Adrian did sleep in a hypoxic environment while he did his most recent training with me. This was his choice, not our recommendation. Steve and I both remain unconvinced as to the efficacy of using these tents for pre-acclimatization and consider their use to enable ‘speed ascents’ of 8000 meter peaks as questionable and potentially very dangerous. One thing that goes unmentioned about these speed ascents is the oxygen flow rate that these climbers use. As you can imagine; it is possible to lower the effective altitude significantly with the mere turn of the regulator dial. Provided that the cost of the bottled oxygen is not an object and you have enough Sherpa support to carry the extra O2, one could theoretically take a fit person right from sea level and get them up Everest.
Leaving aside the ethical concern of lowering the effective elevation of an mountain whose principle difficulty is that very elevation, our fear is that offering what may appear as a miracle way to climb big mountains in a hurry can persuade people to forego training. In our experience with most folks (including Steve’s and my) use of these Hypoxic tents, their big draw back is that they inhibit recovery from the high work load we need to impose on these climbers. Sleeping in a reduced 02 atmosphere will not allow deep sleep thus your ability to handle work will be lower and so your fitness gains will be less. In short: we don’t see the use of hypoxic tents in and of themselves harmful (nor useful for their stated purpose). It is their impact on the training that concerns us. Adrian has an exceptionally high work tolerance and a great deal of experience at altitude that may make his use of the tent and a high volume of training anomalous.
I have extensive experience in using Hypoxcio tents in the preparation of Olympic level endurance athletes for competition. For the purpose of improving sea level performance of elite athlete I have seen enough results to know that they work. So I am not discounting these tents without any experience.
Based on our extensive experience accrued over 2 lifetimes of climbing big mountains and working with many mountaineers; we KNOW that the most critical factor for both safety and success that lies within our, or the climber’s control, is fitness. Of course their are many other factors beyond anyone’s control that can impact the success on such mountains. So, fitness alone is no guarantee. We do know that Adrian’s fitness is now far superior to what it was in the past. Another consideration that you need to be aware of and whose cause is unknown is that people who have been exposed to high altitudes in the past tend to acclimate faster and preform better each time they return to similar altitudes. Someone with Adrian’s experience at altitude is by default going to have a distinct advantage over an 8000m neophyte when it comes to acclimatization rate and his response to altitude.
The physiology of high altitudes is a field with more anecdotal than scientific study. We re very complex organisms and multiple, interlinked factors will determine each individual’s response to altitude. While some guidelines exist your won results may vary.
I hope this helps,