Buoyancy & CO2 Poisoning

Please register or login

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. Log in or Register now!

OP
mrGaribaldi
Messages
2
Reaction score
5
Location
Los Angeles
# of dives
0 - 24
Hi all,

TL;DR I learned to use my lungs as a BCD instead of using a BCD at all when learning scuba and accidentally CO2 poisoned myself repeatedly. I don't know how I should approach trying to learn a better way and stay safe while doing it.


A couple months ago I got scuba certified abroad via a PADI center with excellent reviews online. I did about half the online classes in advance and half during the 3 day course itself. I must have misunderstood the section on how to use your BCD appropriately or it wasn't detailed enough for someone with as thick a skull as mine because I never once touched my bcd except to deflate fully at the surface and then inflate fully again after the dive at the surface during the course or in my ~9 dives after. I really just thought it was a fancy life vest (sorry!!!).

During the course, when we were practicing buoyancy in the pool, I had a really hard time staying below the water. It felt like as soon as I breathed in, I went shooting to the surface. My assistant instructor explained that I was breathing too deeply and that I should exhale sooner, more quickly, and fully. I asked if that meant I should be taking short, shallow breaths with my lungs mostly empty the whole time so I wouldn't float away as much. She said yes. When I adopted this sort of approach, I nailed neutral buoyancy. It felt really awkward and uncomfortable, but it wasn't terrible and it wasn't a new feeling either.

A short aside is that a few years back I had a massive pulmonary embolism, so I have a lot of experience with awkward and uncomfortable breathing (the first thing I did after getting cleared was cry a bunch in relief, then sign up for a scuba class). If anyone's ever taken a spirometry test, you know exactly what I mean. During that sort of test, they have you take a deep breath and then "blow out the candles" and keep exhaling as much as you can, past the point where it seems reasonable, past the point where your brain is screaming at you to please for the love of god stop. After the class, I told my partner that scuba diving felt just like spirometry, and that I felt extra prepared for this because of all the lung **** I went through.

Also after the class, I had a splitting headache. I basically went straight to my hotel room and laid down in the dark, waiting until I could fall asleep and work off the headache. I got headaches basically every time after diving, which became more brutal and intense the longer I dove. I asked my instructors if this was a common side effect of diving and they said no, not really, but it can take time for new divers to get used to breathing under water and with more practice I would become more comfortable underwater and that would stop happening.

Well, I actually felt really comfortable underwater and I was killing this "lungs empty + small breaths" approach. It was pretty annoying to have to keep my lungs super empty though, and it seemed like it'd be a lot more comfortable if I could keep my lungs at like 50% full and whatever amount of breath I needed to go up and down. I mentioned to my instructors that sometimes I even had a really difficult time getting to the bottom of the dive site. I said I couldn't touch the bottom if I wanted to, even with my lungs as empty as I could make them, and that maybe more weight would help me. I said that of course I know I'm not supposed to touch the bottom (I just wanted to give some reference), but they said not to worry because I shouldn't touch the bottom anyway.

Anyway, we passed the course and the instructors said we were some of the best students they've seen (woo!) and went off to go dive more elsewhere. On my final dive, I just had the worst headache known to man. The site was gorgeous - manta rays - but I felt wicked. It was normal though? Like, worse than usual, but I got headaches every time I dove, so I didn't think anything bad was happening? I was so happy when my buddy ran out of air and we surfaced though.

On past dives, I started to feel a little better after surfacing. Not this time though. There are no words for how god awful I felt. I noticed at the surface that in addition to the splitting headache I felt weak and deeply nauseous. I used my remaining strength to climb the ladder to the boat, and then crawled on my hands and knees to the side of the boat. I felt like sobbing but didn’t have it in me. I did have vomit in me, though, and I soon hurled over the side into the sea repeatedly. Felt less nauseous after that but my head still hurt like crazy.

After puking, the divemaster from this dive said not to worry, that I probably just had CO₂ poisoning. New divers often take rapid shallow breaths because they’re more anxious underwater and that with time I’d learn to breathe underwater more normally like I do on land. I was too out of it to have a full conversation, but I immediately put together that I was doing what he said on purpose because that’s how I thought scuba diving worked.

He also explained in more detail about increased dead space in the breathing passageways and all that jazz. See, while I knew in theory about the increased dead space, I just didn’t understand well enough what that meant practically. I wasn’t actually getting a whole lot of new air when I breathed in, because the air from my tank was just getting exhaled without actually making it down my bronchial tubes.

I couldn’t believe how stupid I had been. My symptoms were getting worse as I kept diving, because I kept getting better at keeping my lungs empty and not breathing. Not only had I been repeatedly poisoning myself for nearly ten dives, but I also didn’t learn how to dive safely. I was super scared and canceled the last dive I had planned for the trip, and haven’t been diving since.

It’s been long enough since that bad experience and I love ocean wildlife enough to want to try to start diving again, but I have no idea where to start. I’m technically certified, and in theory I know what to do now, but this is a dangerous activity and I do not want to die. I almost want to start from the beginning and take another course, but it’s not like that worked the first time around. Any thoughts on how to move forward?

Thanks :)
 
A 3rd purpose of the wing is to compensate for wetsuit compression. This can be 2-3x the change in gas weight (the erroneously stated "sole purpose" for the wing at depth).

They also claim being overweighted means lungs cannot be effectively used for depth control. I consider this false. If I'm 15 lbs overweight, I'll simply use the wing to provide 15 more lbs of lift than were I correctly weighted. I'd then be neutral, and the same slightly larger inhale/exhale initiates ascent/descent as normal. (Being substantially overweighted is still undesirable for various other reasons, of course.)
 
I don't see much wrong with the video but I'm willing to learn if a solid argument can be presented.
Anyone who has dived with 2 or more steel tanks in a thick wetsuit will quickly realize the the BCD is essential to offset the tank weight and suit compression...in addition to usefulness for the weight of the gas carried/used and the need for buoyancy at the surface.
 
So, if a person does simple single tank diving without a thick wetsuit, there's nothing wrong with using breathing control as long as you put an appropriate amount of gas in the wing when leveling out at a new depth correct?
 
there's nothing wrong with using breathing control as long as you put an appropriate amount of gas in the wing when leveling out at a new depth correct?
Correct. Use lungs to initiate depth changes, and the wing is adjusted to allow the lungs to be in their normal range during steady-state -- especially the end of exhalation point as it has potential to cause CO2 buildup.

ETA: works the same regardless of wetsuit thickness. The "appropriate amount of gas in the wing when leveling out" takes care of suit compression / expansion, wing compression / expansion, and gas decrease. The point being, your lungs don't have to handle all these things.
 
It's astonishing that the instructor decided you didn't need any more weight. That's just absurd. A new diver isn't going to be diving with big steel tanks and metal back plates so all that chatter isn't really helpful. Find a decent dive master who can help you do a standard buoyancy test to determine the correct weighting and then enjoy your superior ability to use breath control to go up or down in small increments once you've gotten to depth. Most of the time you should be breathing pretty normally (with the caveat that you are breathing through a regulator).

You don't need a whole course. You just need a good instructor to work with you specifically on buoyancy. Go to a different shop, though.
 
I watched the video. While some of the techniques described are technically true in terms of buoyancy control/physics/Archimedes principle I think the entire premise of depending so much on breath control to adjust your buoyancy throughout a dive is probably dangerous.

What makes it dangerous is CO2 buildup from the lack of relatively constant gas exchange in your lungs. I strongly advise against depending on the techniques described in the video as a primary means of controlling and/or adjusting buoyancy.
 

Back
Top Bottom