Acclimatization and Altitude Sickness on Kilimanjaro

Acclimatization And Altitude Sickness On Kilimanjaro – How To Prepare And What You Need To Know

Safety is our Number one priority: At 19,341ft, Kilimanjaro presents a unique set of challenges, the most dangerous of which being altitude sickness. A significant proportion of people who climb over 9,000ft develop some symptoms relating to altitude.

Climbers typically refer to three main levels of altitude. The first level, aptly called ‘high altitude’, describes the altitude zone between 2,500m and 3,500m. Altitudes between 3,500m and 5,500m are referred to as ‘very high altitude’. The third level is called ‘extreme altitude’ and is characterized by zones above 5,500m. There are other zones above extreme altitude, but these are limited to the highest mountains in the Himalayas – like the ‘death zone’ which is above 8,000m!

When it comes to trekking at altitude, most people can ascend from sea level (say your hometown) to 2,400m without experiencing altitude illness symptoms. Once you get beyond this height though, changes in oxygen and pressure levels begin influencing the body’s physiology.

At sea level oxygen air saturation is about 21 per cent and barometric pressure is approximately 760mmHg (millimetres of mercury). As one ascends oxygen saturation stays about the same but air density decreases, which means the percentage of oxygen per breath reduces. You can imagine this as oxygen molecules moving further and further away from each other at higher altitudes, hence the term ‘thin air’.

The good news is that as oxygen per breath decreases, the body very quickly and cleverly starts to adapt to the new environment.

Four main changes occur.

Breathing becomes a lot faster and deeper (even at rest).
Blood concentration changes – red blood cells, the part of your blood responsible for carrying oxygen, increases.
The third change occurs in your lungs and is a result of increased pressure in your pulmonary capillaries. This forces blood into areas of the lungs that are not used when breathing at sea level.
The final change involves the secretion of an enzyme that promotes more effective transfer of oxygen from your haemoglobin to your blood tissue.

With these changes and, assuming you have given yourself enough time to rest at a ‘reasonable’ starting altitude, the body will acclimatize. Progressing to higher altitudes on a slow and incremental scale thus becomes possible.

Acclimatization Line

To demonstrate acclimatization in action, trekkers and mountaineers have come up with a term called the acclimatization line – an arbitrary altitude line that describes the point at which someone’s altitude sickness symptoms appear.

For instance, let’s assume that your altitude line is around 3,000m. On the first day of your trek you ascend to 3,000m and remain asymptomatic as you are on or just below your acclimatization line.

Resting at this altitude for a night or two should ensure that you are fully acclimatized to this altitude and your line might move to around 3,800m.

Trekking to 3,700m will ensure you remain asymptomatic, but if you continued further to say, 4,000m, it is likely that you will start experiencing altitude illness symptoms.

Descent back down to below your acclimatization line (in this example, 3,800m) to rest for a few days should resolve any symptoms. Continued ascent would only result in the deterioration of your condition.

So what is the learning?

If you want to acclimatize properly make sure you build in rest days as you ascend, make sure to take note of your altitude if symptoms present themselves.

Near your acclimatization line altitude sickness symptoms typically resolve after a day or two, but continued ascent before you have properly acclimatized will almost certainly lead to the worsening of your symptoms and further acclimatization will not occur.

The only sure way to improve is to get below the altitude line where your symptoms first occurred.

Effects of Altitude on Kilimanjaro

Kilimanjaro has become a very popular trek as it’s a way for ordinary hikers to experience a high mountain summit with no technical skill. Being what’s known as a “walk-up”, without the need for ropes and climbing gear, some people underestimate the potential for serious, life-threatening situations as a result of the altitude.

Kilimanjaro’s summit falls into the “extreme altitude” category, along with Aconcagua and Denali (Mt McKinley). Everest and K2 are “ultra” altitude, where acclimatization is impossible.

A Brief Introduction to Altitude

At the summit of Kilimanjaro there is approximately 49% less oxygen than at sea level. However, it’s not the percentage of oxygen in the air that changes, it’s the barometric pressure (air pressure) of the atmosphere that’s reduced.

The percentage of oxygen in the air is the same 20.9%, but it’s availability is reduced by the reduction in air pressure. What this means, in simple terms is that for any volume of air you breathe in, there are less molecules of oxygen available.

The reduced air pressure has other problems associated with it as well, allowing fluid to collect outside of the cells, around the brain (High Altitude Cerebral Edema) and the lungs (High Altitude Pulmonary Edema), both very serious conditions.

Altitude Sickness: What is it?

Mountain sickness has three main forms: Acute Mountain Sickness (AMS), High Altitude Cerebral Edema (HACE) and High Altitude Pulmonary Edema (HAPE). Additionally, AMS can be mild (very common and manageable with the right treatment), moderate, and severe (immediate descent necessary).

Altitude illness (aka Acute Mountain Sickness (AMS) or altitude sickness), is a condition caused by fast ascents to high altitudes. Susceptibility to altitude sickness increases for most people at around 3,000m, some can experience altitude illness symptoms as low as 2,400m.

There is little in the way of identifying whether you are susceptible to altitude sickness as there is no correlation between age, fitness, health, gender, or indeed previous experiences of going to high altitude. What we are sure about is that climbing more than 500m a day from 2,400m increases the probability of altitude illness; exerting yourself at high altitude and dehydration also exacerbates symptoms.

Let’s take a closer look at these conditions.

Acute Mountain Sickness – Symptoms

According to Dr. Peter Hackett of the Institute for Altitude Medicine, AMS can affect anyone above 6,000ft. The initial sign is usually a headache, which confusingly can also be a sign of dehydration or over-exertion. If other symptoms develop, then a diagnosis of AMS is probable.

In general, symptoms of altitude illness fall into three categories – mild, moderate and severe. Typically one moves from mild to more acute symptoms as the condition worsens.

That is to say that there are usually early warning signals that you are suffering from altitude illness and that your condition is getting worse. Severe variants of altitude sickness, like HACE and HAPE, can occur as one’s condition deteriorates. Transition to these severe conditions is often very rapid!

Mild AMS
Moderate AMS
Severe AMS

Mild altitude sickness symptoms include:

Headaches.
Fatigue.
Nausea and Loss of appetite.
Shortness of breath.
Dizziness.
Disturbed sleep.

A clear sign that one is suffering moderate altitude illness include the following:

Awfully bad headaches that can’t be relieved with medication (think the worst migraine you have ever had).
Strong feelings of nausea, which sometimes result in vomiting.
High levels of fatigue and muscle weakness.
Shortness of breath.
Ataxia (i.e. a feeling of decreased coordination).

Severe altitude sickness symptoms are characterised by a worsening of all the conditions above, but also include:

An inability to walk.
Severe shortness of breath.
Inability to think straight (poor cognitive abilities).
Hallucinations.
And ultimately, fluid build up in the lungs.

High Altitude Pulmonary Edema (HAPE)

High Altitude Pulmonary Edema (HAPE) is another fatal altitude illness condition. It occurs when fluid breaches the pulmonary capillaries and enters the lungs. Fluid in the lungs inhibits the effective exchange of oxygen to the blood.

Confusingly, it’s possible for a climber to develop HAPE even if they don’t seem to have symptoms of severe AMS. Look out for:

Coughing up blood or mucus.
Abnormal lung sounds.
Extreme listlessness.
Difficulty in breathing.
Lips going blue.
Confusion, lack of coordination.

Anyone at altitude who feels as though they have a respiratory infection should assume it’s HAPE until a medical professional proves it to be otherwise. If HAPE is suspected, oxygen is often administered in conjunction with immediate evacuation to a medical facility.

As oxygen levels in the blood drop, the brain can suffer from lack of oxygen, leading to HACE.

Like HACE, descent is paramount, but caution should be taken not to exert the person suffering from HAPE as this can worsen the condition. Any available oxygen can and should be administered. The drug, Nifedipine, has also been shown to help ameliorate the condition, but descent is the only.

High Altitude Cerebral Edema

HACE is a very dangerous condition that requires immediate medical treatment. As fluid builds up around the brain, the climber comes increasingly confused, lethargic and drowsy, incapable of walking and behaving strangely. Look out for:

Disorientation, confusion, hallucinations, talking nonsense.
Lack of coordination, staggering, inability to walk.
Irrational behavior.
Severe headache, sometimes accompanied by nausea and vomiting.

HACE cannot be treated without immediate evacuation to a medical facility.

Generally HACE tends to strike at night and the condition can worsen rapidly. Hence, time shouldn’t be lost in getting someone down to lower altitudes if they have suspected HACE. Do not wait for daylight. Descend immediately.

Oxygen can be administered along with a steroid called Dexamethasone, However, these should only be used in tandem with fast descent.

How is Altitude Sickness Diagnosed?

In our daily health checks, our guides will use a pulse oximeter to measure your oxygen saturation and pulse rate and use this data along with any symptoms you are presenting to build up a picture of your situation.

Lake Louise Scoring System

Developed in 1991 and reviewed as recently as 2018, the Lake Louise Scoring System remains the basis for most diagnosis in the field of a climber’s condition. Our guides use this as a framework when they assess your condition. The ‘score’ attaches a number depending on the severity of your condition.

Lake Louise Scorecard

The Lake Louise altitude sickness system is the most common way to test how bad your altitude illness symptoms are. A score between three and six is a sign of mild to moderate altitude sickness, scores over six indicate severe altitude sickness.

AMS Clinical Functional Score

Overall, if you had AMS symptoms, how did they affect your activities?

0—Not at all.

1—Symptoms present, but did not force any change in activity or itinerary.

2—My symptoms forced me to stop the ascent or to go down on my own power.

3—Had to be evacuated to a lower altitude.

Golden Rules To Avoid AMS

The purpose of going through the symptoms of altitude sickness above is not to scare you but rather to enlighten you of the potential conditions so that you can avoid them. It is important to remember that severe altitude illness and HACE and HAPE are rare on treks. Only a few treks in the world go to extreme altitude (above 5,500m) and in general all routes in the country have good altitude profiles that allow for good descents after going over high passes.

Below we have set out a a number of golden rules to remember:

If you feel sick at altitude, assume it is altitude illness until proven otherwise.
If you are suffering from altitude illness symptoms do not ascend further.
Get over high passes / summit climbs quickly and then descend.
If symptoms continue to worsen after resting at a certain altitude, continue to descend immediately.

Additional Tips To Follow

On your trek make sure to build in acclimatization days where you relax and drink lots of fluids.
Ensure you remain very well hydrated on the trail – drink two to three litres of water a day.
Go slowly and don’t over-exert yourself.
Avoid alcohol, smoking and stimulants whilst trekking (although there is some evidence that suggest caffeine can help with acclimatization).
Work with a respectable operator or guide who understands the risks of altitude illness and is trained / has the equipment to deal with any potential problems.
Try to ascend in small increments of 500 meters a day, this can include trekking high (say 700m up) to sleep low (500m from the start point from that day).
Consider taking a preventative medication like Acetazolamide (Diamox) as an extra precaution.

Prescribed Medication – Diamox

Diamox, clinically known as Acetazolamide, is a prescription drug that effectively helps mitigate altitude illness. It is a preventative medication (aka a prophylactic), and not a cure. This means that it helps with promoting faster acclimatization and thus prevents the potential onset of altitude illness, but does not cure it.

Depending on where you live in the world you may need to get a doctor’s prescription, but more often than not it can be bought over the counter at a pharmacy. We recommend you consult your doctor before using it. The drug should not be taken by pregnant women or people with kidney and liver issues.

Side effects of the drug include frequent urination; taste alterations; numbness and tingling in toes, finger and nose; and drowsiness, nausea and vomiting. Many of these side effects can be misdiagnosed as altitude illness. To avoid confusion we recommended that you take a short dose of Diamox a few weeks before departing for your trek to test if you experience any side effects.

Diamox is usually sold in a 250g tablet. Most hikers take 125g in the morning and the remaining 125g in the evening, starting one day before starting a trek and finishing on the day one returns to the trek start point.

In our opinion we think it is worthwhile taking Diamox as a preventative measure if you plan to do a trek that goes above 5,000m but recommend consulting your doctor before you do so.

Acclimatization: Preventing Altitude Sickness

The term acclimatization or “acclimation” refers to the body’s compensatory processes to adapt to the low-oxygen, low-atmospheric pressure environment. From day one, your body will start to make adaptive changes to compensate.

Things you’ll notice:

Breathing deeper, sometimes faster
Elevated resting heart rate
Potentially higher blood pressure.

As you ascend slowly, your body has certain mechanisms it uses to adapt:

Producing more of the oxygen carrying hemoglobin
Higher erythropoietin production, this is a hormone from the kidneys that increases the manufacture of red blood cells
Lower volume of plasma, which can increase risk of dehydration.
Higher kidney function as excess bicarbonate ions are excreted as a result of changing acid/alkali balance of blood.

All of these changes are a gradual process, which is why the best and safest summit success rates are had on routes with a good acclimatization protocol. The longer it takes to reach high altitude, the longer your body has to adapt.

By building in acclimatization days “hike high, sleep low” and rest days increases your chances of adequate adaptation, resulting in lower incidence of mountain sickness.

Acclimatization is a complicated process, some people seem to have no problem at all. There are no tricks or hacks, it’s a matter of time, although the medication Diamox has been shown to up regulate the body’s natural acclimatization processes and can help speed it up.

How to Avoid Altitude Sickness on Kilimanjaro

Take a longer route. Instead of choosing the quickest way up Kilimanjaro, opt for a route that builds-in some acclimatization time. Also Kilimanjaro climb training and preparation is very important.
Hike slowly. You’ll hear your guides reminding you of this “pole pole” (slowly, slowly in Swahili). You don’t want to tire yourself out, always try to be the last person into camp.
Even if you’re very fit, you need to conserve your energy, avoid over-exertion. Fatigue is believed to be a major contributor to AMS.
Stay hydrated. Keeping your fluids up prevents dehydration in the dry air which can compromise your ability to acclimatize
Ask your doctor if Diamox is right for you.
Don’t climb higher if you are suffering any symptoms of altitude sickness.
Avoid narcotic pain killers, sleeping pills, alcohol or stimulants
Always tell your guide if you have a headache, nausea or any other symptom
Keep eating, particularly carbohydrates. The US Army studies show that carbohydrates increase ventilation, and are the most efficient fuel for high altitude exertion.
Stay warm. Hypothermia is dangerous, never stay in wet clothes.

Does Altitude Training help Acclimatization?

Altitude Training is becoming increasingly popular among st would-be mountaineers. Some athletes use these training protocols to enhance performance, and studies have shown a “per-acclimatization” process as a result.

The protocols vary from training in a simulated altitude chamber, sleeping in a hypnotic tent, and even intermittent exposure to hypoxic air at rest. You can read our in depth guide to altitude training for more information.

The best pre-acclimatization method would be to climb Mt Meru, or some peaks in your home country prior to traveling to Kilimanjaro. This isn’t possible for everyone, nor is it necessary but if you do have access to some high altitude you’ll get a good idea of how well you acclimatize.

Effects of Altitude on existing Conditions

Your doctor will advise you of whether your medical history prevents you from traveling to altitude. Many people with well-controlled pre-existing conditions are able to climb Kilimanjaro successfully.

Anyone with heart, lung or neurological conditions will need to have a medical sign-off from their doctor before joining one of our climbs. It’s particularly important for your doctor to assess how the altitude may affect your current medications and condition. Be aware that certain medical conditions may make getting adequate travel insurance more difficult.

Effects of Altitude on Sleep: Cheyne-Stokes Breathing

One of the main reasons for sleep disturbance at altitude is periodic breathing. This is not necessarily associated with altitude sickness, but can be uncomfortable and disruptive. The Institute for Altitude Medicine explains that it’s a “battle in the body over control of breathing during sleep”. The oxygen sensors tell the parasympathetic nervous system to breathe more deeply, whilst the carbon dioxide sensors tell it to stop.

The result is usually deep breathing followed by the breathing stopping, and then a deep-breath as it restarts. Diamox often helps with this condition.

Other Health Considerations on Kilimanjaro

While altitude sickness is the main concern, you need to take a pro-active view of your health whilst climbing.

Hypothermia

Never stay in wet clothes. Whether from rainfall or perspiration, once you stop moving, a slight chill can turn to hypothermia in a short time, especially higher up the mountain. Make sure you carry adequate layers in your day pack, as rapid changes in temperature are quite common as you ascend.

The Sun’s Rays

Always wear sunscreen, preferably factor 40+, cover exposed parts of your body, including your head and neck. As you ascend, there is less atmosphere to filter out the harmful UV rays, and the sun’s rays are harsh.

Most importantly, wear sunglasses that block 100% of the UV rays. Wraparound glasses are best, to prevent reflected UV off glaciers and snow from damaging your eyes. Snow blindness is not common, but it’s a definite risk if you don’t protect your eyes.

Gastro-intestinal issues

Any travel to remote places comes with a risk of gastro-intestinal trouble. Different foods, sub-standard hygiene, and exposure to bacteria and viruses can cause stomach problems. Always use anti-bacterial gel or wipes on your hands, especially before eating.

Your main risk for stomach trouble is before your climb. Avoid eating at street stalls, stay away from tap water, salads, and fruit you can’t peel. On the mountain we adhere to strict food hygiene protocols and provide safe purified water at all times.

Our Safety Procedures

We take your safety very seriously. Our trained guides will monitor you closely, but to do that, they also need your help. If you feel in any way unwell, you should inform your guide immediately. Keep an eye on other members of your group, if you see someone behaving strangely or they appear to be suffering, tell your guide.

Every day your guide will check your oxygen saturation with a pulse oximeter, question you about how you are feeling, and listen to your chest for unusual lung sounds. Catching it early is the best way to prevent mild altitude sickness escalating.

We carry emergency oxygen and portable stretchers on every climb. If a climber is suffering and cannot proceed, we have partnered with Kilimanjaro helicopter rescue for emergency evacuation.