WARNING: THIS ARTICLE CONTAINS GRAPHIC IMAGES OF DEAD BODIES
There is an area, above 8,000 meters elevation, where your body will no longer replenish its oxygen store. No matter how much you breath, no matter how much you have prepared, with an oxygen concentration only 1/3 of that which is at sea level, you have at most 48 hours before you run out. Only 14 mountains in the world allow you to step past this elevation, called the death zone. Everest is one.
Because at this elevation each individual climber is struggling for their own existence, most climbers reach a realization that if anyone is injured, they will have no way to help. An even more sobering realization is that if you make any mistakes, no one else will have the strength to help you.