A brief breathing exercise that blunts altitude sickness

Altitude sickness has always been a numbers problem: the higher you go, the less oxygen is available in each breath, and the body has only a narrow window to adapt before headaches, nausea and dizziness set in. Acute mountain sickness affects up to half of people who ascend quickly to high elevation, and while acclimatization schedules and drugs like acetazolamide remain the standard defenses, researchers have long wondered whether breathing itself, deliberately controlled, could offer a faster and more accessible fix. A new pilot trial out of the Institute of Sport in Warsaw, published in Scientific Reports, puts that question to the test.

A breathing technique built to avoid the usual side effects

The technique under investigation is called voluntary isocapnic hyperpnoea, or VIH. It looks like hyperventilation — fast, deep breathing — but with one key difference: a rebreathing bag keeps carbon dioxide levels stable throughout, preventing the drop in blood CO2 that normally causes the dizziness and tingling associated with overbreathing. That distinction matters physiologically. Ordinary hyperventilation raises oxygen levels partly by scrubbing out CO2, which constricts blood vessels in the brain and can itself become a problem if carried too far. VIH is designed to get the ventilation benefit — more air moved, more oxygen picked up — without that trade-off, using devices such as the ISO-BWB-S system paired with a breathing-pace app.

Inside the trial

Eighteen healthy, active adults completed two sessions, a week apart, inside a normobaric chamber simulating 4,200 meters of altitude — roughly the elevation of Mont Blanc’s summit region. In one session they simply sat in the hypoxic air for two hours; in the other, after the first hour, they performed five minutes of VIH at 20 breaths per minute. Researchers tracked blood oxygen saturation, blood gases, heart rate, blood pressure and Lake Louise mountain-sickness scores throughout both sessions, in a randomized crossover design so each participant served as their own control.

What five minutes of controlled breathing did

The shift was immediate and sizeable. Before the breathing exercise, 15 of the 18 participants met the clinical threshold for hypoxemia; immediately afterward, only 4 did — a drop from 83.3% to 22.2%. Reported mountain-sickness symptoms fell too, from 11.1% to 5.5% of assessments. Blood oxygen saturation rose from an average of 85.5% to 91.1%, and blood oxygen partial pressure climbed alongside it, with large effect sizes across the board. Comparing the two full sessions, oxygen saturation diverged sharply at the midpoint but converged again by the two-hour mark — the benefit was real, but it faded once the extra breathing stopped.

How it stacks up against other approaches

That transience places VIH in an interesting spot relative to existing options. Acetazolamide works over hours by nudging the body toward mild metabolic acidosis, which drives ventilation up in a more sustained way; VIH instead produces a fast but short-lived surge by direct mechanical means. A related trial comparing voluntary sustained hyperventilation to acetazolamide during a rapid ascent found the breathing approach raised oxygen saturation and lowered CO2 as well, though its effect on actual sickness rates looked less reliable than the drug’s. Other breathing-based countermeasures, like positive expiratory pressure devices, have shown more mixed or promising results depending on the study. VIH’s edge is that it is drug-free, immediate, and — because CO2 is held steady — avoids the lightheadedness that makes plain hyperventilation an uncomfortable strategy to repeat.

A useful contrast with the classic Wim Hof Method exercise

The isocapnic design is what sets this technique apart from the breathing exercise at the center of the Wim Hof Method, and the contrast is worth drawing out. The classic Wim Hof Method round of controlled hyperventilation deliberately lets CO2 fall — that drop is exactly what produces the tingling, light, almost weightless sensation practitioners describe before the breath hold. VIH does the opposite by design, holding CO2 constant so ventilation can be pushed harder and for longer without triggering that same cascade. Both approaches rely on voluntary control over breathing rate and depth to shift blood gases in a hurry; they simply aim at different targets, one embracing the CO2 shift as part of the experience, the other engineering around it. Seeing both studied side by side is a reminder of how much room there still is to explore within voluntary breathing control, even before altitude, cold or meditation enter the picture.

Where the evidence stands

The researchers behind the trial are candid about its limits. The sample was small, only two of eighteen participants developed measurable mountain sickness during the two-hour exposure, and the benefit to oxygen saturation had faded by the end of the session — all of which makes this a proof-of-concept rather than a green light for VIH as a standard altitude strategy. What it does establish is that a few minutes of carefully controlled breathing can shift blood oxygen and gas chemistry quickly and safely under real hypoxic stress, in a normal chamber setting rather than a lab curiosity. Longer or more vigorous VIH protocols, tested with people already showing clear symptoms, are the logical next step — and a promising one for a field that has had surprisingly few non-drug options to compare against acetazolamide.