Oxygen saturation is described as the level of oxygen. It is the level of oxygen saturating the hemoglobin in blood. The normal range of oxygen saturation for a healthy adult is 94 to 99%. Patients with saturation levels lower than 90 require oxygen supplementation. The flow of oxygen is decided according to the saturation levels. Saturation levels can be tested by a pulse oximeter or arterial blood gas levels (ABGs). Conditions like COPD, Asthma, Heart failure, upper respiratory tract obstruction or poisoning can cause the blood saturation to fall. Management is to substitute oxygen and treat the cause.