Dr. K K Aggarwal, President Heart Care Foundation of India and Group Editor in Chief MEDtalks, will explain overnight pulse oximetry in details in this video. Many a times, the patient’s overnight oxygen desaturation needs to be checked. It is generally done in patients with asthma, sleep apnea, COPD, heart failure, etc. and check for more than 4% desaturation. If the patient has more than 10 levels of desaturation levels in an hour then it is a positive desaturation index.