5.) The Death Zone may be a myth, or — probably more accurately — everyone may have their own personal death zone:
It’s widely stated as fact that above 8,000 meters (26,000 feet) every human being is dying, no human can acclimatize, and the race is on to get back below that altitude before the body is damaged beyond its ability to repair itself. This hard-limit is widely publicized in reputable, mainstream publications such as National Geographic. There’s a certain logic to such a limit. In response to the diminished pressure of oxygen, the body produces more hemoglobin (that’s acclimatization), but the bloodstream can only take up so much hemoglobin.
Mark Horrell, in his mountaineering blog, challenges the idea of a one-size-fits-all hard limit, and provides anecdotal examples that contradict the 8,000 meter cap.
4.) Sticking one’s face in water allows one to hold one’s breath longer:
Sensory cells in the face and nostrils sense wetness and this sensation triggers a slowed heartbeat (bradycardia) and constriction of blood vessels (vasoconstriction) so as to reduce blood flow to the extremities.
A more detailed explanation can be read here.
3.) Mouth-to-mouth resuscitation works because our lungs only capture about 20% of the oxygen in each inhalation:
If we had super-efficient lungs, our exhalations wouldn’t contain enough oxygen to sustain the patient receiving cardiopulmonary resuscitation (CPR.)
This and many other fascinating respiratory facts can be found on the Crash Course videos on the subject.
2.) In two weeks time the breath you’re exhaling right now will have spread out around the globe.
Sam Kean’s book, Caesar’s Last Breath, discusses this subject in great depth. In fact, the title is a reference to the fact that in each breath it’s likely that one inhales a molecule of Caesar’s dying breath.
1.) When you lose weight, most of it (84%) is lost in exhaled carbon-dioxide:
This may not be a question that ever occurred to you, but I bet you find it fascinating once it’s brought to your attention. It’s not like when you cut 5 kg, there’s a fat pile sitting somewhere. More about this subject can be learned here.