HypoxiaHypoxiaNCT04075565
The Psychophysiological Effect of Simulated and Terrestrial Altitude
A study testing Terrestrial altitude and Cloud 9 in people with Hypoxia and Altitude Hypoxia, run by University of Applied Sciences and Arts of Southern Switzerland at 3 sites in Switzerland.
Trial summary
The aim of this study is to compare the psychophysiological effects of terrestrial altitude with a normobaric, hypoxic situation. Read more about this study
- Who is it for?
- Ages 18 to 50 yearsHealthy volunteers can take part
- Conditions the study is for
- Hypoxia, Altitude Hypoxia, Altitude Sickness
- What is being tested?
- Terrestrial altitude and Cloud 9
- Type of treatment
- Lifestyle or therapy programme
- Could I receive a placebo?
- No, everyone receives an active treatment
- How many people
- 20 participants
- Where
- 3 sitesSwitzerland
- Study dates
- 24 Jun 2019to 30 Apr 2022
- Phase
- Interventional
- Are there results?
- Yes, posted in the registrySummary in the doctors' view
Key requirements
Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.
- Ages 18 to 50 years
- All sexes
- Healthy volunteers accepted
- Adult
Who may be able to join
- Healthy, adults aged 18 to 50 years
- No cardiovascular disease and / or surgery
- no surgery on the cardiovascular system.
- No current injuries and / or pain
- Regular and adequate sleep
- No terrestrial altitude of 1000 m exceeded last month (including flights)
- No form of hypoxia exposed last month
Who cannot join
- Age over 50 years
- current injuries of any kind and / or pain
- Acute and / or chronic pain conditions Known general diseases (e.g., diabetes mellitus)
- fear of hypoxia
- fear of heights or sensitivity to terrestrial altitude
- Regular use of medicines (also bought by yourself), except for contraceptives
Show all 10Show fewer
- Cardiovascular diseases or abnormalities
- Anomalies of the blood analysis or ECG
- Psychological disorders
- pregnancy / lactation
Trial locations and contacts
3 sites in 1 country.
Switzerland3 sites
Fachhochschule Südschweiz
Landquart, Kanton Graubünden, 7302
University of Applied Sciences and Arts of Southern Switzerland (SUPSI)
Landquart, Kanton Graubünden, 7302
Fachhochschule Südschweiz
Landquart, 7302
About this study
The aim of this study is to compare the psychophysiological effects of terrestrial altitude with a normobaric, hypoxic situation.
Read the detailed description
Research has consistently shown that exposure to extreme environments (such as high altitude stays) may affect cognitive function. For logistical reasons and to control the experimental set-ups, most of these examinations are carried out in the laboratory. By testing under such controlled conditions, researchers can remove any co-foundational factors and isolate the cause of stress, thereby better understanding the mechanisms by which impairment can occur. However, when people are exposed to such environments in the "real world" (such as altitude), they often experience a number of other additional stressors at the same time, which can also affect their performance. Surprisingly, however, little attention has been paid to the study of these additional stressors in combination.
Although the oxygen content remains constant at various altitudes (20.93%), the air pressure decreases exponentially as the altitude increases. As a result, the oxygen partial pressure in arterial blood and tissue is reduced (hypoxia), leading to a deterioration in both physical and cognitive performance. Hypoxic conditions also alter the perception of pain, which may be particularly relevant for patients suffering from hypoxic conditions. According to the authors' knowledge, there is limited literature investigating and comparing simulated and real psychophysiological responses.
- Conditions
- Hypoxia, Altitude Hypoxia, Altitude Sickness, Altitude, Mountain Sickness, Hypoxia, Altitude
- Being tested
- Terrestrial altitude, Cloud 9
- Keywords
- hypoxia, altitude, physiology, cognition
- Medical subject headings
- Hypoxia, Altitude Sickness
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
Terrestrial altitudeBehavioural
Terrestrial altitude: The volunteers are in an SAC hut at an altitude of 3000 m. By means of this exposure the psychophysiological effect under hypobaric and hypoxic conditions is determined. The subjects spend the night in this SAC hut and the measurements are repeated the next day.
Cloud 9Behavioural
Cloud 9 is a solid, certified product that complies with European Directives on Electromagnetic Compatibility, Machine Directive, Air Pressure Equipment and Low Voltage Equipment (89/336 / EEC, 91/368 / CEE, 93/68 / CEE, 97/23 / EC, EN61010-1 All directives are in writing in the Supplements to this Ethics Application.
Simulated height: The subjects are in the laboratory of our institution and are connected to the Cloud 9 by means of a mask. Subjects are exposed to a simulated altitude of 3530m under normobaric conditions. By means of this intervention the psychophysiological effect under normobaric and hypoxic conditions is determined.
| Study group | Role | What they receive |
|---|---|---|
| Simulated altitude | Active comparator | The participants are exposed to simulated altitude in a normobaric situation. Receives: Behavioral: Cloud 9 |
| Terrestrial altitude | Experimental | The participants are exposed to terrestrial altitude in a hypobaric situation. Receives: Behavioral: Terrestrial altitude |
| Control | No intervention | the participants are exposed to a normoxic and normobaric environment. |
What is being measured
The primary outcome is the main question the study is designed to answer.
Oxygenation of the Brain
Brain oxygen saturation is measured non-invasively using a deep tissue oxygenation monitor (moorVMS-NIRS, moor instruments, www.moor.co.uk). For this purpose, adhesive electrodes are applied over the muscle and the forehead. This measurement is taken during the baseline measurements, and during the cognitive performance test. This outcome measure reports the change from baseline for the oxygenation of the brain.
Measured: Baseline (participants seated for 15 minutes) and during the cognitive performance under normobaric hypoxia, hypobaric hypoxia, and control conditions (mean over time)
Oxygenation of the Blood
The oxygen saturation of the blood (SpO2) is measured with a portable pulse oximeter with finger clip probe (Nonin 7500, Nonin medical B.V., Plymouth, USA). This measurement is taken during the baseline measurements and after the step-up task. This outcome measure reports the change from baseline for the oxygenation of the blood.
Measured: Continuously during the 15-minute seated baseline period before each trial (mean over 15min) and at the end of the step-up test (point measurement)
Mean Arterial Pressure
Blood pressure was measured using an automated sphygmomanometer monitor from the left brachial artery. MAP was calculated using the following formula:
MAP = diastolic blood pressure + (systolic blood pressure-diastolic blood pressure) / 3.
Measured: At the end of the 15-minute baseline seated period before each trial and at the end of the 3-minute submaximal step-test (Point measurements)
Heart Rate
The heart rate is measured using a pulse belt and an additional 2-point ECG (Actiheart, Camntech Ltd., Cambridge, UK). This measurement is taken during the baseline measurements and after the step-up task. This outcome measure reports the change from baseline for the heart rate.
Measured: at baseline and the end of the submaximal step test (point measurements)
Concentration of Blood Lactate
Lactate measurements are performed by capillary blood measurement. This measurement is taken during the baseline measurements and after the step-up task.
Measured: at the end of 15min baseline period and the end of the step-up test (point measurements)
Sleep Quality
Sleep quality of the night before the experimental day was assessed using the validated and reliable GSQS, consisting of a 16-item true or false questionnaire. GSQS scores ranged from 0 to 16 whereas higher scores indicated lower subjective sleep quality.
Measured: Before the cognitive performance test (point measurement)
Altitude Sickness
Altitude sickness is measured with "Lake Louis acute mountain sickness scale", choosing the most appropriate answer from 5 questions. Questions range from 0 (=no symptoms) to 4 (=severe symptoms). LLAMS symptoms were assessed at the end of each experimental measurement.
Measured: After performing the 3-min step-test (point measurment)
Concentration of Salivary Cortisol
Salivary cortisol was assessed from the n = 10 female participants to assess the daily stress level after each experimental day. Through a straw, 3mL of saliva was collected and stored in a refrigerator until the analyses were performed the next day using the enzyme-linked immunosorbent assay (ELISA) method.
Measured: After each experimental day, in the evening between 8:30 PM and midnight, measured once before participants went to bed (point measurment)
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted30 Aug 2019
- Study start24 Jun 2019
- Primary completion31 Mar 2021
- Study completion30 Apr 2022
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Posted resultsParticipant flow, outcome measures and adverse events reported by the sponsor.
- Publications (1)Papers the sponsor has linked to this study.
- Other trials for HypoxiaStudies of the same condition, open and under way.
- What the trial phases meanHow a treatment moves from first tests in people to approval.
More details
For doctors and researchers: how the study is designed, who runs it, and its registry IDs.
Study design
- Study type
- Interventional
- Phase
- Phase N/A
- Primary purpose
- Basic science
- Allocation
- Randomised
- Intervention model
- Crossover
- Model description
- The study design is a crossover design.
- Masking
- Single blind
- Who is masked
- Investigator
- Enrolment
- 20 participants (actual)
Sponsor and investigators
- Lead sponsor
- University of Applied Sciences and Arts of Southern Switzerland
- Sponsor type
- University, hospital or other
- Collaborators
- University of Portsmouth, Vrije Universiteit Brussel
- Responsible party
- Sponsor
- Investigators
- Ron Clijsen, PhD, Principal investigator, University of Applied Sciences and Arts of Southern Switzerland (SUPSI)
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT04075565
- Sponsor's protocol ID
- 2019-00504
- Other IDs
- 2019
- Acronym
- Hypoxia
- Status last verified
- Jan 2026
- First submitted
- 7 Aug 2019
- Last updated
- 19 Feb 2026
- Results posted
- Yes, on ClinicalTrials.gov
- Data monitoring committee
- No
- FDA-regulated drug
- No
- FDA-regulated device
- No
- Individual data sharing
- No
Publications
Hohenauer E, Freitag L, Costello JT, Williams TB, Kung T, Taube W, Herten M, Clijsen R. The effects of normobaric and hypobaric hypoxia on cognitive performance and physiological responses: A crossover study. PLoS One. 2022 Nov 10;17(11):e0277364. doi: 10.1371/journal.pone.0277364. eCollection 2022.
PubMed 36355846
Study at a glance
From the registry record, last updated by the sponsor on 19 Feb 2026. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- The Psychophysiological Effect of Simulated and Terrestrial Altitude
- ClinicalTrials.gov ID
- NCT04075565
- Acronym / sponsor ID
- Hypoxia / 2019-00504
- Conditions
- Hypoxia, Altitude Hypoxia, Altitude Sickness, Altitude, Mountain Sickness, Hypoxia, Altitude
- Keywords
- hypoxia, altitude, physiology, cognition
- Study type
- Interventional
- Recruitment status
- Completed
- Enrolment
- 20 participants (actual)
- Lead sponsor
- University of Applied Sciences and Arts of Southern SwitzerlandUniversity, hospital or other
- Collaborators
- University of Portsmouth, Vrije Universiteit Brussel
- Study start
- 24 Jun 2019 (actual)
- Primary completion
- 31 Mar 2021 (actual)
- Study completion
- 30 Apr 2022 (actual)
- First posted
- 30 Aug 2019 (actual)
- Results
- Posted 19 Feb 2026
Clinical summary
The research question as the sponsor registered it. This describes what the study plans to test, not what it found.
The aim of this study is to compare the psychophysiological effects of terrestrial altitude with a normobaric, hypoxic situation.
Detailed description
Research has consistently shown that exposure to extreme environments (such as high altitude stays) may affect cognitive function. For logistical reasons and to control the experimental set-ups, most of these examinations are carried out in the laboratory. By testing under such controlled conditions, researchers can remove any co-foundational factors and isolate the cause of stress, thereby better understanding the mechanisms by which impairment can occur. However, when people are exposed to such environments in the "real world" (such as altitude), they often experience a number of other additional stressors at the same time, which can also affect their performance. Surprisingly, however, little attention has been paid to the study of these additional stressors in combination.
Although the oxygen content remains constant at various altitudes (20.93%), the air pressure decreases exponentially as the altitude increases. As a result, the oxygen partial pressure in arterial blood and tissue is reduced (hypoxia), leading to a deterioration in both physical and cognitive performance. Hypoxic conditions also alter the perception of pain, which may be particularly relevant for patients suffering from hypoxic conditions. According to the authors' knowledge, there is limited literature investigating and comparing simulated and real psychophysiological responses.
Study design
- Primary purpose
- Basic science
- Allocation
- Randomised
- Intervention model
- Crossover
- Masking
- Single blind (investigator)
- Number of arms
- 3
- Model description
- The study design is a crossover design.
| Arm | Type | Receives |
|---|---|---|
| Simulated altitude | Active comparator | Behavioral: Cloud 9The participants are exposed to simulated altitude in a normobaric situation. |
| Terrestrial altitude | Experimental | Behavioral: Terrestrial altitudeThe participants are exposed to terrestrial altitude in a hypobaric situation. |
| Control | No intervention | –the participants are exposed to a normoxic and normobaric environment. |
Who may qualify
- Ages
- 18 to 50 years
- Sex
- All
- Healthy volunteers
- Accepted
- Age groups
- Adult
Key inclusion criteria (7 listed)
- Healthy, adults aged 18 to 50 years
- No cardiovascular disease and / or surgery
- no surgery on the cardiovascular system.
- No current injuries and / or pain
- Regular and adequate sleep
Key exclusion criteria (10 listed)
- Age over 50 years
- current injuries of any kind and / or pain
- Acute and / or chronic pain conditions Known general diseases (e.g., diabetes mellitus)
- fear of hypoxia
- fear of heights or sensitivity to terrestrial altitude
Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.
Interventions
| Intervention | Type | Arms |
|---|---|---|
| Terrestrial altitudeTerrestrial altitude: The volunteers are in an SAC hut at an altitude of 3000 m. By means of this exposure the psychophysiological effect under hypobaric and hypoxic conditions is determined. The subjects spend the night in this SAC hut and the measurements are repeated the next day. | Behavioural | Terrestrial altitude |
| Cloud 9Cloud 9 is a solid, certified product that complies with European Directives on Electromagnetic Compatibility, Machine Directive, Air Pressure Equipment and Low Voltage Equipment (89/336 / EEC, 91/368 / CEE, 93/68 / CEE, 97/23 / EC, EN61010-1 All directives are in writing in the Supplements to this Ethics Application. Simulated height: The subjects are in the laboratory of our institution and are connected to the Cloud 9 by means of a mask. Subjects are exposed to a simulated altitude of 3530m under normobaric conditions. By means of this intervention the psychophysiological effect under normobaric and hypoxic conditions is determined. | Behavioural | Simulated altitude |
Primary outcome
Oxygenation of the Brain
Time frame: Baseline (participants seated for 15 minutes) and during the cognitive performance under normobaric hypoxia, hypobaric hypoxia, and control conditions (mean over time)
Brain oxygen saturation is measured non-invasively using a deep tissue oxygenation monitor (moorVMS-NIRS, moor instruments, www.moor.co.uk). For this purpose, adhesive electrodes are applied over the muscle and the forehead. This measurement is taken during the baseline measurements, and during the cognitive performance test. This outcome measure reports the change from baseline for the oxygenation of the brain.
Oxygenation of the Blood
Time frame: Continuously during the 15-minute seated baseline period before each trial (mean over 15min) and at the end of the step-up test (point measurement)
The oxygen saturation of the blood (SpO2) is measured with a portable pulse oximeter with finger clip probe (Nonin 7500, Nonin medical B.V., Plymouth, USA). This measurement is taken during the baseline measurements and after the step-up task. This outcome measure reports the change from baseline for the oxygenation of the blood.
Mean Arterial Pressure
Time frame: At the end of the 15-minute baseline seated period before each trial and at the end of the 3-minute submaximal step-test (Point measurements)
Blood pressure was measured using an automated sphygmomanometer monitor from the left brachial artery. MAP was calculated using the following formula: MAP = diastolic blood pressure + (systolic blood pressure-diastolic blood pressure) / 3.
Heart Rate
Time frame: at baseline and the end of the submaximal step test (point measurements)
The heart rate is measured using a pulse belt and an additional 2-point ECG (Actiheart, Camntech Ltd., Cambridge, UK). This measurement is taken during the baseline measurements and after the step-up task. This outcome measure reports the change from baseline for the heart rate.
Concentration of Blood Lactate
Time frame: at the end of 15min baseline period and the end of the step-up test (point measurements)
Lactate measurements are performed by capillary blood measurement. This measurement is taken during the baseline measurements and after the step-up task.
Sleep Quality
Time frame: Before the cognitive performance test (point measurement)
Sleep quality of the night before the experimental day was assessed using the validated and reliable GSQS, consisting of a 16-item true or false questionnaire. GSQS scores ranged from 0 to 16 whereas higher scores indicated lower subjective sleep quality.
Altitude Sickness
Time frame: After performing the 3-min step-test (point measurment)
Altitude sickness is measured with "Lake Louis acute mountain sickness scale", choosing the most appropriate answer from 5 questions. Questions range from 0 (=no symptoms) to 4 (=severe symptoms). LLAMS symptoms were assessed at the end of each experimental measurement.
Concentration of Salivary Cortisol
Time frame: After each experimental day, in the evening between 8:30 PM and midnight, measured once before participants went to bed (point measurment)
Salivary cortisol was assessed from the n = 10 female participants to assess the daily stress level after each experimental day. Through a straw, 3mL of saliva was collected and stored in a refrigerator until the analyses were performed the next day using the enzyme-linked immunosorbent assay (ELISA) method.
Results and safety
Loading the posted results from ClinicalTrials.gov…
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 19 Feb 2026.
- Posted resultsParticipant flow, baseline, all outcome measures and adverse events.
- Results publication: PubMed 36355846Hohenauer E, Freitag L, Costello JT, Williams TB, Kung T, Taube W, Herten M, Clijsen R. The effects of normobaric and hypobaric hypoxia on cognitive performance and physiological responses: A crossover study. PLoS One. 2022 Nov 10;17(11):e0277364. doi: 10.1371/journal.pone.0277364. eCollection 2022.
- fullversion of publicationLink provided by the sponsor.
- Individual participant dataSharing planned: No
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Referral and contact
AzTrials does not enrol participants or take referrals. Contact the study team or a site listed below; they decide who can take part. This study is not recruiting at the moment.
Ron Clijsen, PhD principal investigator
University of Applied Sciences and Arts of Southern Switzerland (SUPSI)
3 sites in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
A study testing Terrestrial altitude and Cloud 9 in people with Hypoxia and Altitude Hypoxia, run by University of Applied Sciences and Arts of Southern Switzerland at 3 sites in Switzerland.
The full registered description is in the About this study section and the official record.
Who may be eligible to take part?
The sponsor lists 7 inclusion and 10 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.
Is this clinical trial currently recruiting?
The record says: finished, as of the sponsor's last update on 19 Feb 2026. Status can change between updates, so confirm with the study contact before making plans.
Where is the study taking place?
The record lists 3 sites in Switzerland. Whether a site is taking part right now should be confirmed with that site. See every site.
What are the possible benefits and risks?
They depend on the study and the treatment, and no study can promise a benefit. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.
Are results available for this study?
Yes. Results are posted in the registry (first posted 19 Feb 2026). A summary is in the For doctors view, and the full results are on ClinicalTrials.gov.
How can a doctor refer a patient or contact the research team?
The record lists no contact. The official record names the sponsor, who can be asked directly. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
Oxygenation of the Brain (time frame: Baseline (participants seated for 15 minutes) and during the cognitive performance under normobaric hypoxia, hypobaric hypoxia, and control conditions (mean over time)). The study lists 8 primary outcomes in all. It is what the study was designed to measure, not a finding.
Where can I read the original study information?
On the ClinicalTrials.gov record for NCT04075565, which also lists 1 linked publication.
Does a listing mean the treatment is approved or proven to work?
No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.
How often is this information updated?
AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 19 Feb 2026.