Intermittent HypoxiaHI-LOOPNCT07409649
Influence of Intermittent Hypoxia on Loop Gain in Healthy Subjects
A study testing Intermittent hypoxia and Normoxia in people with Intermittent Hypoxia and Healthy Volunteers, run by Poitiers University Hospital at 1 site in France.
Trial summary
Sleep apnoea-hypopnoea syndrome (SAHOS), which causes numerous comorbidities, particularly cardiovascular ones, is widespread worldwide today and incurs significant healthcare costs. Read more about this study
- Who is it for?
- Ages 18 to 45 yearsHealthy volunteers can take part
- Conditions the study is for
- Intermittent Hypoxia, Healthy Volunteers
- What is being tested?
- Intermittent hypoxia and Normoxia
- Type of treatment
- Surgery or procedure
- Could I receive a placebo?
- No, everyone receives an active treatment
- How many people
- 40 participants
- Where
- 1 siteFrance
- Study dates
- 20 Oct 2026to Dec 2027
- Phase
- Interventional
- Are there results?
- Not yet: the study is under way
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 45 years
- All sexes
- Healthy volunteers accepted
- Adult
Who may be able to join
- Healthy subjects aged 18 to 45
- BMI between [18-25] kg/m2
- No known sleep disorders
- Free subjects, not under guardianship or curatorship or subordination
- Persons affiliated with or beneficiaries of a Social Security scheme
- Signature of informed consent after clear and honest information about the study
Show all 26Show fewer
- Non-inclusion Criteria:
- Active smoking or cessation within the last 3 months and total consumption > 10 pack-years
- Alcohol or drug addiction
- Excessive coffee consumption (> 3 espressos/day)
- History of acute mountain sickness (presence of symptoms such as dizziness, headaches, nausea/vomiting, and incapacitating fatigue during or after a stay at high altitude)
- Living at high altitude (above 3,000 meters, continuously for more than 6 months during the last 10 years)
- History of respiratory and/or cardiovascular and/or renal and/or neurological disease (migraines, epilepsy)
- Diabetes
- Anemia, sickle cell anemia
- Any medication associated with oxygen metabolism and any psychotropic medication (anxiolytics, sedatives, antidepressants, neuroleptics, muscle relaxants, etc.) that may interfere with motor and respiratory control, muscle strength, or sleep quality
- Women of childbearing age who do not use effective contraception (hormonal/mechanical: oral, injectable, transcutaneous, implantable, intrauterine device, or surgical: tubal ligation, hysterectomy, total ovariectomy)
- Concurrent participation in another clinical research study affecting respiratory control or respiratory muscles
- Persons benefiting from enhanced protection, namely minors, persons deprived of their liberty by judicial or administrative decision, persons staying in a healthcare facility
- Post-inclusion exclusion criteria:
- SpO2 < 97% in ambient air at rest.
- Detection of pregnancy in women of childbearing age.
- Detection of acute mountain sickness (Lake Louise score > 0).
- Abnormalities in spirometry, ventilatory polygraphy, electrocardiogram, and/or hemoglobinometry prior to randomization.
- Ventilation minute signal, PETCO2 or PETO2 unusable.
- Irreversible deterioration in the volunteer's health during the study period, likely to affect the experimental conditions.
Who cannot join
None listed.
Trial locations and contacts
1 site in 1 country. Contact the study team or a site near you to ask about taking part.
France1 site, 1 recruiting
- Recruiting
Poitiers University Hospital
Poitiers, 86000
Vanessa BIRONNEAU, MD, 05 49 44 34 49 ext. +33, vanessa.bironneau@chu-poitiers.fr
About this study
Sleep apnoea-hypopnoea syndrome (SAHOS), which causes numerous comorbidities, particularly cardiovascular ones, is widespread worldwide today and incurs significant healthcare costs.
Current research in this field focuses on identifying different phenotypes in affected patients in order to provide more personalised treatment.
Read more
One of these phenotypes appears to be linked to instability in ventilatory control due to an increase in loop gain (LG) in these subjects.
However, the pathophysiology of this ventilatory control instability due to increased LG is not fully understood. It is still difficult to determine whether subjects have an intrinsically high LG or if exposure to intermittent hypoxia during OSA promotes an increase in LG.
It has also been demonstrated that OSA causes vascular hyperreactivity by increasing oxidative stress through elevated ROS production. This leads to endothelial dysfunction in response to intermittent hypoxia associated with apnoea. Extracellular vesicles (microvesicles and exosomes) have been shown to play a role in this endothelial response. These extracellular vesicles are essential for intercellular communication in both physiological and pathological situations, such as SAHOS.
Therefore, the objective of this research is to determine whether exposure to intermittent hypoxia and changes in microvesicle phenotype could influence LG, which could lead to new therapeutic advances in the context of SAHOS.
- Conditions
- Intermittent Hypoxia, Healthy Volunteers
- Being tested
- Intermittent hypoxia, Normoxia
- Keywords
- loop gain
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
Intermittent hypoxiaProcedure or surgery
The volunteer will remain at rest in the hypoxic chamber, experiencing intermittent hypoxic conditions cyclically every 6 minutes. During one third of the cycle, they will be exposed to hypoxia in order to reduce SpO₂ to between 85% and 90%. Then, during two thirds of the cycle, they will receive oxygenation at a rate of 1 L/min (with possible subject-dependent modulations), with the aim of achieving an SpO₂ of greater than 95%.
To make the hypoxia intermittent, the volunteer will also be given a medium-concentration oxygen mask that provides intermittent airflow, controlled by the D-6341 mass flow controller.
NormoxiaProcedure or surgery
The participant will remain at rest in the hypoxic chamber under normoxic conditions. To prevent the volunteer from becoming aware of the conditions to which they are exposed, an air flow rate of 1 L/min will be used to simulate intermittent oxygenation.
| Study group | Role | What they receive |
|---|---|---|
| Arm A : ambient air then intermittent hypoxia | Experimental | T1 : Conduct the experiment in ambient air (without hypoxia) for six hours. T2 : Then, after a washout period of at least seven days, conduct the experiment in intermittent hypoxia via the hypoxia chamber for six hours. Receives: Procedure: Intermittent hypoxia; Procedure: Normoxia |
| Arm B : intermittent hypoxia then ambient air | Experimental | T1 : Conduct an experiment involving intermittent hypoxia in the hypoxia chamber for six hours.
T2 : Then, after a washout period of at least seven days, conduct an experiment involving ambient air (without hypoxia). Receives: Procedure: Intermittent hypoxia; Procedure: Normoxia |
What is being measured
The primary outcome is the main question the study is designed to answer.
The change in Loop Gain before and after 6 hours of experimental condition (intermittent hypoxia or ambient air).
Loop gain is the product of 'controller gain' (ventilatory responsiveness to CO₂ above eupnoea) and 'plant gain' (the ventilatory increase required for a given reduction in PaCO₂).
The following ventilatory parameters will be measured using a gas exchange measuring device to calculate loop gain, plant gain and controller gain: PETCO₂ (in mmHg), PETO₂ (in mmHg) and Minute ventilation (VE) measured in mL/min (tidal volume x respiratory rate).
For each experimental condition (test-hypoxia or control-ambient air), loop gain will be measured before the experimental condition (after 30 minutes of rest) and after the experimental condition (20 minutes before leaving the hypoxic chamber).
The change in loop gain is defined as the difference between the average values (over 5 minutes) of the loop gain before and after the experimentation.
Measured: after 6 hours of experimental condition
Secondary outcomes (5)
The change in controller gain before and after 6 hours of experimental condition (intermittent hypoxia or ambient air)
The following ventilatory parameters will be measured using a gas exchange measuring device to calculate loop gain, plant gain and controller gain: PETCO₂ (in mmHg), PETO₂ (in mmHg) and Minute ventilation (VE) measured in mL/min (tidal volume x respiratory rate).
For each experimental condition (test-hypoxia or control-ambient air), controller gain will be assessed before the experimental condition (after 30 minutes of rest) and after the experimental condition (20 minutes before leaving the hypoxic chamber).
The change in controller gain is defined as the difference between the average values (over 5 minutes) of the controller gain before and after experimental condition.
Measured: after 6 hours of experimental condition
The change in plant gain before and after 6 hours of experimental condition (intermittent hypoxia or ambient air)
The following ventilatory parameters will be measured using a gas exchange measuring device to calculate loop gain, plant gain and controller gain: PETCO₂ (in mmHg), PETO₂ (in mmHg) and Minute ventilation (VE) measured in mL/min (tidal volume x respiratory rate).
For each experimental condition (test-hypoxia or control-ambient air), plant gain will be assessed before the experimental condition (after 30 minutes of rest) and after the experimental condition (20 minutes before leaving the hypoxic chamber).
The change in plant gain is defined as the difference between the average values (over 5 minutes) of the plant gain before and after experimental condition.
Measured: after 6 hours of experimental condition
The change in the quantity of extracellular vesicles before and after 6 hours of experimental condition (intermittent hypoxia versus ambient air)
The quantity of extracellular vesicles is assessed from blood samples using flow cytometry with specific antibodies. Blood samples are collected before the experimental condition (after 30 minutes of rest) and after the experimental condition (after leaving the hypoxic chamber).
This change is expressed as the difference in the following extracellular vesicle concentrations before and after experimental conditioning:
- EVs from platelets expressing CD41
- EVs from erythrocytes expressing CD235a
- EVs from leukocytes expressing CD45
- EVs from endothelial cells expressing CD146
- EVs from granulocytes expressing CD66b and CD11b
- EVs from activated leukocytes expressing CD62L
- EVs from activated endothelial cells expressing CD62E
- EVs from activated platelets expressing CD62P
- CD62P/platelet ratio
- EVs carrying the PSGL-1 ligand expressing CD162
- EVs carrying phosphatidylserine expressing annexin V
Measured: after 6 hours of experimental condition
Correlation between the change in quantity of extracellular vesicles and change in loop gain
The change in the quantity of extracellular vesicles is defined as the difference of the extracellular vesicle concentration before and after the experimental condition (intermittent hypoxia and ambient air). The change in loop gain is defined as the difference of the loop gain values before and after the experimental condition (same definition as the primary outcome).
We are interested in the following extracellular vesicles: CD41, CD235a, CD45, CD146, CD66b, CD11b, CD62L, CD62E, CD62P and CD62/platelet annexin V.
Measured: after 6 hours of experimental condition
Change in loop gain before and after experimental condition (intermittent hypoxia or ambient air), in the subgroup of patients with hyperventilation syndrome and in the subgroup of patients without hyperventilation syndrome.
The change in loop gain is defined in the same way as the primary endpoint, i.e. as the difference between the measurements taken before and after the experimental condition. Hyperventilation syndrome is defined as a Nijmegen score of 23 or above at the inclusion visit.
Measured: after 6 hours of experimental condition
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted13 Feb 2026
- Study start20 Oct 2026 (estimated)
- Primary completionDec 2027 (estimated)
- Study completionDec 2027 (estimated)
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Other trials for Intermittent HypoxiaStudies of the same condition, open and under way.
- More trials run by Poitiers University HospitalThe sponsor's other registered studies.
- 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
- Prevention
- Allocation
- Randomised
- Intervention model
- Crossover
- Masking
- Single blind
- Who is masked
- Participant
- Enrolment
- 40 participants (estimated)
Sponsor and investigators
- Lead sponsor
- Poitiers University Hospital
- Sponsor type
- University, hospital or other
- Responsible party
- Sponsor
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT07409649
- Sponsor's protocol ID
- HI-LOOP
- Other IDs
- 2025-A02282-47
- Acronym
- HI-LOOP
- Status last verified
- Oct 2026
- First submitted
- 6 Feb 2026
- Last updated
- 28 Oct 2026
- Results posted
- No
- Data monitoring committee
- No
- FDA-regulated drug
- No
- FDA-regulated device
- No
- Individual data sharing
- Undecided
Study at a glance
From the registry record, last updated by the sponsor on 28 Oct 2026. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- Influence of Intermittent Hypoxia on Loop Gain in Healthy Subjects
- ClinicalTrials.gov ID
- NCT07409649
- Acronym / sponsor ID
- HI-LOOP / HI-LOOP
- Conditions
- Intermittent Hypoxia, Healthy Volunteers
- Keywords
- loop gain
- Study type
- Interventional
- Recruitment status
- Recruiting
- Enrolment
- 40 participants (estimated)
- Lead sponsor
- Poitiers University HospitalUniversity, hospital or other
- Study start
- 20 Oct 2026 (estimated)
- Primary completion
- Dec 2027 (estimated)
- Study completion
- Dec 2027 (estimated)
- First posted
- 13 Feb 2026 (actual)
- Results
- Not posted in the source record
Clinical summary
The research question as the sponsor registered it. This describes what the study plans to test, not what it found.
Sleep apnoea-hypopnoea syndrome (SAHOS), which causes numerous comorbidities, particularly cardiovascular ones, is widespread worldwide today and incurs significant healthcare costs.
Current research in this field focuses on identifying different phenotypes in affected patients in order to provide more personalised treatment.
One of these phenotypes appears to be linked to instability in ventilatory control due to an increase in loop gain (LG) in these subjects.
However, the pathophysiology of this ventilatory control instability due to increased LG is not fully understood. It is still difficult to determine whether subjects have an intrinsically high LG or if exposure to intermittent hypoxia during OSA promotes an increase in LG.
It has also been demonstrated that OSA causes vascular hyperreactivity by increasing oxidative stress through elevated ROS production. This leads to endothelial dysfunction in response to intermittent hypoxia associated with apnoea. Extracellular vesicles (microvesicles and exosomes) have been shown to play a role in this endothelial response. These extracellular vesicles are essential for intercellular communication in both physiological and pathological situations, such as SAHOS.
Therefore, the objective of this research is to determine whether exposure to intermittent hypoxia and changes in microvesicle phenotype could influence LG, which could lead to new therapeutic advances in the context of SAHOS.
Study design
- Primary purpose
- Prevention
- Allocation
- Randomised
- Intervention model
- Crossover
- Masking
- Single blind (participant)
- Number of arms
- 2
| Arm | Type | Receives |
|---|---|---|
| Arm A : ambient air then intermittent hypoxia | Experimental | Procedure: Intermittent hypoxia, Procedure: NormoxiaT1 : Conduct the experiment in ambient air (without hypoxia) for six hours. T2 : Then, after a washout period of at least seven days, conduct the experiment in intermittent hypoxia via the hypoxia chamber for six hours. |
| Arm B : intermittent hypoxia then ambient air | Experimental | Procedure: Intermittent hypoxia, Procedure: NormoxiaT1 : Conduct an experiment involving intermittent hypoxia in the hypoxia chamber for six hours. T2 : Then, after a washout period of at least seven days, conduct an experiment involving ambient air (without hypoxia). |
Who may qualify
- Ages
- 18 to 45 years
- Sex
- All
- Healthy volunteers
- Accepted
- Age groups
- Adult
Key inclusion criteria (26 listed)
- Healthy subjects aged 18 to 45
- BMI between [18-25] kg/m2
- No known sleep disorders
- Free subjects, not under guardianship or curatorship or subordination
- Persons affiliated with or beneficiaries of a Social Security scheme
Key exclusion criteria (0 listed)
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 |
|---|---|---|
| Intermittent hypoxiaThe volunteer will remain at rest in the hypoxic chamber, experiencing intermittent hypoxic conditions cyclically every 6 minutes. During one third of the cycle, they will be exposed to hypoxia in order to reduce SpO₂ to between 85% and 90%. Then, during two thirds of the cycle, they will receive oxygenation at a rate of 1 L/min (with possible subject-dependent modulations), with the aim of achieving an SpO₂ of greater than 95%. To make the hypoxia intermittent, the volunteer will also be given a medium-concentration oxygen mask that provides intermittent airflow, controlled by the D-6341 mass flow controller. | Procedure or surgery | Arm A : ambient air then intermittent hypoxia, Arm B : intermittent hypoxia then ambient air |
| NormoxiaThe participant will remain at rest in the hypoxic chamber under normoxic conditions. To prevent the volunteer from becoming aware of the conditions to which they are exposed, an air flow rate of 1 L/min will be used to simulate intermittent oxygenation. | Procedure or surgery | Arm A : ambient air then intermittent hypoxia, Arm B : intermittent hypoxia then ambient air |
Primary outcome
The change in Loop Gain before and after 6 hours of experimental condition (intermittent hypoxia or ambient air).
Time frame: after 6 hours of experimental condition
Loop gain is the product of 'controller gain' (ventilatory responsiveness to CO₂ above eupnoea) and 'plant gain' (the ventilatory increase required for a given reduction in PaCO₂). The following ventilatory parameters will be measured using a gas exchange measuring device to calculate loop gain, plant gain and controller gain: PETCO₂ (in mmHg), PETO₂ (in mmHg) and Minute ventilation (VE) measured in mL/min (tidal volume x respiratory rate). For each experimental condition (test-hypoxia or control-ambient air), loop gain will be measured before the experimental condition (after 30 minutes of rest) and after the experimental condition (20 minutes before leaving the hypoxic chamber). The change in loop gain is defined as the difference between the average values (over 5 minutes) of the loop gain before and after the experimentation.
5 secondary outcomes
The change in controller gain before and after 6 hours of experimental condition (intermittent hypoxia or ambient air)
Time frame: after 6 hours of experimental condition
The change in plant gain before and after 6 hours of experimental condition (intermittent hypoxia or ambient air)
Time frame: after 6 hours of experimental condition
The change in the quantity of extracellular vesicles before and after 6 hours of experimental condition (intermittent hypoxia versus ambient air)
Time frame: after 6 hours of experimental condition
Correlation between the change in quantity of extracellular vesicles and change in loop gain
Time frame: after 6 hours of experimental condition
Change in loop gain before and after experimental condition (intermittent hypoxia or ambient air), in the subgroup of patients with hyperventilation syndrome and in the subgroup of patients without hyperventilation syndrome.
Time frame: after 6 hours of experimental condition
Results and safety
This study is still under way. Results are not available in the source record yet.
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 28 Oct 2026.
- Individual participant dataSharing planned: Undecided
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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.
1 site in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
A study testing Intermittent hypoxia and Normoxia in people with Intermittent Hypoxia and Healthy Volunteers, run by Poitiers University Hospital at 1 site in France.
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 26 inclusion and 0 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: looking for participants now, as of the sponsor's last update on 28 Oct 2026. Status can change between updates, so confirm with the study contact before making plans.
Where is the study taking place?
The record lists 1 site in France. 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?
This study is still under way. Results are not available in the source record yet.
How can a doctor refer a patient or contact the research team?
Contact Vanessa BIRONNEAU, MD (05 49 44 34 49 ext. +33, vanessa.bironneau@chu-poitiers.fr), or a site near the patient. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
The change in Loop Gain before and after 6 hours of experimental condition (intermittent hypoxia or ambient air). (time frame: after 6 hours of experimental condition). It is what the study was designed to measure, not a finding.
Where can I read the original study information?
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 28 Oct 2026.