BLOOD OXYGEN SATURATION
The body decrease blood oxygen saturation (SO2) as ascends to higher altitudes by breathing faster and deeper (even at rest) so as to increase the oxygen content in the blood. Blood oxygen saturation decreases to nearly 80% at 6,000m (just above Kilimanjaro summit).
OXYGEN SATURATION LEVELS AT ALTITUDE
Kilimanjaro Altitude Zones
On Kilimanjaro there are three altitude zones;
- High altitude 2,500 – 3,500 meters
- Very high altitude 3,500 – 5,500 meters
- Extreme altitude above 5,500 meters
Most people can ascend to 2,400 meters without experiencing the negative effects of altitude. However, as one enters the high-altitude zone changes in air density and available oxygen begin to impact one’s physiology. One’s susceptibility to these changes is very difficult to predict, though, as there is very little correlation to factors of gender, age, fitness etc. We do however know that going too high, too fast is the key cause of AMS. Other contributing factors are dehydration and over exertion at altitude. A proper acclimatization strategy involves not going too high, too fast whilst also ensuring you don’t overexert yourself and remain well hydrated. To illustrate this point it is worth thinking about a term that climbers call the acclimatization line.
The term is used to describe a point at which someone’s altitude sickness symptoms occur. For example, let’s say a person’s acclimatization line is 3,000 miters on day one. After trekking to this height and spending a night or two there, the body would acclimatize to that altitude and that person’s line might move to 3,800 metres. If they then climb to 3,700 metres they will remain asymptomatic, but if they climb to 4,000 metres they would begin to experience altitude sickness symptoms. Very near to one’s acclimatization line the body can continue to adjust and a day or two’s rest at that height will usually result in the resolution of symptoms. However, if one continues to ascend beyond one’s acclimatization line it is almost guaranteed that symptoms will worsen and further acclimatization will not occur. It is critical that one gets below the point where symptoms began in order to see improvement. This last point illustrates why it is so dangerous to ascend with any symptoms of altitude sickness.
How the body adapts to higher altitudes
Here’s the good news – your body is very good at adapting to changes in its environment. Given enough time your body can adapt to high altitude. Four main body changes are worth mentioning. As you ascend:
- Breathing becomes a lot deeper and faster
- Red blood cell count increases which allows more oxygen to be carried in the blood
- Pressure in your pulmonary capillaries increases which forces blood into areas of the lungs that are not used when breathing at sea level
- More of a particular enzyme is produced which causes oxygen to be released from hemoglobin to the blood tissue
It is important to remember that your body can cope at altitude it just needs time to acclimatize.
Acute Mountain Sickness (AMS)
Acute Mountain Sickness (AMS) also know as altitude sickness or altitude illness is a pathological effect on humans caused by going to high altitudes too fast, where lower levels in oxygen inhibit normal physiological processes. People typically start experiencing Acute Mountain Sickness symptoms at about 10,000 feet (3,000 m). Some people can experience symptoms as low as 8,000 feet (just over 2,400 m).Due to Kilimanjaro rather rapid ascent profile altitude sickness amongst trekkers is unfortunately quite common.
There are three levels of Acute Mountain Sickness symptoms such as mild, moderate and serious.
These include: Fatigue, Headaches, Nausea and Dizziness, Shortness of breath, Disturbed sleep and Loss of appetite. If you suffer any of the symptoms above it is important to communicate to your climbing partners and guide how you are feeling. These symptoms generally disappear if you rest for a day at the level at which they originally started. This is why an acclimatization day where you climb high and sleep low is so important.
These include: Very bad headaches that is not relieved with medication, Feeling very nauseous which often resulting in vomiting, Very fatigued and weak, Decreased coordination (known as ataxia) and Shortness of breath.
A clear sign that you are experiencing moderate altitude sickness symptoms is when one or all of the mild symptoms start getting worse to a degree that becomes debilitating. Typically people experiencing moderate symptoms have very bad headaches and usually vomit. A feeling of decreased coordination is common. People can often walk on their own when experiencing moderate AMS, however ascent under such symptoms will almost certainly result in worsening of the symptoms to a degree where one cannot walk anymore. This would necessitate a stretcher evacuation, which should be avoided at all costs.
Ascending under moderate symptoms can lead to death.
It is important you descend at least 1000 feet (300m), but more if necessary, and remain at a lower altitude until the symptoms subside. Once the symptoms have disappeared you have acclimatized and you can ascend again.
Serious or Severe Symptoms
These include: Inability to walk, Shortness of breath whilst resting, Loss of mental capacities and hallucination and Fluid build up on the lungs. Ascent under serious Acute Mountain Sickness symptoms is extremely dangerous and should never occur. People experiencing serious AMS are usually unable to walk, struggle to breathe and lack their mental capacities to think straight.
There are two conditions associated with serious AMS, each of which occurs when fluid leaks through the capillary walls either into the lungs (this is called High Altitude Pulmonary Edema – HAPE) or into the brain (this is call High Altitude Cerebral Edema – HACE). Both conditions are rare but almost always occur because of ascending too high, too fast, or because one has stayed too long at very high altitude.
High Altitude Cerebral Edema
High Altitude Cerebral Edema (HACE) is a condition associated with severe Acute Mountain Sickness. It occurs due to swelling of the brain tissue from fluid build up in the cranium. It is a life threatening condition.
On Kilimanjaro, people suffering from HACE should descend immediately and seek medial attention when they get to the lower reaches of the mountain.
HACE can be identified if someone is suffering from the following symptoms:
Severe headaches which cannot be relieved by medication, Hallucination, Loss of consciousness (Coma), Disorientation, Loss of coordination (ataxia) and Memory loss.
Do not hang around until morning if someone in your group is suffering HACE symptoms at night. The longer you wait at altitude the greater the probability of fatality (death). Descend immediately even under darkness. Under no circumstances should one ascend if they have suspected HACE symptoms. If you have oxygen it can be administered along with a steroid called, dexamethasone, but these should only be used in conjunction with rapid descent.
High Altitude Pulmonary Edema
High Altitude Pulmonary Edema (HAPE) is a condition associated with Acute Mountain Sickness and occurs because of fluid build up in the lungs.
Fluid in the lungs prevents the effective exchange of oxygen and thus a decrease of oxygen into the bloodstream.
HAPE almost always occurs because of ascending too high, too fast. It is a life threatening condition and therefore every precaution should be taken to avoid it when trekking Mount Kilimanjaro.
Clear symptoms that one is suffering from HAPE include:
Very short of breath, even while resting, Very tight chest, The feeling of suffocation, particularly while sleeping, Coughing that brings up white frothy fluid, Extreme fatigue and weakness Confusion, hallucination and irrational behavior. If the last symptom occurs (i.e. confusion, hallucination and irrational behavior) one can assume that the pulmonary edema has started to affect the brain due to a lack of oxygen in the bloodstream.
Any available oxygen should be administered. The drug, Nifedipine, has been shown to ameliorate the condition, but descent is the only cure. Trekkers should take care to ensure that the person descending with High Altitude Pulmonary Edema doesn’t exert themselves as this can result in worsening of the condition. A stretcher evacuation is the preferred method of descent. Once the person has reached the lower limits of the mountain, medical support should be sought immediately.
Lake Louise Altitude Sickness Scorecard
There are a number of ways to monitor altitude sickness symptoms. The most common method uses the Lake Louise Altitude Sickness.
Scores between 3-7 are a sign of mild to moderate AMS. Scores above 7 are a sign of severe altitude sickness.
African Beyond Tours use a combination of the Lake Louise scorecard method and spot oximeter and pulse readings to monitor your performance on the mountain. If you score over 8 on the Lake Louise scorecard or have an SO2 reading below 75%, it is likely that you will need to forego your summit attempt and descend.
Trekking Kilimanjaro need not be a very risky or dangerous adventure as long as you follow some basic rules.
- If you have a chance to pre-acclimatize before trekking Mount Kilimanjaro, do so. A good option in Tanzania is to trek the neighboring Mount Meru (4,566 m) before attempting Kilimanjaro
- If you are a novice high altitude trekker then choose a route itinerary that is at least seven days long (6 up, 1 down). In our opinion, the 7 days Machame or 8 days Lemosho are the most suitable routes for the average trekker.
- Ensure the route allows for a good climb high sleep low opportunity (both the Machame and Lemosho do).
- When on the mountain make a point to go as slowly as possible, do not overexert yourself, even on the lower reaches.
- Drink loads of water (2.5-4 liters a day)
- Do not drink alcohol, take stimulants, smoke or consume caffeine on the mountain
- We recommend taking acetazolamide (Diamox)
Finally, as recommended by the charity, Altitude.org, always remember these three Golden Rules when at altitude:
- If you feel unwell, you have altitude sickness until proven otherwise.
- Do not ascend further if you have symptoms of altitude sickness.
- If you are getting worse then descend immediately
Preventative Medications – Diamox
Acetazolamide, or Diamox, is a drug that has been proved to be effective at mitigating altitude sickness.
The drug helps to increase the acidity of the blood by acting as a diuretic and promoting urination. Increased acidity in the blood is equated by our bodies as increased CO2, and hence one starts breathing deeper and faster to get rid of the CO2. Deeper, faster breathing increases the amount of oxygen received by the blood and this helps prevent the onset of AMS symptoms.
It is important to note that Diamox is a prophylactic (preventative medicine), and does not cure the symptoms of AMS. Once altitude sickness symptoms have started, the only way to stop them is descent. Under no circumstances should Diamox be used to continue an ascent with AMS.
Diamox is also a prescription drug so it is important that you first consult your doctor to check whether it is a suitable drug given your particular medical history. It is not suitable for pregnant women or anyone with kidney or liver disease issues. We recommend taking Diamox for 2-3 days 2 weeks before departure to test whether you experience any side effects.
Typical side effects associated with Diamox are:
Frequent urination – everyone experiences this when taking Diamox. It can result in the development of kidney stones so it is important that you drink loads of fluids whilst taking the medication.
Numbness and tingling in the fingers, toes and face – Many people experience this side effect when taking Diamox. The sensation is a little discomforting but not dangerous Taste alterations (some foods and might taste weird). Nausea, vomiting and diarrhea – this is rare. These side effects should be identified during your test before departing for Kilimanjaro. Unfortunately these side effects are common with AMS and therefore can easily be misdiagnosed as AMS. Drowsiness and confusion is also possible – again these side effects can be confused with AMS
Diamox comes in 250mg tablets. Most people take half a tablet in the morning and half in the evening. You should start taking tablets one day before arriving in Kilimanjaro and continue taking the same dosage for all ascent days. You can cease taking Diamox on descent.