(With apologies for bad terminology)
I follow (as a layman) the theories about nitrogen loading (while at depth or descending), and nitrogen "off gassing" as you ascend.
My question is : what happens with/to the nitrogen in the body at the surface-for non divers as well as divers.
Does it just "stay there"?
Is it replaced, if so how? ordinary breathing lacks the pressure differential of a dive?
Are non-divers like saturation divers at 1 atmosphere?
Thanks in advance.
This may be more information than you want, but here goes.
When we breathe, the gases in air enter our lungs, where they get into our bloodstream and circulate through the body. the molecules are small, so even though they are being carried rapidly through the tissues in the blood, they can exit the blood vessels and get into the tissues as they go. At the same time, the molecules in the tissues are going back into the blood vessels and returning to the lungs. It is all pretty random, and by sheer law of averages, the amount of gas entering the tissues equals the amount leaving them.
When you descend on scuba, each breath you take requires more gas to fill the lungs. At 33 feet of sea water, every breath you take has twice as many molecules as on the surface. At 66 feet, each breath has 3 times as many molecules. That means twice as many molecules are entering the tissues as are leaving it. Your tissues begin to gain nitrogen. As they do, they work toward the balance you had on the surface. That means that as time pases, the tissues begin to even out, and the process slows down considerably.
Different tissues take on nitrogen at different rates, depending upon how liquid they are and how much blood flow they have. Let's say you have been at 66 feet for a while. Before long, the fastest tissues will have evened out with the gas you are breathing. They will be gaining and losing nitrogen at the same rate, so we say they are at equilibrium. This is also called being saturated. When you start to ascend, your inhalations will have less nitrogen than before, so now your tissues will have more nitrogen than your lungs. those faster tissues are supersaturate. That means more nitrogen will leave your body than is entering it as your body moves back toward equilibrium.
To avoid DCS, your tissues cannot be too supersaturated. A certain amount is OK. When you are ascending slowly and/or doing a safety stop, your tissues are moving toward a safe level to ascend. The fastest tissues will lose enough nitrogen to be safe, and the slower tissues, which are still taking on nitrogen, cannot get too much at that depth. You can ascend.
When you reach the surface, all your tissues, including the slow ones, are supersaturated, meaning more nitrogen is going out with your blood flow than is coming in with your blood flow. The longer you are on the surface, the more your tissues will lose their excess nitrogen. Eventually you will be at equilibrium again.
