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Breathing Technique and SpO2 in Thin Air

A 2026 pilot trial put 18 adults in a chamber set to 4,200 m. Five minutes of fast, guided breathing lifted average SpO2 from 85.5% to 91.1%, but an hour later the gap to the no-breathing session was no longer significant.

PulseOxTracker Team
Infographic. 5 minutes of fast breathing in thin air. Average SpO2 was 85.5% just before and 91.1% just after. An hour later it was 88.3%. Who was studied: 18 healthy, active adults aged 18 to 39, 8 women and 10 men, all living at sea level, in two 2-hour sessions in a chamber set to 4,200 m. What the study found. SpO2 below 90%: 15 of 18 people just before, 4 of 18 just after. At the 2-hour mark: SpO2 88.3% with breathing, 86.3% without, not significant. Oxygen pressure in blood: 46.9 to 51.8 mmHg across the 5 minutes. Symptom score: 0.94 to 0.83 points, no significant change. Mountain sickness score of 3 or more: 2 people just before, 1 just after, counts only. Heart rate and blood pressure: no significant change. What it cannot show: it was a pilot with 18 people, 2 hours and a chamber. It cannot show whether the technique changes mountain sickness on a real climb. The comparison was sitting still, and the staff knew the readings. The authors say there is not enough evidence to recommend it. Source: Kowalski et al. 2026, Scientific Reports.
A summary of the 2026 pilot trial: 18 adults, a chamber set to 4,200 m, and 5 minutes of fast, guided breathing.

Breathe faster and your SpO2 goes up. The catch is that you also blow off carbon dioxide, which can leave you dizzy.

A pilot trial published in January 2026 tested a way around that. It lifted SpO2 straight afterwards, and showed little beyond that.

What was the technique?

It's called voluntary isocapnic hyperpnoea. You breathe deep at a guided 20 breaths a minute through a device with a bag that feeds some of your breathed-out air back to you. That's meant to hold your carbon dioxide steady.

Who was studied?

  • 18 healthy, active adults aged 18 to 39, 8 of them women.
  • All lived at sea level.
  • Each sat for 2 hours in a chamber with the oxygen cut to match 4,200 m.
  • They did this twice, on back-to-back days, in random order.
  • In one session they did 5 minutes of the breathing after the first hour.

What happened to SpO2?

  • Average SpO2 went from 85.5% just before the breathing to 91.1% just after.
  • 15 of the 18 were below 90% before, and 4 after.
  • At the same point in the session with no breathing, the average was 85.3%.
  • At the 2-hour mark it was 88.3% with breathing and 86.3% without, a gap that wasn't statistically significant.
  • By then 10 of 18 were below 90% with breathing and 13 without.

The authors call the lift short-lived.

Did they feel better?

The trial couldn't tell.

  • The symptom score went from 0.94 to 0.83 points, which wasn't a significant change.
  • 2 people met the cut-off for mountain sickness before the breathing and 1 after.
  • Heart rate and blood pressure didn't change significantly.

The authors say 2 hours may not have been long enough to bring on symptoms. They call that an oversight.

What can't it show?

  • It was a pilot: 21 people volunteered and 18 finished both sessions.
  • The comparison was sitting still, with no dummy breathing task.
  • The staff knew the readings, and the symptom score was self-reported.
  • Carbon dioxide still drifted down, from 38.3 to 35.8 mmHg, which fell just short of significance (p = 0.068).

The authors say the evidence isn't enough to recommend the technique for mountain sickness.

What does it mean for your own readings?

Not a medical device. Does not diagnose, treat or prevent any condition. Discuss results and changes with a clinician.

References

  1. Kowalski T, Rębiś K, Wilk A, Szwed P, Grochowska J, Debevec T. Effectiveness of voluntary isocapnic hyperpnoea for mitigating hypoxemia and acute mountain sickness in normobaric hypoxia: a randomized crossover pilot trial. Scientific Reports. 2026;16(1):4784. doi:10.1038/s41598-026-35131-2