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Hans,

Thanks for this excellent description. From my (admittedly limited)
knowledge of physiology, this explanation (of the joint stiffness) makes
perfect sense.

And to the Miss Manners types out there - THIS is what you should be getting
from (or giving to) the list, not etiquette lessons.

Rich L



----- Original Message -----
From: Hans Petter Roverud <proverud@on*.no*>
To: <kirvine@sa*.ne*>
Sent: Monday, August 23, 1999 8:19 PM
Subject: Stiffness at depth


> At 06:33 AM 8/23/99 -0400, you wrote:
> >Richie is talking about something else with the stiffness. What you are
> >talking bout is baratrauma, and the joints get it from working under
> >high pressure.
> >
> >We conserve our motion to reduce this, and use anti inflammatories.
> >
> >What we are discussing is that feeling like you get from dehydration,
> >lack of potassium or hypercapnia. Anyone havae any ideas on that?
>
> Hi George!
>
> For some reason the techdiver server has been kind of funky lately. I've
> tried to post several times, only to receive some error message. Still, I
> get all the messages.
>
> Stiffness: Osmotic imbalance during rapid descents causing synovial fluid
> to be drawn out of the joints.
>
> Reason: As ongassing occurs in fast tissues first, their osmolarity
> increases. A gas load makes tissues draw water from tissues with a lesser
> gas load. This is just like salt(er) water drawing water from fresh(er)
water.
>
> Result: Joints are temporarily going dry (drier). This leads to lack of
> "lubrication" and pain.
>
> Eventually, as the entire body reaches / approaches saturation this
osmotic
> imbalance levels off. Sat divers get slight joint pain at 330' upon a fast
> descent. However, after half an hour's stay at this depth they're fine
> (equilibrated) and may proceed to greater depths.
>
> Other quips:
>
> On the cold water -- helium thing:
> It's all about heat capacity versus heat conductance. Helium has a lower
> heat capacity than air and a much higher heat conductance. Since the gas
> you inhale will be heated to body core temperature anyway, a higher
> conductance makes no difference. The real issue is the caloric price of
> heating it (heat capacity) which is somewhat LOWER for helium than for air
> / nitrox. Conductance, on the other hand, is the main issue when you use a
> gas as an insulator. That's why helium is bad in a dry suit -- it doesn't
> cost much to heat the helium, yet it's constantly drawing (conducting)
heat
> from your body to the water.
> Bottom line: it's NOT colder to breathe helium than nitrox, but NEVER use
> it for suit inflation!
>
> On counter-diffusion:
> The problem is to breathe air or argox while in a helium atmosphere. Since
> we do it the other way around -- breathing helium mixes in an argon (suit)
> atmosphere there's no problem.
>
> On mitral valve defects:
> The only defect that will increase the susceptibility to DCS is the one
> causing blood to bypass the lung filter. The congenital left-over from
> fetal circulation -- patent foramen ovale -- is the only defect that will
> cause this.
>
> regards,
> Hans
>
>
>

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