After record-breaking Everest climbers revealed they use hypoxic tents to get altitude ready without acclimatizing on the mountain, we look at how the technology works

Hypoxic tent.

Around 800 people attempt to climb Mount Everest each year, braving extreme conditions for the chance to say they've stood on top of the world.

Along with rigorous physical and mental training, hopefuls need to prepare for the harrowing effects of altitude atop Earth's tallest mountain, where the amount of oxygen taken in with each breath is drastically lower than at sea level.