Altitude Illness Prevention: What Every Hut-Goer Needs to Know
Altitude illness is not a problem reserved for Himalayan expeditions. In the European Alps, a hiker sleeping at 3500 m for the first time — say, the Cabane des Vignettes CAS or the Rifugio Capanna Regina Margherita — can develop symptoms that range from inconvenient to life-threatening. The physiology is simple: above about 2500 m, reduced atmospheric oxygen forces the body to adapt, and when ascent is faster than adaptation, things go wrong. The encouraging news is that almost all altitude illness is preventable with planning.
What altitude illness actually is
Altitude illness is an umbrella term covering three conditions that exist on a continuum. Acute Mountain Sickness (AMS) is the mildest: headache, fatigue, loss of appetite, and disrupted sleep after arriving at altitude. High Altitude Cerebral Oedema (HACE) is AMS becoming a neurological emergency, with confusion, loss of coordination, and potentially death. High Altitude Pulmonary Oedema (HAPE) is fluid accumulating in the lungs — the most common cause of altitude-related death — and can develop rapidly without prominent headache, making it dangerous to dismiss.
The critical fact is that HACE and HAPE can develop from untreated or ignored AMS. Taking symptoms seriously at the AMS stage is what prevents escalation.
The Lake Louise Score
The Lake Louise AMS Self-Assessment Questionnaire provides a structured way to evaluate symptoms. The scoring assesses headache (0–3), gastrointestinal symptoms (0–3), fatigue (0–3), and dizziness (0–3). A score of three or more with headache present meets the diagnostic criterion for AMS.
The value of the score is not the number itself but the habit it creates: it forces self-assessment rather than normalising symptoms as "just tiredness." Hut keepers at well-managed huts — including the Konkordia Hütte above the Aletsch Glacier and the Britanniahütte above Saas Fee — are familiar with the signs and will ask how guests are feeling on arrival.
The ascent rate rule
"Climb high, sleep low" is the foundational principle. Above 3000 m, the standard guideline is to not increase sleeping altitude by more than 300–500 m per night. This is why a staged approach to high objectives matters: an acclimatisation night at 2500 m before pushing to 3500 m changes the risk profile significantly.
For the classic Haute Route (Chamonix to Zermatt), the hut sequence is designed — partly by terrain, partly by tradition — so that most parties ascend gradually enough to avoid serious problems. The trouble comes when people attempt to skip huts, push through a rest day, or arrive at the Cabane des Vignettes having flown into Geneva the morning before.
The Diamox debate
Acetazolamide (Diamox) accelerates acclimatisation by stimulating faster, deeper breathing, which increases blood oxygenation. The standard prophylactic dose is 125 mg twice daily, starting 24 hours before ascent. The therapeutic dose for AMS is 250 mg twice daily.
The debate among alpine practitioners is not whether Diamox works — it does — but when it is appropriate. Using it prophylactically to sleep at 4000 m without acclimatisation masks the body's signals without resolving the underlying physiological deficit. If Diamox suppresses AMS symptoms while HAPE is beginning, the consequences can be severe. Opinions differ: some guides routinely prescribe it for all clients above 3500 m; others use it only for therapeutic intervention once symptoms appear.
Diamox is a sulphonamide and is contraindicated for people with sulpha allergies. Increased urination is a nearly universal side effect; staying well hydrated is essential.
Hydration and alcohol
Dehydration accelerates the onset of AMS symptoms and is easy to confuse with altitude headache. Drinking 3–4 litres of water per day above 3000 m is a standard recommendation. Alcohol dehydrates, suppresses normal breathing response during sleep, and impairs the self-assessment that catches early symptoms. A small glass of wine with dinner at a rifugio is unlikely to cause problems; multiple rounds of schnapps before sleeping at 3800 m is a different calculation.
Sleep
Symptoms are typically worst at night. The reduced breathing rate during deep sleep at altitude produces a cyclical pattern called Cheyne-Stokes respiration — alternating periods of deeper and shallower breathing that produces a restless, unsatisfying sleep. Hut sleepers at high altitude commonly report waking repeatedly and feeling worse in the morning than when they arrived. This is normal at first exposure. If symptoms significantly worsen overnight rather than improving, that is a warning sign.
The descent rule
This is the rule that should override all others: if a person is worsening at altitude, descend immediately. Do not wait for morning. Do not complete the scheduled stage. Do not assume it will pass.
Descending 500–1000 m is usually sufficient to stop and begin reversing both HACE and HAPE. Portable altitude chambers (Gamow bags) are carried by some mountain rescue teams and simulate descent by pressurising the interior, but they are not a substitute for actual descent — they buy time.
HAPE requires supplemental oxygen and rapid descent. HACE requires the same. If you are unsure which condition a companion has developed, assume the worst and move.
Recognising HAPE
High Altitude Pulmonary Oedema deserves special attention because it is the most common cause of altitude-related death and is frequently dismissed as tiredness or a mild cold in its early stages. The early signs of HAPE include dry cough, reduced exercise tolerance that is disproportionate to exertion level, and mild breathlessness at rest. As the condition progresses, the cough may produce frothy or pink-tinged sputum; resting heart rate rises significantly; and the person looks progressively unwell.
The key distinguishing feature of HAPE versus simple tiredness is breathlessness at rest. A person who is short of breath while sitting quietly in a hut after arriving at altitude is not simply tired — they need to be assessed for HAPE. Do not wait for the morning to see if it improves. HAPE progresses rapidly, particularly at night when breathing rate decreases during sleep.
The Gamow bag
Portable hyperbaric chambers (Gamow bags, after inventor Igor Gamow) simulate descent by pressurising to an equivalent altitude 1500–2500 m lower than the actual location. They are used by some mountain rescue teams and well-equipped expedition groups for HACE and HAPE management when actual descent is impossible — in a storm, at night, or on terrain that cannot be safely descended in the dark.
The bag's value is that it buys time: a person placed in a Gamow bag will typically improve enough within 30–60 minutes of pressurisation to be stable for evacuation. It is not a cure and should never delay actual descent if descent is possible. The bags are heavy (approximately 6 kg with the foot pump) and are not practical for casual hut walkers; they appear in guided expedition kit and SAR (search and rescue) team inventories.
Oxygen at high huts
Some permanently staffed very-high huts — most notably the Capanna Margherita at 4554 m on Monte Rosa — maintain supplemental oxygen for guest emergencies. The Margherita's position at 4554 m means that guests with no previous high-altitude exposure will almost certainly experience some level of AMS, and the gardiens are experienced in managing the overnight deterioration that commonly occurs at this elevation.
Below 4000 m, supplemental oxygen is rarely available or necessary at standard Alpine huts. Above 4000 m, it is worth confirming with the hut management whether emergency oxygen is on site.
Keep exploring
Huts at varying elevations — from valley-level starting points to glacier outposts above 4000 m — are all plotted on the Open the map. Use the elevation filters to plan a staged ascent profile before you leave.