Blood oxygen at Haleakala summit, USA

What 3,055 m does to a reading

At this height readings in the low 90s and high 80s are common in the first days. Above about 2,500 m periodic breathing in sleep is common: a repeating cycle of deeper and shallower breaths that appears on an overnight recording as a regular wave in SpO2.

For comparison, an airliner cabin at cruise is limited to 8,000 ft (2,438 m), so the air here is thinner than an airliner cabin is designed to reach. The oxygen on a plane tool estimates the cabin altitude for your flight.

A reading on the summit

Most people spend minutes or hours on a summit, not nights. A reading taken there is affected by exertion, cold fingers and wind as much as by the height, so sit down, warm your hand and wait a minute before trusting it. If you rode or drove up in a day, the range for a new arrival applies as it stands.

The Wilderness Medical Society guidelines advise that above 3,000 m, the height you sleep at should go up by no more than 500 m a day, with a rest day every 3 to 4 days.

Tracking it across the trip

• Record a night at home before you leave, so you know your own starting figure.
• Record each night at Haleakala summit, USA 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 Haleakala summit, USA?

A healthy adult arriving from low altitude typically reads about 90% at rest, usually between 87 and 93%, in the first day or two at 3,055 m. The same person typically reads about 97% at sea level.

How much less oxygen is there at 3,055 m?

Standard air pressure at 3,055 m is about 696 hPa, against 1,013 hPa at sea level. Each breath delivers about 67% 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 Haleakala summit, USA?

Usually, yes. Breathing slows in sleep, so overnight readings commonly sit a few points under a daytime reading at the same height. Above about 2,500 m periodic breathing adds repeated short dips on top of that.

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: Haleakala (10,023 ft).
• 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.
• Ascent rate: Luks AM, et al. Wilderness Medical Society clinical practice guidelines on acute altitude illness: 2019 update. Wilderness Environ Med. 2019;30(4S):S3-S18.