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Feb 242014

Felling the Altitude at the South ColA collection of well known Everest guides are questioning the conventional wisdom around time spent acclimatizing on Everest. As a result, capsule they are reducing the time it takes to climb the big Hill by weeks. However there is a big ‘but’ to their trick.

One of the reasons an Everest expedition takes almost two months is the time required for multiple rotations up and down the mountain to help the body adjust to the thin air.

A typical Everest climber will spend 10 to 15 days sleeping high on the mountain above Base Camp before going on their summit attempt. They sleep at ever-increasing altitudes to trick the body into making the necessary physiological changes, especially with respect to respiration, the key to survival at extreme altitudes. This ‘climb high, sleep low’ program has been in place since modern-day explorers began climbing the large peaks.

Of note, of the 6,871 summits through February 2014, only 192 climbers summited without supplemental oxygen, about 2.8% according to the Himalayan Database.

The Oxygen Science

The air we breath has a mixture of gases including oxygen and nitrogen. The atmosphere contains about 21% oxygen at all altitudes. What changes as we go higher is the air pressure. Gravity pulls on gas molecules in the air. The closer to the Earth’s surface, the more pressure. At the summit of Everest, the pressure was measured in 1981 by the American Medical Research Expedition and later documented in a Nova movie at 253 mmHG. At sea level it is 760 mmHG.

The reason for the lower pressure is that there is less atmosphere pushing down from above. This reduced pressure allows the air molecules to scatter. This means that on Everest the air is not as dense or “thick”. In other words there is the same percentage of oxygen but the molecules are scattered thus the term “thin air”. So in each breath, there is less oxygen. To be precise about 66% less!

In looking at how the body reacts to this reduced oxygen level, Everest legend Tom Hornbein explained it to the American Lung Association this way:

The lower oxygen stimulates chemoreceptors that initiate an increase in breathing, resulting in a lowering of the partial pressure of CO2 and hence more alkaline blood pH. The kidneys begin to unload bicarbonate to compensate. Though this adaptation can take many days, up to 80% occurs just in the first 48 to 72 hours. There are many other physiologic changes going on, among them the stimulus of low oxygen to release the hormone, erythropoietin to stimulate more red blood cell production, a physiological and still acceptable form of blood doping that enhances endurance performance at low altitudes. Adaptive changes are not always good for one’s health. Some South American high altitude residents can have what’s called chronic mountain sickness, resulting from too many red blood cells; their blood can be up to 84-85% red blood cells. The increased blood viscosity and sometimes associated pulmonary hypertension can result in right heart failure.

Climb High, Sleep Low

The age old approach to acclimatizing is the climb high, sleep low technique. This animation I created shows the schedule many teams have used for years:

As this animation shows, climbers spend a lot of energy going up and down the mountain. In fact, they almost climb it twice! Thus many guides have looked at ways to shorten the time spent on the mountain to reduce risk and time away from family and work. Those few who climb without using supplemental oxygen will go to the South Col or near 8000m to sleep before their summit attempt.

Personally, I think spending time on the mountain is the reason for going in the first place, but not everyone has the luxury of time or shares my view.



As a method to jump start the acclimatization process, an emerging trend for mountain climbers is to use so called altitude tents where the oxygen level is reduced through introducing more nitrogen into the mix. Athletes have used this system for years and many claim great success.

In essence, you spend a significant amount of time living inside a clear canopy, aka tent, breathing this adjusted mixture. Your body reacts to this with a series of changes.

As if spending $50,000, and two months away from home was not enough to put a strain on any relationship, try asking your spouse to sleep in a tent with you for two months before you go!

Everest guide Adrian Ballinger of Alpenglow, swears by the system and has many of his members use it before arriving in Kathmandu. Adrian offers Everest climbs for as short as one month, half of the standard schedule.

Because I have no personal experience with these systems, I reached out to world-renowned high altitude doctor, Peter Hackett who also runs the excellent site Institute for High Altitude Medicine and Brian Oestrike, CEO of Hypoxico, the industry leader, for his thoughts.

First up is Brian:

Q: What is the mix of your typical customer?

A: We’re fortunate to work with a wide range of athletes, mountaineers, researchers, and members of the armed forces.  Historically the bulk of our business came from endurance athletes, specifically runners, cyclists and triathletes.  This still holds true but we have seen a big uptick in interest from ultrarunners, many of whom are competing at high altitudes, as well as families using the equipment prior to their high-altitude climbs and vacations.  In addition, new research has confirmed that short interval hypoxic training can be used to enhance performance in sprint-based sports such as basketball and football, so we have been working with different NBA and NFL teams more recently.

Q: Have you seen an increase in Everest climbers over that past few years and what results did they report?

A: We’ve definitely seen a steady increase in Everest climbers pre-acclimatizing with our equipment over the past few years. What’s more exciting is that we’re seeing more climbers utilizing our equipment to add flexibility to their itinerary and specifically reduce trekking times to Base Camp. 

In fact, we had at least 8 members complete Everest last year in less than 35 days. In general we’ve seen more interest in pre-acclimatization from climbers on smaller, less challenging mountains. A stat that we’re especially proud of is that our summit success rate for Kilimanjaro climbers is roughly 98%, which involves hundreds of climbers over the last 5 years. I think that stat is more telling than on the more hardcore mountains because it involves a large sample size, weather is less of a factor in summit success rate, and because the members are generally relative novices at altitude.
Q: What is your recommendation for duration of using the system before an Everest climb?

A:  For an Everest climber looking to maximize the potential of the equipment we generally advise at least 8 weeks of both tent and mask-based training. The suggested altitudes will vary based on the on-mountain itinerary and how the athlete responds to the altitude.  We suggest trying to get 8-10 hours of time in the tent each day and ideally three to five, one hour exercise altitude workouts per week. 

We utilize a pulse oximeter during training and target blood oxygen saturations around 90% for sleeping and typically the low 80’s for active training; by sleeping and training at progressively higher altitudes, the body continues to adjust and becomes more tolerant to hypoxia. 
Q: Do you recommend any other training changes for Everest climbers who use your system?

A: We’ve found that many of our Everest members choose to equipment at least 6 months prior so they are normally working with a longer training plan in mind. We suggest to use the equipment to increase fitness levels and to build a more thorough acclimatization base leading into the final 8 weeks.

Then depending on the specific itinerary and response from the athlete we tweak the training to focus as much as possible on creating a resistance to hypoxia; we often do this by increasing the amount of IHT (intermittent hypoxic training) which involves sitting with a mask on at 9% o2 or roughly 21,000ft. To mimic the stresses of altitude experienced on the mountain we recommend increasing the total volume and intensity of active training and IHT sessions.
Q: Do you have third party analytical proof the Hypoxico system accelerates high altitude acclimatization

A: Individuals and outfitters are using the equipment to dramatically cut itinerary times, and we receive a huge number of testimonials from successful summits and high altitude endurance events and really these serve as the third party proof that our equipment accelerates acclimatization.   While the mechanisms behind AMS are still being studied, we believe that there is no other way to gain resistance to hypoxia while at sea-level.  

And although oxygen saturation is only one of several factors, we believe that having higher o2 saturations on the mountain (and as a result more oxygen available in the blood) is a good indicator of resistance to altitude. By progressively sleeping at higher altitudes, and training at lower oxygen saturations we gradually see that each individual builds a tolerance to hypoxia. In our experience this resistance is at least part of the story as to why our member do not have the same challenges at altitude.

Q: What is you reaction to the Outside Magazine article saying the Hypoxico system does not increase red blood cell count because it uses nitrogen to replace part of the oxygen mix which is different than the reduced pressure that disperses oxygen molecules at high altitude?

A: In general we’ve found that many studies don’t use high enough altitude or sufficient exposure times to induce RBC changes in the blood. Research has shown that an elevated RBC count doesn’t always correlate to a high level of acclimatization.

While the hypoxic effect of being at real altitude is slightly stronger than being inside one of our tents (because of the pressure factor), the system does lower the bodies oxygen saturation level sufficient to create new RBC.  Furthermore, we regularly receive blood work from our members that consistently show substantial increases in RBC, hemoglobin mass and hematocrit.

You can rent an altitude system starting at $700 per month but typically Brain say most members go with a 6-8 week rentals. The price for a sleeping set-up starts at $3350. They allow members to put part of the rental towards a . 

For further reading, this is the link the Outside Magazine article and this article by Nick Grantham goes into detail on the science.

The Doctor’s Thoughts

In discussions with Dr. Hackett, he advised that the science is still unproven although there does seem to be evidence that altitude tents help some athletes but not necessarily high altitude climbers. He would like to see a well done, objective study, “using a control group that does the same amount and type of training, same nutrition, same sleep and recovery, etc  but in a non-hypoxic environment to establish whether short-term hypoxia really confers any advantage.”

He told me that spending 7 to 8 hours a day in an altitude tent does help jump start the acclimatization process by:

… raises hemoglobin (or RBC’s) and that is definitely associated with increased performance at low altitude. BUT, the reason to use it for pre-acclimatization is different, kick-start the acclimatization process, which involves much more than increasing hemoglobin. AND, increased hemoglobin at altitude does not translate into increased performance like it does at low altitude.

And this is the key, according to Dr. Hackett:

What is more important is the oxygen saturation of the blood. People who pre-acclimatize will have higher SpO2, less mountain sickness, and many cellular advantages. It is not that different than spending time at high altitude prior to going on an expedition. But of course, 24 hrs a day of hypoxic exposure is even better than 8 hrs a day.

He goes on to say:

Physical performance has not been studied much, nor acclimatization except as using AMS as a marker of acclimatization. That is, if the technique prevents AMS on rapid ascent to high altitude, then it is considered successful. Using this criterion, artificial hypoxia works if it is used for a minimum of one week and 7 hrs per day, and the altitude in the field is not more than 1500-2000 m above the artificial altitude.

The short-term techniques have been shown to have either a very slight effect or no effect, even when exercising in hypoxia.

Bottom line: if you want to acclimatize with sea-level hypoxia, you need to be hypoxic for 7-8 hrs per day, which practically speaking, means sleeping in a hypoxic tent. The “altitude” should be gradually raised as tolerated, to reach about 1500-2000 m below maximum sleeping altitude. Not everyone will respond to this, but most people will.

Thus acclimatizing at home to say, 14,000 feet will adjust your body for sleeping at perhaps 20,000 feet meaning you still need to do acclimatization rotations on Everest where you sleep at 26,300 feet and go on to 29,035 feet even with supplemental oxygen.

A Climber’s Experience

If you are going to a South American 18,000 foot peak then the tent technique probably works well, a statement supported by climber Kent Stewart:

 As far as the altitude tents, all I can attest to is how they worked for me. I just returned from Ecuador where I summited Rucu Pichincha, Illiniza Sur and Cotopaxi in a 5 day accelerated program. Prior to the trip, I spent 27 nights in the hypoxic tent eventually sleeping at an “altitude” of 13,000 feet. Again, I am not a strong climber nor am I a super athlete but I went from basically sea level here in Birmingham, Alabama to the summit of Rucu Pichinacha (15,700’) in less than 24 hours with zero side effects.

By comparison, the last two trips I made to Colorado, I was crushed tying to go from sea level to the summit of any 14er. The only time I felt the altitude the entire time in Ecuador was the last 300’ or so on Cotopaxi which was over 19,000’.  In my opinion, there is no way I could have done that without the use of the tent. I know that everyone is different but it sure seems the tent is working for me which is great news.

By the way, Kent is going to Everest this spring with Alpenglow and is currently enjoying his nights in the tent at home.

To inject my own opinion here, I have seen teammates who used altitude tents on Everest and on other high altitude mountains; they did well. But also, they trained incredibly hard before coming, both mentally and physically, and did the same set of rotations I did and I did not use an altitude tent. In many ways, making the investment in an altitude tent is a proxy for your desire to reach the summit and to what end you are willing to make sacrifices to reach your goal.

The O Factor!

So moving on to the old fashion way of climbing Everest, training hard at home and then using supplemental oxygen, this is changing as well.

I recently spoke with one Everest guide who mentioned that he no longer takes members to spend a night at Camp 3 on the Lhotse Face at 23, 500′. He felt that the effort to climb to C3 outweighed the acclimatization benefits. In conversations with another he had similar thoughts but still takes his members to at least 7000m or to tag C3.

This seems to be more common as climbing the Lhotse Face has become more dangerous recently with rock fall. Many guides now try to avoid it by acclimatizing on nearby trekking peaks thus hopefully only making one climb up the Lhotse Face during the final summit push.

But the wild card for some of these teams is that they begin using supplemental oxygen lower than in previous years. Some will start from Camp 2 instead of the more traditional Camp 3. This gives the climbers a huge benefit even running at a relatively low flow rate of 1.5 liters per minute (lpm). Most climbers today climb at 4 lpm from the South Col to the summit, twice as much as 10 years ago.

The risk of starting oxygen too low is that if the climber runs out of oxygen or has a system failure, the chance of edemas or altitude sickness is high as the body is not acclimatized to those extreme altitudes thus many guides insist on not using supplemental oxygen below 8000m or 26,246 feet. Also, more oxygen means more work, and danger, for the Sherpas to ferry canister up and down the mountain thus more expense for the members.

As an aside, this is one of the reason some operators are looking to use helicopters to stage gear at Camp 2 in the Western Cwm thereby avoiding multiple trips through the Icefall for their Sherpas.

The O Debate

frostbiteThis additional oxygen is dramatically increasing summit rates in my view. Of course, critics of supplemental oxygen cry foul saying it is equivalent to doping aka Lance Armstrong. A study posted on National Geographic states that using supplemental oxygen on Everest effectively lowers the altitude by 1000 meters or 3,000 feet.

Using supplemental oxygen is the way to avoid frostbite because it keeps the body’s core warm thus allowing blood to flow to the extremities. But to be clear, it is not a panacea. Many people who use O’s still do not summit. See this article where I go into detail on the systems used on Everest for 2014.

Shortcuts to the Top?

Ed Viesturs’s book No Shortcuts to the Top described how he climbed all the 8000 meter mountains without using supplemental oxygen. He argued that you had to put the work in to earn the summit. Well, not everyone has his physiology and can climb without using supplemental oxygen. But everyone has the option to put the work in on the mountain.

My opinion is that Everest is a climb to be savored and enjoyed, not rushed. But that is just me and my opinion. I was on one climb where a teammate was so obsessed with speed that he didn’t even take a summit picture because he wanted to get back down. He returned the next year to slow down and enjoy the experience.
Everest is a milestone in every sense and not a climb to be ticked off a list – at least that is my view. I think the argument of shortening the climb to avoid dangers is a bit overblown as most deaths are due to climber error and natural causes. Statistically, Everest is one of the safest 8000 meter mountains to climb.
I fully get the point that time advances and we don’t need to climb like Mallory in the 1920’s sailing to India and walking for months just to reach Base Camp. However with so many new options available to shorten a climb, where do you draw the line? Why not helicopter to C2 and use O’s from there up and fly off from C2 back to Kathmandu? At some point aids become counter to the spirit of climbing. I’m just not for rushing it for the sake of rushing.

In summary, Everest has become more accessible to regular people based on altitude tents, an abundance of  supplemental oxygen, improved gear, helicopters, weather forecasting plus reducing the unknowns by using standard routes and commercial guides. No, it is not the same as climbing 50 years ago but neither is flying in an airplane.

Climb On
Memories are Everything

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