Can skin diving be made safe?

Can Skin Diving

Be Made

Safe?

ROBERT W. KEAST,* M.D., Mill Valley, California has become increasingly common in the past few years, particuIarIy on the West coast, to read newspaper headlines such as “Skin Diver Drowns WhiIe Trying Scuba Unit in Surf for First Time.” In an effort to decrease the mortaIity statistics (one death per month in CaIifornia) of my favorite hobby, skin diving, I wouId Iike to point out a few basic, inteIIigent and common sense ruIes of behavior for divers. Many of the tragedies which have occurred are a resuIt of man’s basic incompatabiIity with underwater Iife. They are a resuIt, in large part, of ignoring the physica Iaws which govern the physiological reactions of the body to gases under pressure. In presenting these causes and effects, I hope to make it very cIear that there is no reason to beIieve that man wiI1 ever be capabIe of advancing the underwater frontier by diving into pressure, whether it be with “hard-hat” deep-sea diving rigs or scuba (seIf-contained underwater breathing apparatus) units. The use of such free-diving mechanisms as the bathyscaphe and remote underwater television cameras is of infiniteIy more practical vaIue and wiI1 probably be unaccompanied by needIess loss of Iife.

I

T

CAISSON

DISEASE

This is “the bends” caused by an increased voIume of nitrogen in solution in the bIood stream under pressure. (A gas dissoIves in a Iiquid in direct proportion to its partial pressure above that Iiquid, and exerts the same pressure as if it occupied the space aIone.) After a Iength of time, when pressure is released, the nitrogen, if decompression is not sIow enough, may form bubbIes in the capiIIaries and cause ischemia with IocaI damage. The areas of worst damage are the “tight” tissues with poor bIood supply, such as tendons, and the areas most sensitive to pressure, such * AnesthesioIogist, American

Journal

of Surgery,

St. Joseph’s, Mary’s

Volume

98,

September,

lgsg

as the spina cord. The symptoms are pain (over go per cent of cases), puImonary edema with coughing and choking, and in severe cases nerve paresthesias and paraIysis. This disease, or accident to be more accurate, is a resuIt of both time and pressure. The standard decompression tabIes of the U. S. Navy give an accurate picture of what may be accompIished with the standard 70 cubic feet scuba tank of compressed air. Times are measured from the time of Ieaving the surface to the time of Ieav-

Depth (ft.)

30 40

Unlimited 120

90 100

78 55 43 35 30 25

II0

20

120

I5

2 ;:

ing the bottom. The Navy’s ruIe of thumb is: From 120 to 140 feet, Iimit diving time to fifteen minutes (do not descend faster than 23 feet per minute as a genera1 ruIe). Beyond 140 feet, decrease diving time by two minutes for every IO feet. Ascend at a rate not to exceed 25 feet per minute. Stop at the IO foot IeveI for decompression and spend five minutes there for every IO foot increment beyond 120 feet, with an absoIute Iimit of 200 feet. This ruIe of thumb tabIe is on the safe side as far as decompression time goes and was designed for that purpose, when no recompression faciIities are availabIe (as in practicalIy IOO per cent of amateur sport diving). A brief computation will show that beIow 170 feet it is impossible to

Help and Chinese HospitaIs, San Francisco,

506

Time (min.)

California.

Can

Skin

Diving

descend at the prescribed rate and have any time whatever on the bottom before having to start the return trip. This is one of the main reasons that no amateur diver should ever (in an! but lifesaving emergencies) dive below 150 feet. This opinion is shared by members of my own skin diving organization, the Marin Skin Divers, Inc., who recentIy amended their constitution to forbid any member from diving below this fevef without the approvaf of a twothirds majority of the Club membership, and such dives are for medicaf research only. Zero-decompression diving is the term used to describe a dive in which the only decompression necessary is the 25 foot per minute rate of ascent. NITROGEN

NARCOSIS

This phenomenon, romanticahy caIIed by “raptures of the deep,” is a Capt. Cousteau peculiar result on the body of nitrogen under pressure. This gas, compIeteIy inert at one atmosphere pressure, causes euphoria and intoxication simiIar to that of aIcoho1 with the same duIIing of judgment. In some divers this may- appear at as IittIe as 150 feet and in others at as much as 200 feet or more, but it rnu~’ affect any given person at any Ievel, depending on his physical and menta1 condition on different days. Its very insidiousness is its danger, being also Iike aIcoho1 in that respect. A diver may be perfectIy aware that hc has only three or four minutes to stay at 200 feet, but may be so affected by the “rapthat he cannot even read his watch tures,” clcarfy. This, then, is a second reason that no amateur diver shouId ever dive beIow 150 feet. AIR

Be blade

Safe

The lungs need onIy be one-third tiffed at 66 feet to be tilled at the surface. It is now obvious what happens when a panicky diver takes a deep breath of compressed air belo\c the surface and swims up rapidIy. nlarked o\,erdistention ma?; occur and cause miJc1 rupture of the aIveoli and even pulmonarv hemorrhage in a mild case. In severe cases violent shattering of the Iung tissue and puJmonar!veins occurs, with introduction of air into the vessels, thus the name “air embolus.” Prophylaxis of’ this accident is relativeIy simple: “ Never ascend while holding your breath. Breathe freely aff the way up.” As Jittle as 3f,i feet of water wiJJ exert a pressure of IOO mm. Hg, and such pressure is capable of rupturing any lung under the right circumstances. SubsternaJ and diaphragmatic pressure will normaIIy give the diver adequate warning to exhale, but the diver who is panicky may have practically a spasm of the glottis. The actual pain associated with tearing of the lung tissue is not severe, and if pain is the first symptom there is already damage to the Jung. OXYGEN

POISONING

Breathing 100 per cent oxygen under increased pressure, as is done with the so-called rebreathing type of scuba, ma!’ cause this accident. If the diver is working harcl, swimming fast or doing salvage work, oxygen under pressure may cause nausea, headache, muscle twitching, convuIsions and coma in as shaIIow a depth as 30 to 50 feet. SusceptibiIity varies tremendousIy among people and therefore this type of apparatus should not be allowed below 30 feet. Symptoms subside when the patient is removed to reduced pressures.

EMBOLUS

Boyfe’s Iaw of gas behavior states that if the temperature remains constant, the voIume of a gas varies inverseIy with the pressure. Each 33 feet that a diver descends beIow the surface of the ocean adds one full atmosphere of pressure on the air he has within his body: surface, one atomsphere; 33 feet, two atmospheres; 66 feet, three atmospheres; gg feet, four atmospheres, and so on down. A human Iung that is fuI1 at the surface wouId only be halffull at 33 feet, one-third at 66 feet, etc. ConverseIy, a human lung haIf-hIled at 33 feet and brought to the surface rapidIy without exhalation would be completeiy IifIed at the surface.

DO’S

AND AND

DONT’S THE

OF

SKIN

DIVING,

REASONS

I. Be boringiy famiIiar with your equipment and its Iimitations. There is no way to overemphasize the importance of doing tfre right thing instantly, without having to think consciously about it. Herein Iies a major key t:o safe diving. 2. Never overestimate your own capabiIities as to swimming ability, endurance and physical condition on any given day, and reappraise that capability as often as necessary to make sure exhaustion wiI1 not become a major hazard to the day’s diving.

Keast 3. Use a float. An oId inner tube is perfectIy adequate; it not onIy serves as a pIace to rest and regain strength after a strenuous dive but aIso is very handy for storing fish stringers, cameras, spear guns and other diving gear. 4. Do not dive aIone. Many divers have IiteralIy had their Iives saved by a buddy. Dive in pairs, with the back man keeping an eye on the front man and trade pIaces in mid-dive. 5. In scuba diving, wear an accurate depth gage and waterproof watch. This needs no comment. 6. Avoid very rough water. A diver was drowned this year because his eagerness to try out his new equipment overshadowed sensibIe caution about diving in rough water in bad weather. There wil1 be Iots of good diving days. Use common sense. 7. Do not dive if you have a coId. Lack of patency of the eustachian tubes may lead to ruptured ear drums if pressures are not equaIized. Even if nasa1 decongestants aIIow equaIization, nasal puruIence may be carried into the middIe ear. 8. Be very carefu1 of heavy keIp. One death in the Northern CaIifornia area was due to this troubIe when the diver became entangIed in our

heavy “bull keIp” could be extricated.

and drowned before

he

SUMMARY

Most, if not aI1, skin diving fatalities are caused by accidents and not diseases. ProphyIaxis, then, is much more important than treatment because of the simpIe fact that drowning intervenes before the victim can be brought to medica attention in the severe cases. In the milder ones treatment is usuaIIy unnecessary. “The bends ” is the exception and can be handIed onIy by the nearest Navy decompression chamber and the Navy personne1 famiIiar with it. No amateur diver should ever dive beIow 150 feet with a single-tank scuba. A very large majority of diving fatahties are absolutely preventabIe if adequate education and experience with equipment precedes actua1 ocean diving. NAVMED-P 5054, “Submarine Medicine Practice,” obtainable from the Superintendent of Documents, U.S. Government Printing O&e, Washington, D.C. for $2.00, contains a tremendous amount of information and is strongIy recommended for further reading by those interested.