Acute mountain sickness (AMS) is the classic tax you pay when you gain altitude faster than your physiology can keep up. Headache, nausea, fatigue, poor sleep, that “my brain is wrapped in cotton” feeling. It is common, it is miserable, and in some cases it can progress to serious conditions like high altitude cerebral edema (HACE) or high altitude pulmonary edema (HAPE), which are medical emergencies. Acute mountain sickness treatment has historically been complicated.
The good news is that altitude medicine has clear, evidence-based tools. The more interesting news is that we are starting to see early scientific evidence for a non-drug, non-tank intervention that matches what we observed on the trail to Everest Base Camp in 2019.
This post updates our original Everest story with new research led by Tomasz Kowalski (Tomek) in Scientific Reports.
AMS treatment basics: what works right now
If you are searching “AMS treatment” or “altitude sickness treatment,” here is the unglamorous truth: the most important intervention is still pacing and altitude management.
- Stop ascending if symptoms appear. Do not keep climbing “through it.” This is a key principle in major guidelines. Wilderness Medical Society
- Descent is the most important treatment when symptoms are significant or worsening. Oxygen can help as an adjunct if available. American Family Physician
- Medications have a role. Acetazolamide helps acclimatization and is widely used for prevention and sometimes treatment. Dexamethasone can treat AMS and HACE but does not promote acclimatization in the same way and is typically positioned as treatment or as an adjunct to descent.
- Portable hyperbaric bags and supplemental oxygen can stabilize severe cases when descent is delayed, but they are not a substitute for getting lower when serious illness is suspected. Emergency Care BC
This matters because any new tool has to be framed honestly: an additive option that fits within best-practice altitude care, not a replacement for it.
Our 2019 Everest Base Camp experience: the field version of “rapid relief”
In 2019, my wife and I hiked to Everest Base Camp with a tight timeline: Lukla to EBC and back in 9 days rather than the more typical 15 days. That is a rapid ascent profile, and I have had altitude issues before, so the risk was real. Isocapnic: Tales from EBC
We brought our Isocapnic Breathe Way Better system, a capnometer (to track CO2), and a finger oxygen saturation device. Early in the trek we used it daily, typically once in the morning and once before bed, tracking O2 and CO2 each time.
By day 3 we saw resting oxygen levels dropping, and each time we used the device, “the numbers normalized and we felt great.”
By day 6 we were in Gorakshep at 5164 m, just below base camp, and the low oxygen environment was very obvious. Hiking slowed, and we were feeling many symptoms of AMS.
At that point, we escalated to 4 to 6 sessions per day. The pattern was consistent: within a few minutes our oxygen saturation climbed back up while we kept CO2 in a normal range, and symptoms settled quickly.
In practical terms, this was a game changer for us. It allowed us to keep moving on a compressed schedule without needing oxygen tanks or drug intervention in our case. That is not a claim that others should copy a rapid ascent, it is a description of what happened for us under real-world pressure.
What Tomek’s 2026 study adds: controlled evidence for an acute oxygenation boost
Tomek’s team ran a randomized crossover pilot trial in a normobaric hypoxic chamber simulating 4200 m, comparing a control session versus a session that included a short isocapnic intervention. Nature Journal
The protocol
- 18 healthy, physically active participants
- Two 2-hour hypoxic exposures in randomized order
- In the experimental condition: a 5-minute voluntary isocapnic hyperpnoea session after 1 hour at 20 breaths per minute
- They used ISO-BWB-S devices with 6-liter breathing bags and the Isocapnic mobile app for rhythm and timing
- They tracked SpO2, blood pressure, heart rate, blood gases, and the 2018 Lake Louise Score Nature Journal
The key results, translated into human language
Immediately before the 5-minute session, most participants were below 90 percent saturation. Immediately after, far fewer were.
- Clinical hypoxemia (SpO2 < 90%) dropped from 83.3% to 22.2% immediately after the session Nature Journal
- SpO2 rose from 85.5% to 91.1%
- Blood oxygen partial pressure pO2 rose from 46.91 to 51.76 mmHg Nature Journal
- The effect was acute and transient. They saw better SpO2 kinetics around the intervention timepoint, but not a clear difference at the final timepoint. Nature Journal
On AMS, the study signals potential but does not yet prove a clinical breakthrough:
- AMS incidence based on their criteria shifted from 11.1% to 5.5% immediately after the intervention, but overall symptom scores were low and changes in the Lake Louise score were not significant in the pre vs post comparison. Nature Journal
Why this makes physiologic sense
The authors outline a simple rationale: increase alveolar ventilation to improve oxygenation, while maintaining isocapnia using a dedicated rebreathing system, which avoids the typical CO2 drop that comes with plain hyperventilation. Nature Journal
They also connect controlled breathing and stable CO2 with potential benefits for cerebral blood flow stability, sympathetic nervous system dampening, anxiety, restlessness, and sleep disturbances.
Why the study fits what we saw on the trek
Here is the cleanest link between lab and mountain.
Tomek’s study shows a short isocapnic session can create a rapid, measurable improvement in oxygen saturation during severe hypoxia, but that improvement fades. Nature Journal
Our Everest routine was essentially repeated dosing. Morning reset, pre-sleep resaturation, plus extra sessions when symptoms started creeping back in. In the original blog, we described starting with morning and pre-bed sessions, then increasing frequency to 4 to 6 sessions per day at higher altitude when symptoms were strongest. Isocapnic: Tales From EBC
So the lab result explains the “why” behind the field experience: if the benefit is acute, you would expect repeated sessions to be more impactful than a single session in a two-hour window.
Limitations: what this study does not prove yet
This part is important, because altitude medicine is not the place for hype.
- Pilot study, small sample (n = 18). Great for feasibility and signal detection, not definitive clinical guidance. Nature Journal
- Short exposure window (2 hours) and low AMS incidence. That makes it hard to draw strong conclusions about symptom prevention in the wild, where exposure is days and sleep disruption matters. Nature Journal
- Normobaric hypoxia is not the full mountain environment. Cold, dehydration, exertion load, and multi-night sleep effects are not captured here.
- Single 5-minute session in the lab. Our field experience suggests the real value may come from repeated sessions timed to symptom flare-ups and pre-sleep periods. Nature Journal
- Individual variability was substantial. That means dosing strategy and individual response likely matter. Nature Journal
- The article is presented as an early access manuscript and may still undergo edits before final publication. Nature Journal
So where does Isocapnic breathing fit in AMS treatment?
Based on the combination of our Everest experience and Tomek’s controlled data, the most responsible summary is:
- Isocapnic voluntary hyperpnoea appears capable of temporarily improving oxygenation in severe hypoxia, which is directly relevant because low SpO2 is strongly linked to AMS severity in the broader literature the authors cite. Nature Journal
- It may become a valuable adjunct tool within altitude medicine, especially for rapid symptom management and potentially sleep-related comfort, but it is not a substitute for appropriate ascent strategy, clinical judgment, and standard treatments like descent, oxygen, and indicated medication. American Family Physician
That is exactly why this is exciting. It is rare to see a practical field strategy line up this neatly with a controlled physiologic signal.
FAQ for people searching AMS treatment
What is the best treatment for acute mountain sickness?
Stop ascending, rest, and if symptoms are severe or worsening, descend. Oxygen and medications like acetazolamide or dexamethasone may be used depending on the situation and clinician guidance. Wilderness Medicine
Is this the same as hyperventilating?
No. Voluntary isocapnic hyperpnoea is designed to increase ventilation while maintaining CO2 via controlled rebreathing, rather than driving CO2 down the way typical hyperventilation does. Nature Journal
Does Isocapnic breathing prevent AMS?
The early evidence suggests it can temporarily improve oxygen saturation in severe hypoxia and may reduce hypoxemia events, with preliminary signals on AMS. Larger and longer real-world studies are still needed. Nature Journal
When is altitude sickness an emergency?
If there are signs of HACE or HAPE such as confusion, ataxia, severe breathlessness, or worsening symptoms, treat it as an emergency and prioritize immediate descent and urgent medical care. Merck Manual
Written By: Luke Way, ChPC
