Deep Air?

[MaxBottomtime]

I was in the same boat. I had weekly dives with buddies from 165' to 180' with the occasional 200'+ dive on air. I never had a problem telling my buddy I was ascending if I felt I was getting too narced. I didn't feel too narced on most dives including one to 240'. I found two lights and a slate on the bottom. One light was heavily encrusted so I left it there. The second one still worked so I clipped it off. I read the slate and knew the instructor's name on it so I clipped it off as well. I made a normal ascent and had no problems at all. A week later I was very narced on a 100' wreck dive. Go figure.

Sometimes I would get narced from a workload such as moving the anchor. I learned to stop, take two long slow breaths and the feeling went away. These days I'm diving with buddies who only use nitrox so we don't go deep. If I make a deep air dive such as the UB88 in 180-190' I go solo and only stay 6-10 minutes. I have used trimix and if were cheap I would likely use it more but I don't make enough deep dives to warrant the expense.

 

[Diver0001]

Oh... and I should add this.... As a PADI instructor I have a searing allergy for the manner in which deep training is done.

I worry SO much about how we approach both the advanced course as the deep specialty that I'm very reluctant to teach advanced if the student does not want to seriously learn how to dive deep. As a result I seldom teach advanced because I can't stand to see students being certified to dive to 30m when the vast majority are (a) not really interested and (b) not ready.

The advanced courses I HAVE done have all been with students who were hooked on diving and wanted to clean up their skills... I don't believe I've ever done one with a student who didn't really want to work for it.

 

[OrangeCountyScuba]

@Diver0001
Thank you very much for the straight no bs answer. It is actually rather refreshing that someone has actually said "this is what I do and if you dont like it f*** off", of course your actions are going to get some feedback that may be a bit hostile, fire proof pants…..good idea. I find it ironic that you dont drink, do drugs but you live in one of the only countries that is alright with the use of certain substances. It seems to me you are a bit of a junky though, you just happen to tie in a little bit of "excitement" while you are getting your fix, haha. Whether or not I agree with you, at least you are upfront and realistic with your reasons for doing so, I respect that. I have done some intentional "narc" dives myself but never pushed it as far as you have, if I remember correct I think I went to around 160 and was quite enjoying myself for a few minutes. I worked as a commercial diver for awhile, I was the DMT on the crew and occasionally(not while offshore), we would hop in the chamber and get ourselves narced out of our gourds, to "test" the plumbing in the chamber, haha.
Your going to get a lashing for saying, its more "challenging" to do a dive without trimix. I completely agree with you that the advanced cert that introduces deep is kinda useless, but that would depend on the instructor also. I appreciate you taking the time to write that all out for me, it was exactly what I was looking for. Cheers

 

[decompression]

Diver0001's post is refreshing and possibly indicative of many of us that do a majority of teaching in cold, dark current swept water. Too many instructors see the standards as gospel and don't have awareness that there should be more to it. Certainly as depth poses new issues to deal with.

 

[Kevrumbo]

Use Helium at depth when you need cognitive clarity & N2 Narcosis mitigation while navigating/laying line inside an overhead such as a cave or wreck; also use He when you expect physically challenging conditions such as strong currents to work against, in order to minimize exertion Hypercapnia & extreme CO2 Narcosis.

Here's a practical example where having a robust easier to breath 18/45 Trimix gave this group of Tech Divers an "error margin" (e.g. CO2 retention moderation and a deeper MOD margin to deal with a strong downcurrent) and note in this incident, no mention of debilitating narcosis:
http://www.scubaboard.com/forums/ne...um-gas-underwater-climbing-drifting-away.html

(What would have happened if they used Air?)

Carbon dioxide acts as a respiratory stimulant and can cause depression of the central nervous system (CNS). The effect depends on the level of carbon dioxide in the blood. Deep diving produces elevated blood carbon dioxide levels for several reasons, which include:

1. the resistance to breathing caused by breathing denser gas [especially Deep Air] through a regulator and against a higher ambient pressure;
2. reduced ventilation efficiency due to the denser breathing gas; and
3. reduced transport, and, hence, elimination of carbon dioxide.

Hypercapnia increases narcosis and the likelihood of CNS oxygen toxicity. In addition, it may increase heat loss, alter heart rhythm and predispose to decompression illness. If the carbon dioxide level gets too high, and it can on deep scuba dives -- especially if a diver is very anxious and / or exerting him/herself -- the diver may go unconscious without warning. Certain divers are more susceptible to severe hypercapnia for a variety of reasons and are therefore more at risk.

CO2 Retention/Hypercapnia and Narcosis: Deep Air with increased Gas Density & Work-of-Breathing Dyspnea; then throw in Physical Exertion or a Stress Condition, resulting in overbreathing the regulator --all leading to the Vicious Cycle of CO2 Retention and sudden Narcosis (also known as the panicky feeling "Dark Narc"). Can result in severe cognitive impairment at depth or worst case stupor and ultimately unconsciousness. . . In order to break this CO2 build-up cycle, you have to relax with a few minutes of full slow controlled inspiration breathing: --cease & desist all physical exertion that stimulates hyperventilation and abort the dive if indicated.

Taken from Undersea Biomedical Research, Vol 5, No. 4 December 1978 Hesser, Fagraeus, and Adolfson:"Studies on the narcotic action of various gases have shown that the ratio of narcotic or anesthetic potency of CO2 and N20 approximates 4:1, and that of N2O and N2 30:1. From these figures it can be calculated that CO2 has at least 120 times the narcotic potency of nitrogen. Our data would suggest that the narcotic potency of CO2 is even greater, i.e., several hundred times as great as that of nitrogen.

"

Originally Posted by TSandM
Overbreathing the regulator MEANS a CO2 hit . . . It means the increased work of breathing of using a regulator is enough, at the current demand, to prevent you from exhausting all your CO2. All regulators can deliver more gas, faster than you can use up oxygen, but the small increase in resistance involved in trigger the inlet valve and opening the exhaust valve can make the difference between being able to keep your CO2 normal under heavy work loads, and not being able to keep up.

Panic in the experienced diver?

Originally Posted by TSandM
CO2 in the bloodstream is completely determined by minute ventilation, assuming the gas you are breathing does not contain additional CO2. Bailing to open circuit definitely makes it POSSIBLE to reduce the blood CO2 level, assuming you can achieve a higher minute ventilation than what's required to keep the CO2 where it is (which is in part related to level of exertion). It may not, however, be possible to reduce CO2 fast enough to clear your head and get rid of the panicky feeling, in part because the natural tendency when panicky is to breathe as fast as possible. On scuba, this means reducing the efficiency of the ventilation, because too much of it is just going to [dead space] in the trachea and large bronchi, which don't exchange gas [like the deeper lobar capillary alveolar bed]. That's why we are taught in OW that, if we begin to "overbreathe our regulator" (meaning the diver feels short of breath despite breathing as much as he can), we are to STOP, hang onto something (reduce exertion) and breathe SLOWLY and DEEPLY. It is then possible to reduce CO2. What may not be possible is to stay rational long enough to do it.

Panic in the experienced diver?

 

[DevonDiver]

Individual susceptibility to narcosis is certainly a factor. So is individual perception of that susceptibility. The problem with narcosis is that it doesn't really conform to the classical "martini rule".

If divers actually believe that narcosis presents only through symptom understood from the analogy of alcohol intoxication, then they will miss all of the more subtle, insidious signs and symptoms that'd otherwise indicate reduced mental faculty.

There are, I strongly believe, also 'placebo effects' because of this alcohol intoxication analogy. I've seen divers 'acting drunk' underwater at mediocre depths... just as I've seen kids 'acting drunk' when unknowingly imbibing non-alcoholic beers.

- American Psychological Society: Study Finds that Alcohol Placebo Impairs Memory
- BBC NEWS | Science/Nature | 'Fake alcohol' can make you tipsy


Placebo effects aside... Narcosis is insidious because the very effect of reduced mental perception shields the diver from being aware of the decline in their intellectual capability. In short, stupid people don't realize they are stupid.

What matters is whether the diver, regardless of reduced mental performance (known or unknown) is still functional at depth. I believe that functionality stems from ingrained skills, drills and procedures. Reduced mental faculty doesn't impinge on functions that are second-nature to the diver; at least, not until the narcosis becomes debilitating physically and/or neurologically.

Only when the diver observes impairment to their second-nature capabilities do they perceive the impact of narcosis.

The need to problem-solve, or the presentation of novel situations, brings a much more immediate perception of narcosis impairment.

For a novice diver, with few ingrained second-nature capabilities, perception of narcosis occurs quickly - at shallower depths. Mild narcosis exposes the fact that they are still problem-solving, rather than unconsciously performing, rudimentary diving functions.

As a diver gains experience and undergoes (effective) training, a wider spectrum of competencies are made second-nature and performed unconsciously. More skills are ingrained. More problems are encountered and solved; becoming planned reactions rather than novel issues to be solved.

Routine dive functions don't expose narcosis impairment until that impairment reaches a very severe level where it degrades autonomic functionality. Novel dive problems expose narcosis impairment rapidly.

Perceptions of narcosis impairment vary greatly; which means that the definition of what constitutes a 'deep' dive also vary.

There is increasing debate on the impact of CO2 increasing narcosis. I don't doubt that CO2 retention significantly increases the severity of narcosis and reduces the depth of onset.

Again, this factor favors those with more diving experience and skill. Within the parameters of a given dive, skill and technique can modify the need to resort to physical exertion. Breathing techniques are better. Stress management is improved. Experience acquisition tends towards better self-awareness; in particular, the recognition that respiration becomes elevated and the wisdom that exertion needs to be reduced or stopped.

All of the preceding issues factor into a very personal decision on narcosis management.

The competency to make decisions on narcosis management becomes clearer as experience and skillfulness develop. To the casual observer, this may seem like a very 'do as I say, not as I do' attitude by higher level divers. If that is the case, then it under-estimates the very real relationship between narcosis impairment and the level of autonomic dive function.

New article: Nitrogen Narcosis and Perceptions of Susceptibility

 

[sea_ledford]

I regularly do working dives to 150 on air. By "working" I mean scientific dives where I need to use my head, not digging/cutting/welding work. I can usually handle the narc without problem although sometimes a novel issue will result in head scratching, the inability to figure it out or worse, the inability to recognize there is an issue to begin with. 160 is my hard limit though. I have done air to 180 several times but the last time I had to swim hard for about 5 seconds, chasing after my buddy. I was instantly completely gooned out of me head. One of my tasks was to video my buddy testing sand depth with a metal stick and a pounder. He handed me the camera (already recording), and I had no idea why he was giving it to me. All I had to do was point the thing at him, and I was unable to do that without prompting. My buddy was on a rebreather and trimix, so he was just laughing at me. I still wonder if I would have been able to deal with a serious issue that I had trained for in that state.

Lesson learned from that one is deep air works fairly well, for specific tasks, until a problem arises. I consider it the equivalent to diving with no redundancy.

-Chris

 

[scubadada]

I was curious to see if there are any agencies or groups out there that still believe diving deep air. I know that many prior to the standardization and/or faith in trimix were nervous about moving away from deep air since that is what was the "norm". Also, someone diving deep air would have to contest a large amount of nitrogen narcosis, prolonged decompression, and should not dive past about 219 feet, if following the 1.6ppO2.
Just curious about deep air since I was not diving at the time trimix was introduced and at this point the industry and agencies alike use trimix with little thought now because it has been "proven" to be safer etc etc. Any thoughts?

You mean 220 feet at a ppO2 of 1.4

 

[Jim Lapenta]

When I was first getting certified the shop I was going through had an AOW class scheduled as well. One of the students was so worried about being narced on the deep dive that I look back now and think he may have actually talked himself into being worse off than he was. That said when it came time for my AOW class I looked at the deep dive as something that could possibly affect me rather than would. As such I don't think I took it as seriously as I should have.

Referring back to Rob's post this is one of the things I looked at when I became an instructor and realized the deep dive of the AOW or Advanced class for damn near all agencies was approached in the standards and the materials really half-assed. This was based on my now experience with technical diving and how the approach to any dive is so different.

As a result,within the standards of SEI, I wrote my own deep dive standards (in fact the entire Advanced course I offer) that more closely reflected the approach to dives from a tech standpoint. As such I talk a lot about narcosis and the different forms it can take. Also talk a great deal about "managing" it and how those management techniques can be effective for 10, 20, even 30 dives; but let one variable be a little different on that one day and all those techniques go right out the window.

I've been to 135 on air in 38 degree water. I knew I was narced but still able to function. To a degree. I would not attempt deeper than that without some helium in the mix. I discovered first hand that it doesn't take much. I had some 21/28 left over from a dive in lake Erie.

Was going to hit a lake in W.Va that was warm water (like 80 degrees at 110 feet) and rather than dump the mix I topped it off with air and ended up with 11% He as I recall. I had done this dive at least 50 times before on air and nitrox. That little bit of He made a staggering difference. I saw details and features that I had never noticed before with incredible clarity.

It was enough to know that unless it's is simply not available I really don't want to dive to 110+ without some He in the mix.

It was also enough to know that deep air ( more than 130), for me (especially when instructing), is not a risk I am willing to take on.

 

[OrangeCountyScuba]

You mean 220 feet at a ppO2 of 1.4

Uh no, I did mean 1.6 ppO2 at 219 fsw. Unless, the math has changed and I am not aware.
1.6ppO2/.21O2= 7.62ATA-1ATA= 6.62ATAx33= 218.46 fsw, is this math wrong? Someone else want to confirm this for me?