Originally posted by devjr
Oh, BTW, don't worry about skip breathing causing headaches. I'm a freediver and SCUBA diver. I hold my breath for 3 minutes, and I also used to skipbreath when air fills were hard to obtain or afford. Have never had a headache, except if I stayed up the previous night partying. Clearly, you don't need to skipbreath but if you are made anxious by an old wive's tale it could bring one on.
----------------
NOTE: This got kinda out of hand (long) once I got on a roll.
----------------
Ummm.... Well, maybe some people do have a higher tolerance for CO2 than others but...
Perhaps freediving and SCUBA are not the best combination.
Navy studies indicate that some people are "natural CO2 retainers". These people make better freedivers but also tend to have more dificulty with decompression and are more likely to have an occurence of DCI than a "non-CO2 retainer" given the same dive profile.
Freediving helps make the body acclimate to higher CO2 levels due to long breatholding dives. There are dangers associated with this such as shallow water blackout. http://www.scubadiving.com/training/lessons/april98.shtml
The trigger for needing to breath is elevated CO2 levels in the blood. We don't yawn directly as a result of being tired. We yawn due to elevated CO2 levels caused by a natural slowing of the breathing WHEN we are tired.
By training yourself to ignore or delay these signals, you can build up more CO2 than another diver might without even realizing it.
"skip-breathing" or taking long pauses between breaths, causes CO2 levels in a divers blood to rise.
At deeper depths (especialy under stress), this becomes even more important as CO2 is WAY more narcotic than nitrogen or oxygen and has been shown to significantly increase the chances of having DCI problems as well.
The blood CO2 levels are kept low by the constant gas exchange of breathing. This does not mean you should breath faster. Just relax and take full, deep breaths each time.
The shallower you breath, the more air you will waste. You may find a better description of the following in the section on snorkeling in your basic open water manual. Probably some diagrams as well.
The volume of gas (air) in your throat between the beginning of your lungs and your lips is "dead space". This "dead space" is made longer/larger by the use of a snorkle and even a little bit by a regulator as well. Each time you inhale, you "rebreath" the part of your last breath "left over" in your throat from the previous breath.
By breathing slow deep breaths, you make better use of your air supply as the "leftovers" from the previous breath make up a smaller percent of the incoming breath. Also, the "dead space" ends up full of fresh, unused air with each indrawn breath. This unused air is lost when you breath out. The shallower each breath you take is, the higher the percentage of fresh, unused air that is lost with each exhale.
Rapid, shallow breathing is a sure way to burn up a tank fast. It can also be a factor in actualy causing divers to panic.