Blood oxygen at Thimphu, Bhutan

What 2,320 m does to a reading

At this height a resting reading a few points under your figure at home is the usual result. Most people feel nothing beyond getting out of breath sooner on stairs and hills.

For comparison, an airliner cabin at cruise is usually held between about 6,000 and 8,000 ft (2,438 m), so a reading here is close to one taken on a long flight. The oxygen on a plane tool estimates the cabin altitude for your flight.

The first nights

If you reach Thimphu, Bhutan by road or air in a day, your first night is spent at the full 2,320 m with no time to adjust. That night usually gives the lowest readings of the stay. Breathing speeds up within hours, and resting SpO2 typically rises by a few points over the first week.

Tracking it across the trip

• Record a night at home before you leave, so you know your own starting figure.
• Record each night at Thimphu, Bhutan and open the file in the free session viewer. It shows the lowest SpO2 and how much of the night was under 90%.
• Put the first night next to a later one in compare nights to see whether your overnight oxygen is rising.
• A finger sensor can be off by a few points, more so with cold hands. The oximeter accuracy tool shows the range a reading could really be.

Blood oxygen at altitude covers what to expect night by night.

Common questions

What SpO2 should I expect at Thimphu, Bhutan?

A healthy adult arriving from low altitude typically reads about 93% at rest, usually between 90 and 95%, in the first day or two at 2,320 m. The same person typically reads about 97% at sea level.

How much less oxygen is there at 2,320 m?

Standard air pressure at 2,320 m is about 764 hPa, against 1,013 hPa at sea level. Each breath delivers about 74% of the oxygen it does at sea level. The share of oxygen in the air stays at about 21% at any height; it is the pressure that falls.

Will my reading be lower at night at Thimphu, Bhutan?

Usually, yes. Breathing slows in sleep, so overnight readings commonly sit a few points under a daytime reading at the same height.

How long does it take to acclimatise?

Breathing gets faster and deeper within hours. Resting SpO2 at a given height usually climbs by a few points across the first week, and red blood cell production rises over the following weeks.

Does a low reading mean altitude sickness?

No single number shows it. Altitude illness is judged on symptoms such as headache, nausea, dizziness and breathlessness at rest. If you feel unwell, stop going higher and get medical help, whatever the oximeter says.

Sources

• Elevation: Wikipedia: Thimphu.
• Air pressure: International Standard Atmosphere (ICAO Doc 7488).
• Expected SpO2: the reference table behind the altitude oxygen calculator, which explains how the figures are worked out.