• Welcome to ScubaBoard

  1. Welcome to ScubaBoard, the world's largest scuba diving community. Registration is not required to read the forums, but we encourage you to join. Joining has its benefits and enables you to participate in the discussions.

    Benefits of registering include

    • Ability to post and comment on topics and discussions.
    • A Free photo gallery to share your dive photos with the world.
    • You can make this box go away

    Joining is quick and easy. Login or Register now by clicking on the button

Cardiovascular Fitness & CO2

Discussion in 'Basic Scuba Discussions' started by NavyDoll, Oct 21, 2003.

  1. NavyDoll

    NavyDoll Nassau Grouper

    Here's a question that I've been pondering since late last week...

    Is it possible to be TOO cardiovascularly fit for diving??

    I'm an avid scuba diver (imagine that?!)... and I run, cycle and swim to keep in shape and stay healthy! I have naturally low blood pressure (resting ~ 100/65 sometimes lower) and a low resting heart rate (50-55bpm).

    When I dive... my SAC rate is usually between 0.40 CFM & 0.50 CFM. I'm very relaxed in the water at depth and breath at the same rate throughout my dives.

    Last Friday, on a deep dive (137ft)... I experienced a bout of dizziness and shortness of breath. The major thought I had was... "oh ****... I'm going to pass out... I need to go shallower". We began a slow ascent and the symptoms started to disapate above 110-115ft..

    After the dive we discussed the possibility of my being narc'd... but the symptoms didn't really seem to indicate narcosis. Then I looked into CO2 Retention... and it seemed to better describe what I'd experienced.

    We have since concluded that although I breath deep enough... I don't breath often enough (NO.. I'm not SKIP BREATHING)!! I may have reached a point where I'm too cardiovascularly fit... to dive and breath the way that I normally do!!

    So.. my question... has anyone else experienced something similar?? Does anyone else have a high level of cardiovascular fitness that has affected them while diving?? Looking forward to any insight!!


  2. Big-t-2538

    Big-t-2538 Divemaster

    # of Dives: 100 - 199
    Location: Dayton, OH
    Rest assured....you were Narc'd....
  3. Warren_L

    Warren_L Instructor, Scuba

    # of Dives: 2,500 - 4,999
    Location: Toronto, Ontario, Canada
    Yep, that sounds pretty well like what happened to me the first time I got narc'd. Symptoms would be alleviated by ascending to a shallower depth.
  4. pipedope

    pipedope Great White

    Will not cause CO2 buildup, As long as you are not skip breathing.

    Breathing too shallow will.

    Overbreathing a so-so reg also can cause CO2 buildup.

    I would also tend to think narcosis first but check everything, including the reg to make sure you are not having a problem with CO2.

    It could be a very light CO2 hit along with being narced. I don't know exactly how you felt or how your normal responses to trouble are.
    I will tend to *think* "Oh sh**, I gotta go up" when it is mostly a narcosis problem. In a CO2 hit I am at or near panic and there is not really much thinking going on. In the hit I took I was still functioning (barely) but I don't remember much thinking. Training took over and I acted to get out of the situation, i.e. purge the mask, ascend, breath deep and slow as possible.
  5. DocVikingo

    DocVikingo Senior Member Staff Member

    The good news is, no, it is not possible to be "TOO cardiovascularly fit for diving."

    The line that demarcates breathing too slowly ("I don't breath often enough") and skip breathing may not always be that clear. In any event, it's all a matter of venting C02 and one could breath slowly enough to cause hypercapnia.

    The signs/symptoms of CO2 retention include rapid respiration, rapid pulse rate, shortness of breath, dizziness, convulsions & unconsciousness. It can also include a whopping headache, usually with onset well into or after the dive.

    Best regards.

  6. 100days-a-year

    100days-a-year Solo Diver

    # of Dives: 5,000 - ∞
    Location: NE Florida
    I have about the same metabolic rates, but my size precludes a sac that lo.I see it that a high cardio conditioning state can influence your sac and have an effect on narcosis due to lowering the amount of CO2 present,but(caveat here)there are more variables.Depth and PPN2 of course being most important.Wetsuit constriction,equipment efficiency and dead space,air purity,smoking,hydration,and a whole slew of psycological implications from what kind of day you were having to any stress increasing metabolic rates or causing tenseness.What you described to me would be exactly how I would expect someone to feel upon reaching 137' on an air mix in cool water wearing a wetsuit or even a mildly constrictive drysuit even with good equipment.Especially if it was the 1st time at that depth or that site.Rest assured the biggest enemy you had was being Narced.
  7. CameronMartz

    CameronMartz Fitness Instructor

    Congratulations on your level of fitness. It can do much to help improve your safety and enjoyment of diving. Keep diving, and you'll likely see your SAC get even lower.

    If you ever take a mix course, you'll get to see how narc'd you were at 60ft.:)


Share This Page