CO2 Retention

[dkatchalov]

What are the biggest contributing factors to CO2 build up when breathing UW?

Overexertion, skip breathing, fast breathing, anything else? I'm wondering because when I breathe underwater, I generally pause for 2-3 seconds on each inhale and exhale. Then when I inhale and exhale I make sure I really clear out my lungs. I'm not sure if my pauses between breathing in and out contribute to CO2 buildup? I certainly don't feel any different, but I don't want to blackout, etc. due to CO2 buildup. I also don't want to develop bad breathing habits.

Thanks.

 

[Colliam7]

What are the biggest contributing factors to CO2 build up when breathing UW? Overexertion, skip breathing, fast breathing, anything else?

Yes, yes, yes, and shallow breathing. These may all be related. If you have increased demand, yet breath in a rapid but shallow manner, you may not achieve good gas exchange. You are partially recycling a body of high-CO2-content air in your upper airway. Regular, deep breathing, even if a bit rapid, is far better than rapid shallow breathing or skip breathing. But, if you control your inhalation, and take a full deep breath each time, that will help control rate.

 

[seaducer]

Overexertion for sure does. It is amazing, we do a "race" in the aquarium against kids outside the glass. I am not in tip top shape, but I do train for triathlons and can swim, bike, run a good distance. After a race I fins myself out of breath, but it doesn't hit until a minute or so later.

I don't think the regulator can supply enough air to satisfy my body's needs and as a result of over breathing it you start to take shallower breaths and then it hits. There it is no big deal, out in the blue it could get bad for a prolonged effort.

I am pretty sure as long as you empty your lungs you shouldn't have a problem pausing, as long as your airway is open. I pause also, it's just part of my breathing pattern uw or on land...

 

[TSandM]

What determines CO2 levels in the blood is the balance between CO2 production (which is determined primarily by one's level of muscle activity) and CO2 removal, which is determined entirely by the VOLUME of air moved through the lungs in a given time.

On land, increased activity leads to increased minute ventilation, and keeps the CO2 normal.

Underwater, because of the increased work of breathing, it's much easier to get an imbalance between CO2 production and removal, and have CO2 elevated in the blood. This is aggravated by breathing patterns that are either shallow (where too high a proportion of the air moved is only ventilating the trachea and major bronchi, where no gas exchange occurs -- this is called the "dead space") or involve too long a pause between breaths (skip breathing).

Slow, rhythmic breathing, a bit deeper than what one normally does at rest on land, is the most efficient way to make use of one's gas supply. A very brief pause at the end of inhalation and exhalation keeps the rhythm slow, but two to three seconds is a long pause. Most people, when CO2 begins to build up, will feel short of breath and anxious, but there are data to show that some divers adapt to high CO2 levels, and do not show those symptoms. However, the elevated CO2 levels still potentiate narcosis and oxygen toxicity, so it is best to avoid breathing patterns with a high likelihood of producing CO2 retention.

 

[don Francisco]

CO2 retension is more of a problem with a snorkle than in Scuba, because of the much larger air space in the snorkle. In either case shallow breating is the biggest culprit because it doesn't exchange the dead air in your breathing passages and snorkle/reg. Full exhales ensure that depleted air is fully exhausted. Otherwise maintaining a natural breathing does the trick. Don't fret over problems that you don't have, as New Englanders might say, "if it ain't broke, don't fix it."

 

[ClayJar]

I certainly don't feel any different, but I don't want to blackout, etc. due to CO2 buildup.

On scuba, you're not likely to suddenly black out due to CO₂ retention. You're more likely to feel "starved for air" or a pressing urge to breathe more. Of course, the most obvious symptom of elevated CO₂ levels is usually a headache. If you have headaches during or right after a dive, and they're not due to sinus congestion or hitting your head on the hull, I'd say you're trying too hard to breathe "better" and shooting yourself in the foot by doing so.

I also don't want to develop bad breathing habits.

Too late.

I'm of the group that believes that trying to breathe "better" is the major cause of divers breathing worse. It seems almost invariably that divers reporting CO₂ headaches are divers who were trying to "improve" their breathing. If you catch yourself breathing shallow breaths, certainly breathe a bit more deeply. Otherwise, if you're thinking about it, you're doing it wrong. :biggrin:

 

[Gene_Hobbs]

Lanphier and Camporesi describe Lanphier's (1-4) work at NEDU to answer the question 'why don't divers breathe enough?'

1. Higher Inspired Oxygen (PiO2) at 4 ata (404 kPa) accounted for not more than 25% of the elevation in End Tidal CO2 (etCO2) above values found at the same work rate when breathing air just below the surface.
2. Increased Work of Breathing accounted for most of the elevation of PACO2 (alveolar gas equation) in exposures above 1 ata (101 kPa), as indicated by the results when helium was substituted for nitrogen at 4 ata (404 kPa).
3. Inadequate ventilatory response to exertion was indicated by the fact that, despite resting values in the normal range, PetCO2 rose markedly with exertion even when the divers breathed air at a depth of only a few feet.

References:
1. Lanphier. Nitrogen-Oxygen Mixture Physiology, Phases 1 and 2. NEDU Report 1955-07. RRR ID: 3326
2. Lanphier, Lambertsen, and Funderburk. Nitrogen-Oxygen Mixture Physiology - Phase 3. End-Tidal Gas Sampling System. Carbon Dioxide Regulation in Divers. Carbon Dioxide Sensitivity Tests. NEDU Report 1956-02. RRR ID: 3327
3. Lanphier. NITROGEN-OXYGEN MIXTURE PHYSIOLOGY. PHASE 4. CARBON DIOXIDE SENSITIVITY AS A POTENTIAL MEANS OF PERSONNEL SELECTION. PHASE 6: CARBON DIOXIDE REGULATION UNDER DIVING CONDITIONS NEDU Report 1958-07. RRR ID: 3362
4. Lanphier. Nitrogen-Oxygen Mixture Physiology. Phase 5. Added Respiratory Dead Space (Value in Personnel Selection tests) (Physiological Effects Under Diving Conditions). NEDU Report 1956-05. RRR ID: 3809

 

[Tienuts]

CO2 retension is more of a problem with a snorkle than in Scuba, because of the much larger air space in the snorkle.

Try again - CO2 retention is a very real problem in SCUBA, it happens quite often, and can happen for a number of reasons. In our trimix classes, the students are made to swim hard in a pool with doubles and stage bottles to feel the effects of CO2 buildup, and how it makes you feel. There is seldom a student who doesn't bolt to the surface from 3-4 feet of water.

I myself took a CO2 hit after a real hard swim against current on the Tenenco towers a few years ago. At the time, I had no idea what was happening to me - all I felt was sheer panic, and the desire to bolt to the surface. I knew it was a bad move, and was clinging to the side of the Towers until my breathing got under control.

In this video, you can see an open circuit diver who is having CO2 episode. Now this is normally a very controlled diver with good trim and buoyancy. You can see here how she is flailing around, and then bolts for the surface.

YouTube - CO2 Panic

 

[Noboundaries]

Fascinating short video. Watching her bubbles you can see how fast she is breathing. Thanks for the video post.

 

[String]

Exertion does it for me still sometimes. A lot of the time its if i've rushed kitting up and had a tiring surface swim to a buoy then dropping down without catching my breath.

When i was starting out it was actually my buoyancy - trying to do too much on my lungs resulting in a very erratic breathing rhythm. Once i worked that out i managed to cure that one.