In our November ‘09 SK Newsletter we recommended readers take a look at Roger Schumann’s article “Waiting to Inhale: Breath-Holding Drills for Sea Kayakers.” That prompted one of our readers to write:
I enjoyed the article in the on-line newsletter about breath holding techniques. Although the article doesn't suggest breath holding underwater I would always include a warning about shallow water blackout. Basically breath holders shouldn't hyperventilate before diving. When I was a kid I used to see how long I could hold my breath in the family pool. I was almost always alone and I'd usually hyperventilate. Very risky.
Will Nettles
Los Angeles
Will is correct about the danger of hyperventilating. John Reseck addressed the issue of shallow water blackout in our Summer 1990 article: “Swimming for your Supper: Free Diving for the Sea Kayaker.”
Most people believe that when we get low on oxygen we want to breathe. This is not the case. There is no mechanism in the body that works rapidly enough to tell us that we need oxygen. Fortunately we get a high enough level of CO2 to tell us to breathe before we pass out. In diving it is possible by improper breathing to purge all of the CO2 from the system and then hold your breath until the oxygen is used up; without enough CO2 to signal the brain again we would pass out. This is a shallow water blackout. In breath-hold diving we must be careful not to purge so much CO2 out of our system by maximum breathing (hyperventilation) that we do not have enough left to tell us we need to come to the surface and breathe. The rule is: Never take more than three maximum breaths immediately before a breath-hold dive. Follow this rule. If you ignore it you will have no warning that you are about to pass out.
Like Will, my friends and I used to see how far we could swim underwater. One afternoon, three of us managed to swim underwater the length of a 25-yard-long pool, touch the far wall and make it another few yards before surfacing. Dale took his turn and got to the far end, turned around and swam all the way back. He touched the wall where he had started and turned around as if to take another lap. Suddenly he went limp and slowly rolled over. He was always one for practical jokes, but this time it was no joke. He had passed out. Fortunately we were right there to see what had happened and pull him up for air.
Will pointed out a Wikipedia article on shallow water blackouts:
http://en.wikipedia.org/wiki/Shallow_water_blackout
If you are going to use breath-holding drills to train for snorkeling or free diving, Will’s right, you need to know how to hold your breath and dive safely.
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