Posted by Wayne on November 07, 2001 at 12:46:33:
In Reply to: Re: Faith posted by MHK on November 07, 2001 at 12:14:52:
I know you know this, Mike, but for those who may not understand it, here is an attempt to explain some of how we pass gas -- through the lungs.
That good old fashioned osmotic stuff goes on and gasses diffuse across barriers based on their pressures. Nature tries to even everything out and wants to have the same pressure on both sides of the barrier.
Putting a person on O2 will increase the partial pressure of the oxygen (PPO2) while decreasing the partial pressure of the nitrogen (PPN2) in the lungs.
What this means is the engine that drives the nitrogen gas transfer (partial pressure differences) is dramatically increased by changing to pure O2. This is because the air in the lungs will have very low N2 content and the dissolved N2 in the blood will at a much higher pressure. So the N2 will more quickly move from the blood into the lungs where it is exhaled. This lowers the PPN2 in the blood causing a more rapid transfer from the tissues to the blood. If we wait long enough the N2 levels throughout the body will all stabilize based on the partial pressure of what we are breathing.
Maintaining elevated pressure in a hyperbaric chamber does different things. It reduces the size of bubbles that may be present (Boyle gets the credit) and it increases the soluability of the blood and other tissues. Increased soluability means that the gas (bubbles) will be more easily re-dissolved into the blood and tissues for transport back to the lungs where it can move out of the body based on partial pressure differences. Reducing bubble size has obvious benefits. The benefit of making the bubbles go away by absorbing the gas into the blood should also be obvious.
This is a simplification, of course, illustrative of the process and why a combination of oxygen and hyperbaric pressure is used. I hope it helps those who did not know how this works.
Wayne