Effects of Altitude

Climbing, hiking and mountaineering to high or extreme altitude is exhilarating and adventurers from all walks of life are drawn to highest places on Earth. However, humans are just not meant to be at extreme altitude, and few people in the world live at high altitude.

Why does high altitude cause potentially serious medical problems?

What is happening to us as we go to higher elevations?

What can we do to overcome these problems and stay safe whilst at high altitude?

THE SCIENCE BIT...

The effect of Earth’s gravity pulls all the air downwards in exactly the same way that it pulls on everything else (including us) and prevents us from floating away into space. At low altitude the amount of air above us, that is being pulled by gravity is large, but as we rise in altitude the amount of air above us becomes less and less.

Imagine a group of gymnasts all standing on each other's shoulders in a tall column. The person at the bottom is feeling the weight of every person above them. The next gymnast only feels the weight of the people above them and not below them...and so on.... up to the top person who does not feel the weight of anyone at all. Air works in exactly the same way- the air at the bottom (low altitude) is feeling the weight of all the other air above it, it gets compressed slightly and therefore the air pressure is higher.

The weight of all the air above creates air pressure which is the air pressing against everything. As you go to higher altitudes there is less air above so the weight pressing downward is reduced and so the air pressure is lower.

Our bodies are used to operating and functioning at a particular altitude, which for most people around the whole world is at sea level or a little bit above. There are people who live at higher altitudes but they are far outnumbered by those living lower. Living at a reasonably constant altitude means our bodies expect a certain air pressure exerted on it all the time. We occasionally feel slight variances such as driving down a steep hill and feeling our ears pop, feeling a little different during a storm as the weather can effect air pressure, or flying in a pressurised plane cabin but in general the majority of people live nearly all their lives within the same altitude and our bodies enjoy this (more or less) constant pressure.

THE SPORTS...

There are many sports that can take us to high altitude; climbing, mountaineering and skiing are obvious examples but there are many more, and as mentioned above, some people do live at high altitude so it is possible to simply visit a city at high altitude. Sometimes we may only rise a little in altitude and barely feel the difference but at other times we may travel for days (or longer) at high altitude or go even higher to the realms of extreme altitude.

Numerous outdoor sports will involve some sort of exertion even if it is just walking. The effects that high or extreme altitude has on the body are more noticeable the more that you exerts yourself. If you are only relatively high you may not notice the effects until you begin exercising or taking part in sport. At much higher altitude or extreme altitudes you may experience the negative effects of lower air pressure without undertaking any activity although the effects will be much more pronounced when you begin your sport.

Whatever sport or activity you are taking part in at high altitude; your body is going through the same difficulties of trying to function in a place where the air pressure is different and your body is not designed to work in these conditions.

The effects of high altitude can add an addition risk, especially if you already undertaking difficult or potentially dangerous activities already, but with careful planning and following some rules you can minimise the risks and still enjoy your favourite activities.

THE EFFECTS

When and how you feel the effects of the rarefied air at higher altitudes depends on a few factors which include how much higher you have gone, how quickly you ascended and your current state of health and well-being.

However, for most people, as you begin to go up higher than about 10,000 feet above sea level you will begin to feel some mild to moderate effects of lower air pressure. Some people will experience a lot of symptoms and other people may experience less so it can vary from person to person.

One of the most obvious signs is how quickly you get out of breath when exerting yourself. At sea level, jogging up a short flight of steps may not get you out of breath but at high altitude, simply walking up the same flight of steps may leave you breathless. Mild headaches, a general feeling of tiredness and mild nausea are also very common.

The initial mild effects when you first arrive at higher altitudes are a bit like an uncomfortable hangover; which goes on for days, and leaves you tired, grumpy and feeling a bit sick.

The changes in air pressure have some unexpected effects on your sleeping patterns. Not only can the mild effects you experience during the day make it more difficult to get to sleep but there is also something else going on in your blood chemistry that can leave you constantly waking up.

Your body carefully measures the amount of carbon dioxide in your blood and uses this as an important indicator or how much you need to breathe. At higher altitudes your increased breathing rate and lower external air pressure means your body can get confused by how frequently it needs to take a breath.

Your body is constantly measuring the carbon dioxide (which is always being produced by the cells in your body) in your blood. When you are at rest, the amount of carbon dioxide in your blood is lower as you are burning less energy and your cells are producing less of this waste product. As you start to exercise you body starts to produce much more carbon dioxide which your body detects in your blood. This higher level is an indication to your body that you need to breathe more and without even thinking about it your body sends messages to your lungs telling them to breathe faster.

Faster breathing means the carbon dioxide can be released faster through the lungs, and faster breathing obviously means that more oxygen gets into the body. When you stop exercising you continue to breath faster for a while but when the raised level of carbon dioxide in your blood reduces; your body realised that is can again slow your breathing down.

At high altitude you breathe heavier than normal as the lower air pressure means there is less “quantity” of oxygen being taken into your lungs with each breath. However, the increased breathing, even at rest, means that your body is getting rid of carbon dioxide quicker too and as your body uses the levels of carbon dioxide in your blood to indicate how much to breathe it creates a problem; particularly when at rest and even more so when asleep.

When resting and sleeping you have absolutely no control over your breathing rate and the body’s attempt to get more oxygen is thwarted when the carbon dioxide leaves you body quickly so your body get confused and thinks you do not need to breathe as much, causing your breathing rate to decrease and the supply of oxygen to your body is also reduced.

It is common for people at high altitude to wake up suddenly (and frequently) during the night and be out of breath as your body struggles to understand how much to breathe.

Disturbed sleep patterns at high altitude is a very common problem but thankfully is not usually serious, however, lack of sleep coupled with already feeling ill because of other high altitude symptoms can leave you feeling even worse.

If you travel to very high altitude the air pressure will be even less and the symptoms can be much more pronounced and there is a higher potential for more serious complications.

When the cells of your body do not get enough oxygen your body tries to keep the important areas going first, but eventually all your body functions can be impaired. Your digestive system can stop working as well meaning you will not be getting the nutrition you need, your muscles can ache and you can get cramps more often, your ability to think clearly can become clouded and extreme tiredness, irritability, confusion, nausea, swelling, blue/white skin can set in, in addition to being unable to catch your breath. Whilst the majority of these conditions will not affect most people there is always a risk and that risk increased dramatically the higher you go.

THE REALLY SERIOUS STUFF...

At any high altitude there is the potential for some very serious conditions, often referred to as Acute Mountain Sickness or AMS, although the risk gets increased at higher altitudes. These are Pulmonary Oedema (often spelt Edema and sometimes referred to as High-Altitude Pulmonary (O)Edema- HAPE) and Cerebral Oedema (again often spelt Edema and sometimes referred to as High-Altitude Cerebral (O)Edema- HACE). These are conditions that can be caused by the effect of low air pressure on the body. If untreated these conditions can be fatal and you should always be aware of the signs and symptoms and ways to treat these conditions if you travel to high altitude.

Pulmonary Oedema is caused when the lower pressure air pressure can cause fluid to collect in the lungs (potentially) seriously affecting the ability of the lungs to work properly. This condition can be fatal as it can cause hypoxia which means the body cannot get enough oxygen to survive.

Common signs and symptoms are;

Breathlessness (Often severe)
Coughing up blood (in the form of pink frothy sputum)
Pale coloured skin
Excessive Sweating
Anxiety

Cerebral Oedema is caused by a build up of fluid in the brain which effects how the brain operates and can lead to severe complications if not address quickly. This condition can be fatal and should be treated immediately upon detection.

Common signs and symptoms are;

Loss of coordination
Headaches (usually severe)
Disorientation and confusion
Weakness and tiredness
Memory loss
Hallucinations

Whilst the majority of people at high altitude will experience the milder effects of lower air pressure, the risks of Pulmonary Oedema and Cerebral Oedema is always present so learn how to minimise the risks, recognise the symptoms and know what action to take.

THE PRECAUTIONS

There are a number of precautions that can easily be accommodated if you are travelling to high altitude. They can help to minimise the milder effects of living/travelling in a lower pressure area and can reduce the chances of developing more serious AMS conditions.

One of the most important things you should do is take time to ACCLIMATISE properly when travelling to high altitude. Although our bodies have trouble coping with low air pressure; over time they can learn to adapt to their new atmospheric conditions. This process is called acclimatising.

Acclimatising is much more effective if it is done slowly, in fact the slower the better. It takes time for your body to adapt; and the adaptations for high altitude are quite complex and include your body changing the chemical make-up of your blood slightly to compensate for the lower carbon dioxide levels. Therefore, acclimatisation is a process that needs time, and also will need to happen again if you move to another altitude.

Best practice for acclimatising to high altitude is to travel up slowly. Where possible travel overland in cars, trains or buses to reach high altitude rather than simply stepping off a plane into low air pressure. If you are travelling to very high altitude or extreme altitude it is important to acclimatise in stages moving up to higher and higher altitudes in increments and giving your body time to adapt to each one. The higher you go, the slower you should travel up.

When you first arrive at a high altitude, give yourself plenty of time to rest rather than engaging straight away with exercise or other exertions.

Drink plenty of fluid to stay hydrated and avoid alcohol as this can make the symptoms of high altitude worse.

It is best not to smoke as this can impair lung function and limit the body’s ability to absorb and transport oxygen around the body.

Ease in to exercise, start of gradually and build up as you feel stronger. Some evidence suggests that young, fit people are more likely to suffer more serious effects of high altitude as they will go too quickly into exerting themselves in sports or activities. Acclimatisation really does take time and you must allow your body to rest whilst it is adjusting to the lower air pressure.

Eat healthy food and avoid big heavy meals for a few days as your digestive system might be take a little while to adapt and if you are feeling a bit queezy then lighter meals are best.

THE TREATMENTS...

If someone is suffering from Altitude Sickness, especially if they have Pulmonary Oedema or Cerebral Oedema it is very important for them to get treatment.

The simplest and most effective treatment possible is...descending! If you are having trouble with altitude then head downwards, it really can be that simple. Descend as far as you can and as quickly as you can. Generally the symptoms of AMS will subside once you reach a higher air pressure.

Getting to a lower altitude is a highly effective way of dealing with altitude sickness and should be done immediately if you are concerned about your, or a member of your parties health. Do not try to be brave and simply push ahead....altitude sickness can kill! The only reason you should not descend is if the weather, darkness or other variable make it too unsafe for you to travel, but do head down as your first opportunity.

There are a number of medications that can alleviate and, to a degree, treat altitude sickness but these should not be used without proper medical advice from a doctor who can properly prescribe the drugs to you. In addition there are some herbal and natural remedies (such as chlorophyll extract) that some people believe can help prepare you body for high altitude but it would be up to you to decide if these are for you or not.

Another method of treating altitude sickness, in the short term, is a Hyperbaric Chamber. These are available from specialist stockists and are essentially a large inflatable bag that one person can fit inside. The air pressure on the inside of the bag can be increased to allow the person on the inside to experience normal air pressure. This should alleviate the effects of low pressure and has the same effect as descending as the ill person will experience higher air pressure. However, generally this device can only be used for short periods as the person cannot stand up or walk, or perform many tasks whilst inside the chamber.

Hyperbaric chambers are particularly useful if you are stuck in a place where you cannot safely descend and it can allow you to treat the person for a while until it is safe to move down to a lower altitude.

THE TOP OF THE WORLD

There does exist an altitude above which it is thought to be impossible for humans to survive at without wearing oxygen masks. 8,000 metres (26,247 feet) and above is classed as the Death Zone as the air pressure is simply too low for humans to get enough oxygen to keep them alive. Mountaineers do frequently climb this high but supplementary oxygen in the form of a tank and a mask is always required. Climbing into the death zone should only be undertaken by very experienced and well trained persons, or those under close guidance by trained professionals. It is not possible to fully acclimatise at these altitude regardless of the length of time spent on these extreme elevations.

TEA TIME

As pressure decreases with altitude there is another noticeable effect and this is on your food and drink. At lower air pressures, the water (liquid) molecules can turn to steam (gas) much easier and require less energy to do so. Therefore, water boils at increasingly lower temperatures the higher you go. Whilst this might seem trivial it is important as food will take much longer to cook and you should be prepared to have more fuel for your stove with you than you would normally require at low altitude. In the unlikely event that you are trying to purify water by boiling it at high altitude you should know that water will probably not get hot enough to have the desired bug killing effect. It also means that making the perfect cup of tea is a real challenge as the water never gets hot enough!

OVERVIEW

The effects of high to extreme altitude can have mild to very serious effects and it should not be ignored or overlooked. If you are travelling to a high place, ensure you are properly prepared for the effects and allow yourself time to adjust with each new altitude that you go to. Travel upwards as slowly as possible and keep a look out for signs of Cerebral Oedema and Pulmonary Oedeme and descend if you think yourself or a member of your group has these conditions.

Professional training and experience is very important so you can fully understand the effect low air pressure will have on you, make adjustments when required, and treat those who become ill.

Altitude can be serious fun but has serious potential dangers...stay safe; adventure is much more fun when you’re alive!