ISMM 2026 · Hathersage

Effective Hypoxic Dose.
A relative, sensitive measure
of hypoxic exposure.

Currently used IHT protocols lack standardisation, limiting safety and performance. Existing dose measures combine altitude with exposure time but ignore exercise-induced variation in individual oxygenation. We propose Effective Hypoxic Dose (EHD): a continuous-SpO₂ metric that is both relative to the individual and sensitive to the nature of the exposure.

Study Design Monozygotic twins
IHT Sessions 18 · FIO₂ 0.126–0.145
Field Validation Mera Peak · 6,476 m
Sampling Continuous SpO₂ @ 1 Hz

01 – Headline Findings

A 14.7x per-session
dose differential between twins.

Genetically identical participants, divergent training. EHD captures the difference where altitudextime methods cannot – revealing within-session variation that simpler averaging obscures.

CP Cumulative EHD

16,044EHDU

Intervention twin · 18 IHT sessions · 21.4 h hypoxia

GP Cumulative EHD

727EHDU

Control twin · 12 sessions

Per-session Differential

14.7x

Per-session hypoxic-dose ratio between participants

Per-session range

158–1,916EHDU

Within-participant session variability captured by EHD

* 1 EHDU = 1 %²·hrs (the time-integral of squared SpO₂ deficit below baseline).

02 – EHD vs AltitudexTime

Two sessions at the same
altitude can produce
radically different dose.

Across the 18-session block, EHD and the conventional km·hrs metric diverge sharply. Sessions with identical altitudextime exposure produce up to 3x differences in EHD – driven by individual desaturation depth that altitude alone cannot see.

Per-session EHD bar chart compared with km-hours environmental dose. Blue bars show internal hypoxic stimulus (EHD); orange line shows external altitude-time exposure. The two metrics frequently diverge across 18 IHT sessions.

Per-session EHD (blue, internal hypoxic stimulus) vs km·hrs (orange, external environmental dose) across 18 IHT sessions. Where the two diverge, an altitudextime measure misses the physiological reality.

Summit panorama, Mera Peak, April 2026 – climbers on the ridge with the Khumbu Himalayan range visible to the horizon.

Mera Peak summit ridge · 6,476 m · April 2026

03 – Field Deployment

Mera Peak, April 2026.
Continuous SpO₂ across
an 8-day ascent to 6,476 m.

The same methodology was deployed in the field on a real expedition. From Kothe (3,600 m) through Mera Base Camp to the summit at 6,476 m, our platform captured continuous SpO₂ for the full ascent, with seven on-trail step tests anchoring the dose-response curve. Full EHD analysis of the Mera dataset is the subject of forthcoming work.

Reference cumulative-dose curve over the Mera Peak expedition shown in conventional altitude-time units, with seven step-test anchors T1 through T7 marking the ascent profile.

Reference profile in conventional altitude·time units (Mera Peak expedition, 16–24 April 2026) with on-trail step-test anchors T1–T7. EHD analysis of the same continuous-SpO₂ dataset is forthcoming – it will resolve within-individual variation that the curve above cannot.

04 – Method

Continuous SpO₂,
integrated over time.

EHD is calculated as the time-integral of the SpO₂ deficit below an individualised resting baseline, with weighting tuned to the disproportionate physiological impact of deeper desaturations. SpO₂ was acquired at 1 Hz via FDA-approved wearable oximetry (OxiWear) and transmitted via Bluetooth to a custom platform with automated artefact rejection. The same platform supports real-time feedback for FIO₂ adjustment in IHT, on-mountain monitoring, and post-expedition analysis. The full methodological paper is forthcoming in High Altitude Medicine & Biology.

05 – Related Publication

Peer-reviewed, 2026.

Letter · Wilderness & Environmental Medicine · 2026

Passive Normobaric Hypoxic Exposure and High-Altitude Acclimatization in Monozygotic Twins on Mount Everest.

Read on SAGE Journals →

06 – Authors

A clinical, scientific,
and field team.

Dr. B. Wainwright

Carnegie School of Sport, Leeds Beckett University

Dr. P. Jonetzko

University Hospitals Plymouth NHS Trust

C. Parrott

Frontier Performance – Platform & Data

G. Parrott

Frontier Performance – Field & Operations

07 – Get in Touch

Working in altitude
physiology, sport science,
or expedition medicine?

We're actively engaged with research collaborators, mountain-medicine clinicians, and elite-sport groups exploring continuous-SpO₂ dose tracking. If our methodology might apply to your work, we'd like to hear from you.

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