Buoyancy & CO2 Poisoning

[mrGaribaldi]

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

 

[johndiver999]

Not to mention, breathing in an inefficient manner is going to be detrimental to your gas consumption rate if you continue the practice for any extended time. It makes little sense not to use a BC for its intended purpose.

Your primary objective should be to breathe as efficiently as possible and to reduce unnecessary stress. Using the BC properly can aid in that pursuit.

The fastest way to dump buoyancy and sink quickly is to exhale, fully and quickly. Something like that is fine, if you do it infrequently and don't inhale for 5-8 seconds while you deal with whatever the situation is - say a weightbelt fell off, or your power inflator stuck on, but deliberately restricting your ability to breathe for an extended period of time instead of pressing an up or a down button, is silly.

 

[crofrog]

I'm a nerd, and I've spent a lot of time white boarding to help people understand what my view is on how they should manage their buoyancy, over a few years of helping myself and others fine tune. Some people learn this stuff intuitively but others need to have a bit more of a plan for how to do it.

These 3 diagrams are what I use to describe the process.

Just some definitions.

Tidal breathing is "normal" breathing like you're doing right here at your computer, see this diagram. It's how you should be breathing when you're diving to be relaxed, and to avoid CO2 retention.

from: https://www.researchgate.net/figure...cluding-normal-tidal-breathing_fig6_349728103


Trim: Is being flat with your torso, arms and upper legs parallel to the environment. Being in trim makes maintaining buoyancy easier because you're presenting a larger cross section of your body to the water column and any propulsion you're creating with finning is moving you laterally not up or down. If you've ever stopped kicking and found yourself going up or down, being out of trim is likely masking buoyancy issues.

Top of lung: Feeling like you have to hold your breath with full lungs, you're breathing inside your IRV in the diagram above. This looks like like this in the water. "Big fast inhale, hold, big fast exhale"

Bottom of lung: Feeling like you have to hold your breath with empty lungs, you're breathing inside your ERV in the diagram above. This looks like like this in the water. "Big fast inhale ,Big fast exhale, hold"

 

[mrGaribaldi]

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.

Thanks. I wish I knew enough to know when an instructor is good!

 

[ZzzKing]

Thanks. I wish I knew enough to know when an instructor is good!

There are some excellent threads on here regarding selecting and evaluating instructors. Do a search.

 

[divingdudeisrael]

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

You can use your breathing to regulate buoyancy, but it should be comfortable. Meaning if you are using your breathing so much that it feels like a workout, you are doing it wrong. The idea is like if you want to go over a rock and then go back down again, it's easier to mess around with breathing than to inflate and deflate your bcd. But if you have to basically do a chi gong exercise just to stay off the bottom, add a squirt to your BCD.

Think of it this way. You should use your bcd to ensure that you are neutrally buoyant, but you use your lungs to make minor corrections, and you shouldn't have to do it throughout the entire dive.