Aconcagua — The Summit Without Oxygen: A Challenge Above the Clouds

Mount Aconcagua (6,962 m) is the highest point in South and Western America, the "roof" of the Western Hemisphere.

Despite its impressive height, in purely technical terms, the northern routes of Aconcagua are considered "dry mountaineering" — without the need for complex ropes, hooks, or ice axes (in "regular" seasons).

The main obstacles, however, are the lack of oxygen at high altitudes, extreme weather conditions, and physical exertion.

Interestingly, classic ascents of Aconcagua were made without using oxygen tanks. This style of climbing (without oxygen) is often considered a "pure" approach, a test of the body's capabilities in "natural" conditions.

How Climbing Without Oxygen Works

Physiology of Altitude: Hypoxia, Acclimatization, and Adaptation

– At high altitudes, air pressure significantly drops, and while the oxygen content remains ~21%, the amount of "molecules available to the lungs" is much less.
– In response, the body increases the frequency of breathing and heart rate, and produces more red blood cells (to transport more oxygen).
– But these adaptations are not instantaneous — gradual acclimatization (breaks, overnight stays at middle altitudes) prevents altitude sickness and improves chances of success.
So, "without oxygen" doesn’t mean "without protection" — it means relying on your physiological reserves and proper planning.

Why Going Without Oxygen Is Difficult But Possible

Pros:

• A clear understanding of your limits — there is no "safety cushion" in the form of oxygen.

• Easier logistics: no need to transport and refill tanks.

• A sense of pure achievement — "clear style".

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Cons and Risks:

• Increased strain on the heart, lungs, and blood vessels.

• A smaller "reserve" in case of deterioration of well-being.

• Risk of altitude sickness (pulmonary or cerebral edema).
  In some seasons, snow or strong winds make climbing without oxygen particularly difficult.
  Some organizers offer oxygen as an option during the final stage to reduce risk or ease the final push, especially under adverse weather conditions.

How the Ascent Proceeds (Sample Route)

To put the description into context, here’s an outline of the classic route (northern approach) as part of one of the tours:

• Trek to the base camp (Plaza de Mulas) through intermediate camps.

• A series of acclimatization trips: overnight stays at middle altitudes, "up-down".

• A dangerous summit day: wake-up in the deep night, departure at dawn, climb through icy/snowy sections, the upper part of the route (Canaleta, Grotto, etc.).

• Descent to the lower camp, rest, then return to civilization.

For example, one program from ExtremeGuide.PRO describes the following approach:
"The ascent starts around 3:30-4:00 AM to beat the main crowds and reach the summit by noon. The route includes sections with crampon crossings, bypassing snowy parts, and the final section through a steep channel. The descent is faster."

They also plan reserve days in case of bad weather.