sleep center of Thammasat prior to polysomnography. All participants in this study will 1\. Undergo polysomnography according to Sleep center of Thammasat protocol 2. Wear Wellue O2 ring when undertaking polysomnography If the polysomnography is switch to PAP titration Wellue O2 ring will be taken out. Data of Oxygen data from Wellue O2 ring are collected and compared with AHI. Investigators will find the best ODI to screen for obstructive sleep apnea.