Don Boorse/Special to The Explorer, Compression-only CPR classes were taught Saturday at Oro Valley Hospital and several other locations throughout Tucson. Chest compression-only CPR was researched and developed at the University of Arizona Sarver Heart Center. It is recommended for sudden cardiac arrest. Teaching the class was Nicole Smith, a 2005 graduate of Ironwood Ridge High School and second-year medical student. Smith instructed with her sister Elizabeth, a pre-med student, and Karen Hauca, EMT, public educator for the Golder Ranch Fire District.