Oxygen

Of all the health recommendations one could make, the best might be to recommend adequate oxygenation to our bodies.  Although there are free divers who can survive 10 minutes underwater without oxygen, most of us would have trouble staying alive after 3 minutes without oxygen.  Luckily, our ambient atmosphere is about 21% oxygen and it is readily available to us whenever we need it.  We seem to get an adequate amount too because if we check our blood through a pulse oximeter, we will see that for most of us it regularly reads that our blood is 95-99% saturated with oxygen. 

Despite what the pulse oximeter reading on the left shows is an adequate amount of oxygen in the red blood cells, what it fails to measure is the amount of oxygen in the blood plasma.  This key distinction is the basis for oxygen therapies such as hyperbaric oxygen chambers and a newer therapy called E.W.O.T. (exercise with oxygen therapy).