Yep. Wrong direction. I agree with you. I ordered Nitrox, boat brought air. Yes I did switch computer. The times listed were total dive time, bringing the average depth up. But the bottom was consistent without much variation in depth so I was at bottom with exception of slow accent and safety stop. No computer warnings and computer did not go into deco mode. DAN reviewed dive profiles for both days and felt comfortable with dives, but I’m still researching and learning. Went back to the same dive sites last week. Dove one more dive, deeper dives but shorter bottom times and with no problem. Also switched to 100% O2 at safety stop.
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Just to double check, the dive depths you posted were average depths as calculated by the computer and NOT max depth? It might be interesting to post a picture of the dive profiles for the four dives.
I.e., on the second day you did a 30 minute runtime dive on Air with an average depth of 105' followed by a SI of about two hours and then did a 32 minute runtime dive on Air with an average depth of 98'?
If I assume (yes, I know the old saying) a 30 fpm descent and a 30 fpm ascent with a 3 minute safety stop and a square profile then on your first dive you essentially had 9 minutes of transit/stop time and 21 minutes on the bottom. Correct?
If I assume you had a square profile at a constant max depth of 105' for 21 minutes of bottom time (not even using that as the average depth), then we can run an approximate dive plan for your first dive on the second day. I come up with about 15 minutes of deco (if you are using air for deco) and the runtime with that deco schedule would be about 38 minutes.
Either we aren't agreeing on terms (i.e., why it would be good to post the actual profiles) or you definitely exceeded NDL diving. YMMV and that doesn't even consider the second dive which was basically the same depth profile.
- brett
Your assumption on descent and ascent will be close although the ascent was longer than the descent. I normally get to 100’ in less than a minute, but take my time coming up and with a little longer than 3 minute rest stop. Second day dive 1 average depth 63’ max 105’. Second dive average depth 60’ max 98’. At max depth roughy 60% of total dive time. Profile of first dine pretty square. Flat bottom. Second dive a little more variable.
Degenerate
Contributor
If your dive profile was square or thereabout then the dives you listed for day 2 would be deco dives.
If I punch in 30 minutes at 30m with air in MultiDeco, with GF 50/80 I get a 15 minute deco stop for that dive.
I would ask if it is possible that your dive computer is set to gauge mode which wouldn't show you things like NDL etc, but I find it very unlikely that the person you were diving with would also have made the same mistake.
Max depth on air has little relevance here, compared to time spent breathing it at depth.
Edit: Just saw the profiles you posted.
Looks like you did a deco dive (or very nearly at least).
Surprised your computer didn't call it out, which again leads me to believe it might have been set to gauge mode...
Yes computer does show NDL and I was not it deco. It also adds a warning to my log if I hit deco. No warning. Dove time was ok. I think it’s more physiological that a mistake reading my computer. Air was set properly. Risk level moderate at L3.
Hi
I understand you want to get an explanation to your previous hit expecially when everything seems to be within the normal parameters.
But, regarding diving, a lot is unknown and a bit of fatalism might help a bit as the body is complex and what is fine one day may not be fine another day.
If I may suggest, I will make the last part of your dive a bit longer if you have the gas and are not cold. Staying a bit longer within the last 12 m.might help and with a single s80 (or similar) you can get an one hour dive.
You dive to see the underwater world so enjoy it
I understand you want to get an explanation to your previous hit expecially when everything seems to be within the normal parameters.
But, regarding diving, a lot is unknown and a bit of fatalism might help a bit as the body is complex and what is fine one day may not be fine another day.
If I may suggest, I will make the last part of your dive a bit longer if you have the gas and are not cold. Staying a bit longer within the last 12 m.might help and with a single s80 (or similar) you can get an one hour dive.
You dive to see the underwater world so enjoy it
Your second profile is a bit up and down.
There are always very small bubbles, your lung filters them out. If you have a PFO those bubbles can by pass the lungs and get from the veins to the arteries. Arteries get smaller away from the heart and the small bubbles may block flow. Similarly, going deeper will squash bubbles so the can pass the lungs, then going up they become bigger while on the arterial side where they are more of a problem.
in your example you had not spent a long time at depth before the initial ascent, so I would not claim cause and effect, but it is better avoided.
@Hortondon , not knowing the circumstances I'm not judging your particular case here, but just for the sake of posterity reading this, being bent without the need for hyperbaric oxygen therapy is a statement that can only be made after the final outcome is known. The gold standard for treating decompression illness is HBO2, and the determination not to treat should only be made by a qualified medical professional.
All that said, it looks like there have been some very reasonable answers to your questions here. I don't know of any research out there that directly compares the benefit (whatever that benefit may be) of breathing O2 at your safety stop vs breathing it during your surface interval, so I think it would be a personal choice. If you want to do it under water, I'd highly recommend taking the appropriate training first. Breathing it during your surface interval would speed off-gassing but the time/dose effect would be difficult to quantify and I would certainly not use it as a reason to dive more aggressively on the second dive. I think that the risk of O2 toxicity from this would be negligible with the diving that you're describing.
Best regards,
DDM
The diagnosis was may be DAN and the hospital. Not being sent to a HBC was partly
The diagnosis wasn’t self-diagnosed. It was made between DANa nd the doctor at the hospital. A DCC would be nice if there is one in working order wherever it is that we dive. In this can there is one in the city I was in but it was broken. The flight to the next DCC was 1,000 miles. Fortunately my case didn’t require a DCC to treat me.
Lots of good answers here to try to point out why this happened but I was not in deco as many think. The logical answer is that everyone’s physiological make-up is different and one’s make-up can be different based on environmental conditions and health of the diver on that particular day. I do know that I was diving at the limit which comes with more risk. It wasn’t my day.
I am just researching the effects of using O2 as a pre- and post-treatment. There does seem to be some evidence that it does work to reduce the likelihood of DCS but O2 itself comes with risks.
I appreciate your post.
This is the best explanation I’ve heard and do suspect that I had certainly reached the point VGE where the bubbles come out of the cells and into the blood stream.and I believe you are likely correct that bubbles were bypassing the heart and into the veins, hence the bends.
I appreciate your observation of the bottom profile. Viz was about 10 feet so you follow what you can see. It will cause me to think about this in the future on deeper dives in poor viz. It had not occurred to me that the variation in my dive profile rather than total time at depth could be a contributed. I appreciate your observation and sharing it with me.
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