Aging, DCS, and Deeper Diving

[Lopaka]

I think it's extremely important to set your computer accurately to nitrox, then dive air TABLES if that's the plan.

Heh heh, didn't say I do it, never did, just answering the question of why do it.

So you are planning on using your computer as just a logging device and O2 clock, and diving square table air profiles? Since we have the same issues, I am curious about your strategy for the future. Other than getting a much more conservative computer than my Oceanic (reading up on that, microbubbles and so forth) I have not thought it all the way through yet.

 

[Amazz]

I'm trying to get back in the water as soon as it's safe. I'm miserable staying dry. The Doc says 3 months and I respect that. If I can cut that by just a couple of weeks, it mentally gives me something to look forward to. My plan the first time I'm in the water is to dive the richest mix the depth allows. This would be 40% in the 75 ft. range. I would stay off the reef a little more shallow and I'll limit the dive time to 20-25 minutes. I would set my computer to 40% and come up after 20-25 min. At least the computer would give me accurate data. I felt the need to post my opinion because several people told me to set my computer to air while diving these high mixes. I think that's wrong.

 

[diver 85]

hey hey to the OP, I'm thinking I know who you dove with---Aren't they wonderful.....2 for 1 almost.

 

[Kern]

Our research shows these ascent rates are resulting in lower microbubble formation. Our sample size is not large enough at this time to prove a chi square greater than .05, with respect to specific rates, but within the test divers we have measured in our study, all have shown a statisticallly significant decreases in precordial doppler signatures / minute, using these ascent rates in non-deco dives with maximum depth less than 100 FSW. Perhaps I should not suggest these ascent rates until we have published and have peer review (but the results thusfar have certainly caused me to modify my personal dive profiles). Would be happy to listen to any suggestions KERN has for my study.

OK, quick paradigm shift from neo Haldanian; if you don't exceed critical supper saturation , you don't get bubbles, if you don't get bubbles you don't get bent..... to..... dual phase; if you don't exceed critical gas volume in the free phase, you don't get bent because the bubbles you do get are sub clinical. Yes I know, very simplistic, but I want to keep it short.

I have no problem with the fact that very slow ascent rates will show less sub clinical bubbles than one done at the algorithms standard ascent rate. I'd say it's not only intuitive, but there have already been studies that show this to be the case. Non the less, the off gassing at these slow rates is not as effective & the extra time spent at depth means that some tissues aren't off gassing at all, but rather on gassing during the ascent.

So you come out of the water with less bubbles. But do you come out of the water with lower or higher tissue saturation?

The bubbles most of us exit the water with using a 10mt/min ascent rate & for many in the past even double that, are sub clinical (not even fatigue). I don't quite see the point of supper slow ascents that may lead to leaving the water with a higher level of tissue saturation.

Possibly when your research is published I'll have some more to think about. Until then & just for interest....
is there a working title for your paper?
is the number of bubbles/ascent rate you've mentioned a sub set of a more holistic study?
could you give a concise H_o for the test you mentioned.
what was your sample size?
your p value was less than 5%, what was the exact p value?
how many categories were you using, (what was the df)?
how did you arrive at the expected bubble count v's the observed result?
how were you counting the bubbles?

 

[gcbryan]

To the above poster, why would the choice have to be getting out of the water with fewer bubbles but more nitrogen? You can stay in the water until you have whatever level of nitrogen that you choose even if it means a longer deco.

To the OP, it seems to me (no evidence) that it's not a bad idea to go a little more for quality rather than quantity regarding dives as you get older. Do you really need or enjoy 4 dives a day for 16 days in a row? I would think sitting out a dive every now and then and perhaps doing something else every few days while on vacation would be a good idea as well.

 

[promocop]

I'm 62 and try to go below 100 ft. Ever. I think you were really pushing the limits going that deep and doing that many dives. I diveEAN and don't find it that much better. Besides I really don't see much better sealife at that depth anyway. As I age I personally see the effects that deep dives have on my body. I just finished my Master Diver Certification and continue to take classes to keep in touch with trends/safety issues. Deep dives are not part of my agenda

 

[ianr33]

In addition to not having an alarm for maximum ppO2, you also will not be monitoring OTUs.

OTU's are irrelevant for recreational nitrox diving.
Follow a few simple rules and CNS oxygen can be forgotten about as well ( Dive 32%. No deeper than 110 feet. No deco)

If anyone is worried about diving nitrox with a computer set to air use 2 computers. One set for air,the other to nitrox. Ue the air computer for deco limits and the nitrox computer for O2 limits and as a backup.

 

[JCR]

To the OP, it seems to me (no evidence) that it's not a bad idea to go a little more for quality rather than quantity regarding dives as you get older. Do you really need or enjoy 4 dives a day for 16 days in a row? I would think sitting out a dive every now and then and perhaps doing something else every few days while on vacation would be a good idea as well.

Fair question --- my personal preference is to dive as much as my physical limits allow when I do go diving. Some days that might be four or none. If I feel tired or other circumstances come up, then a day off is fine. Given my preference for doing multiple dives for multiple days -- and we all have our styles and preferences--, my question is about any consideration related to aging that I should factor into my preference. If I attend to physical conditioning and some of the other considerations noted in other posts, then it seems as if age itself is not a limitation for me to exercise my preference. There might be other non-age related issues, but I am trying to tease out any that are age-related.

I'm 62 and try to go below 100 ft. Ever. I think you were really pushing the limits going that deep and doing that many dives. I diveEAN and don't find it that much better. Besides I really don't see much better sealife at that depth anyway. As I age I personally see the effects that deep dives have on my body. I just finished my Master Diver Certification and continue to take classes to keep in touch with trends/safety issues. Deep dives are not part of my agenda

I am trying to identify the science that would indicate that deeper dives for that many days is problematic as it relates to age anyway. If I stay within limits indicated by my computer -- and I realize that has its own issues -- and I factor in some conservatism and my physical conditioning allows me to do those dives without feeling tired or show any DCS symptoms, then is there a problem based on what is indicated by existing science? If each of us makes a risk assessment based on a variety of subjective factors, then are there some objective findings in existing science or clinical experience that indicates we aging divers should do anything different?

I am curious about how you experience the effects of deeper dives? I am sure I have something to learn there.

Thanks for the comments and observations.
JR

 

[promocop]

With all due respects, diving with two computers set to different air
blends is a accident waiting to happen. No certification agency that I know of condones this practice. Big mistake!!!

 

[ianr33]

With all due respects, diving with two computers set to different air
blends is a accident waiting to happen. No certification agency that I know of condones this practice. Big mistake!!!

Why? (Provided that the O2 content is not set to more than the actual mix on either computer) How is that different to diving with both a conservative computer and an aggressive computer?

The only possible problem I can see in setting a computer to air when diving nitrox is diving deeper than 111 feet (assuming 32% nitrox) provided you can talk and chew gum at the same time thats not a problem.

Again,if you are that worried about it,put nitrox in the tank,set the computer to air,dont dive deeper than 111 feet. Put the backup computer set to nitrox in a pocket,check it for O2 loading after each dive. If its anywhere near the limit (which it wont be) take a day off.

Personally I would set the computer to nitrox and back off from NDL's if concerned about N2 loading. Instead of ascending when the NDL is zero ascend at 5, or 10 or whatever.