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EBC Day 06 – Acclimatisation at Namche Bazaar

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Namche Bazaar

The day started off slow and relaxed with a bit of coffee and lemon tea (NPR70+150) before I went out to look around the quaint little shops that were scattered around town. Namche Bazaar (Nepali : नाम्चे बजार) (elevation : 3440 m) is considered the business capital of the Khumbu region and is the site of a weekly market where you can find all sorts of goods and trekking paraphernalia. I ended up stocking up on quite a few things that I felt I needed - a mesh bag (NPR400), another water bottle (NPR250), some filtered water (NPR100), and extra toilet paper (NPR100). I also paid for accommodation for the two days that I stayed in Namche (USD5, NPR520 per day).

I had plenty of time to relax and to admire the majestic peaks that towered over the town, namely Kongde Ri (elevation : 6187 m) and Nupla (elevation : 5885 m), as the day was to be dedicated to just staying put for acclimatisation.

Location of Namche Bazaar

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Acclimatisation

Acclimatisation is absolutely mandatory at high altitudes due to the negative effects that the decreased partial pressure of oxygen has on your body. At high altitude, your breathing rate increases (both at rest and during exercise), less oxygen ends up getting diffused from both your lungs into the blood and from the blood to the tissues, and your VO2 max decreases by 8-11% for every 1000 metres - in my case, my VO2 Max which has peaked at 70 ml/kg/min would only be around 45 ml/kg/min in Namche Bazaar, a reduction of 35%!.

In order to counteract all these ill-effects of high altitude, your body reacts by decreasing the blood volume via the reduction of plasma levels, thus increasing the density of the blood as well as the amount of haemoglobin per unit of blood. Cardiac output also increases to compensate for the decreased oxygen that reaches the bloodstream.

When acclimatising, your body starts to make changes (that occur slowly over time) to the decreased oxygen that it is now getting. Your depth of respiration starts to increase, pressure in your pulmonary arteries is also increased, your body produces more red blood cells as well as produces certain enzymes that help facilitate the release of oxygen from hemoglobin to your body's tissues.

The key to acclimatisation is to ascend slowly and to periodically take a rest day every few days. The general rule is to not exceed an altitude gain of 500 metres in a day and to take a rest day for every 1000 metres of altitude gained, but how well each person acclimatises differs greatly and depends on many different factors. There is a common maxim that you might hear being used amongst mountaineers, "Climb High, Sleep Low"; or even amongst competitive athletes, "Live High, Train Low".

Kongde Ri (elevation : 6187 m) on the right of the image and Nupla (elevation : 5885 m) obscured by the clouds

There is a medication called Acetazolamide (normally sold under the brand name Diamox®) that can be used to reduce, or even prevent, the symptoms of altitude sickness such as headache, fatigue, nausea, shortness of breath, and dizziness. It supposedly speeds up the acclimatization process by causing the kidneys to excrete bicarbonate, which is the base form of carbon dioxide, which helps to counteract the effects of a decrease in oxygen. It does have a few side-effects however and is a diuretic, so make sure you are aware of any allergies that you might have and consult your doctor before taking it.

I normally take 125mg twice a day, and start a day before the hike begins. I have to say however that during the entire three weeks hiking in the mountains, not once did I notice the presence of any of the symptoms of acute mountain sickness (AMS). I am uncertain if this was because of fitness level, genetic factors, and because I kept myself very well hydrated (with a few exceptions!) or if Acetazolamide had a role to play at all.

Next (Day 6) : Acclimatisation at Namche Bazaar (Part 2)

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