Dive tables are proliferating rapidly in the industry. The primary reasons for this trend include new developments in table theory and design, and new experimental data. Other reasons include the need by the industry to avoid potential liability for "unsafe" products, and perhaps a marketing or profit motive on the parts of some table sponsors.
Where does this leave the instructor in the field? This was the purpose of this issue's Forum question, to examine which tables, or what information about dive tables, should be presented to an entry level class.
Most of the respondents replied that the U.S. Navy tables, or tables based on the information in the U.S. Navy tables, were the favored tables for use. The large amount of empirical data behind these tables justified their opinions. Other members suggested other tables might be better to teach and use, including the DCIEM tables developed in Canada, "No Bubble" tables, and "No Bends" tables. Each of these tables were selected because they were more conservative than the U.S. Navy tables, and hence "safer" for use.
In a more interesting vein, some members explored what we should be teaching students about all tables. Background in the theory and development of tables, risk factors of decompression sickness, risks and weaknesses of all tables, tissue times and tissue compartments, and supporting data/experimental evidence for the validation of tables were all suggested or implied. The same information regarding the development of dive computers was also recommended.
Traditionally, all of these factors have historically been covered to some degree in entry level courses. However, with the rate at which the field is progressing, much more time would have to be spent on these topics to achieve the same level of understanding of these concepts. It would also be necessary to see that the students integrated the information sufficiently to apply the concepts to each of the various types of tables. This may not be realistically possible.
It does point to the need for instructors to understand these concepts, and to be aware of the implications of the new work which is occurring. Students depend on the opinion of the instructor to guide their diving practices. This occurs whether the instructor expresses an "opinion" overtly, or does so by teaching or personally using a particular set of dive tables. Because of this trust, instructors should review new information available, and arrive at an opinion that is carefully considered.
In my opinion, this is no time to remain set in one's ways because of inertia. This particular aspect of the diving field is rapidly changing. We need to follow developments closely to see that our membership, and our instruction, does not stagnate. It is every instructor's responsibility to see they keep abreast of these developments.
QUESTION: "Given the multitude of dive tables on the market, which tables should be taught? Why?"
A. The program at Scripps Institution of Oceanography has historically used the U.S. Navy tables.
I had the good fortune to know Bob Workman and to work with Ed Lamphier during the 1958 atomic tests in the Pacific. The tables had just been promulgated and we put them through just about every kind of repetitive dive profile one could dream up. There were four of us from Scripps and we had an eight man Navy team working with us. Our main task was implanting and retrieving tsunami recorders near blast sites, but during that three month period we logged over 1200 dives, to depths in excess of 190 fsw.
In the years following we conducted research dives to document the sand movement in the Cabo San Lucas and Los Frailes submarine canyons. On many dives we were on the extreme exposure tables and on many others the 190-foot repetitive dive table. These projects usually involved six of us, and were conducted for a three week period each six months, over a number of years.
The Scripps program has over 200,000 cumulative dives since the early 1950s. We have had only a single case of decompression sickness. It occurred during a multi-day, multi-dive kelp research cruise. Six people made the last dives, all on the same profile. Ironically, the person who hung off at ten feet for two minutes got hit.
We find that use of the U.S. Navy tables is safe and adequate. Our university guidelines for diving safety state that "Any dive table used must be at least as safe as the U.S. Navy tables."
--James R. Stewart, NAUI A-88; La Jolla, CA (Diving Officer for Scripps Institution of Oceanography, and the National Science Foundation. Has extensive research diving and instruction experience worldwide. Member, NAUI Board of Advisors, Recipient of the Leonard Greenstone Award, NOGI Award, and other awards. Has authored diving safety guidelines for a wide variety of governmental and private institutions.)
A. Not one set of tables has proven to be the best for every diver. The most conservative would be the safest to use in the sport diving industry, but which is the most conservative? This is a complex issue, maybe NAUI can run a special issue in the technical section of SOURCES comparing, pro and con, all the most commonly used tables and any new table being developed. If such an article has already been published it may be outdated and the revision can be published. With NAUI pushing to use a new set of tables this can be an opportune time to promote the benefits of using and investing in a new table.
--James Weston, NAUI ????; Santa Cruz?, CA (Private Professional Instructor, had taught for Fort Ord, dive stores and universities.)
A. I feel that we should continue to teach the NAUI/US Navy decompression tables. With the proper safeguards and safety measures that have become widely recognized and used, they have proven to be safe, efficient, and easy to use. There is an incredible data base of dive profiles which prove their utility.
To be sure, there are a number of decompression tables that may be more conservative than the NAUI/USN tables, but if these are presented briefly during training, then certainly individual divers can make their own choices as to the acceptable levels of risk that they feel comfortable with.
--John Heine, NAUI 5924; Moss Landing, CA (Diving Safety Officer at the Moss Landing Marine Laboratories of the California State University. Course-director for 3 ITC's. Past Mid-Pacific Branch manager. Serves as Secretary of the American Academy of Underwater Sciences, and is a contributing editor of Sources. Holds a masters degree in marine biology.)
A. The issue is really straight-forward. As instructors, we have the responsibility to teach acceptable table usage, and we are afforded considerable freedom in how we do just that. Whenever NAUI is able to produce a product that allows us to teach within our motto, "Safety Through Education," then we, as NAUI members should promote that product. If, though, NAUI's product is inferior, then out of concern for our students, we must utilize whichever product is safest. Fortunately for us, NAUI's sport diving tables are the best there are. They are concise, easy to read, easy to understand, and easy to teach.
I use the NAUI tables exclusively, but with back-up from the U.S. Navy tables and altitude conversion chart. I have reviewed virtually every table available but always come back to NAUI's own. It's tops!
--Bill Gee, NAUI 9190; Santa Fe, NM (Instructor Trainer who teaches all levels from Openwater I to ITCs. President of "Alpine Divers" scuba club.)
A. I believe that the U.S. Navy dive tables should still be used for teaching and actual diving purposes. These time tested tables still do not show sufficient evidence that they should not be used. However, they should not be abused. A minus five to ten minutes deduction from the bottom time should always be taught as a good rule of moderation.
Although this table was designed primarily for a working Navy diver with a standby chamber topside, the dive industry and the community alike have been using this table it its designs, researches and other activities since time in memorial. If there are any errors in it, it has not caused enough symptoms during all these years.
I agree, there should be another dive table for the sport diver. I feel that the industry has got to get together and commission all these dive table designers to make a standard one for the entire community. An endorsement from DEMA and most leading dive organizations should make this project a success.
Still, this future set of tables will have to gather enough barnacles and updating. Until then, back to the U.S. Navy tables.
--Carlos N. Santos-Viola, NAUI 5687L; San Francisco, CA (Former Training Director and General Manager of Aquaventure Phils, Inc. Has taught all levels to ITCs. Former Safety Chairman for the Amphibians Scuba Club.)
A. Currently we are using the NAUI tables, which are basically the U.S. Navy tables. While these may not be the safest tables, they are a good compromise between ease of use and dive safety.
We should continue to teach these tables as our primary instruction, but should also introduce students to other tables on the market. The DCIEM tables appear to be safer, and could be covered in entry level courses. Because our motto is "Safety Through Education," we should introduce students to as many tables as possible, along with other pros and cons, to improve student understanding while not overloading or confusing them.
--Struther MacFarlane, NAUI 6676; Toronto, Ontario, Canada (As a private professional educator, has taught all levels from introductory to serving as ITC Director. Recipient of the NAUI Canada Silver Pin and Special Recognition Awards.)
A. Student divers and beginner graduate divers should be introduced first to the NO-BENDS dive table. The reason is obvious...no-bends diving is what they should be doing (no-bends diving is what we should all be doing, for that matter).
The NO-BENDS table is an easy to use arrangement of abbreviated forms of the U.S. Navy's "No Decompression" limits and repetitive group table, surface interval credit table, and the repetitive dive timetable (Table 1-6, 1-7, and 1-8).
The NO-BENDS table was developed over a period of several years. The purpose of the NO-BENDS table is to prevent student divers and beginner graduate students from making many long, deep dives in any one day, because such dives are beyond the experience of these people.
The NO-BENDS table limits dives to a depth of 100 feet and allows only two dives per day. The exposure times contained in the NO-BENDS table are no greater than 100 minutes and in most cases are at least five minutes less (for any depth) than the maximum exposure times listed in the U.S. Navy "No Decompression" table. Even with enjoyable dives of satisfying duration in that portion of our activity's environment where most sport diving is done.
The NO-BENDS table is easy to use, has no moving parts to get out of alignment, requires no batteries (and it can't leak). The NO-BENDS table will keep our student divers and graduate divers straight, and us out of court.
--Fred Calhoun, NAUI 380; Boston, MA (Private Professional Instructor, has taught all levels of diving to ITCs. Producer of the Boston Diving Show. Past North Atlantic Branch Manager. Recipient of NAUI Outstanding Service Award.)
A. Basic background information should be given on the development of dive tables. This should include "tissue times" (fast versus slow) used to develop specific tables. A brief overview of experimental and empirical data used in developing these tables should also be covered. The Navy tables should still be the standard in the industry, based on extensive empirical data. The no-bubble tables are now being used by some institutions and dive computer companies, and therefore should be introduced to the students as an alternative. Having participated in the field trials for the PADI Wheel, I suggest not using these tables.
--Don Canestro, NAUI 5877; Santa Barbara, CA (Research diver at the University of California, Santa Barbara. Has taught extensively in university settings.)
A. Although it is somewhat premature to comment on available diving tables, I think a comment is needed for this point in time. Consider that the DAN committee on Decompression tables will shortly announce their findings on the PADI recreational dive planner (the "wheel"), which is based on new tables that have been partially tested. The DAN committee statement is currently being formulated, and we should wait for their review before deciding on any new tables. Also consider that the USN has recently reviewed their Air Decompression Tables and has made revisions of the No-D tables which have been tested and considered to be the operational version of the Navy tables. My colleagues involved in this Navy work promise me that they will publish their data for the sport diving community in the near future. There is one other set of tables that merits consideration, those are the DCIEM tables from the Canadian Navy which have yet another schedule of decompressions for air No-D dives. These tables were tested to be nearly bubble free using doppler bubble detection.
My experience with many sport divers and instructors is that there is not enough teaching of the basic principles behind decompression tables (the articles by J. Bookspan and B. Wienke in Sources of Jan/Feb 1990 are helpful). The major effort should be on teaching safe diving behavior as well as table theory and use. Dive times and surface intervals are all to be handled the same way from any table. At present, the choice of which table is not clear, but the long record of safety behind the USN tables still makes them my choice. I and many of my colleagues have repeatedly advocated conservative interpretation of the USN tables. That means shortening bottom times, making a safety stop (10 or 15 feet), keeping repets to three or less in one day, and diving no deeper than 100 feet. We are likely to see these rules formalized in some of the new tables. Past use of the USN tables in this way has kept the incidence of decompression sickness at less than 0.1%. To date, no other tables have been this good.
A dive computer is not the ultimate solution to decompression sickness. Like tables on a plastic card, the computers should be used conservatively. The DAN experience to date shows that computers do not guarantee protection from bends.
We need to teach safe behavior, table use and table theory, to protect our students from decompression sickness. The exact table may not be important if these other concepts are well instilled.
--Fred Bove, MD, PhD, NAUI 3055L; Rosemont, PA (A diving physician and researcher, has written on widely varied aspects of diving medicine for a multitude of diving and medical publications.)
A. Again the diving certification agencies have confused and complicated a very simple issue. There is only one set of dive tables, the U.S. Navy dive tables. They are not NAUI, PADI, or NASDS tables, they are U.S. Navy dive tables.
We have done an injustice to the new diver with so many versions of the tables. Two sayings bear repeating, "If it works don't fix it" and "Keep it simple." We have violated both of the above.
The Navy tables have been used for many years and with a reasonable amount of success. And until such time comes that the proper research and testing can be done, I feel we should stay with the Navy tables, forget about any wheels, limit the modifications to the Navy tables to colors, and leave the numbers alone. NAUI's slogan id "Safety Through Education" not "Safety Through Modification."
--Walt Amidon, NAUI 3091; Puyallup, WA (Full time dive industry professional and instructor. Recipient of the NAUI Outstanding Service Award.)
A. The "Buhlman Tables" should be taught. Most dive computers are based on Professor Buhlman's 16 tissue values. Students can better understand computers if the tables they are originally taught are "similar." High altitude diving is also safer as the tables have been tested and found valid at reduced atmospheric pressure.
In Europe the training organizations are not moving together. It is good to have different teaching methods, but it is rubbish to have as many different tables as there are organizations. There should be only two tables used worldwide for sport diving, the revised U.S. Navy and the Buhlman. -
-Norbert Zanker, NAUI 9657; Giessen, West Germany
A. Before we commit ourselves to another never ending dispute, let us first decide what we want to teach, SAFETY or how to increase BOTTOM TIME. Up to now, the USN tables were the only game in town. They are simple and easily adaptable to sport diving procedures. To increase safety, we only had to teach our divers not to approach the no decompression limits, and for multi-day diving trips have everyone calculate their first dive of the day as though they were "A" divers. Everyone was diving the same tables.
Today we have a kaleidoscope of dive tables in many shapes and mechanical constructions, with apparently safer no decompression limits, shorter surface intervals, and inconspicuously increased bottom times during repetitive dives when compared to the USN tables. Some tables on the market now have a first dive no decompression limit significantly shorter than the USN tables, but on the first repetitive dive allow more than twice the bottom time I would consider safe when compared again. Can we increase safety and extend bottom time simultaneously? In my opinion, NO!
I believe we should continue teaching the USN tables, with the NOT to be approached zero decompression limits in red color as they are now, and one group before in yellow as a caution zone, and emphasizing the "A" category as a vital part of dive planning during multi-day diving profiles.
Another recommended alternative is to adopt the Michigan Sea Grant Dive Tables as standard limitations for sport diving activities. The no decompression limits and the ANDLs on these tables have been consistently reduced to produce much safer dive profiles. If we do change the dive tables, safety and standardization should be our foremost concern.
--George Safirowski, NAUI 8921L; Hackensack, NJ (Instructor at Underwater Sports of N.J. and Staff Trainer for Lifeguard Systems, teaching all levels of diving to ITCs, as well as Underwater Photography, Video, and Diver Rescue specialties.)
A. I regret the current dive tables controversy especially since we have allowed ourselves to become involved. This past year I wrote NAUI HQ several times asking for justification for the changes that I could share with my students and fellow instructors. I wanted facts and statistics such as, "How much have bends cases increased and by what percentage might our new tables hope to decrease them?" No one answered these questions.
I guess the changes were arbitrarily made because it seemed like a good idea. This must be the season to monkey around with the tables because everyone is doing it. I do not believe we should fall in line and further muddy the water. We do not have the resources and facilities to scientifically research this question.
Since the beginning of sport diving everyone has depended on the USN tables. If the Navy, with its vast resources, decides it is time for a change we should adopt that change. If we make changes on our own we will probably be asked in court to prove they are accurate or why we did not make them sooner. In the past we could always pass these questions along to the Navy and their sacred cow tables. Not many lawyers have the nerve to sue the government.
Now we are on our own. Next time some gung ho diver, using our tables, ends up in the chamber you can expect a knock on your door.
--Roy Damron, NAUI 207; Kona, Hawaii (Diving Instructor, current NAUI Board of Advisors member. Past NAUI Director, Chapter Leader, West Pacific Branch Manager, and ITC Director. Recipient of NAUI Outstanding Service Award.)
A. We have all these many dive tables, models, and algorithms simply because none of our present dive tables can be considered adequate on both theoretical and empirical grounds. Derivatives of the Haldanian model (e.g. USN, DSAT) use a dissolved gas model that fails to account for undissolved gas, i.e. bubbles in body tissues. Bubble dynamics models handle the bubbles well, but fail to fully factor in the statistical nature of DCS. Maximum likelihood statistical models, critical (bubble) volume models, and so on attempt to deal with all this empirical and statistical uncertainty. But a typical four dive weekend could generate over 100 million dive profiles near the tables edges alone. Even the most extensively tested sport diving tables involved only a few hundred dives. If you are out there near any of these table edges, chances are good you are taking part in a physiological experiment as a volunteer table tester. Good luck! I hope you make it!
The solution is simple--use the NAUI-CUE dive table recommendations. Always take a safety stop in the 10-30 range for 5-10 minutes. Always avoid the last two repetitive dive groups (boxes) on the standard USN dive tables. Obey other dive table rules (60 ft/min or slower ascent rate, deepest dive first, back off if risk factors such as cold or strenuous dive, recent injury, etc). Following the NAUI-CUE dive table recommendations will help you avoid bubbling, and the DCS and "silent tissue death" that may be associated with bubbling. Prayer also helps. -
-Robert Monaghan, NAUI 8256; Dallas, TX (Five years in diving retail/instruction, has taught extensively in many specialties and ITCs. Consultant and author on diving risks analyses.)
A. The U.S. Navy dive tables should be taught because: (1) They have a very impressive track record, despite the negative press they have been getting. (2) They are the industry standard, whereas the validity of other tables are still under scrutiny. (3) Teaching tables with different theoretical bases, as well as teaching tables that utilize the figures of the USN tables yet alter the basic definitions, creates confusion and ultimately mistrust of all tables. (4) It is well publicized that errors exist in their tabulation. That speaks for their conservative nature, since they remain safe despite these errors. Studies where the USN tables were grossly violated without incident also attest to their intrinsic safety. (5) The problem lies not with the USN tables but with how they are taught and the relative complexity of their utilization. That attribute will not be mitigated by introducing other tables or changing definitions.
--E. Esat Atikkan, PhD, NAUI 6274; Rockville, MD
A. When the new PADI tables first came out, I thought this was just what the industry needs: more conservative tables specifically designed for the sport diver. However, if you work profiles side by side with the U.S. Navy tables you may be surprised. The PADI Recreational Dive Planner is sometimes much less conservative especially on deep repetitive dives.
Of course, no one should dive any table or device to the limit. The new NAUI tables are the best set I have seen so far. I think we should teach the most conservative, safest tables available. I also feel we should make our students aware of the different tables on the market.
--James T. O'Neal, NAUI 9024; Atlanta, GA (Training Officer for the Dekalb County Public Safety dive team, and an instructor for Head First. Has taught Openwater I to Assistant Instructor.)
NOTE: The views expressed in this column are opinions held by the individual members referenced, and are not those of NAUI or the editors of NDA News.]Questions for the next issues:
Questions for the next issues:
For the May/Jun issue: "Should instructors be required to have oxygen administration equipment and training to remain in teaching status?"
For the July/August issue: "Should an instructor/dive operator be permitted to confiscate a C-card on the spot for obviously incompetent/unable divers? Why/why not?"
All members are encouraged to respond. This column is for you, the membership, to develop. Answers should be kept fairly brief, preferably no more than two or three paragraphs. Responses to each question will be collated by the editor, condensed if necessary, and printed in this section. New questions may also be posed for discussion. Questions should be concise, and should stimulate a wide cross‑section of the membership. Include with your responses or questions the following information: your name, address, phone number, NAUI membership number, dive‑related employment, past diving accomplishments, and a review of your dive teaching experience. Send your materials to Jeffrey Bozanic, c/o NDA News, P.O. Box 14650, Montclair, CA 91763‑1150.
Compiled and Edited by Jeffrey Bozanic, NAUI 5334L
Sources, Mar/Apr 1990, (2:2), pp. 11-15.
NAUI Members' Forum #16
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