CO2 buildup - Cause, Effects and Solutions

[fisheater]

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.

The problem is that, in common usage, the term hyperventilation appears to mean two, opposite things. True hyperventilation involves very deep exhales, ridding the body of CO2. The term also can be used to refer to rapid, shallow breathing, which fails to rid the body of excess CO2

Hence, you could say that "to stop hyperventilation, you should hyperventilate."

 

[B.L. Justice]

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.

I think it has to do with rapid, shallow breathing. Ken's post makes a lot of sense. The trigger for hyperventilation is a build up in CO2 but it is also stress or cold related. The first time this happened to me, I was at the surface and had plenty of fresh air. It was my first OW training dive, from a boat and my instructor had failed to mention that the water was in the 50s. I think they call it the mammalian diver response. Rapid pulse and sudden gasping for air. A feeling of being oxygen starved and wanting to climb on top of the first person I saw. Took a little bit to settle down - no thanks to my instructor who was oblivious to it all.

Could be wrong but it made sense to me.

 

[Scott L]

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.

Hopefully TSandM will chime back in to correct any misinformation received from me but the term hyperventilation is used to describe breathing at a rate faster than your normal breathing pattern. It also occurs when you breathe more, i.e. breathing that is deeper and more rapid than normal breathing. So, a term such as hyper shallow breathing is probaly a more accurate way to describe CO2 inducing breathing patterns. TSandM, please help me!

 

[lowviz]

Valhalla, time to drag out Walter's old post again. Your answer is in the next to last paragraph, but the whole post is worth a re-read. (Wish I wrote it...)

The first step in panic is feeling a lack of confidence in one's abilities.

An ability to swim fairly well is the first step toward confidence in the water. The next step is learning skin diving skills. A combination of swimming ability and mastering skin diving skills eliminates a feeling of being overly dependent on SCUBA equipment.

Skills left out of most classes (because some agencies don't include them in their standards) such as doff & don (removing all equipment on the pool bottom, swimming to the surface then returned to put it all back on) and bail out (stepping into the water while holding one's gear and putting it on during descent) also build self confidence and help to eliminate that first step toward panic.

The second step in panic is when something goes wrong. We can train and practice and maintain our equipment, but we can never eliminate problems arising. When things go wrong, a diver will either have confidence in their ability to handle the problem or they won't. If they do have confidence, they'll solve the problem and move on.

If they lack confidence, they will become scared and as a result start to hypoventilate. Hypoventilation is rapid shallow breathing. It is often, incorrectly, called uncontrolled hyperventilation. These are the next two steps in panic. Hypoventilation causes a buildup of CO2 in the lungs. This is because shallow breathing does not purge the lungs of CO2 on exhalation. As CO2 builds, the urge to breathe becomes even stronger. Hypoventilation increases, making the feeling of not being able to breathe even worse. This is what makes some divers think they are over breathing their regulator. Once hypoventilation starts, full panic is often seconds away. Once the diver is panicked, he will often take inappropriate and usually dangerous actions such as bolting to the surface.

An understanding of this cycle can allow a diver to break it and prevent panic. Most agencies teach divers, Stop, think, act. Some teach it as, Stop, breathe, think, act. This is wonderful, but it doesn't explain why and while the concept is a good one, a better understanding of the panic cycle is essential to breaking it. If a diver feels himself starting to hypoventilate, he needs to know this is an important step that can lead to his (and his buddy's) death if he doesn't take immediate action by slowing his breathing. Slow deep breaths are a life saver.

 

[TSandM]

Yes, the term hyperventilation, as literally construed, means OVERventilating the lungs, and drives your CO2 down. Symptoms can include tingling around the mouth and cramps in the hands and feet. We treat this in the ER in a very high-tech manner -- we make somebody breathe into a paper bag until their CO2 normalizes!

Hyperventilation, as commonly used in scuba parlance, refers to a shallow, panting, rapid respiratory pattern that DOESN'T effectively ventilate the alveoli deep in the lungs, where gas exchange actually takes place. Thus the CO2 climbs.

 

[Bubbletrubble]

Physiologically speaking, hyperventilation is usually defined as increased pulmonary ventilation due to an increased respiration rate, an increased tidal volume, or both. We have to be careful about how we use terminology here so that no one gets confused.

Shallow "hyperventilation" (rapid, shallow breathing) will invariably lead to inadequate ventilation...or hypoventilation. This increases CO2 retention within the body, as reflected by elevated PCO2 in blood (both arterial and venous).

True hyperventilation results in an actual decrease in CO2 levels within the body.

As Dr. Brian points out in his article, during exercise, metabolic CO2 production increases and to compensate for this, under normal circumstances, the body will increase minute ventilation (volume of gas breathed per minute). Here's an important point. Brian later writes:

"Under normobaric and hyperbaric conditions, the single factor that limits the ability to increase ventilation is the rate at which gas can be exhaled from the lungs."

This is where the density of the gas comes into play. Helium mixes have a lower density than nitrox mixes or regular air and therefore, at depth, the gas can be exhaled more easily. This allows an increase in ventilation to compensate for the increased metabolic CO2 production.

This is the benefit of helium mixes to which TSandM was referring. Not only is there less inert nitrogen in a helium mix (for the purposes of nitrogen loading) but the mix is also less dense than nitrox or regular air so it is beneficial in protecting against CO2 retention. Also, helium has less of a narcotic effect than nitrogen and oxygen. So I guess that's 3 good reasons to be breathing helium-containing trimix on deep dives.

Clear?

[Edited later: I see that TSandM was posting at the same time. I think the info in our posts is complementary so I'll leave the post as is.]

 

[Scott L]

Yes, the term hyperventilation, as literally construed, means OVERventilating the lungs, and drives your CO2 down. Symptoms can include tingling around the mouth and cramps in the hands and feet. We treat this in the ER in a very high-tech manner -- we make somebody breathe into a paper bag until their CO2 normalizes!

Hyperventilation, as commonly used in scuba parlance, refers to a shallow, panting, rapid respiratory pattern that DOESN'T effectively ventilate the alveoli deep in the lungs, where gas exchange actually takes place. Thus the CO2 climbs.

So what is your term of choice to describe the event? - scuba nomenclature withstanding. In the meatime, hypoventilation is looking pretty good to this layperson.

"Medical Dictionary

Main Entry: hy·po·ven·ti·la·tion
Pronunciation: -"vent-&l-'A-sh&n
Function: noun
: deficientventilation of the lungs that results in reduction in the oxygen content or increase in the carbon dioxide content of the blood or both —hy·po·ven·ti·lat·ed /-'vent-&l-"At-&d/ adjective "

 

[Bubbletrubble]

So what is your term of choice to describe the event, scuba nomenclature withstanding? In the meatime, hypoventalation is looking pretty good to this layperson.

This may be one of those cases in which, to be absolutely clear, the phrase "hyperventilation" should not be used.

"Rapid shallow breathing" says nothing about tidal volume or true alveolar ventilation. On account of this, it's more accurate than the term "hyperventilation" in describing what we're talking about in this thread. Perhaps that's the phrase we should be using in our scuba discussions.

"Hypoventilation" would probably work...but it is ambiguous in the sense that it could mean a decreased breathing rate, a decreased tidal volume, or both. In my mind, ventilation refers to moving gas in/out of the respiratory tract.

 

[Scott L]

This may be one of those cases in which, to be absolutely clear, the phrase "hyperventilation" should not be used.

"Rapid shallow breathing" says nothing about tidal volume or true alveolar ventilation. On account of this, it's more accurate than the term "hyperventilation" in describing what we're talking about in this thread. Perhaps that's the phrase we should be using in our scuba discussions.

"Hypoventilation" would probably work...but it is ambiguous in the sense that it could mean a decreased breathing rate, a decreased tidal volume, or both. In my mind, ventilation refers to moving gas in/out of the respiratory tract.

Gotta agree with you. Hey, can you type slower? I do not like to be beaten time wise as my posts lose their relevance after your thoughtfull responses. The forum is lucky to have you!

 

[Teamcasa]

There are a lot of different things that contribute to CO2 retention. Excessive exertion at depth can definitely do it.

I would also add that not adjusting your regulator from pre-dive to dive can also lead to problems. I was at 90+ feet on a dive and began to get the tunnel vision. I did the deep exhale followed by the slow deep inhale routine a few times and the tunneling went away. Only then did I realize my regulator's adjustment was set full on pre-dive.