The Journal of Emergency Medicine, Vol. 46, No. 2, pp. 225–227, 2014Copyright � 2014 Elsevier Inc.

Printed in the USA. All rights reserved0736-4679/$ - see front matter

http://dx.doi.org/10.1016/j.jemermed.2013.08.080

RECEIVED: 8 MaACCEPTED: 15 A

MedicalClassics

ALBERT BEHNKE: NITROGEN NARCOSIS

Casey A. Grover, MD* and David H. Grover, PHD, CDR, USNR-RET†

*Division of Emergency Medicine, Community Hospital of the Monterey Peninsula, Monterey, California and †Western Maritime Press,Napa, California

Reprint Address: Casey A. Grover, MD, Division of Emergency Medicine, PO Box HH, Monterey, CA 93942

, Abstract—As early as 1826, divers diving to great depthsnoted that descent often resulted in a phenomenon of intox-ication and euphoria. In 1935, Albert Behnke discoverednitrogen as the cause of this clinical syndrome, a conditionnow known as nitrogen narcosis. Nitrogen narcosis consistsof the development of euphoria, a false sense of security, andimpaired judgment upon underwater descent using com-pressed air below 3�4 atmospheres (99 to 132 feet). Atgreater depths, symptoms can progress to loss of conscious-ness. The syndrome remains relatively unchanged in mod-ern diving when compressed air is used. Behnke’s use ofnon-nitrogen�containing gas mixtures subsequent to hisdiscovery during the 1939 rescue of the wrecked submarineUSS Squalus pioneered the use of non-nitrogen�containinggas mixtures, which are used by modern divers whenworking at great depth to avoid the effects of nitrogennarcosis. � 2014 Elsevier Inc.

, Keywords—nitrogen narcosis; Albert Behnke; divingmedicine

HISTORY

Although born in Chicago, Albert R. Behnke was gener-ally identified as a Californian. He grew up in Whittier,where he graduated from Whittier college in 1925 beforeenrolling in medical school at Stanford. After graduation,he began a 1-year internship at Stanford, during which heaccepted a commission in the Medical Corps of theUnited States Navy, and traveled to the nearby Mare Is-

rch 2013; FINAL SUBMISSION RECEIVED: 5 July 20ugust 2013

225

land Naval Hospital to complete his residency. His firstduty station as a licensed physician was as assistant med-ical officer for Submarine Division 20 in San Diego,which was then commanded by one of the Navy’s risingstars, Captain Chester W. Nimitz of World War II fame(1,2).

In this setting, Dr. Behnke spent his free time construc-tively by learning to dive, using the traditional ‘‘hard-hat’’gear aboard the USS Ortalon, a submarine rescue vesselto which he also rotated. Diving was not a notable spe-cialty of the Navy at the time, and the service was slowin developing the infrastructure for it. As such, Dr.Behnke devoted his efforts to research on the topic of div-ing medicine, as well as developing a more sound under-standing of the biophysics of diving. In 1932, he wrote aletter to the Surgeon General describing some of his ob-servations on arterial gas embolism, which earned himsome accolades from the Navy and resulted in his transferto Harvard’s School of Public Health as a graduate fellow.After 2 years at Harvard, the Navy assigned duty to Dr.Behnke at the Navy’s submarine escape training towerat Pearl Harbor. He worked extensively here on devel-oping techniques for rescuing personnel from disabledsubmarines on the sea floor. In 1937, he was one of threeNavy physicians assigned to the Navy’s ExperimentalDiving Unit. This team worked on improving the rescuesystem, plus updating the diving recompression tablesoriginally developed by the British in 1908 (1�3).

Among the discoveries that Dr. Behnke made duringthis time at both Harvard and Pearl Harbor, his discovery

13;

226 C. A. Grover and D. H. Grover

of nitrogen as the cause of what we now know as nitrogennarcosis is one of the greatest. The intoxicating effects ofdiving were first described by a French physician namedColladon in 1826, who reported that descent in a divingbell resulted in his feeling a ‘‘state of excitement asthough I had drunk some alcoholic liquor’’ (4). Dr. Colla-don’s reports were corroborated by another French diver,Junod, in 1835, who described that when diving, ‘‘thefunctions of the brain are activated, imagination is lively,thoughts have a peculiar charm, and in some persons,symptoms of intoxication are present’’ (4). The etiologyof this phenomenon remained largely unknown until the1930s, when the British military researcher Damant againhighlighted the issue, and reported very unpredictablebehavior in his divers during descents as deep as 320feet during the British Admiralty Deep Sea diving trials.Two initial theories arose as to the etiology for this effect,the first being from psychological causes by Hill andPhillip in 1932, and the second being from oxygentoxicity by Haldane in 1935 (1,4).

Dr. Behnke and his colleagues at the Harvard Schoolof Public Health had another idea as to the etiology ofthis phenomenon. In 1935, based on observation of indi-viduals in experiments with a pressure chamber, Dr.Behnke published an article in the American Journal ofPhysiology in which he posited that nitrogen was the eti-ology of the intoxicating effects of diving (5). He openedwith a brief description of the phenomenon, namely that:

Air at high barometric pressures produces a narcoticeffect on man. The changes which first appear at 3 atmo-spheres of pressure are expressed in alterations ofbehavior, slowed mental activity, and impaired neuro-muscular coordination. (5)

Dr. Behnke went on to point out that, based on previ-ous research that he had published in 1934, oxygen wasnot likely to be contributing to the intoxicating effectsof diving (6):

Oxygen breathed for a period of several hours maydisturb the coordination of finer movements, but euphoriais not present. In contrast with the effect of oxygen, thesymptoms at higher air pressures are immediate in theironset. The increased partial pressure of oxygen, there-fore, cannot be a significant factor in the etiology of thechanges. (5)

Dr. Behnke continued with a rationale as to whynitrogen was responsible for the narcotic phenomenonof diving:

If oxygen is excluded, then the atmospheric nitrogen canbe considered as mainly responsible for the narcotic ac-tion of air at high pressures. Although nitrogen is chem-ically inert, the physical property which renders this gasanalogous to narcotic substances is its high solubility inlipoid matter.

This discovery clearly had enormous practical impli-cations for divers, as the effects of nitrogen on concentra-tion, motor skill, and behavior at depth made working atdepth using compressed air nearly impossible. As such,Dr. Behnke concluded the article with the suggestionthat ‘‘an artificial gas mixture for divers is essential ifoperations at great depths (above 300 feet) are carriedout’’ (5).

Dr. Behnke became internationally well known in1939 when he served with several other Navy diving of-ficers in directing the rescue of the United States (US)submarine USS Squalus, which sank in 240 feet of wateroff of the New England Coast. Based on his previousresearch of the effects of nitrogen on divers at depth,Dr. Behnke provided his divers with a mixture of heliumand oxygen known as Heliox during their efforts to rescueboth 36 members of the crew of the Squalus as well as thevessel itself. None of the divers, despite the prolongedwork at great depth, complained about any decrementin coordination or cognitive function, which served tosupport Dr. Behnke’s theory that nitrogen was the etio-logic agent in the intoxicating effects of diving (1).

The Squalus rescue became one of the great news stor-ies of its time, and thrust its architects into the spotlight ofworldwide recognition. It also marked a watershed fordiving in the US Navy, which henceforth provided inter-national leadership in support of undersea and spaceexploration, national security during the Cold War, andthe advancement of hyperbaric medicine.

Dr. Behnke quickly rose to the top of his profession,conducting research in a variety of disciplines. The inter-national diving community honored him by creating theAlbert R. Behnke Award, now the most prestigious awardin undersea achievement. He retired from the Navy in1959 after 50 years of service, and died in California in1992 (2).

COMMENTARY

Nitrogen narcosis, described as ‘‘rapture of the deep’’ byJacques Cousteau, still remains a relatively commonoccurrence in modern diving, despite major advances indiving technology since Behnke’s initial description ofthe pathophysiologic cause of the condition in 1935.The development of symptoms of this condition variesfrom diver to diver, but usually begins when a depth of4 atmospheres (132 feet) is reached in divers using com-pressed air. More sensitive divers can develop symptomsat only 3 atmospheres (99 feet), and other divers may notbe affected up to depths as high as 6 atmospheres (198feet). Interestingly, tolerance to nitrogen narcosis can bedeveloped by frequent diving and exposure to the effectsof compressed air at depth, similar to the tolerance

Albert Behnke 227

developed to the effects of alcohol by repeated alcoholconsumption (4,7,8).

Symptoms tend to develop insidiously, with the firstsymptoms tending to be lightheadedness, euphoria,impaired judgment, and a false sense of security or over-confidence (4,9). As such, this disease can produceextremely dangerous circumstances. An impaired andoverconfident individual under the effects of alcoholcauses plenty of trouble out of water; placing such anindividual affected by nitrogen narcosis at underwaterdepths of > 100 feet allows little chance of safe escapeshould a bad decision be made. In one diving database,nitrogen narcosis was estimated to contribute to 9% ofall diving deaths (9).

With advancement to greater depth, the symptomsprogress to significantly impaired concentration andmemory. Divers might also experience peripheral numb-ness and hallucinations with continued descent. The finalphase of the disease involves lethargy, drowsiness, and ul-timately loss of consciousness, with loss of consciousnessdeveloping between 10 and 13 atmospheres (between 333and 429 feet) (4).

Risk factors for the development of this condition, inaddition to diving to greater depth, include exertion whilediving, fatigue before diving, cold conditions, alcoholicintoxication before diving, and apprehension before orduring a dive (4,7). As such, divers with planned deepdiving should avoid alcohol ingestion before dives.

Treatment of nitrogen narcosis is extremely simple.Ascent will reduce the partial pressure of nitrogen inthe blood and therefore will reduce the symptoms ofintoxication. Symptoms resolve rapidly with ascent ofthe affected diver (7,8). As mentioned previously,divers affected by the disinhibition and self-confidenceof nitrogen narcosis are at very high risk for making arash decision at depth that could be fatal. As such, diversdiving to depths > 3 atmospheres (99 feet) shouldfrequently check on their diving companions for the

development of this condition, as ascent may be lifesaving.

Finally, nitrogen narcosis may be prevented by a num-ber of different precautions. As compressed air is inex-pensive and readily available as a gas for underwaterdiving, it is the gas used in nearly all recreational divingand most shallow commercial diving (9). For thosebreathing compressed air, nitrogen narcosis can be pre-vented almost entirely by simply avoiding diving todepths > 100 to 130 feet (8). For those divers diving todepths > 160 feet, as with Behnke’s rescue of the USSSqualus, a nitrogen-free gas mixture is used to preventthe development of nitrogen narcosis. Heliox (helium-oxygen) or Trimix (helium-nitrogen-oxygen) are twogas mixtures that are used for deep diving, such as thatused for commercial, military, or deep technical recrea-tional diving. Unfortunately, such gas mixes are expen-sive due to the high cost of helium, which prevents theuse of gas mixture for all diving applications (9).

REFERENCES

1. Acott C. A brief history of diving and decompression illness. SPUMSJ 1999;29:98–109.

2. Bornmann R. Dr. Behnke, founder of UHMS, dies. Pressure 1992;21:1�4.

3. Tranchemotagne M. NEDU celebrates 75 years. Faceplate 2003;7:4–5.

4. Unsworth IP. Inert gas narcosis. Postgrad Med J 1966;42:378–85.5. Behnke AR, Thomson RM, Motley P. The psychologic effects from

breathing air at 4 atmospheric pressures. Am J Physiol 1935;112:554–8.

6. Behnke AR, Johnson FS, Poppen JR, Motley P. The effect of oxygenonman at pressures from 1 to 4 atmospheres. Am J Physiol 1934;110:565–72.

7. Spira A. Diving and marine medicine review part II: diving diseases.J Travel Med 1999;6:180–98.

8. Melamed Y, Shupak A, Bitterman H. Medical problems associatedwith underwater diving. N Engl J Med 1992;326:30–5.

9. Levett DZH,Millar IL. Bubble trouble: a review of diving physiologyand disease. Postgrad Med J 2008;84:571–8.