Professor Christian Lambertsen: Inventor of the scuba device known as 'father of the frogmen'

Christian Lambertsen was known as the "father of the frogmen".

Trained as a doctor, he was working for the US Army during the Second World War when he developed the scuba device that allowed divers to breathe underwater and so conduct missions that would previously have been impossible. Some of Lambertsen's frogmen assisted the British in underwater reconnaissance along the coast of Burma; others were deployed for reconnaissance against Japan. They were kitted out 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. Lambertsen was awarded the Legion of Merit for this work.

Christian James Lambertsen was born in 1917 in New Jersey. He gained a science degree from RutgersUniversity in 1939, and went on to study medicine at the University of Pennsylvania, and was awarded an MD in 1943.

As a youth he had worked at resorts along Barnegat Bay and, an expert swimmer, had begun experimenting with home-made diving equipment. In 1939 he built the Lambertsen Amphibious Respirator Unit, or LARU, a forerunner of scuba technology used today. He tried to interest the US Navy in his invention, receiving little encouragement, but the Army referred him to the newly formed Office of Strategic Services (OSS), predecessor of the CIA. He was commissioned into the Army Medical Corps and given the task of training OSS teams in the use of his scuba device in the pool at the US Naval Academy in Annapolis.

He had competition. The first frogman-type operations had been undertaken by the Italian Decima Flottiglia MAS, a commando unit formed in 1938 which saw action from 1940 against the British Royal Navy. The French naval officer Jacques Cousteau was also working on an "aqua-lung".

Lambertsen experimented with his equipment in the Potomac River, finding it allowed trainees to swim more than a mile underwater, submerged for 48 minutes. His device was tested in Operation Cincinnati, in which OSS swimmers infiltrated the perimeter of the US Navy harbour at Guantanamo Bay and blew up an old barge. After these successes "frogmen" used the equipment on active service.

In 1945, with the OSS disbanded, Lambertsen's scuba equipment was declassified and made available to the public. It was taken up by police and fire-service rescue squads, used in mine-rescue work and in salvage operations, and scuba diving became a sport. Lambertsen returned to the University of Pennsylvania as pharmacology instructor, and in 1952 was elevated to professor of pharmacology.

In 1948 Lambertsen salvaged an altitude chamber due for the scrapyard and built a primitive environmental research chamber in co-operation with the newly established Office of Naval Research. He asked to train the Navy's élite underwater demolition teams, the precursors of the Navy SEALs, to use his system. On an exercise in the Virgin Islands, he and a colleague made the first exit and re-entry from a submerged submarine.

Lambertsen continued researching in the 1950s and '60s for the US Navy and the US space programme. In 1968, he founded the University of Pennsylvania's Institute for Environmental Medicine, retiring in 1987. As emeritus professor he continued his research, focusing on employing a medical treatment known as hyperbaric, or high-pressure, oxygen therapy to treat a variety of diseases.

In 1992, Lambertsen registered a patent for "inergen", an environmentally friendly fire-suppression product now widely used which he developed initially to extinguish fires in submarines and spacecraft.

Lambertsen received many honours, including, in 2009, the distinguished service award from the OSS Society.

Christian James Lambertsen, physician and inventor: born Scotch Plains, New Jersey 15 May 1917; married Naomi Hill (died 1985; four sons); died Newtown Square, Pennsylvania 11 February 2011.