So what do we think about hydration and DCS now...?

[DandyDon]

We often hear that dehydration can be a major cause of DCS, but I've seen some conflicting statements in recent years - like it's not that big of deal? The original claims seemed to make sense in that the more fluids one retains while diving, it would seem that N2 loading would have a lessor effect - but was that a misunderstanding?

And what about diuretics that often get blamed in DCS treatments, maybe more so in remote locations - perhaps from doctors who keep doing what they've been doing but don't try to update their knowledge much? Are they getting a bad rap? I know that caffeinated drinks can make me want to urinate often, but doesn't my body retain the water it needs anyway - and the reason for the extra head calls may lie simply on increased intake? Several news sources are quoting this study today claiming that coffee doesn't dehydrate? PLOS ONE: No Evidence of Dehydration with Moderate Daily Coffee Intake: A Counterbalanced Cross-Over Study in a Free-Living Population

From my experiences of many decades as a farmer and cowboy, I usually drank a few quarts of coffee a day and it just never seemed to bother me.

So anyway, can you clear up these old ideas with current understandings please...??

thanks!
​

 

[Steve_C]

In warmer weather and especially if wearing neoprene and in the sun it is very easy to get heat exhausted. I don't know about DCS but I have seen divers who had to bail on a dive or got sick because they did not drink enough fluids and got overheated which can be very dangerous. I am sure that when they did dive they did not function as well and were in a more stressed condition.

 

[DandyDon]

In warmer weather and especially if wearing neoprene and in the sun it is very easy to get heat exhausted. I don't know about DCS but I have seen divers who had to bail on a dive or got sick because they did not drink enough fluids and got overheated which can be very dangerous. I am sure that when they did dive they did not function as well and were in a more stressed condition.

Maybe so. I guess I have decades of acclimation as heat just doesn't bother me much, and I do work at keeping plenty of liquids available on outings. But then I wouldn't wear neoprene long if I was hot anyway. They all have zippers. Still, not what I asked about - but thanks.

 

[Red Sea Shadow]

Associating DCS with dehydration is as old as World War II, when it was reported as a factor that increases the risk of DCS in aviators. The mechanism was not clear at that time, and unfortunately it isn’t, yet.

Our current understanding is that, when a considerable portion of the fluids go out of the body, the body concentrates the rest of the fluids internally and peripheral flow is cut down. This would reduce the off-gassing capability of the tissues, as the capillary gas exchange at the extremities becomes less efficient due to the decreased circulation. So far, this hypothesis is not established.

In 2007, a study was conducted to investigate whether hydration 90 minutes before a dive could decrease bubble formation ^*. It concluded that pre-dive oral hydration using saline–glucose beverage decreases circulatory bubbles, which in turn may reduce the risk of DCS.

* Gempp E, Blatteau JE, Pontier JM, Balestra C and Louge P. Preventive effect of pre-dive hydration on bubble formation in divers. Br J Sports Med 2009;43:224-228. doi:10.1136/bjsm.2007.043240.

 

[Dirty-Dog]

Several news sources are quoting this study today claiming that coffee doesn't dehydrate? PLOS ONE: No Evidence of Dehydration with Moderate Daily Coffee Intake: A Counterbalanced Cross-Over Study in a Free-Living Population

From my experiences of many decades as a farmer and cowboy, I usually drank a few quarts of coffee a day and it just never seemed to bother me.

So anyway, can you clear up these old ideas with current understandings please...??

thanks!
​

Two things immediately catch my eye.
Firstly, the study you reference does not say that caffiene doesn't dehydrate. It says that moderate coffee intake doesn't seem to dehydrate.
Secondly, "a few quarts" is not moderate intake.

 

[DandyDon]

Secondly, "a few quarts" is not moderate intake.

Oh, I know. Somewhere I read that one's body can adjust with regular exposure, but there's much here I'm not clear on. Is much of this an ongoing study?

 

[tajkd]

I won't comment on the "dehydration versus DCS" myth. The pigs from the one study always referenced were fed incredible amounts of ex-lax and forbidden any liquid prior to repeated chamber rides. Oh, and the control group had some casualties as well.

This study, I believe, relates continuous caffeine use and dehydration. I believe the actual study says that, with repeated use, an individual would not be affected by dehydration. It does not address the guy who does not consume caffeine regularly. I know... who doesn't. The point is that it doesn't address anything out of the ordinary. I read that to mean that your regular coffee will not affect your hydration level (if there is such a thing).

 

[Dirty-Dog]

Oh, I know. Somewhere I read that one's body can adjust with regular exposure, but there's much here I'm not clear on. Is much of this an ongoing study?

I don't think there's much ongoing research, no. But the generally accepted wisdom is that the link between caffeine and dehydration is primarily linked to changes in consumption. If you're normally a 2-cup a day drinker and today you drink 4, you're likely to experience some degree of dehydration.

 

[DandyDon]

I won't comment on the "dehydration versus DCS" myth. The pigs from the one study always referenced were fed incredible amounts of ex-lax and forbidden any liquid prior to repeated chamber rides. Oh, and the control group had some casualties as well.

We got the dehydration DCS connection from one study like that?!

Some chamber docs seem to like to blame ice tea and coffee for unexplained hits. It seems more anecdotal than fact, but when a DCS hit is discussed - someone seems to ask about their hydration every time. I used to hear "work at hydrating" but don't now.

 

[tajkd]

We got the dehydration DCS connection from one study like that?!

Some chamber docs seem to like to blame ice tea and coffee for unexplained hits. It seems more anecdotal than fact, but when a DCS hit is discussed - someone seems to ask about their hydration every time. I used to hear "work at hydrating" but don't now.

My pet peeve is the "hydrating" myth. There is some evidence that you don't even need to drink fluids to maintain proper hydration level in the body. Granted that your body needs to be properly hydrated for many reasons, there is little valuable evidence that it influences DCS. In addition, there is no real test that can be done by a diver that can accurately measure "hydration". The pee color test is reportedly accurate but I can only get a measurement once a day (if I'm lucky).