Lambertsen began experimenting with homemade diving equipment as a youth, when he became an expert swimmer while working at resorts along New Jersey's Barnegat Bay.
At the University of Pennsylvania School of Medicine, beginning in 1939, he worked on his diving apparatus by using parts from anesthesia machines.
In 1941, with war imminent, he contacted the military about his apparatus and began working with the Army's Office of Strategic Services.
After graduating first in his class from medical school and completing an internship at the university, Lambertsen received a commission in the Army and trained OSS units to use his scuba gear.
Some OSS members assisted the British in underwater reconnaissance along the coast of Burma during World War II. Others carried out reconnaissance of Japan.
Divers wore camouflage wetsuits and flippers, and were equipped with a mask, breathing tubes, a canister for absorption of exhaled carbon dioxide, a breathing bag and controllable oxygen supply, all mounted on a canvas vest.
After the war, scuba gear was declassified and made available to the public. It was used by police and fire department rescue squads, in mine rescue work and in salvage operations. Eventually, scuba diving came to be used for recreation and sport.
After his military discharge, Lambertsen returned to the University of Pennsylvania as a pharmacology instructor. When the university was about to scrap an altitude chamber it had set up during the war, he salvaged it and in 1948 set up a primitive environmental research chamber in conjunction with the Office of Naval Research.
He conducted a variety of research activities for the Navy and the U.S. space program during the 1950s and '60s.
In 1968, he founded the university's Institute for Environmental Medicine.
Lambertsen retired as director of the institute in 1987 but continued his research as a professor emeritus. His studies were focused on how a medical treatment known as hyperbaric, or high-pressure, oxygen therapy could help people suffering from many diseases.
He continued to invent and conduct research until he was 90.
In 1992, he patented Inergen, an environmentally friendly fire-suppression product now used in commercial buildings. He developed it initially to extinguish fires in submarines and spacecraft.
Lambertsen was born May 15, 1917, in Westfield, N.J., and received a bachelor's degree from Rutgers University.
He is survived by four sons and six grandchildren.