Not diving to greater than 30m/100ft unless with helium

[boulderjohn]

I suspect that I am more tolerant of narcosis than the average diver. I have a lot of dives in the 100-150 foot range without benefit of helium, and the few times that I noticed narcosis was when some issue developed that revealed I was not thinking clearly. I have never actually felt anything different. On a recent dive to about 200 feet, when we analyzed tanks prior to the dive, we realized that the blender had blundered, and one of the sets of doubles only had 20% helium. The most experienced diver in the group (by very, very far) used those tanks, which was only fair, since he was the one who had blended them. After the dive, he talked about how badly narced he had been. I have never felt anything like he described.

That being said, when I was doing my cave training, with much of it at Ginnie Springs, I was very much aware of the fact that while performing my skills at about 100 feet, I felt like I was being unusually dense. The dive plans were simple and well explained, but I had trouble remembering them. I felt like I was fumbling around on skills I could normally do easily. Perhaps it was the pressure of performing in the class that was making things worse, but I felt like I was acting like a dolt.

Lynne and I talked about our experiences like that on a couple of occasions. She had experienced the same thing, and she was convinced narcosis was in play. She said words to that effect many times in many forums.

The point I am trying to make is that in talking about narcosis with her, I believe she was NOT saying that she was unusually impacted by narcosis. She was instead saying that EVERYONE is more impacted by narcosis than they think they are, and EVERYONE should be more cautious because of it.

 

[beester]

The point I am trying to make is that in talking about narcosis with her, I believe she was NOT saying that she was unusually impacted by narcosis. She was instead saying that EVERYONE is more impacted by narcosis than they think they are, and EVERYONE should be more cautious because of it.

Exactly!! To put in one more anecdote in the bowl... Before me joining the religious group called GUE (tongue in cheek), I did quite a lot of air dives to depths of 40m or more. In fact if I look at the first 300 dives I did, about 100 of those were 40m (120ft) or deeper. So you could not say I wasn't prepared/accustomed to depth. Something that happened in those days I always use as an example trying to explain inert gas exposure/narcosis to students who are advancing to cmas *** (let's say between rescuediver and divemaster). Because it identifies a common misconception on narcosis... that it hits hard, and that you'll be totally incapacitated, which of course is not always the case.

"I was doing a dive in a nearby North Sea estuary, with a lot of current if you missed slack tide, bad vis (max 10ft), coldish (10c° at that moment). A very experienced friend (at that moment +1000 dives, me about 270) planned a shore dive at that point. The bottom drops off quite fast to 40m then it levels of and slowly descends to a further 45m (135ft). My buddy was leading the dive... at 40m on the shelf we started swimming out and after about 5 minutes my buddy turned to me and told me to take the lead and head back out. I put up the question mark sign asking what's going on. He showed me his computer (one of the first uwatec sols, which were just launched at that moment... must have been 2007 or 2008). I looked at it but didn't see anything strange... he pointed again at his computer, I examined it again for another 20-30 seconds.. nothing. I thought, well ok... no prob I'll lead out, let's head back out. Back up at 20m, during a short stop, I asked again to see his computer. I immediately noticed that the depth showed "28m", and obviously being at 20m this is wrong and his dc must have crashed."


When I tell this in class, some of the remarks are: it was a DC you didn't know or the screen was cluttered with information. That is all true... however the most obvious digit on the whole thing was depth, as it should be. I'm sure at that depth that I saw the depth... because I looked 2 times at it for a good long 20 to 30 seconds, but my brain simply could not compute the actual issue.

That's why when I want to be totally in tune... my situational awareness needs to be topnotch (like in every cave or deeper wreck dives), well I'd like to keep my END below 30m and rather a lot below that. Of course your mileage may vary (by a lot looking at my club 100m divers).... and a lot has been written about pro and con, when the onset is, if you can manage narcosis, etc...

All I think Lynn was saying is, that depending on circumstances, you may need to re-evaluate your personal narcosis limits. Err on the safe side... maybe she used a high flow Florida cave as a personal example of when she would do that.

 

[Adobo]

Lynne was describing a specific situation in those quotes. I used to get pounding headaches just getting to the mainline ... and that's just at 70 feet. But then, my technique for staying out of the worst of the flow sucked ... particularly if I was laying a line going in. It's a matter of doing it often enough to know what you're doing. Lynne got better at it in time ... but even she just didn't go to Florida often enough to develop the skill particularly well ... that's one reason why most of us from here prefer our cave diving in MX, where you don't have to fight a cave that's trying to spit you out all the time ...

(Grateful Diver)

I've done plenty of dives to 100ft in Northern California in some very unpleasant conditions. Even with that experience/comfort at those depths on 32%, going through the first 200-300 ft of Ginnie still kicks my arse. I get headaches just trying to get through the gallery.

Most experienced cave divers would tell you that its due to my poor technique, which would sound perfectly reasonable to me. As you say, high flow caves and open water recreational dives are very different things.

I haven't paid much attention to what Lynne has written on this topic. Honestly, I don't really see what there is to discuss as it relates to Lynne. She was an advocate of using helium on dives approaching 100ft, particularly if the conditions are challenging. And she had vertigo issues.

Short of suggesting that she should have given up diving altogether, I don't know what else would have been recommended for Lynne.

I mean, if anything, having met and dived with Lynne a few times, the only thing I can think of that might have helped her in general is maybe to do a lot of training in the gym. Cardio and strength training. Because frequently, she was carrying/using gear that looked like it weighed more than she did.

And frankly, the recommendation would not have been specific to Lynne. It's something I would recommend to anyone.

 

[Storker]

"I was doing a dive in a nearby North Sea estuary, with a lot of current if you missed slack tide, bad vis (max 10ft), coldish (10c° at that moment). A very experienced friend (at that moment +1000 dives, me about 270) planned a shore dive at that point. The bottom drops off quite fast to 40m then it levels of and slowly descends to a further 45m (135ft). My buddy was leading the dive... at 40m on the shelf we started swimming out and after about 5 minutes my buddy turned to me and told me to take the lead and head back out. I put up the question mark sign asking what's going on. He showed me his computer (one of the first uwatec sols, which were just launched at that moment... must have been 2007 or 2008). I looked at it but didn't see anything strange... he pointed again at his computer, I examined it again for another 20-30 seconds.. nothing. I thought, well ok... no prob I'll lead out, let's head back out. Back up at 20m, during a short stop, I asked again to see his computer. I immediately noticed that the depth showed "28m", and obviously being at 20m this is wrong and his dc must have crashed."

Although I certified in this decade and try to avoid depths exceeding 30m (I, too, have a low acceptance for being impaired when underwater), I know quite a few divers who have been doing their stuff for a few decades and thus has done more than a few deep air dives. They can tell stories that aren't too different from yours. Scary stuff. Most - if not nearly everyone - of them have quit using air if they go deep. Some of them prefer some He in their mix already from 30m.

 

[Hawkwood]

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[bowlofpetunias]

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[Kevrumbo]

. . .
"I was doing a dive in a nearby North Sea estuary, with a lot of current if you missed slack tide, bad vis (max 10ft), coldish (10c° at that moment). A very experienced friend (at that moment +1000 dives, me about 270) planned a shore dive at that point. The bottom drops off quite fast to 40m then it levels of and slowly descends to a further 45m (135ft). . .

Cold Water immersion especially, which would initially tend to increase breathing rate upon splashing in and descent to depth: you would want an easier breathing Helium mix at depth to help mitigate hyperventilation & CO2 retention/narcosis.

 

[Akimbo]

Cold Water immersion especially, which would initially tend to increase breathing rate upon splashing in and descent to depth:...

I still have the expectation of the "cold water rush" from years of diving a wetsuit, but these days I am almost always overheated in a drysuit and hitting the water is a relief to the onset of hyperthermia. I have actually felt disappointed on several jumps that the cool-down wasn't nearly enough. Kind of weird really. My brain is pre-wired for one expectation but the reality is approaching the exact opposite.

 

[100days-a-year]

Nearly all my dives now are working and 95% past 100' IMNSHO..

Cold water= more restrictive suit+more muscular tension and possible shivering=More C02
Cold water=cold water near the inner and middle ear leading to more likelihood of vertigo
In my case cold is below mid 70s and it is noticeable but not significant the difference in job performance including on video.

Adaptation may or may not be physiologically quantifiable but I am better on day 5 than on day 1,better in November than May when starting fresh and December thru March when cold,this phenomena is common to the guys I dive with,the least experienced of which with over 5K dives.

 

[Steve_C]

I suspect that I am more tolerant of narcosis than the average diver. I have a lot of dives in the 100-150 foot range without benefit of helium, and the few times that I noticed narcosis was when some issue developed that revealed I was not thinking clearly. I have never actually felt anything different.
.....
She was instead saying that EVERYONE is more impacted by narcosis than they think they are, and EVERYONE should be more cautious because of it.

Not sure that your first sentence is totally compatible with the next three. Maybe you are just better trained and have more good habits that you can rely on than most.