Being warm during a dive could be dangerous

[DavidPT40]

I got this in my email.

(By Kelp Princess) In my research i also found an obscure 2006 DAN
study that was conducted by a control group of recreational wesuit
divers in the caribbean, cold water divers in dry suits, and US navy
divers in dry-suits that purposefully held warm water. [SCUBA?]

the conclusion of the study was that warm skin in warm water
CONSISTENTLY absorbed significantly greater amounts of nitrogen at depth!

Fortunately for me, I'm always on the verge of hypothermia during my dives. I remember one dive in the Caribbean in 86 degree water where I shivered the whole time.

 

[DennisW]

I believe the research has found that being too cold can be a contributor to DCS. I am sure someone more knowledgable than me can comment on this.

 

[Gene_Hobbs]

obscure 2006 DAN study

Is interesting by itself. DAN has nothing that is obscure.

Think they could they mean this one by any chance?

DECOMPRESSION SICKNESS (DCS) RISK IS INFLUENCED BY DIVE CONDITIONS AS WELL AS BY DEPTH-TIME PROFILE.
Vann et. al. 2005 UHMS Abstract.
http://archive.rubicon-foundation.org/1786

We have not added the 2007 abstracts yet but a search for "Thermal DCS" yields some nice reading.

Thermal protection strategies will be a topic at the DAN Tech Conference in January as well.

 

[TSandM]

This makes a lot of intuitive sense, because if you are cold (externally or internally) you vasoconstrict in the skin, and therefore there isn't much perfusion there -- thus not much nitrogen. If the skin is perfused, it WILL absorb more nitrogen.

Note that, at least in this small clip of the study, it doesn't say anything about total body nitrogen absorption.

Similarly, being cold reduces perfusion to the skin and extremities, which means they don't offgas well, either -- Thus the increased risk for DCS. So the worst combination is that you start your dive nice and warm, go deep, absorb a bunch of nitrogen, get cold and come up and can't shed it -- And isn't that how a lot of dives go?

 

[polarbeardiver]

food for thought, cold less blood flow to the skin surfaces, less off gassing, later but the models are pretty conservative. So there should really not be a problem under any circumstances. But you should watch it if you have concerns

I like cold water...so it has not stopped me

 

[Puffer Fish]

This makes a lot of intuitive sense, because if you are cold (externally or internally) you vasoconstrict in the skin, and therefore there isn't much perfusion there -- thus not much nitrogen. If the skin is perfused, it WILL absorb more nitrogen.

Note that, at least in this small clip of the study, it doesn't say anything about total body nitrogen absorption.

Similarly, being cold reduces perfusion to the skin and extremities, which means they don't offgas well, either -- Thus the increased risk for DCS. So the worst combination is that you start your dive nice and warm, go deep, absorb a bunch of nitrogen, get cold and come up and can't shed it -- And isn't that how a lot of dives go?

Physics would not seem to support this. Temperature does effect gas absorption in a major way, but it is cold to warm that is the danger. There are lots and lots of recorded hits from people taking a hot showers or going in a hot tub after a cold dive.

To my knowledge, being warm during a dive has no such obvious body of knowledge. It may be true, but the mechanism would have to be something currently unknown. It actually should reduce the amount of gas. And cooling down on the surface should be better for you.

There may be other issues at play, like dehydration, or as you mention, vascular constriction.

Would need to see the data and the definitions of cold and hot to draw any conclusions.

 

[TSandM]

Well, you could argue that being cold at the end of the dive INCREASES the amount of dissolved nitrogen at any ppN2 AND reduces the perfusion to the tissues to carry away the dissolved N2 -- Therefore, when you do eventually warm up, you've got a lot of nitrogen to get rid of. Warm up fast, and exercise doing it (lugging gear and packing, anybody?) and you might be a setup for bubbling.

 

[Puffer Fish]

Well, you could argue that being cold at the end of the dive INCREASES the amount of dissolved nitrogen at any ppN2 AND reduces the perfusion to the tissues to carry away the dissolved N2 -- Therefore, when you do eventually warm up, you've got a lot of nitrogen to get rid of. Warm up fast, and exercise doing it (lugging gear and packing, anybody?) and you might be a setup for bubbling.

I believe that has been proposed for hundreds of hits, but I don't remember anyone ever suggesting the opposite could happen. Wonder what was going on there?

 

[Thalassamania]

Vasoconstruction when you hit cold water is rather fast, once it clamps down, not much uptake. The converse is true, there are lots of paradoxical cooling stories.

These were the reasons that the planned hot tub (er ... "diver rewarming unit") on the porch of the George Bond habitat (now Aquarius) was nixed.

 

[watercooled]

Physics would not seem to support this. Temperature does effect gas absorption in a major way, but it is cold to warm that is the danger. There are lots and lots of recorded hits from people taking a hot showers or going in a hot tub after a cold dive.

To my knowledge, being warm during a dive has no such obvious body of knowledge. It may be true, but the mechanism would have to be something currently unknown. It actually should reduce the amount of gas. And cooling down on the surface should be better for you.

There may be other issues at play, like dehydration, or as you mention, vascular constriction.

Would need to see the data and the definitions of cold and hot to draw any conclusions.

i would think that as you warm you would off gas better than if your were cold. when your cold the muscles tighten and shake trying to warm themselves. requiring the body to use more air to maintain the process. this would make me think that this would null the effect of vasocontriction. you'd intake a greater amount of nitrogen at depth but the dialation effect of getting warmer would help offgas.
i'm just an emt so my physiological knowledge isn't surgical grade but i try.