worked as an assistant secretary at a bank. He graduated from high school at age 16 and enrolled at the University of Utah, graduating in 1945 with a Bachelor of Arts and Phi Beta Kappa membership. While at the University of Utah, he was a member of the Beta Epsilon chapter of Sigma Chi and Owl and Key. Nelson then attended the University of Utah School of Medicine, graduating with a Doctor of Medicine degree in 1947 ranked first in his class. Nelson began his first year of medical school while still an undergraduate, and completed the four-year MD program in only three years. After medical school, Nelson went to the University of Minnesota for his medical residency. While at Minnesota, he was a member of surgeon Clarence Dennis's pioneering research team developing the heart-lung machine that in April 1951 supported the first human open-heart surgery using cardiopulmonary bypass. Nelson received a PhD from Minnesota in 1954 for his research contributions. Medical career Nelson served a two-year term of duty in the U.S. Army Medical Corps during the Korean War, and was stationed at Walter Reed Army Medical Center in Washington, D.C. While on duty, he was assigned to a research group formed by the commandant of the graduate school at Walter Reed, Col. William S. Stone and led by Dr. Fiorindo A. Simeone, a professor of surgery at Case Western Reserve University in Cleveland who had been a clinical investigator in the Mediterranean Theater during World War II. This team was focused on ways to improve the treatment of wounded and was sent to all five MASH units active in Korea along with two major evacuation hospitals, several field station hospitals, a prisoner of war camp and larger evacuation hospitals in Japan, Hawaii, and the mainland United States in order to implement such improvements. At one point, the team came close enough to the front that they received fire from enemy artillery positions, which missed them. After 20 months in service, he left active duty at the rank of captain. Following his military service, he did a year of work and surgical training at Massachusetts General Hospital. In 1955, Nelson returned to Salt Lake City and accepted a faculty position at the University of Utah School of Medicine. There he built his own heart-lung bypass machine and employed it to support the first open-heart surgery in the United States