Oxygen Enriched Air: A New Breathing Mix?

by Larry "Harris" Taylor, Ph.D.

This is an electronic reprint of an article that appeared in IANTD Journal 93-3(Sept/Oct 1993). This material is copyrighted and all rights are retained by the author. This material is made available as a service to the diving community by the author and may be distributed for any non-commercial or Not-For-Profit use.

The first preparation of oxygen was by the English chemist Joseph Priestly in 1773. Shortly thereafter, the French chemist, Antoine Lavoisior determined that oxygen was vital to life. Lavoisior named the gas "oxygen" (means "acid former" because he incorrectly believed this new gas to be the essence of acids). By 1794, the English physician Reddoes had established breathing oxygen enriched air as a medical procedure. Paul Bert published the results of some 670 experiments with oxygen enriched atmospheres using a hyperbaric chamber in 1878. Earlier, in 1874, Bert furnished balloonists with bags containing 40 and 70% O2 so that they could survive the hypoxia associated with their balloon ascensions. Bert was also the first to propose that CNS oxygen toxicity was a function of the oxygen concentration.

The first documented dive using oxygen-rich air was conducted by a Mr. Fleuss, Master Diver for Siebe, Gorman & Co. of London. Breathing an estimated 50-60% O2, Mr Fleuss spent an hour in a large tank. The dive was conducted in 1879. By 1912 Robert Davis and Leonard Hill had devised a self-contained rigid diving helmet which utilized a 50% oxygen-nitrogen mixture. This apparatus was used under the guidance of J.S. Haldane to a working limit of 100 fsw. Since the nitrogen concentration was much less than air, this device demonstrated the then-remarkable decompression advantage available from using an oxygen enriched air breathing mixture.

A self-contained commercial diving dress was demonstrated by the Westfalia Machinenfabrik in Geisenkirchen, Germany. In 1912 they used their suit with a mixture of 45% or 55% O2 for depths to a 100 feet and a 30% O2 mix for diving to depths of 200 feet. This suit was not widely distributed. However, this unit was the basis for the 1913 production of a similar device by Draegerwerk which automatically mixed nitrogen and oxygen supplies to produce a 60 percent O2 mix. Some time before WW I, the Fleuss-Davis SCUBA unit appeared. This device consisted of two 10 cubic foot tanks; one for compressed air and one for oxygen. The gases were mixed in a manifold between the two tanks and the diver's mouthpiece. The manufacturer claimed success of this unit to depths of 66 feet.

Between the two world wars Siebe, Gorman & Co. introduced the technique of using different concentrations of oxygen mixed with nitrogen. The concentration of oxygen varied to minimize decompression obligation. However, since diving on air was much less expensive than oxygen enriched air, this technique was not widely used.

By 1942, it had been established that oxygen concentrations greater than 2 Ata could not be tolerated by divers for extended periods of time without difficulty. The divers affected by this incapacity and convulsions associated with high O2 concentrations invented a mythical monster, "Oxygen Pete," who was supposed to lurk on the bottom of the sea waiting to molest unwary divers. Oxygen toxicity hits during this time were referred to as "getting a Pete". In order to minimize oxygen toxicity problems, a number of oxygen nitrogen mixtures were investigated by the British Navy. One of the best kept secrets of WW II was the use of 32.5, 40 and 60% oxygen -nitrogen mixtures in closed circuit breathing systems by the Royal Navy in commando operations. These mixes lowered the oxygen toxicity problems associated with 100% O2 and the decreased nitrogen (compared to air) increased bottom time available without decompression obligation in the 60 - 100 foot range.

The secrecy of the British operations was so well maintained that Lanphier, working for the US Navy in 1954, faced many of the same problems with closed circuit oxygen enriched air breathing gas mixtures that the British Royal Navy had examined in 1943. In addition the French and Swedish Navies developed closed circuit oxygen enriched air devices in the years following WW II.

Dwyer calculated nitrogen-oxygen dive tables for the Navy EDU in 1955. Workman developed decompression schedules for nitrogen-oxygen and helium-oxygen diving and published these tables in 1965. By this time, the US Navy was using oxygen-enriched air to significantly lower decompression obligations. In the late seventies, the Canadian research institute DCIEM was asked to develop a diving apparatus for the Canadian military to be used in clearing mines. The ideal system would not disturb mine sensors which would detect motion, magnetic fields, and/or sound. It was decided to utilize a semi-closed system which would use a nitrogen-oxygen mix which would vary in O2 concentration at depth to supply a constant pO2. The constant pO2 is delivered via a pneumatic manifold, as opposed to an electronic pO2 sensor controlled relay system. This system was made available in the late 80's.

By 1970, Dr. Morgan Wells, Diving Officer for NOAA had begun instituting oxygen enriched air procedures for NOAA diving. In 1978 NOAA formally established procedures for a standard mixture of 68% N2 / 32% O2. It is known as NOAA Nitrox I. A second standard mix which contains 36% O2 is known as NOAA Nitrox II. NOAA has developed a reasonable compact shipboard continuous gas mixing system to supply Nitrox for diving operations.

In 1985, Dick Rutkowski formed International Association of Nitrox Divers to bring the NOAA Nitrox technology to the recreational diving community. Another recreational training agency, American Nitrox Divers Inc. was formed by Ed Betts in 1987. During the last five years, approximately 28,000 logged dives using Nitrox were surveyed. Although rigorous statistical analysis is not yet complete, the trend is that Nitrox is a safe, easily handled mix when used by properly trained divers. The sanctioning of Nitrox training by recreational training agencies NAUI and NASDS indicates that Nitrox mixtures are becoming a permanent part of the recreational diving community.

Newness?

The US Navy Nitrox applications report (1991) simply states, "Nitrogen-Oxygen (Nitrox) diving is an old concept."

Kenneth Donald (1992) stated, "The oxygen-nitrogen mixtures used in self-contained counterlung diving have not changed greatly in the last 50 years."

Conclusion: There are serious considerations about the use of oxygen enriched air breathing mixtures. However, since divers have been breathing oxygen enriched air for more than one hundred years, the lack of a long, successful history of utilization is not one of these concerns!

REFERENCES

Benedict, F. & Huggins, H. "Effects On Men At Rest Breathing Oxygen- Rich Gas Mixtures," American Journal Of Physiology, 28(1), April, 1911, 1-28.

Betts, E. THE APPLICATION OF ENRICHED AIR MIXTURES, ANDI, Freeport, NY. 1992, 128 pages.

Chimiak, J. U.S. Navy Nitrox Diving Applications, NEDU Report No. 93- 91. NEDU, Panama City, FL. 1991, 23 pages.

Davis, R. DEEP DIVING AND SUBMARINE OPERATIONS, St. Catherine Press, London, England, 1962, 713 pages.

DeLatl, P. & Rivoire, J. MAN AND THE UNDERWATER WORLD, G.P. Putnam's Sons, New York, NY. 1956, 400 pages.

Dille, J. "Paul Bert Believed," Pressure, 15(2), Mar/Apr. 1986, p. 14- 15.

Donald, K. OXYGEN AND THE DIVER, The SPA, Ltd. Hanley Swan, Worchester, Great Britain, 1992, 237 pages.

Dugan, J. MAN UNDER THE SEA, Collier Books, New York, NY. 1965, 443 paages.

Hamilton, R. WORKSHOP CONCLUSIONS, Scuba Diving Resource Group, Boulder, CO, 1992, 22 pages.

Larsen,H. A HISTORY OF SELF-CONTAINED DIVING AND UNDERWATER SWIMMING, National Academy of Sciences, Washington, D.C. 1967, 50 pages.

Marx. R. INTO THE DEEP, Van Nostrand, New York, NY. 1978, 198 pages.

Miller, J. & Koblick, LIVING AND WORKING IN THE SEA, Van Nostrand Reinhold, New York, NY. 1984, 433 pages.

Rutkowski, D. NITROX MANUAL, Hyperbarics International, Key Largo, FL. 1989, 103 pages.

Schilling, C. A HISTORY OF THE DEVELOPMENT OF DECOMPRESSION TABLES, Undersea Medical Society, Bethesda, MD. 1981, 131 pages.

About The Author:

Larry "Harris" Taylor, Ph.D. is a biochemist and scuba instructor at the University of Michigan. He has authored more than 100 scuba related articles. His personal dive library (See Alert Diver, Mar/Apr, 1997, p. 54) is considered by many as one of the best recreational sources of information in North America.