Hypoxemia is a below-normal level of oxygen in your blood, specifically in the arteries. Hypoxemia is a sign of a problem related to breathing or circulation, and may result in various symptoms, such as shortness of breath. Hypoxemia is determined by measuring the oxygen level in a blood sample taken from an artery. It can also be estimated by measuring the oxygen saturation of your blood using a pulse oximeter.
Causes of hypoxemia include airway obstruction, anemia, ARDS, certain medications such as narcotics which depress breathing, congenital heart disease, COPD, Emphysema, high altitudes, etc.
Hypoxemia, Mayo Clinic (Jan. 11, 2018), https://www.mayoclinic.org/symptoms/hypoxemia/basics/when-to-see-doctor/sym-20050930