Graded Exercise Hypoxia Testing

The purpose of this study is to develop a single, standardized test to determine how individuals tolerate acute hypoxia in a stepwise fashion. We aim to evaluate the association between multiple factors, such as ventilatory compensation, heart rate response, acid-base changes, sex, pulmonary function, etc, which may explain why some individuals tolerate exercise in hypoxia better than others. Identifying these factors of association will inform future pharmacological and non-pharmacological attempts to combat acute hypoxic exercise.

Active, Not Recruiting

This study is active but is not currently recruiting participants.

Key information

Conditions

Hypoxia Pathological Conditions, Signs and Symptoms Signs and Symptoms Signs and Symptoms, Respiratory

Age range

18 year–65 year

Sex eligibility

All sexes

Study type

Observational

Primary location

Mayo Clinic, Rochester, Minnesota, United States

Who can participate

Healthy volunteers accepted: Yes

Only the study team can determine whether someone qualifies for participation.

Inclusion criteria

Physically active (≥150 minutes of moderate physical activity per week)

Exclusion criteria

Contraindications to exercise testing
Currently pregnant
Musculoskeletal or metabolic disease
Allergies to lidocaine
Body-mass index ≤18 or ≥35 kg·m-2
Pacemaker
No confounding cardiorespiratory disease
Persistent tobacco use (>15 pack years)

Treatment and study plan

Graded Exercise Test

Diagnostic Test

Participants will perform a graded exercise test on either a cycle ergometer or treadmill. The testing protocol will begin with a 5- 10 min warm-up of either cycling or running/walking at the participants preferred pace.

If the graded exercise test is on a bike, exercise will begin at wattage that elicits ~50% of their heart rate max, HRmax = 208 - 0.7 × age and increase by either 10W, 15W, or 20W every two minutes in a stepwise fashion until symptom limitation. The step of the wattage increase will be at the discretion of the investigators.

If the graded exercise test is on a treadmill, the test will begin at a speed that elicits ~50% of predicted HRmax. Following, the speed of the treadmill will increase 0.5 mph (0.8 km/hr) every two minutes in a stepwise fashion until symptom limitation. If the participant maxes out the speed of the treadmill, we will increase the grade 2% every 2-minutes until symptom limitation.

Graded Hypoxia Exercise Test

Diagnostic Test

Participants will perform a single constant work rate exercise tests during graded hypoxia. They will be outfitted with either a facemask or mouthpiece connected to a uni-directional breathing valve. During inspiration, subjects will breathe from a closed-system Douglas bag balloon reservoir (~200 L) connected to the value on the inspired side via air-tight clean-bor tubing.

The participant will complete the same mode of exercise as they did during visit 1, either bike or treadmill. The resistance on the bike or incline of the treadmill will be set to elicit an intensity equivalent to ~50% of their V̇O2max determined during visit 1. Participants will complete 5-minute stages over a range of FiO2 values. The exercise test will begin in an FiO2=0.21 (i.e. room air). Following this first 5-min stage the FiO2 will increase to 0.25, afterwards, participants will complete another stage at FiO2=0.21 and then decrease in a stepwise fashion every 5-minutes.

Primary outcomes

PaO₂/FiO₂ Ratio

Time frame: 30 minutes

The PaO₂/FiO₂ ratio is a widely used measure of oxygenation efficiency in the lungs. It compares the arterial oxygen partial pressure (PaO₂, measured in mmHg) to the fraction of inspired oxygen (FiO₂, expressed as a decimal). The ratio provides insight into the ability of the lungs to transfer oxygen into the bloodstream. A PaO₂/FiO₂ ratio of 300-400 is considered to be mild hypoxemia. Participants are considered as poorly tolerating hypoxia if their ratio is <400 and good at tolerating hypoxia if their ratio is >400.

Sponsors and collaborators

Lead sponsor

Mayo Clinic

Other

Registry information

Important dates

Study start: 2025
Primary completion: 2027
Study completion: 2028
First posted: Mar 28, 2025
Registry last updated: Jan 30, 2026

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

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Active, Not Recruiting