48 replies to this topic

[ScubaDrew]

Hi everyone,

It seems the more I learn about things, the less I really know. DCS is no exception. I thought I had a pretty decent grasp on the issues surrounding DCS, but there is always so much more to learn.

To start with, I never really paid it too much attention, as my dive profiles are always short and shallow, and until this year I never made any repetitive dives outside of a dive class. I always thought getting bent was the domain of the deep diver, or someone who breached their NDL for any given dive, not for someone who dives "safe" profiles well within NDL, and never rushes to the surface. And I am not talking about joint pain symptom DCS, but full blown critical condition rush to the chamber type of event.

I am learning that there are things called "undeserved hits", in which people do everything right, and still get bent. What type of things can cause that? Are there things that predispose divers to DCS? I know about the issues with alcohol, and smoking, but what else is there?

I guess I was pretty naive, but I am hoping to take a rescue class within the next year and do alot more diving, and different types of diving where I might see DCS, and I want to be prepared.

And does anyone know of a good book or other resource that doesn't read like a dry clinical manual?

Thanks...Drew

[Craig]

Good point/topic! I'm interested in hearing all the responses as well.

[WreckWench]

SingleDivers.com helps DAN (Divers Alert Network) with PDE research using Cochran Computers to help ascertain WHY divers get bent. They are trying to obtain 1 million dive profiles from REAL divers like you and me. We are not Navy Seals and we are not 24 years old. We are aging, sometimes out of shape and we don't always do everything as well as we should. For example we don't eat as well as we should. We are over tired when we show up on a trip and probably overstressed. All of these factors do impact the body's ability to recover after diving.

DAN has been learning that most of the hits today occur due to divers being dehydratedd and exhausted. When dehydrated the blood is too thick to properly absorb the nitrogen back into the blood that escaped when you were at depth. Exhaustion and lack of sleep also affects the body's ability to reabsorb nitrogen back into your blood stream.

Basically at depth the pressure is so great that nitrogen separates from your blood. As we rise slowly and do our safety stops that nitrogen is reabsorbed back into the blood stream. (Granted this is an oversimplification so if it is inaccurate please correct my misunderstanding.)

So while it appears that you took an undeserved hit...it may be that factors such as hydration and rest were the culprits.

[divzac]

I have seen people do the most incredibly "stupid", if you will, things and not get into trouble. I also know people that have been right where they are "supposed" to be and I visited them in the chamber..... Basically, (very, I know) being cold, sick, tired, thirsty, overweight are not helpful.....

[ScubaDadMiami]

Another vote for dehydration as a significant factor. I'd like to hear more about the exhaustion thing as I have never heard of that correlation (other than people making mistakes due to lack of awareness due to fatigue).

Take a decompression procedures class for more information and some great sources of research.

Pre-existing medical conditions are issues for some people, such as those with Patent Foramen Ovale, a heart related issue that affects how inert gas travels through the body.

The unknowns: There are a number of cases where people do everything right and still get bent. We will just never know it all. There's theory, and then there's what really happens.

[PerroneFord]

Curious term, underserved hit. From what I've seen these hits have a number of root causes.

1. Hydration - People don't take this seriously. Without adequate hydration the blood thickens, as wreckwench mentioned.

2. Fatigue - Another root cause for DCS.

3. Alcohol - Alcohol dehydrates the body. It has no place around diving. And contrary to popular belief, the body needs time for the uptake of hydration. Having some water or gatorade an hour before the dive isn't going to cut it. My hydration routine starts 2 days prior to the dives, and continues 2 days after. I don't consume alcohol in this period as it negates the hydration.

4. Diuretics - Substances like tea (black or green) cause us to expel more water from the body than normal. Reducing hydration. I view this in the same light as drinking alcohol.

5. Poor fitness - The number of people who are couch potatos then decide to go do a bunch of dives, lifting heavy gear and hoisting themselves into a boat or doing long beach walks with gear on their back amazes me. Maintaining some basic fitness level will help the cause.

6. Poor profiles. I think this is where the most misconception happens. Recreational divers seem to think that if they don't exceed NDLs and do an hour surface interval, they can avoid problems. Sadly, they don't realize that repetitive dives really load up the nitrogen, and shallow dives are often the worst. Doppler tests show that the body is showering bubbles HEAVILY about 20-30 minutes after the dives, and may not subside for several hours. So repetitive divers jump back in the water while all this nitrogen is coming out, re-compress the bubbles, and put themselves at risk for a DCS hit. That 3 minute safety stop at 15ft isn't doing anything for you really.

6. Poor gas choice - Air is about the worst thing you can breathe underwater. The incredibly high inert gas level, means you're going to offgas for hours after leaving the water. Nitrox helps but then people go and push the nitrox tables to the limit. So they lose much of the benefit.


7. Repetitive dives - Doing 4 or more dives a day really pushes things in terms of offgassing. You simply don't give the body time to do what it needs to do to get rid of the inert gas. You are also increasing fatigue, and it's made worse if you aren't very fit.


So looking at the behavior of many vacation divers I read about on other boards, it's not hard to understand why we see these incidents. Many are unfit. They don't hydrate well, they do repetitive profiles, often up to 4-5 dives a day on liveaboards, they consume alcohol during the trip, they spend lots of time in the sun, they dive on air, or push nitrox to it's limits, etc. It's a recipe for problems.

[ScubaDadMiami]

I drink a lot of black, green and white tea. However, I stick to the decaffeinated type. Is that still a diuretic?

I will be the first to admit that I should consume more water. I just get tired of it.

[PerroneFord]

I think the caffeine is the problem. Same issue with coffee. Water is a GREAT thirst quencher, but not the best hydrator. Drink something else.

[WreckWench]

I drink a lot of black, green and white tea. However, I stick to the decaffeinated type. Is that still a diuretic?

I will be the first to admit that I should consume more water. I just get tired of it.

Caffeine is the primary dehydrating element.

YES you should consume more water. Add lemon or a small amount of juice for flavor but an uncomplicated body desires, craves and NEEDS water.

Americans flush their system with fluids but they are NOT hydrating fluids. Water is a hydrating fluid. The only exception is if you are in the desert sweating out buckets of water and then you'll need electrolites as well as water and some sugars.

Most of us do not exert or exercise to that extreme. The body is made of 70% water and the brain approx 85%. Not tea, not soda, not coffee, not koolaid/crystal light etc....but WATER.

[netmage]

Pay attention to your body..., recognize how you feel, and pay attention to the 'subclinical' symptoms which might be indicators of you pushing things... aches, pains, fatigue

A few of the tech manuals might be a good place to start..., and yea, avoid the NAUI text's... they are written for the typical Phd candidate... I don't mean to turn this into a DIR discussion, but the GUE books are pretty good in layman's speak...

Having been through two full blown type 2's, there are just certain things I do, and I do 150-200 dives a year.
Always dive nitrox, always do slow ascents, full and/or extended safety stops, I don't do repetitive deco and if something is on the deep end, I bring along 50% or O2...

Now you might be saying, oh he's one them tech divers.., well, hindsight is 20/20, and 3-4 years ago, on a trip to coz I'm now more than ever thoroughly convinced I sub-clinically bent myself daily doing NDL dives on air by computer. (a conservative uwatec no less.) I have strong indicators I have a PFO, had the TTE and it came back negative. Working on when I can get the TEE scheduled.

[Scubatooth]

<erased>

Never-mind

Edited by Scubatooth, 23 August 2007 - 09:18 PM.

[netmage]

The body is made of 70% water and the brain approx 85%. Not tea, not soda, not coffee, not koolaid/crystal light etc....but WATER.

Maybe this is why my brain turned to dust and I can't re........ uh what was I typing?

-Tim

[PerroneFord]

The trouble with water is that it is a GREAT thirst quencher. Nothing is better for it. The problem is that since it so effectively quenches thirst, it often triggers the body's response to do so before we are adequately hydrated. Having coached some elite athletes over the past 13 years, I've done some work with Dr. Don Kirkendall at UNC on this (Physiologist for UNC women's soccer as well as the US Women's National Soccer team) as well as the Gatorade Sports Science Institute in Gainesville. In their clinical trials as well as my own subjective tests over a 5 year period, I have found that I tended to have better hydration results when my players consumed good sports drinks (Gatorade, Powerade, Accelerade) instead of water. Not that water wouldn't do the job, but just that they "had enough" well before they had consumed enough to be helpful. Similar results were obtained with the Manchester United Men's team in England. Perhaps some of the fittest and best trained athletes in the world. They simply were not drinking enough water in the trials to replace what they were losing.

In my own tests while diving, I have found that by beginning my hydration cycle 2 days prior to the weekends, and continuing that cycle two days after diving, and using Gatorade, I've had the best results. Every so often I do just water, or water alternated with other drinks. I consistently feel my best with Gatorade.

The WKPP exploration divers have also done a number of tests with hydration for diving. They use a mix called eFuel. It seems to work very well for them on their marathon 18-25 hour dives. I realize this is well beyond what anyone here will do, but it does point out that hydration is crucial.

I would say if you can hydrate properly with water, then do so. If you can't force yourself to drink enough water (I sure can't) then something like Gatorade might be the better way to go.

[annasea]

<snip>
The WKPP exploration divers have also done a number of tests with hydration for diving. They use a mix called eFuel. It seems to work very well for them on their marathon 18-25 hour dives. I realize this is well beyond what anyone here will do, but it does point out that hydration is crucial.

<snip>

I'm curious... what's in eFuel? I googled it and all I found was a post of yours on another board, P.

[ScubaDadMiami]

Gas selection, in theory, should not matter so much if adequate decompression is carried out. However, I can only say that I feel 10 times better after helium dives than without it. So, I tend to use helium mixes even when not "called for" due to depth and narcosis issues. Of course, using a CCR, it makes the cost just slightly higher than using air diluent.