Is it OK to snorkel?

[H2Andy]

three things you don't want to do after a dive:

1. heavy excercise: this tends to create microbubbles which can come out of
solution and get you bent. so if you snorkel, don't swim strenously. take it easy.


2. descend to depth and quickly ascend: (bounce dive) again, this can release
nitrogen out of your system before it can be safely relased and get you bent.
so if you're snorkeling, stay on the surface and don't go diving down.

3. impede gas exchange (i.e. hold your breath): not nearly as big a factor
as the other two, but every bit helps. you want to keep that nitrogen flowing
out of your system with every breath you exhale, so holding your breath
for long periods of time is probably not a good idea. when snorkeling, keep
breathing.

 

[Amphibious]

It is not possible to get DCS from Snorkling or Freediving (with a few extreme exception left out)

Scuba diving before freediving can put you in a high risk group for DCS.

one of the above posters started quoting tissue groups and such. this is SOLID BS. the dynamics of breathhold diving a nearly imposible to calculate in such a fassion.

I suggest if you want to know more you chat with the Freedivers at www.Deeperblue.net. we have quite a few World Champions and Freedive Science Geeks that are informed enough to answer this question.

 

[Courtneyf82]

Thanks for all the help guys, I just went by myself yesterday. Its only another couple weeks till he can dive again so I guess Ill just wait till then, better safe than sorry. Of course if we had that attitude earlier, he might not have taken a hit at all, oh well, good learning experience, Im just glad I avoided the chamber, I heard it stinks!

 

[pescador775]

Courtney, best of luck to you two, too. Over the years I've heard a bunch of theories about freediving and bubble formation and growth. The more technical talk and equations that I see, the more evident that these folks have no useful experience and are styling out or parroting. I do agree that some mathematicians have made artful, even compelling arguments, but don't usually square with what I've actually seen and experienced. For example, when talking about heavy exercise and micronuclei and bubbles. The exercise problem can be fixed by drinking liquid stuff (mostly non alcoholic) immediately after the dive. The real problem appears to be related to straining. When this occurs after the dive it appears that a bubble may sometimes be driven against the flow or through a PFO perhaps, to show up in the arterial side, not a good thing. I believe this is a reasonable theory even though medical researchers have found no comparable risk in the non diving population, that is to say no increased risk of coronary events in people with PFO's. Anyway, the moral is--no heavy lifting after a deep dive, and take your dump before the dive, not after. With regard to freediving and the theoretical risk of bubble growth through a kind of "rectified diffusion", I don't believe this occurs because the frequency of the up/down occillations is much too low. Bounce dive theorists will disagree. It's a free country. However, dehydration and accumulated dissolved nitrogen does occur in deep freedivers despite what some bubble tester or statistician may or may not suggest. Consequently, some precautions are prudent. I have discussed those in above posts.

The "gas exchange" thing is probably a non issue for freedivers except where it involves oxygen uptake and CO2 dispersal. That is life or death, obviously. There is more than enough nitrogen in one lungful of air to cause the bends, if dissolved in the body fluids and tissue. However, whether gas is dissolved or not is a function of partial pressures. Whether gas is expelled or not is likewise a function of PP's plus circulatory factors. When surfacing, gas exchange quickly balances the relative levels or atmospheric gas. If there were actual problems in this area freedivers would quickly become subject to acidosis due to carbonic acid, etc. Most freedivers don't even get the reputed CO2 headaches that are spoken of so glibly in the SCUBA instructor community. I've never heard of it happening and I've taken the plunge with some well known personalities, spearos, all. Not a headache around except perhaps after drinking a liter of tequila or falling off a dirtbike.

 

[John C. Ratliff]

Courtney, best of luck to you two, too. Over the years I've heard a bunch of theories about freediving and bubble formation and growth. The more technical talk and equations that I see, the more evident that these folks have no useful experience and are styling out or parroting...The "gas exchange" thing is probably a non issue for freedivers except where it involves oxygen uptake and CO2 dispersal. That is life or death, obviously. There is more than enough nitrogen in one lungful of air to cause the bends, if dissolved in the body fluids and tissue. However, whether gas is dissolved or not is a function of partial pressures. Whether gas is expelled or not is likewise a function of PP's plus circulatory factors. When surfacing, gas exchange quickly balances the relative levels or atmospheric gas. If there were actual problems in this area freedivers would quickly become subject to acidosis due to carbonic acid, etc. Most freedivers don't even get the reputed CO2 headaches that are spoken of so glibly in the SCUBA instructor community. I've never heard of it happening and I've taken the plunge with some well known personalities, spearos, all. Not a headache around except perhaps after drinking a liter of tequila or falling off a dirtbike.

There can be a serious risk of decompression sickness in free divers who descend below 33 feet. This has been shown in historical information from even the 1950s and 1960s. E.R. Cross first documented it in papers he wrote on "Taravana." Here's a paragraph from Glen Egstrom, Ph.D., and one of the foremost diver/researcher of the 20th Century, about this:

"I spent some time in the Tuamotus and worked with some French doctors who studied this problem. The free divers work to depths 150 fsw or more. During the "season" there are incidents of Taravana, which I believe means 'crazy'. There is a detailed discussion by E.R.Cross in the book 'Breath-hold Diving' a proceedings of a workshop in Japan that I had the pleasure to attend in 1965. It is publication 1341 National Academy of Sciences, National Research Council Wash. D.C. 1965. It was not unusual for the natives to hyperventilate for 2 - 10 minutes before descending to depth and staying 30 - 60 seconds up to 2 min. on shell collecting dives. They go down with a lead weight between their feet and leave the weight near the bottom. I dove with a couple of them for nearly a month and even got my depth down to 100. Those were the days, we went on scuba and watched them work in shark infested waters with little of no concern. Paulev, a Danish M.D., also has his paper on DCS following repeated breath-hold dives in a Norwegian submarine escape tank. He bent himself quite badly and made the lecture circuit discussing his exploits. He and I spent quite a bit of time together at the conference and I was struck by his story. Bottom line- there is little doubt that one can sustain serious DCS while breath hold diving but you really must work pretty hard at it."

You can see the information at:

http://www.scuba-doc.com/breathhold.html

At the bottom are the references in the literature. The fact is that there are several documented cases of decompression sickness occurring to breath hold divers. They have occurred at the U.S. Navy's submarine escape tanks, for instance, and to pearl divers and Ama divers. Here's the references:

References:

Suk-Ki Hong in Breath-hold Diving section of Bove's 'Diving Medicine', p. 69. 1997.

Paulev, P. "DCS following repeated breath-hold dives". J.Appl. Physiol. 20(5): 1028-1031. 1965.

Edmonds, C. "Diving & Subaquatic Medicine". 1981.

Cross E.R., Taravana - Diving Syndrome in the Tuamotu diver. In 'Physiology of breath-hold diving and the ama of Japan.' National Academy of Science - National Research Council Publication 1341. 1965; 207-219.

Bove, A.A., 'Diving Medicine', Taravana

Wong, RM, Taravana Revisited: Decompression Illness After Breath-hold Diving,
SPUMS Journal, Volume 29, No.3, September, 1999

SeaRat

 

[Brand0n]

Yeah ill correct you, to get more then normal nigtrogen in your body your gonna be have to be breathing compress air under pressure.

You cant get bent from snorkeling, You can get shallow water black out from hypoxia (lack of oxygen) but thats if your holding breath

 

[John C. Ratliff]

Yeah ill correct you, to get more then normal nigtrogen in your body your gonna be have to be breathing compress air under pressure.

You cant get bent from snorkeling, You can get shallow water black out from hypoxia (lack of oxygen) but thats if your holding breath

BrandOn,

That is simply wrong. You can get decompression sickness from snorkeling, if you are really, really good at it, dive repeatedly and dive over 33 feet deep. It has nothing to do with whether you are "breathing" or holding your breath; the gas (nitrogen) will transfer to the blood stream under pressure if it is present in the lungs.


Good free divers can get up to 1 minute 30 seconds on a dive, with about a minute bottom time. If they go to 66 feet for those dives, they can accumulate over the required amount of bottom time in a day's free diving. Let's say that a diver goes to 66 feet for a half minute of bottom time, and dives on a cycle of 1.5 minutes down, 1 minute up. That would mean that (s)he's diving 24 dives an hour, and accumulating 12.5 minutes of bottom time in that time. That would mean that in 5 hours, he could potentially accumulate 50 minutes of bottom time, which was the no-decompression limit for diving using the old U.S. Navy Diving Tables. There are free divers who have actually done this, and gotten bent. But you have to be very, very good at free diving, and try very, very hard to get to that point.

This has been documented in the studies I cited above since the 1960s. But this is not something that someone who has not been diving for awhile can do; it happens to the "experts" who can dive long enough and deep enough on a single breath, repeatedly, to get enough nitrogen absorbed into the blood stream to cause problems. Most beginning scuba divers don't know enough about free diving to get to this stage of expertise though, and probably never will.

SeaRat

 

[tedwhiteva]

What's a snorkel?




Sorry, you guys seemed to be getting heated

 

[John C. Ratliff]

A snorkel is that j-shaped tube...tedwhiteva, thanks, I needed that on a Friday evening.

It's been cloudy, raining for over a month here, but I was able to get some snorkeling in at noon today. We have a pool here that is 25 yards wide, and 18 feet deep. So it is relaxing to go into the pool and snorkel/free dive under the lap swimmers (they use the surface, and I was using the bottom in three dimensions rather than their two dimensional swimming). I was working about a 30-45 second dive every 1.5 minutes or so, which was a pretty good workout.

A lot of people just do not realize that in tropical areas (nice, warm water) it is possible to get significant bottom time in while breath-hold diving. I'm now 60 years old, and can comfortably hit 50-60 feet with significant time on the bottom.

BrandOn, my apologies if I came on too strong above.

SeaRat

 

[Chad Carney]

Searat,

A freediver capable of 66' deep 1.5 minute dives for hours on end, will spend longer than 1 minute at the surface between dives. If he's that good he'll know to breathe up for at least twice the dive time. That's a lot of surface time collectively, and in 5 hours the diver will likely be out much longer; to drink, move the boat, etc... even during a spearfishing tournament. (The one time freedivers have a tendancy to rush their SIs the most.)

There is no way to compare Navy table NDLs to the dives a freediver makes.

Chad