In this episode, we discuss two main causes of hypoxia as well as the utility of the A-a gradient to help determine the underlying etiology. We discuss different methods of oxygen delivery and briefly review etiologies that may cause hypoxia. Our medicine minute discusses the discovery and current controversy regarding pulse oximeters. Episode written by: Dr. Anna Tyker (Internal Medicine Resident)Reviewed by: Dr. Christine D’Arsigny (Respirology and Critical Care) and Dr. Amelia Wilkinson (General Internal Medicine)Sound editing by: Kiera Liblik (Medical Student)Support the show