The Air Up There

ByABC News
May 8, 2006, 1:00 PM

May 9, 2006 — -- We humans have a lot in common with fish.

We are, for instance, both carbon-based life forms who share a largely identical DNA, and we both have to be totally immersed in the medium from which we get our oxygen in order to stay alive. Our respective oxygen-gathering equipment is markedly different, of course, in that fish collect oxygen by using a dynamic flow of oxygenated water filtered through their gills while we humans use air pressure to force oxygen from air through the membranes of our lungs.

The point here is that when we climb to higher altitudes in an unpressurized airplane and the atmospheric pressure goes down, our ability to force the oxygen into our bloodstream correspondingly goes down. If we climb too high, not enough oxygen will make it into our bloodstreams, resulting in wooziness, unconsciousness and eventually death.

If you fly at all, you need to have a solid grasp of this altitude-oxygen-atmospheric pressure thing.

These are the bedrock basics for unpressurized flight for a normal, healthy, nonsmoking human with no alcohol in the bloodstream (alcohol impedes oxygen transfer):