CO2 buildup - Cause, Effects and Solutions

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!

Teamcasa

Sr. Moderator
ScubaBoard Supporter
Messages
12,121
Reaction score
445
Location
Near Pasadena, CA
# of dives
500 - 999
This issue was brought up in another thread but I think it needs to be posted here as well.

(edited) Shallow hyperventilation is sort of like panting. When someone starts to get nervous (even if they don't realize it) or maybe starts working harder than planned, it can be a common breathing pattern.

The problem with shallow hyperventilation is that you are now not exhaling fully. So what's happening is that the CO2 your body is producing, which would normally have been expelled when you exhale, is slowly building up.

As you were (hopefully) taught in your basic class physics discussion, CO2 is the stimulus to breathe. The more CO2 we have, the more urgent that need feels like.

When you shallow hyperventilate and the CO2 builds up, you start to feel like you can't catch your breath. You may take a breath off the reg and it doesn't satisfy the feeling of air starvation. But it has nothing to do with you not getting enough air IN. It has to do with you not getting enough CO2 OUT.

So if you find yourself in this situation, the thing to do is . . . EXHALE. As big as your can. Take a breath. Exhale BIG again. Take a breath. Exhale BIG again. Generally two, three, or four BIG exhales will blow off enough CO2 that the not-getting-enough-air feeling will go away.

And once you get rid of that need-more-air feeling, you can decide whether or not to continue the dive. To me, this is all part of the walk-away lesson from your experience. Thanks for sharing.

- Ken

Also from that thread:

Ken - Sounds similar to what happened to me the first time I was 85 ft. I started experiencing tunnel vision and felt my reg was not giving me enough air. I looked at the other divers around me to see if they looked the same as how I felt, they did not. I looked at my SPG which told me I had more than enough air so I took deep inhales and exhales until the tunnel vision went away. I felt comfortable enough to continue the dive after the tunnel vision went away. My first and last time I ever had that experience.

FWIW, there's research to suggest that CO2 retention exacerbates the effects of narcosis. At the very least, it interferes with adequate oxygenation of...the brain. Ken's recommended technique to slowly inhale and exhale fully can effectively head off these problems before they become a real issue. This is definitely something that should be taught to students before the deep dive of the AOW specialty.
 
CO2 is thought to be a contributor to "Darc Narc." This is a type of narcosis that gives you a feeling of dread, doom, overall malaise. I've experienced this feeling during an exit in a cave that I'd dove many times.

Unrecognized and untreated I can see how it could easily build up and lead to feelings of claustrophobia and panic.

As others stated, long, full exhales are key to getting breathing under control and dispelling the effects of it.

I've also had a headache that I attributed to CO2 buildup. As someone that used to get migraines, I have to say the CO2 headache ranks as one of the worst I've had and there was no relief from it until it wore off.
 
Greetings Teamcasa and this is a great thread that would be very useful on the new divers forum as well. The breathing control and or regaining control is priceless. It is right on the money the big exhales allows the built up C02 to escape this is a practice that I have had to implement twice thus far in my time diving. Once at 120' and 137'. The post dive break down was very valuable, over stressed due to junk fins and slightly over weighted. Both were easy to correct but allowed for C02 to build up. Both times I closed my eyes and gained breathing control by using the big exhale method. I find it easier to relax when I breath long in and long out even a little past the all out phase.
This would be a really great addition to the new diver forum because it goes hand and hand to getting the point of normal breathing patterns under water nailed down.
Good material and that is what makes Scuba Board awesome!
CamG Keep diving....keep training....keep learning!
 
There are a lot of different things that contribute to CO2 retention. Excessive exertion at depth can definitely do it -- I've come out of Ginnie Springs several times sick as a dog from overworking. A poorly adjusted regulator can do it -- a friend bought a new reg, and dove it, and couldn't figure out why she always felt as though she couldn't breathe, and ended the dive with a headache. Turned out the cracking pressure on her second stage was three times what it should have been.

Diving the wrong mix contributes, too -- gas density at depth begins to play a significant role in alveolar ventilation. I'm not sure whether I like helium as much as I do because of nitrogen narcosis, or because it reduces CO2, but the difference, even at 130 feet, is night and day.
 
This is a great thread. I have had that OOA feeling at depth a couple of times. I have overcome it by slowing down and trying to focus on a simple task. Until reading these entries, I didn't realize that CO2 had that big an effect.

I wonder if doing some deep breathing to purge CO2 before dropping down would help to reduce the build up? Anyone have any thoughts on this?
 
No -- deep breathing before diving would lower your CO2 for a minute or so, perhaps, but certainly within five minutes, you'd be equilibrated again.
 
I am a little confused here (it might be excessive CO2 levels) but I would like to know where the idea that hyperventilation causes an increase in CO2 levels comes from. Every medical book I have ever read states that hyperventilation actually decreases levels. Even Dr. Brian's excellent article states this and nowhere mentions that CO2 levels are increased by hyperventilation. While CO2 buildup can initiate hyperventilation it is not the other way around. If I am missing something please edumacate me.
 
Diving the wrong mix contributes, too -- gas density at depth begins to play a significant role in alveolar ventilation. I'm not sure whether I like helium as much as I do because of nitrogen narcosis, or because it reduces CO2, but the difference, even at 130 feet, is night and day.

This is were I break ranks with the High Springs boys. In recreation dives under 130ft while not using using HE I am maximizing FO to a PPO of 1.60 as I feel a heck of lot better at the end of the dive as a consequence. Team concept is not broken down completely as my dive partners are also using the same mix as I fill their cylinders after dive sites are selected and dive planning is complete...Often time when hunting with gusto gas is the limiting factor on such dives which results in less nitrogen loading and consequently greater conservatisim. Please don't tell on me...:)
 
Last edited:
https://www.shearwater.com/products/peregrine/

Back
Top Bottom