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Risk, Readiness and Respect – A Confidence and Safety Series
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Limits of fitness
A Q&A with Dr James Knox
Briefly …
Many travellers assume that fitness, experience or determination will protect them at altitude. In this conversation, Dr James Knox explains why acute mountain sickness can affect anyone above 2,500 metres, how to recognise the warning signs early, and why gradual ascent remains the most effective protection.
Acute Mountain Sickness (AMS) is the most common form of altitude illness and usually occurs after ascending too quickly to higher elevations, typically above about 2,500 metres. Common symptoms include headache, nausea, dizziness, fatigue, shortness of breath, poor sleep, and loss of appetite. It can progress into more serious conditions like HAPE – High Altitude Pulmonary Edema (fluid in the lungs) and HACE – High Altitude Cerebral Edema (swelling in the brain).
One thing many doctors emphasise is that mild AMS can feel deceptively similar to “just being tired from travel”, which is one reason travellers sometimes ignore the early warning signs. Commentary often focuses on the importance of what are known as “ascent profiles”, such as the significance of a gradual ascent over “fitness” and how often travellers underestimate symptoms.
A strong theme that emerges throughout these conversations is that even experienced or very fit travellers are not immune to altitude sickness, and medical guidance continues to stress that ascent profiles matter more than confidence or physical conditioning. So, can we count on physical fitness as protection? Does ‘summit mentality’ – the psychological pressure to continue regardless – present additional challenges for our health and wellbeing? How do we distinguish between normal fatigue from the early signs of AMS?
Many travellers assume that being fit protects them from altitude sickness. How true is that, medically?
High-altitude illness affects people indiscriminately above around 2,500m, even those who are physically fit. The reduced oxygen content in the air at high altitudes triggers a suite of physiological changes as the body attempts to compensate. These include increases in breathing rate and heart rate, vascular changes to improve oxygen uptake in the lungs and oxygen delivery to the brain, and release of more red blood cells to carry oxygen around the circulation. The process of acclimatisation also involves regulation of at least 3,000 genes, which help our cells better manage the decreased level of oxygen at high altitudes.
Having a good exercise tolerance before travelling to altitude doesn’t seem to speed the acclimatisation process or confer any other added advantages. Among adults without underlying medical problems, those who are physically fit are just as susceptible to the effects of high-altitude illness as others. Altitudes above 2,500m can be a particular problem for those with underlying medical problems, including but not limited to certain diseases of the heart or lungs. Anyone with underlying health issues should seek medical clearance before planning travel.
What are the earliest warning signs of altitude sickness that solo travellers should never ignore?
It’s important to distinguish AMS from more severe forms of high-altitude illness. AMS symptoms include headaches, tiredness, nausea and occasionally vomiting. These symptoms occur in 19% of unacclimatised people at 2,500m. They can be managed by resting at the same altitude and taking simple analgesics for headache if needed.
The American Centres for Disease Control and Prevention offers the following advice:
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Know the early symptoms of altitude illness and be willing to acknowledge when symptoms are present.
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Never ascend to sleep at a higher altitude when experiencing symptoms of altitude illness, no matter how minor the symptoms seem.
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Descend if the symptoms become worse despite rest or treatment at the same elevation.
More severe forms of the illness require immediate descent to prevent progression of symptoms and possible fatality. High-altitude pulmonary oedema (HAPE) can occur anywhere above around 2,500m but is more common above 4,300m. It begins with shortness of breath, coughing or weakness. Be suspicious if a member of a hiking group drops off the pace and can no longer keep up with the others. Immediate descent is required to prevent progression to life-threatening illness.
High-altitude cerebral oedema (HACE) is rare below 4,300m. It starts with poor balance and coordination. Without immediate descent it can progress to confusion, drowsiness and extreme fatigue, which can make descent more difficult. These can be followed by unconsciousness and death. Loss of balance at high altitude needs to be taken very seriously.
There is increasing discussion around medications like acetazolamide (Diamox). Who should realistically consider using it, and what misunderstandings do travellers commonly have about it?
Acetazolamide can be prescribed by your doctor as a preventive therapy for high-altitude illness, but it’s no substitute for gradual ascent. Gradual ascent involves avoiding flying into areas where the elevation is more than about 3,000m above sea level. Instead, it’s preferable to stay at least one night at an intermediate altitude of around 1,500m. After reaching 3,000m ascend no more than 500m each day and have one rest day for every 1,000m gained. Staged ascent is even better if time allows. This involves spending five to seven days between 3,000 and 4,000m before climbing higher. It’s also a good idea to avoid sleeping tablets, alcohol and over exertion during the first few days at altitude.
Doctors will generally assess the risk of high-altitude illness based on whether a traveller has had any form of high-altitude illness in the past and the proposed itinerary. For itineraries where gradual ascent is not achievable, then acetazolamide can be helpful for some people.
What can be the biggest mistakes travellers make once symptoms begin, particularly if they are determined to “push through”?
The tragic consequences of high-altitude illness are well documented in medical journals. Common themes in these cases are hikers who were either unaware of the warning signs or ignored them thinking they could postpone descent. In these cases, reducing altitude becomes much more difficult when hikers or climbers can no longer walk. Even with treatment, the natural history of HACE and HAPE is to worsen if travellers don’t descend. Under these circumstances, death can occur in a matter of hours.
If you’re planning to hike or climb at high altitudes, work out your itinerary well in advance to factor in gradual or staged ascent. Make sure you’re aware of the symptoms of AMS, HAPE and HACE, be prepared to acknowledge when these are present, and manage your elevation appropriately in each case. See a travel doctor before you go, particularly if you have underlying health problems or your itinerary does not allow for gradual ascent. All but the most experienced should travel with a guide who is familiar with all forms of high-altitude illness and their management. Expedition doctors, if present, can utilise injectable dexamethasone, supplemental oxygen and other equipment which may provide a lifesaving addition to descent.
Dr James Knox, BSc(Med), MBBS, DTM+H, FRCPA, FRACP, is an Australian Infectious Diseases specialist and the Director of Glide Online Travel Clinic. You can connect with James via our ‘Solo Smart’ Traveller Directory here and the Glide Online Travel Clinic website here https://glideonlinetravelclinic.com.au/
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