Tech class and narcosis?

[Kevrumbo]

I did an SSI DP course over 10 years ago where the maximum depth was 55m (180ft) on air. Skills like removing mask swimming whilst reeling a line and back in were done at 40 and 45m I had to do mine at 50m because we ran out of bottom time on the 45m dive for the three of us all on the course to do the skill, I was shitting myself because of the narcosis, I got through it just!! Then the final dive was to 55m a hot drop on to sand about 4nm off shore, do our 15min bottom time and then ascend. Vis was poor there was a moderate current and rather dark on the bottom, as the end of 15 minute bottom was coming to an end I started to feel rather anxious, my breathing started to build along with an uneasy feeling, we began our assent, and there is a period of the assent I can't remember, I just remember struggling to ascend, I was breathing like freight train my vision was narrow I had no idea what was going on around me, at one point I remember my instructor looking me in the face asking if I was ok and I gave him the not sure signal. Anyway arrived at 30m and things cleared up and really had no idea what just happened. We swapped to our first deco gas and got a shock when I looked at the content gauge of my back gas and was around 40 bar (should have been at 100 plus bar). Then had to deploy an SMB and went to remove it from its location at the base of my wing and was not there. By this stage my instructor was arriving at our level and he had my DSMB. What happened was my DSMB had unrolled itself and become wrapped around my legs inhibiting my ability ascend (all oblivious to me at the time). The instructor handed me my DSMB and I deployed and completed the deco and dive. All through the 30 or so minutes of deco I was wondering what just happened as had very little recollection of the assent from the bottom to around 30m, and thought I had flunked the course, a horrible feeling hanging there in mid water.

Back on shore and going through a debrief afterwards we discussed the troubles I had pointing to narcosis and discovered a few other things going on around me that I was not aware of like the dive master on the course having to help me assessed as I was apparently sinking at one stage, no idea this was happening at the time. I thought for shore I had failed. My instructor spoke to us individually and acknowledged the issues I had with narcosis and explained I had passed the course as was pleased with the way I had regained my composure. In the end I was just happy to get through it and vowed never to do a dive like that again. The course pushed me to my limits.

I have since gone on to do numerous deep air deco dives some to 55m, but always made sure we used a shot line or was adjacent to a wall/ steep reef and only when conditions were good. I had a number of horrible narcosis moments feelings of impending doom etc, but was always close to the shot or near the wall so would start to ascend and would soon clear. I went on to do OC trimix and eventually a rebreather and MOD2 trimix which has been a real godsend no more narcosis and horrible feelings of impending doom.

Thankfully now days it seems those deep air extended range type courses now have the option of using helitrox which I would have made use of if it was an option when I did my course all those years ago now.

Along with max working ppO2 and optimal END of your bottom mix, another lately important and new parameter to consider is gas density value in grams/liter. Anything 6 g/l and above at deep depth is badly conducive for generation of Work-of-Breathing CO2 Retention, especially with hard physical exertion/activity at depth. @Tassi Devil Diver ,your symptoms of anxiety and hyperventilation back then were classic signs of metabolic CO2 build-up with exertion, complicated further by Nitrogen Narcosis.

For example, in this case at 55m (180ft), the gas density of Air is a whopping thick 7.3 g/l, while a standard Trimix of 18/45 is around 4.5 g/l. The point is if you're going to do a
deep tech dive breathing Air, you better have a scooter/DPV providing your mobility especially if you have to make headway against currents at depth.

 

[northernone]

Along with max working ppO2 and optimal END of your bottom mix, another lately important and new parameter to consider is gas density value in grams/liter. Anything 6 g/l and above at deep depth is badly conducive for generation of Work-of-Breathing CO2 Retention, especially with hard physical exertion/activity at depth. @Tassi Devil Diver ,your symptoms of anxiety and hyperventilation back then were classic signs of metabolic CO2 build-up with exertion, complicated further by Nitrogen Narcosis.

For example, in this case at 55m (180ft), the gas density of Air is a whopping thick 7.3 g/l, while a standard Trimix of 18/45 is around 4.5 g/l. The point is if you're going to do a
deep tech dive breathing Air, you better have a scooter/DPV providing your mobility especially if you have to make headway against currents at depth.

I always enjoy your writeups.

That's a significant factor in my experience and when I finally learned why a few years ago it made sense.

Regards,
Cameron

 

[_Ralph]

On a tech dive, narc'd and CO2 sucks!!!!!

So much so, that on some dives, I'll go 30/30 instead of 32% because of it.

Also true for fun recreational diving, but I don't mind that as much (in nice clear, warm water with lots of things to look at or to amuse. Here in cold, dark, nothing much to look at dives ... eh nope!)


As for which path to go down,

The GUE route is ~$3000 + gas/charters (Just under 2 weeks of instruction, both Fundamentals and Tech 1) to get 170ft/51m 45% He and 30min of deco vs .... ?? I don't know the other routes unfortunately. **Plus 25 dives between courses**

_R

 

[Kevrumbo]

I always enjoy your writeups.

That's a significant factor in my experience and when I finally learned why a few years ago it made sense.

Regards,
Cameron

OMG, especially what you experienced Cameron (Blackout. Currents. Rebreather): glad you're still here to talk & advise about it!

I think every tech student for both OC & CCR should view and review this video by Simon Mitchell -it covers and best explains the pathophysiological effects of CO2/Hypercapnia, especially hearing the spooky coughing exhalations indicating "Dynamic Airway Compression/Collapse" of the late David Shaw on his CCR as he began to lose consciousness . . .

On a tech dive, narc'd and CO2 sucks!!!!!

So much so, that on some dives, I'll go 30/30 instead of 32% because of it.

Also true for fun recreational diving, but I don't mind that as much (in nice clear, warm water with lots of things to look at or to amuse. Here in cold, dark, nothing much to look at dives ... eh nope!)


As for which path to go down,

The GUE route is ~$3000 + gas/charters (Just under 2 weeks of instruction, both Fundamentals and Tech 1) to get 170ft/51m 45% He and 30min of deco vs .... ?? I don't know the other routes unfortunately. **Plus 25 dives between courses**

_R

Unless you plan to go all the way to the JJ CCR with GUE, it's going to be very expensive just to keep your Tech ratings. From their website, "GUE divers are required to perform twenty-five dives at their highest level of certification over the three-year period to re-qualify for an additional three-year period", which is do-able, but strict helium -no deep air- open circuit diving is now becoming a high price commodity within GUE's model just to keep up to their certification standards. Well worth the training, but again very costly to stay current.

 

[Tassi Devil Diver]

Along with max working ppO2 and optimal END of your bottom mix, another lately important and new parameter to consider is gas density value in grams/liter. Anything 6 g/l and above at deep depth is badly conducive for generation of Work-of-Breathing CO2 Retention, especially with hard physical exertion/activity at depth. @Tassi Devil Diver ,your symptoms of anxiety and hyperventilation back then were classic signs of metabolic CO2 build-up with exertion, complicated further by Nitrogen Narcosis.

O yeah worked out many years ago the main reason for those horrible feelings of impending doom type narcosis was primarily related to CO2, where I could mitigated it by reducing exertion at depth and latter getting trimix certified.

 

[stuartv]

On a tech dive, narc'd and CO2 sucks!!!!!

So much so, that on some dives, I'll go 30/30 instead of 32% because of it.

Also true for fun recreational diving, but I don't mind that as much (in nice clear, warm water with lots of things to look at or to amuse. Here in cold, dark, nothing much to look at dives ... eh nope!)

But wait! Are you saying that dive conditions are a factor in the overall experience of being narced? How can that be? I was told that the experience is the same whether you are cold, deep, and in the dark, or if you were even in a hyperbaric chamber. Maybe @Kevrumbo can try explaining it to me again.

 

[Kevrumbo]

But wait! Are you saying that dive conditions are a factor in the overall experience of being narced? How can that be? I was told that the experience is the same whether you are cold, deep, and in the dark, or if you were even in a hyperbaric chamber. Maybe @Kevrumbo can try explaining it to me again.

Go ask to try the Navy Experimental Dive Unit's Ocean Simulation Facility in Panama City Florida, which is a submerged test subject, wet type hyperbaric chamber. Tell them to set you at a depth of 170fsw with surface supplied Air and a water temperature of 52 deg F. Jump on the provided exercise bike, start pedaling and turn off the lights. . .

Otherwise, a dry dive in the Catalina Hyperbaric Chamber to 165fsw is a realistically practical, accessible, and reasonably safer way for a civilian recreational diver to experience the effects of Nitrogen Narcosis. . . More fun too in the company of some Lady Divers getting silly in the "heat of compression."

 

[Diver0001]

So I'm interested in taking a tech class at some point in the future. Looking at TDI AN/DP and GUE Tech 1. My only reservation with TDI is diving that deep and getting narked. What mix do people normally use for AN/DP? 24 or 25%? Air? The max depth is 150' and even if you are using 25%, doesn't that almost guarantee that you will get narked? Being narked makes you stupid and I would prefer to not be stupid, especially so when doing a dive that incurs more risk than what I normally have done so far. Is there any way to do TDI classes from the beginning using some helium?

Actually, I think there is a nuance to be made here. I'm not a TDI instructor but I have followed IANTD and TDI training, so take this for what it's worth. IIRC from my own TDI training the book basically puts the onus on the diver to be smart. If I'm not mistaken the basic message is that since you CAN use air to a given depth that TDI isn't going to "nanny" you and tell you that you aren't allowed. They're going to treat you like a big boy and let you make up your own mind if you think you can handle it or not.

That's basically the tone the book takes. You are used to the agency giving you "rules" to follow but TDI (and IANTD does the same thing) is going to tell you that by the time you're taking tek training that you should be able to process the information without a "recipe book" on how to dive and that's all they give you.... the information. This is very different than my understanding of how GUE does it.

In terms of actually getting that information the IANTD books read like stream of consciousness whereas the TDI books are very succinct and to the point. The training is quite similar but if all things were equal and you had to make a choice based only upon the book then the choice in my mind would be very clear.... TDI has better books. In fact, TDI has quite good books because they tell you exactly what you need to know, they lay it out very clearly and they don't confuse or bore you with a boat load of adjunct information.

Secondly the standard, regardless of agency, will certainly have a "minimum" depth for some dives as well as a "maximum" depth. In my experience during tek training it's the student's call to pick a depth they are comfortable with for the dive (between the minimum and maximum). The instructor may have a suggestion but at this level the students are planning the dives. You are in control here so to decide if you're ok with it or not, you need to look at the minimum depths for the dives, not the maximum depths.

R..

 

[Remy B.]

So I'm interested in taking a tech class at some point in the future. Looking at TDI AN/DP and GUE Tech 1. My only reservation with TDI is diving that deep and getting narked. What mix do people normally use for AN/DP? 24 or 25%? Air? The max depth is 150' and even if you are using 25%, doesn't that almost guarantee that you will get narked? Being narked makes you stupid and I would prefer to not be stupid, especially so when doing a dive that incurs more risk than what I normally have done so far. Is there any way to do TDI classes from the beginning using some helium?

Like most had already make good points.

the only way to know how narced you are is by doing such dives, do you have already your Deep Diver certification ?? if not it will be the basis point before you go to TEC training, if you feel comfortable diving deep ( and I know persons that don't ) then go for TEC diving, as well I will suggest to do a Deep Diver course with a TEC instructors and not with Rec instructors, because all what they do is take you as fast as they can down and as fast as allowed up, at the end you will probably feel like S..T when you are at 40m and you will feel like S..T when you are out of the water.

a TEC instructor will normally take you in a passed manner and go up by levels, there is a big difference on how your body reacts to fast descents vs passed ones, as well on you way up even following the suggested ascent rate it is still to fast and those 3-5min at 10ft will not do any good to not make you feel like S..T out of the water coming from 130ft, a TEC instructor knows the numbers and he know how to passe the ascent as well, it really makes a difference.

I was victim of bad Rec instructors and had seen as well others that had suffer from the same issues, there are a lot of Rec instructors that seems too scary about Deco, and seems to not have well a understanding of how much gas you still have over with a 80cf bottle even if you stay there for 2 min and make the descent in 6 min.

I had a buddy that did the AN/DP but fail to continue with DP because he just can't cope with depth, he feels very uncomfortable, know other persons as well with the same problem ( or maybe fear ), so it will be good that yo first do the Deep Diver course if you don't have it, it brings in as well a lot of knowledge about gas calculation and risks of diving deep, maybe it scares you and you change your mind and safe you some money.

Money is the other factor about TEC diving, everything is Double or triple or even more depending how dedicated you want to be to Tec diving, so bare in mind a big chunk of money comes out for decent equipment.

 

[stuartv]

Like most had already make good points.

the only way to know how narced you are is by doing such dives, do you have already your Deep Diver certification ?? if not it will be the basis point before you go to TEC training, if you feel comfortable diving deep ( and I know persons that don't ) then go for TEC diving, as well I will suggest to do a Deep Diver course with a TEC instructors and not with Rec instructors, because all what they do is take you as fast as they can down and as fast as allowed up, at the end you will probably feel like S..T when you are at 40m and you will feel like S..T when you are out of the water. .

Well, that seems like a gross and ridiculous generalization. The ones I have seen teaching Deep take their students down to NC and dive a wreck that is in a suitable depth range. It's a perfectly normal dive other than doing whatever exercises they do at the beginning of it.

I'm not saying all Rec instructors do that. I'm saying it's not correct to say that all Rec instructors will do the BS that you described.