Thanks to Wired magazine for that gratuitous headline.
Claudia mentioned some of the issues of altitude for respiration. For a long time athletes have explored the benefits of training at altitude. The key benefit is that prolonged exposure to low oxygen concentrations (it's actually a low pressure but the effect is the same) leads to increased red blood cell concentrations.
However the downside is that it is hard to work your muscles at appropriately high intensities at low oxygen concentrations. One solution that has been around for a while is to 'live high, train low'. This works because the advantages of living at altitude come about from simply being there even if you are just sleeping, eating, working, whatever. But you go to low altitude to train at appropriate intensities. However this is inconvenient to say the least. Hence the development of low oxygen sleeping chambers and even low oxygen offices. These don't mimic the low pressure of altitude but simply reduce the oxygen concentration to induce the same effect.
Looks like it's a pretty big business - Hypoxico are one of the main companies and have an intriguing range of products.
But as anyone who has spent any time at altitude will tell you, there's a downside. From the Wired article: Mile-High Club: Do Oxygen Tents Boost Athletic Performance?
Crawford discounts anything beyond a placebo effect, claiming that the
low-oxygen environment hampers recovery and robs the athlete of sleep, a
primary component of any training program. “Why am I starving my
athlete of oxygen that he needs to recover?” Crawford asks.
The ethics of the use of these devices by athletes has been discussed by the World Anti-Doping Agency (WADA), which claimed that it could be equivalent to blood doping and therefore they should be banned. Blood doping is the use of hormones such as erythropoietin (EPO) which boost red blood cell production. These were banned for most sports in 1986. In 2006 the WADA announced that 'the overwhelming consensus of our
health, medicine and research committees – was that, at this time, it is
not appropriate to do so." Presumably because there would be no mechanism to enforce such a ban