An interventional study of Acute high altitude exposure and Acute high altitude exposure, with supplementary oxygen in High Altitude, Hypobaric Hypoxia and Risk Reduction, sponsored by Insel Gruppe AG, University Hospital Bern. Completed at 2 sites in Switzerland. Open to participants aged 18 Years to 80 Years, including healthy volunteers. Per ClinicalTrials.gov, last updated 2026-04-29.
Sponsored by Insel Gruppe AG, University Hospital Bern · Not applicable, Interventional, and Health services research
Rescue services in mountainous regions are frequently called to missions at altitudes >3000 m. Under the difficult conditions of acute exposure to altitude, the crews then have to undertake demanding medical and rescue measures. Previous studies in non-medical personnel, such as astronauts, aircraft pilots, and military helicopter pilots have found that the lack of oxygen associated with acute exposure to altitude may impair cognitive functions. No data exists on the effect this may have on the performance of medical staff in terms of patient examination, communication, decision-making, planning, and overall patient care. This study aims to close this knowledge gap. The investigators of this study aim to make rescue missions to high altitude safer for both the patients and the rescuers.
To assess the effect of high altitude on patient care, the investigators recruit highly trained medical specialists who will perform patient care in simulated scenarios both at high altitude and at low altitude. These scenarios will be recorded and the performance of the medical specialists judged by independent reviewers.
The medical specialists will also perform in simulated scenarios at high altitude two more times: once with supplementary oxygen, and once after spending a night at high altitude. the investigators do this to evaluate whether supplementary oxygen improves their performance, and whether symptoms of acute mountain sickness (which usually develop after spending the first night at high altitude) decreases their performance further.
Rescue services in mountainous regions are frequently called to missions at altitudes >3000 m. Under the difficult conditions of acute exposure to altitude, the crews then have to undertake demanding medical and rescue measures, such as an emergency induction of anaesthesia, resuscitation, treatment of polytraumatized patients, or a winch manoeuvre by helicopter in exposed, fall-prone terrain.
The exponential decrease in barometric pressure at altitude results in hypobaric hypoxia (HH), leading to a reduction in the partial pressure of oxygen at every point along the oxygen transport chain from the ambient air to tissue mitochondria. If the body's adaptive mechanisms fail to compensate for the lack of oxygen, symptoms like headache, nausea, fatigue, and dizziness may occur. In addition, HH may impair higher cortical functions. Individuals affected by high altitude frequently do not recognise a decline in cognitive function and overall performance, which can lead to incidents and even fatal consequences.
Previous studies in non-medical personnel, such as astronauts, aircraft pilots, and military helicopter pilots have explored the influence of HH on multiple cognitive domains. Impairment of working memory was described during hypoxia awareness trainings and in pilots while others reported no effects. Some studies have reported reduced psychomotor vigilance, while others found no effects. To counteract these impairments, the European Union Aviation Safety Agency (EASA) mandates simulated hypoxia training for pilots flying rescue missions to above 4000 m.
Studies in medical personnel are few and mostly focused on the quality of cardiopulmonary resuscitation (CPR) at (simulated) high altitude. High-quality CPR, which can be physically demanding for rescuers even under normoxic conditions, leads to rescuer fatigue faster under HH. Two recent studies have shown that HH leads to a lower quality of CPR at simulated and natural high altitude. A smaller study found simulated altitude to have a negative effect on the quality of ventilation but not on chest compression. A recent study reported a slower reaction time in medical personnel at simulated high altitude. Particularly noteworthy is the fact that rescuers did neither notice the reduced cognitive function nor the decreased quality of CPR they provided under HH, even though they were highly trained helicopter emergency medical services personnel. To the investigators' knowledge, CPR at high altitude has only been studied as an isolated skill. No data exist on the performance of medical staff in terms of patient examination, communication, decision-making, planning, and overall patient care. This study aims to close this knowledge gap. The findings of this study may help to broaden the understanding of HH, and lay the ground for further research in high altitude rescue.
As the primary endpoint of this study, the investigators evaluate medical performance and patient care using validated scores for medical skills and non-technical skills (Modified Simulation Team Assessment Tool (STAT), Concise Assessment of Leader Management (CALM), Team Emergency Assessment Measure (TEAM). These three scores are averaged (25% STAT, 25% CALM, 50% TEAM) to form a composite score. Scores are assessed by an analysis of video recordings of the simulated scenarios by independent outside assessors.
Secondary endpoints are described in detail elsewhere. They involve the measurement of reaction speed, risk assessment ability, cognitive function, the presence/absence of acute mountain sickness (AMS), the self-assessment of cognitive capacity, and basic vital functions. The concrete tests and measurements the investigators imply are:
The investigators will assess medical performance (and all other tests and measurements mentioned above) at four time points (baseline, interventions 1-3).
Testing at 30 minutes after arrival by train at high altitude (the High Altitude Research Station Jungfraujoch, 3450 m, "intervention 1") and at low altitude (Bern, 540 m, "baseline") are performed to answer the main hypothesis; whether acute rescuer exposure to high altitude impairs patient care.
To answer the additional research questions, additional testing will be performed at high altitude 4 hours after arrival with supplemental oxygen (4 litres/min, nasal) ("intervention 2") and after spending the night at 3450 m ("intervention 4").
At the four time points of measurement, the participants will have to run through one of the following four scenarios of simulated patient care:
All four scenarios are designed to be of equal difficulty. However, the order of the scenarios is randomised electronically before the start of the study, so that different participants go through different scenarios at all points of measurements (baseline, interventions 1-3). This is done to avoid skewing of performance due to some scenarios being inadvertently more difficult or easier than others.
Before each scenario, the participants undergo all tests and measurements outlined above (PVT, BART, DSST, LLS, Self-Assessment of Cognitive Capacity on a scale of 1-10, Heart rate, Blood-pressure, peripheral blood oxygen saturation).
Supplemental application of oxygen during intervention 2 might bias the participants. Therefore, they will receive air via nasal cannula at the same flow rate during all other scenarios (baseline, interventions 1 and 3) in the sense of a "placebo administration".
216 studies on the registry are indexed under Altitude Sickness; 46 are open to participants now.
This study's enrollment of 20 is below the median of 34 across 178 interventional studies indexed under Altitude Sickness.
Browse Altitude Sickness studies →Insel Gruppe AG, University Hospital Bern is the lead sponsor of 741 studies on the registry; 180 are open to participants now.
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Medical doctors with certification and experience in preclinical emergency medicine, defined as (all must apply):
Exclusion Criteria (none must apply):
Underlined terms in the criteria open these too. Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Before you join, the study team explains what taking part involves — its purpose, what happens, the risks and possible benefits — and answers your questions, so you can decide freely. Consent is usually recorded on a form (the informed consent form, ICF) signed by you or, where the law allows, by someone legally authorised to decide for you.
You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.
Informed consent
Before you join, the study team explains what taking part involves — its purpose, what happens, the risks and possible benefits — and answers your questions, so you can decide freely. Consent is usually recorded on a form (the informed consent form, ICF) signed by you or, where the law allows, by someone legally authorised to decide for you.
You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Thirty minutes after arrival at the Research Station Jungfraujoch by train, a simulated scenario of patient care ("intervention 1", high altitude at 3450 masl) is performed.
Also known as: Intervention 1
4 hours after arrival at the Research Station Jungfraujoch by train, a simulated scenario of patient care ("intervention 2", high altitude at 3450 masl) is performed, while the participants receive 4 litres / minute of oxygen via nasal route.
Also known as: Intervention 2
After having spent a night at the Research Station Jungfraujoch, a simulated scenario of patient care ("Intervention 3", high altitude at 3450 masl) is performed.
Also known as: Intervention 3
The effect of acute high altitude exposure on medical performance, measured by the STAT score
The investigators asses the quality of patient care at low and high altitude exposure. The primary outcome of the study - a composite score comprising three previously validated scores (25% CALM, 25% TEAM, 50% STAT) - will be analysed by means of a linear mixed-effect regression model to account for the longitudinal study design. In particular, each of the four time points represents a fixed effect (implemented with a factor variable) and a random offset for each participants is included in the model allowing to represent the repeated measurements and associated covariance structure. The analysis of the primary endpoint - the difference in the composite score between baseline and after acute altitude exposure (intervention 1) - will be performed by assessing the pairwise contrast of the estimated marginal means of the linear mixed-effect regression model.
Time frame: Baseline, intervention 1 (30 minutes after arriving at high altitude)
The effect of acute high altitude exposure on medical performance, measured by the CALM score
The investigators asses the quality of patient care at low and high altitude exposure. The primary outcome of the study - a composite score comprising three previously validated scores (25% CALM, 25% TEAM, 50% STAT) - will be analysed by means of a linear mixed-effect regression model to account for the longitudinal study design. In particular, each of the four time points represents a fixed effect (implemented with a factor variable) and a random offset for each participants is included in the model allowing to represent the repeated measurements and associated covariance structure. The analysis of the primary endpoint - the difference in the composite score between baseline and after acute altitude exposure (intervention 1) - will be performed by assessing the pairwise contrast of the estimated marginal means of the linear mixed-effect regression model.
Time frame: Baseline, intervention 1 (30 minutes after arriving at high altitude)
The effect of acute high altitude exposure on medical performance, measured by the TEAM score
The investigators asses the quality of patient care at low and high altitude exposure. The primary outcome of the study - a composite score comprising three previously validated scores (25% CALM, 25% TEAM, 50% STAT) - will be analysed by means of a linear mixed-effect regression model to account for the longitudinal study design. In particular, each of the four time points represents a fixed effect (implemented with a factor variable) and a random offset for each participants is included in the model allowing to represent the repeated measurements and associated covariance structure. The analysis of the primary endpoint - the difference in the composite score between baseline and after acute altitude exposure (intervention 1) - will be performed by assessing the pairwise contrast of the estimated marginal means of the linear mixed-effect regression model.
Time frame: Baseline, intervention 1 (30 minutes after arriving at high altitude)
The effect of supplementary oxygen on medical performance during acute high altitude exposure, measured as a composite of STAT, CALM, and TEAM scores
The investigators asses any changes to the quality of patient care when participants receive supplementary oxygen during acute high altitude exposure. Since acute effects of high altitude exposure are mainly due to hypobaric hypoxia, supplementary oxygen might improve patient care. Patient care is measured through a composite score comprising three previously validated scores (25% CALM, 25% TEAM, 50% STAT). The investigators use the same linear mixed-effect regression model as described under the primary outcome for the assessment of this outcome, but comparing intervention 2 (4 hours after arrival at high altitude, with supplementary oxygen) to baseline) and intervention 1 (at 30 minutes after arrival at high altitude).
Time frame: Baseline, intervention 1 (30 minutes after arriving at high altitude), intervention 2 (4 hours after arriving at high altitude, with supplementary oxygen)
The effect of subacute high altitude exposure on medical performance, measured as a composite of STAT, CALM, and TEAM scores
The investigators asses the quality of patient care under subacute high altitude exposure, i.e. after having spent a night at high altitude. At the altitude at which the study takes place, 30-40% of participants are expected to develop mild to moderate symptoms of acute mountain sickness, which might impair the quality of patient care they provide. The presence and severity of AMS will be assessed by the Lake Louis Score. AMS is present at a score of 3 or higher. Patient care is measured through a composite score comprising three previously validated scores (25% CALM, 25% TEAM, 50% STAT). The investigators use the same linear mixed-effect regression model as described under the primary outcome for the assessment of this outcome, but comparing intervention 3 (after having spent a night at high altitude, no supplementary oxygen) to baseline and intervention 1 (at 30 minutes after arrival at high altitude).
Time frame: Baseline, intervention 1 (30 minutes after arriving at high altitude), intervention 3 (after having spent a night at high altitude)
The effect of gender and age on medical performance during low altitude, acute and subacute high altitude exposure, measured as a composite of STAT, CALM, and TEAM scores
The impact of age and sex on medical performance during all points of testing (baseline, interventions 1-3) will be analysed by including the interactions of two variables (age and sex) with the fixed effect (representing the four time points) in the linear mixed-effect regression model described under the primary outcome. The statistical significance of the interaction will be assessed with a likelihood ratio test. Patient care is measured through a composite score comprising three previously validated scores (25% CALM, 25% TEAM, 50% STAT).
Time frame: Baseline, intervention 1 (30 minutes after arriving at high altitude), intervention 2 (4 hours after arriving at high altitude, with supplementary oxygen), intervention 3 (after having spent a night at high altitude)
The correlations between psychomotor test results (PVT, BART, DSST, self-assessment of cognitive function) and medical performance during low altitude, acute and subacute high altitude exposure, measured as a composite of STAT, CALM, and TEAM scores
Cognitive functions, such as measured by the psychomotor tests the investigators imply, can be impaired by high altitude exposure. The Psychomotor Vigilance Test (PVT) measures reaction speed in milliseconds. The Balloon Analogue Risk Task (BART) measures risk-taking behaviour in three numerical outcome variables. The Digit Symbol Substitution Test (DSST) measures cognitive performance and has a number of correct answers the participant found as its outcome. Participants will also self-assess their cognitive function on a scale of 1 to 10. The investigators will look for statistical correlations between the results of psychomotor testing (PVT, BART, DSST) and the self-assessment of cognitive capacity, and the quality of patient care at all four time points (baseline, interventions 1-3). Patient care is measured through a composite score comprising three previously validated scores (25% CALM, 25% TEAM, 50% STAT).
Time frame: Baseline, intervention 1 (30 minutes after arriving at high altitude), intervention 2 (4 hours after arriving at high altitude, with supplementary oxygen), intervention 3 (after having spent a night at high altitude)
The correlations between vital parameters (blood pressure, heart rate, peripheral blood oxygen saturation) and medical performance during low altitude, acute and subacute high altitude exposure, measured as a composite of STAT, CALM, and TEAM scores
The investigators will measure basic vital parameters of participants (blood pressure, heart rate, and peripheral blood oxygen saturation) by non-invasive means at all time points of testing (baseline, interventions 1-3). They will look for correlations between those parameters and the medical performance. Patient care is measured through a composite score comprising three previously validated scores (25% CALM, 25% TEAM, 50% STAT).
Time frame: Baseline, intervention 1 (30 minutes after arriving at high altitude), intervention 2 (4 hours after arriving at high altitude, with supplementary oxygen), intervention 3 (after having spent a night at high altitude)
Plan to share: No — No individual participant data (IPD) will be shared in the primary publication(s). IPD can be made available at a reasonable request.
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