Initially you may feel that with the relatively modest heights at which most people ski, that the effects of altitude should not cause a problem with day to day skiing. This is substantially correct, but there are situations that you should be aware of, especially as more and more exotic and high altitude mountain ranges are opening up for snowsport oportunities (such as Gulmarg in India, which has lift access upto 4250m, and hiking opportunities many hundreds of meters higher). There are even more mainstream resorts such as Breckenridge in Colorado (skiing upto nearly 4000m) which could potentially pose some difficulties.

Acute Mountain Sickness (AMS )

Unpleasant symptoms associated with altitude have been known to people living in high mountainous regions since at least the 16th century. However as early as 30BC Chinese histories talk of the greater and lesser headache mountains. Similar names have been given by the Tibetan people. Acute Mountain Sickness (AMS ) was fully described by Ravenhill in 1913 and largely forgotten until re-described by Charles Houston in 1946. AMS is associated with headache, nausea and vomiting. The symptoms come on gradually especially at the end of the day, and early signs can include irritability and intolerance of bright light. It should be pointed out that these symptoms are not specific for AMS.

Symptoms of AMS can appear as low as 2,500m and are common above 4,000m. Problems occur with rapid ascent to altitude especially for those staying high. Acclimatisation by a gradual increase in altitude along with going high then sleeping low is a wise precaution. You are unlikely to run into trouble if only spending an hour or two at altitude.

Physical fitness is no bar to the condition, indeed there is some suggestion that young people may be particularly prone. Previous experience at altitude may have some relevance – if you acclimatise well in your twenties this is likely still to be the case later in life. One difficulty is the unpredictability of the condition. There have been fatalities, albeit rare as low as 2,500m and conversely reports of older people performing well above 4,500m.

AMS has started to become relevant as many skiers are visiting high remote regions Such as in the Himalayas and Andean mountain ranges or spending several days at altitude when ski touring in the European Alps. If you suspect AMS there is one golden rule which is to lose height as soon as possible and not to press on. It goes without saying that there is less oxygen to breathe at 3,000m than at sea level.

Other effects of Altitude

Even without feeling ill with AMS, the lack of oxygen can have some effect on brain function. This may not be too important when cruising a gentle blue run but possibly highly relevant in a challenging couloir for example. Coupled with all this you should think about dehydration and diminished quality of sleep.

Sleep
Visitors to high altitudes often have unrestful sleep because, and even at intermediate altitudes many peole suffer from periodic breathing. Periodic breathing, (which is effectively clusters of breaths separated by intervals of apnea (no breathing),occurs during 24% of all sleep at 2,440 meters, and profoundly effects the oxygenation of the blood. Sleep at altitude is also characterized by frequent wakening, and thus produces an unsatisfying sleep and contributes to daytime fatigue….this in turn can greatly effect performance and judgment in critical situations. As with the symptoms of AMS at intermediate altitudes, sleep can be expected to return to normal with acclimatization.

Dehydration
Only a small shortfall in fluid balance – say 1.5 litres can substantially reduce performance. When on a skiing holiday overindulgence in alcohol is common so you may start the day in a mildly dehydrated state. In addition to this there is further fluid loss from sweating and an increased breathing rate in dry air, which is exacerbated while skiing as we try to compensate for the reduced oxygen levels by breathing deeper and more frequenly. Putting all this together, a combination of breathing air which is short in oxygen as well as mild dehydration may be factors in reduced performance or even causing accidents, regardless of whether the skier is suffering from AMS.

There seems to be a widespread shortage of knowledge and information regarding dehydration and the effects of altitude. When skiing many people have only limited time so inevitably there are pressures which may result in questionable decisions. It is worth noting that there are of course other reasons for developing a headache and vomiting after a night out in a ski resort!

Words: Dr John Nixon