Thoughts on Decompression Theory
Eric Keibler Mar 27, 2009
Lost – at least that is what the people I knew thought when they saw me at this year’s Beneath the Sea show in New Jersey. It was common to hear “what are you doing here?” I had a number of reasons for coming to this show this year, among them were to try and find some connections to some students for our Expedition Trimix Course in Grand Cayman this summer.
Friday evening found Dave and I in a presentation by Dr. Gozum about Personal Decompression Strategies. He has been looking at a number of Decompression & Doppler Bubble studies all the way back to the 1940’s. In looking at the raw data, he found that there three groups of divers in these studies:
- Divers who never got bent, no matter what was done to them
- Divers who sometimes got bent and
- Divers who always got bent
His theory is that were individuals that are resistant to DCS. In looking at their Doppler readings, even when they showed a high number of bubbles, they exhibited no signs of DCI. While this population represents a small part of the study, he felt that it is an important finding.
One of the things he advocates is performing Doppler studies on yourself to determine a safer decompression routine for yourself. Since the actual Doppler devices are $400+, a baby ultrasound device ($100) can be used. These less expensive devices have a larger head and are not generally reparable but give reasonable readings to begin a study.
Another point he made is that studies have shown that post dive exertion has lead to DCI. After a dive a diver may show no signs of DCI, and after doing something strenuous, i.e. pulling up an anchor, mneung equipment, etc the suddenly developed DCI. For this reason he recommends refraining from strenuous exertion after a decompression dive. I have seen this exact situation in a diver who because of pride issues moved equipment and immediately began showing signs of DCI. It took a table 6 ride in the chamber to confirm the hit and eliminate the pain.
In talking about this with Larry Elsevier later that evening, he felt that the results could be skewed by the individual diver’s metabolism. According to Larry, in a study at the university of Southern California (he thought) it was shown that DCS was not detected in divers who had 7-8 glasses of water 24 hours before diving but DCI was noted in divers who did not consume water the prior day. The study concluded that an individual’s metabolism, affected by dehydration, played a significant role in the incidence of DCI.
Further, he noted that in some studies while some people did not note any of the traditional signs of DCI, some reported feeling funny. In some cases, this funny feeling was a precursor to more serious DCI symptoms.
In talking with Tom Mount in our Expedition Trimix course, his experience has been that especially on deep dives, what works is not necessarily what the formulas say to do. “You have to listed to your body” and be aware of signs that tell you things are not quite right. By being in tune with yourself, you can modify your schedule to try and get things back in balance before continuing. He calls this Intuitive Decompression. I have been on dives when I felt that I needed to elongate a stop beyond what the computers were telling me to do. I also know that Ann has felt the same way on some of her dives. She will even tell you she “feels the nitrogen” and gets an overwhelming feeling that she needs to pause and spend more time at her current depth.
What does this mean to divers? The first thing we should know is that decompression is not an exact science. There seem to be a number of factors influencing the elimination of inert gasses and the possibility of developing symptoms of DCI. The importance of proper diet and hydration play a major role in preventing DCI as does individual physiology. While there are some individuals who are resistant to DCI, there appears to be a far larger number of diver’s susceptible to DCI. Prevention of symptoms may include using Intuitive Decompression, to modify your decompression schedule depending on how you feel underwater. Additionally, if is important to avoid post dive exercise when possible, especially if you “feel funny.”
