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How do you learn your narcosis depths? Gas switches?

Discussion in 'Diving Physics, Physiology, & Medicine' started by MichaelMc, May 19, 2021.

  1. MichaelMc

    MichaelMc Working toward Cenotes ScubaBoard Supporter

    # of Dives: 100 - 199
    Location: Berkeley, CA
    How do you learn what depths have a mild to strong narcosis effect on you? In the range of say 80' to 130' and no-deco?

    Do you, plan 1:
    Do pairs of dives, one with helium and one without? Remembering how you felt at each of a few of those depths, and then comparing that to your feelings two hours later? Using say 32/15 and EAN32 for two separate dives covering the range 80-100. And 28/25 and EAN28 to cover the deeper range of 110-130 on additional pairs of dives, as needed and given shorter NDL.

    Or, plan 2:
    Compare within a dive, switching between a helium and a non-helium gas during the dive? Noticing the difference in the moment, at each depth, instead of reflecting across different dives. Switching between say 21/15 and EAN32 for a shallow dive, and maybe 21/25 and EAN28 for a deeper dive?

    Or is there concern with such switches, or switching between, say 28/25 and EAN28 for these relatively shallow dives? Or no concern?
  2. tbone1004

    tbone1004 Technical Instructor ScubaBoard Supporter

    # of Dives: I'm a Fish!
    Location: Greenville, South Carolina, United States
    no concern about those gas switches

    unfortunately narcosis is highly volatile and wildly unpredictable so there is no good way to figure it out especially since so much of it is CO2 dependent...
  3. shurite7

    shurite7 Dive Shop

    # of Dives: 1,000 - 2,499
    Location: In transit
    The first time I learned that I had been narced was on my first trimix dive in the same location and depth as the previous dive that had been on air. That is when I learned how much I didn’t notice on the previous dive

    Because narcosis is so variable it can be challenging to recognize it.
  4. rolanddiver

    rolanddiver Registered

    # of Dives: 1,000 - 2,499
    Location: Hungary
    It varies day by day, depending on a lot of factors such as hydration level of your body, stress level, restlessness, fatigue, etc. Most of the times, you won't even notice a mild narcosis, you just simply don't remember some parts of the dive (like seeing a big fish, etc) . Just don't know that you don't remember.


  5. Lorenzoid

    Lorenzoid ScubaBoard Supporter Staff Member ScubaBoard Supporter

    # of Dives: I just don't log dives
    Location: Atlanta, USA
    How narced one feels versus depth is probably a continuous function, although it may not be linear, and it may even begin at surprisingly shallow depths. I doubt there is a useful way to quantify narcosis versus depth.

    I'm not a trimix diver but I did sleep at a Holiday Inn Express, no, wait--I mean but I did get a limited certification to dive "triox" 30/30. On those dives, at just 65 ft. or so but working hard on problem-solving exercises in cave class, I felt the clarity was amazing compared with similar dives I had done involving similar physical and mental exertion. I'm convinced that without the helium I am impaired to some extent at even such modest depths.
  6. wetb4igetinthewater

    wetb4igetinthewater Instructor ScubaBoard Supporter

    # of Dives: 500 - 999
    Location: Seattle
    Maybe that is what fuels denial?
    Miyaru, MichaelMc and RyanT like this.
  7. Akimbo

    Akimbo Just a diver Staff Member ScubaBoard Supporter

    Interesting. My experiences are very different. Recognizing narcosis has never been difficult and is reasonably predictable. I could not agree more that CO2 is a huge factor but, with a little training/experience/awareness, is easily and quickly rectified by deep breathing and exertion control.

    I have had the opportunity to dive air and HeO2 to the same depth up to 4 times per day, alternating air and mix on different dives. The depths were in the 165'/50M range and we were on open-circuit Scuba. It got to the point where we had trouble telling the difference between a mix and air dives except for being colder.

    Other air jobs were surface-supplied in the 180'/55m to 220'/67M range lasting several weeks. The level of impairment was fairly consistent and manageable. We progressively simplified the tasks as depth increased, excepting and working around the expected levels of impairment. All of these were working dives so performance was measurable by completing moderately complex tasks. I never perceived that my resistance to narcosis was much different to others I worked with, as measured against job performance.

    That said, we were all experienced divers and most had military or commercial training. The common denominator was learning to manage narcosis and CO2 slowly and progressively.

    An exception was on a treatment of an unconscious diver in a large multi-chamber saturation complex. Log story short, the patient and a doctor comes alongside and are hustled to the chambers with me as inside tender. We dropped to 60' on a US Navy Treatment Table 6 with no change. We decided to drop to 165' on a Table 5a. The patient started waking up around 155' and was fairly coherent when we stopped at 165'. The patient would start to lose consciousness when we started a normal ascent so we went back to 165' a couple of times. The doctor functioned reasonably normally, taking vitals and discussing the patient's condition.

    We learned that the doctor had almost no hyperbaric knowledge when he requested being let out so he could go back to the hospital after several hours at 165'. We were essentially committed to an air saturation decompression schedule. Granted this is only one data point, but significant because he had not been able to slowly work up to deep air. And yes, inside a chamber is different than in cold water.

    My initial Scuba training in 1962 explained what narcosis was and depths where we could expect to experience onset. We were not taught that is was like an LSD trip or drinking tequila all night. The message was to watch for it and cautiously progress deeper slowly as we learn to manage it and discover our limits.
    Lostdiver71, wnissen, Bob DBF and 6 others like this.
  8. Marie13

    Marie13 Great Lakes Mermaid ScubaBoard Supporter

    # of Dives: 200 - 499
    Location: Great Lakes
    Increasingly deeper and repetitive dives, especially in 2019. I discovered that for me it starts about 115-120ft. At 130ft (the deepest I've gone so far), I'm feel like I'm in slow motion and have what I refer to as "mush brain." That's why I'm doing AN/Helitrox. I want to remember the deeper wrecks I do, and then there's the safety factor if SHTF
    Lorenzoid and MichaelMc like this.
  9. Scuba Client

    Scuba Client Banned

    # of Dives: 500 - 999
    Location: Australia
    Most divers would know their Equivalent Narcotic Depth before using Trimix. If not, the limit recommended is 30 to 40 metres. Advanced Diver Course should let you know how you're feeling at these depths.
    MichaelMc likes this.
  10. decompression

    decompression Instructor...seriously...

    # of Dives: 5,000 - ∞
    Location: Victoria, BC, Canada
    My first thought when I read the post was an analogy......

    would you practice driving drunk to see how it affects you? A bit tongue in cheek but still.....

    certainly dives that are layered in good choices for safety could be used as tests for narcosis affects...but there are so many variables that any results would be highly anecdotal.

    Best to use air/Nitrox for 100’ dives or less and throw some He in there when deeper. Several progressive agencies use an EAD of 100’ for a reason.
    rjack321, Lorenzoid and MichaelMc like this.

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