Question for the Doctor?

[kauai_diver]

I was talking to a friend at work and we were discussing the differences in individual human bodies and tissues etc...I am curious, has there been any studies(scientific with supporting data) that would show that depending on individual differences(ie. weight, life style etc..) where one person would absorb nitrogen faster in the various tissues than another? And conversely, the ability to de-saturate sooner?

I make it a point to be really hydrated the night before a dive(water and some juice) and eat fruits(simple sugars) on the morning of and during surface breaks. Is there a correlation between cell hydration and it's ability to absorb and "drain" nitrogen? Forgive me if this sounds dumb but I can't find alot of info in any of my books IRT this supposed theory.

 

[sky50960]

One of risk factor for DCS is of body fat; nitrogen is very soluble into fat.
If a lot of fat ( high body mass index ) there can be a high nitrogen uptake and nitrogen release when scending
This can lead to bubble formation, if very extensive they can block the pulmonary circulation and even get trough the lungs and cause arterial gas embolism.
They can also got trough a formen-ovale and go straight into the arterial circulation an this will end up with medullar or cerebral embolism
Remember diving tables ( Us Navy 93 ) are not made for “ large” people.

There are other risk factors :

Dive profile
Flying after, or altitude “trip” after diving ( in less than 12 to 24 hours )
Maybe Aging
Females tend to have more DCS (More fat in some nice places… :tease: )
Bad physical condition
Exercise 4 hours before or 6 fours after a dive
Dehydration (wearing diving gear in the sun, heated dry suit, drinking a lot of coffee or alcohol)
High level of CO2 (Strong exercise during dives for example)
Cold water, performing heavy exercise during diving
Paten foramen ovale
History of DCS
Scarring (previous strokes, neurological DCS, spine chirurgy…)
Preexistent diseases (pulmonary problems, bad blood circulation in general including
vascular conditions and blood conditions )


And of course there might be some individual variation, nitrogen uptake and off gassing is a complex perfusion-diffusion related phenomena. Not everybody is alike.

Dehydration is a very important point: if correct this will improve intravascular volume an lead to an excellent tissue perfusion (perfusion diffusion is an important element to evacuate nitrogen) and will eliminate nitrogen from tissues.
Don’t dive if having diarrhea, or if vomiting, taking diuretics.
Don’t drink coffee, tea, alcohol( they stimulat diuresis )
Once you are immersed into water you tend to lose more water :bonk: ( many divers have to pie after a while into water this is caused by immersion diuresis more common in divers performing apnea and snorkeling ); this is due to blood shift, dry tank air, and other complex physiological changes.

Fa

 

[kauai_diver]

I know that hydration always plays a part in any thing that affects cells/tissues. We were just curious about the individual differences of each human and how the effects of nitrogen could differ. Thanks

 

[sky50960]

Well yes, nobody is alike and probably there are physiological difference ( unknown today ) that could explain unexplained decompression sickness. (while diving safe profile and having no patent foramen ovale ).

Have a look here : http://www.scubaboard.com/showthread.php?threadid=1457


The doc's will come up with more.

Fa

 

[Dr Deco]

Dear kauai diver :

Many over the years have pondered this question. The fact is that there does appear to be a difference between DCS susceptibility in divers (and aviators). What is the cause of this difference is not known. You can take individuals into a chamber and bring them to a high altitude. Some will get DCS and some will not.

Studies of this type were made during WW II in an attempt to identify the people who would be best for high altitude bombing missions. The test was to simply place then, twenty or so at a time, in a chamber and remove the ones who bent. To make the test yield more “sensitives”, the bomber candidates were made to perform some type of physical activity such as stepping up and down on a step stool, or lifting weights, etc. The difference between activity and rest was quite large with respect to precipitating DCS in the subjects.

Beyond the effect of exercise, there was never found a physical characteristic that was particularly prognostic of their later DCS sensitivity. Not fat or skinny, short or tall. Neither has one ever found blood components that seem to be indicative of DCS performance or susceptibility. It is been sought - and it may be there- - but it has not been found. Thus, beyond musculoskeletal stress post dive, I know of nothing.

In this remember we are talking about very stressful decompression where the DCS incidence was 50%. What ever was there should appear if it is obvious, but not has been noted - - other than strong physical activity. That is why I continue to stress moderation in activity while on the surface.

For many reason, scientists would like to know what cause susceptibility. It is clear not to make more DCS-susceptible divers, but rather what to do to produce the opposite.

If I ever hear, I will let you know!

Dr Deco