Hello and welcome to our community! Is this your first visit?
Register
Page 2 of 2 FirstFirst 12
Results 11 to 15 of 15
  1. #11
    Established TDF Member nigel hewitt's Avatar
    Join Date
    Sep 2013
    Location
    Brighton, at the Marina end.
    Posts
    2,481
    Likes (Given)
    392
    Likes (Received)
    1691
    Quote Originally Posted by ColinT View Post
    But isn't the tissue supersautrated when the tissue nitrogen partial pressure is 0.8 barr and the lung nitrogen partial pressure is 0? I thought any ratio higher than 2 could cause off-gassing as bubbles rather than in solution in the blood. I must be missing something.
    No.
    Why should what is going on in your lungs affect a tissue elsewhere?
    The is only the gas tension in the tissue and the absolute pressure in the equation.
    This is physics not magic.
    Helium, because I'm worth it.
    Waterboarding at Guantanamo Bay sounded like a radical holiday opportunity until I looked it up.

  2. #12
    New TDF Member
    Join Date
    Aug 2016
    Location
    Cambridge
    Posts
    9
    Likes (Given)
    0
    Likes (Received)
    3
    if what's going on in your lungs has no effect on tissues in the body then I completely misunderstand decompression theory.

  3. #13
    "Three Sheds" Janos's Avatar
    Join Date
    Dec 2012
    Location
    Work in Westminster, live in Surrey.
    Posts
    1,664
    Likes (Given)
    1
    Likes (Received)
    880
    Quote Originally Posted by ColinT View Post
    if what's going on in your lungs has no effect on tissues in the body then I completely misunderstand decompression theory.
    Yes.

    Bubble formation is down to the difference between the ppN2 in your blood, vs the ambient pressure
    Offgassing is about the difference between the ppN2 in your blood vs the ppN2 in yer lungs.
    (Other inert gases are available)

    So,switching to pure o2 at 6m does not affect the former, hence no additional risk of bubbles.
    But switching to pure o2 at 6m dies affect the latter, increasing offgassing rates but with no additional risk of bubbling.

    Janos
    You can lead a horse to water but you can't climb a ladder with a large bell in both hands - Vic Reeves
    Hellfins - a friendly London dive club
    My music video: Dive the UK, cos that's the way it is. Huh!

  4. #14
    Established TDF Member nigel hewitt's Avatar
    Join Date
    Sep 2013
    Location
    Brighton, at the Marina end.
    Posts
    2,481
    Likes (Given)
    392
    Likes (Received)
    1691
    Quote Originally Posted by ColinT View Post
    if what's going on in your lungs has no effect on tissues in the body then I completely misunderstand decompression theory.
    We were thinking that.
    The physics of deco is about small volumes and what happens in them. Gas molecules rush about randomly but the mean flow is from high concentrations to lower concentrations.
    We are talking about distances that are microscopic here.
    What happens in your lungs causes flows and hence affects the tissue tensions over time, nothing more.
    Bubble formation is about gas tensions and ambient pressure, nothing more.
    Clasical theory is only interested in absolute pressure while bubble models factor in rate of change of absolute pressure.
    Last edited by nigel hewitt; 08-02-2018 at 09:56 AM.
    Helium, because I'm worth it.
    Waterboarding at Guantanamo Bay sounded like a radical holiday opportunity until I looked it up.

  5. #15
    Prior Member Tim Digger's Avatar
    Join Date
    Feb 2013
    Location
    West Midlands UK
    Posts
    3,037
    Likes (Given)
    1782
    Likes (Received)
    2155
    Kinetic Theory is all about molecules banging into one another, the more molecules the closer they are packed and the greater the force of collisions, whether they are in solution in a liquid (water) or in a gas in equilibrium, this rate of collisions explains ambient pressure it does not matter what the gas species is it is the change in rate of collisions (because at the bottom of the gravity well they are more closely packed) that causes an excess of pressure in solution when pressure is released and at a certain point (in biological systems dependent on a whole load of other variables) bubble formation occurs, depending on circumstances in a tissue bubble growth then occurs, and after a certain amount of bubble expansion DCI may present clinically.
    Hope that helps it's the best I can do.
    Evolution is great at solving problems. It's the methods that concern me.
    Tim Digger


 
Page 2 of 2 FirstFirst 12

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •