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The primary objective of this research is to measure changes in neurochemical concentrations during stimulation of the primary visual cortex, in both conditions of normoxia (normal oxygen availability) and induced mild hypoxia (reduced oxygen availability).
The goal is to determine the effect of mild hypoxia on human brain energy metabolism of healthy young adult subjects. For this purpose, the Investigator will utilize non-invasive imaging modalities based on functional magnetic resonance spectroscopy (fMRS) to estimate metabolic changes during a visual stimulus, while subjects are exposed to well-controlled gas mixtures that resembles conditions of either normoxia or mild hypoxia. Identifying the impact of mild hypoxia on functional brain energy metabolism in the healthy human brain is a crucial step for generating hypotheses in multiple patient populations that experience mild hypoxia as consequence of their pathological condition, such as in sleep apnea and traumatic brain injury. The Investigator hypothesize that the energetic demands of neuronal activation as revealed by fMRS will not be affected by mild hypoxia.
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| Label | Type | Description | Intervention Names |
|---|---|---|---|
| Mild Hypoxia | Experimental | Subjects are exposed to an intervention that controls the composition of breathed air by using a gas blender (RespirAct). Subjects undergo MRI and MRS while breathing air with both normal oxygen concentration (normoxia) and reduced oxygen concentration (mild hypoxia). |
|
| Name | Type | Description | Arm Group Labels | Other Names |
|---|---|---|---|---|
| Mild Hypoxia | Device | During normoxia, the computer-controlled gas blender provides a gas mixture that generates pressures of expired O2 and CO2 similar to the resting values measured for each subject (32-35mmHg and 100-110 mmHg, respectively). During mild hypoxia, we will target the same expired CO2 of normoxia and a 60 mmHg reduction of expired O2 from the resting value (to a minimum limit of 50 mmHg), which is expected to reduce arterial oxygen saturation to 82-85%. In mild hypoxia, the fraction of inspired oxygen is reduced from ~21% (room air) to ~12% (equivalent to an altitude of 4000 meters). During both conditions of normoxia and mild hypoxia, the brain activity of subjects is monitored with functional magnetic resonance spectroscopy (fMRS) while they are presented with visual stimuli. |
| Measure | Description | Time Frame |
|---|---|---|
| Change in Glutamate Concentration During a Visual Stimulus Measured by fMRS at Normoxia | Relative change in glutamate concentration from rest to visual stimulation as measured by fMRS (with water suppression) in the primary visual cortex during conditions of normoxia. | Baseline and Visual Stimulation at 4 minutes |
| Change in Glutamate Concentration During a Visual Stimulus Measured by Functional MRS at Hypoxia | Relative change in glutamate concentration from rest to visual stimulation as measured by fMRS (with water suppression) in the primary visual cortex during conditions of hypoxia. | Baseline and Visual Stimulation at 4 minutes |
| Measure | Description | Time Frame |
|---|---|---|
| Brain Activity Measured by Blood Oxygenation Level Dependent (BOLD) Signal at Normoxia | Relative change in water signal intensity from rest to visual stimulation as measured by fMRS (without water suppression) in the primary visual cortex during conditions of normoxia. | Baseline and Visual Stimulation at 30 seconds |
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Inclusion Criteria:
Exclusion Criteria:
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| Name | Affiliation | Role |
|---|---|---|
| Silvia Mangia, PhD | University of Minnesota | Principal Investigator |
| Facility | Status | City | State | ZIP | Country | Contacts |
|---|---|---|---|---|---|---|
| Center for Magnetic Resoance Research, University of Minnesota | Minneapolis | Minnesota | 55455 | United States |
| PubMed Identifier | Type | Citation | Retractions |
|---|---|---|---|
| 18396415 | Background | Ho YC, Vidyasagar R, Shen Y, Balanos GM, Golay X, Kauppinen RA. The BOLD response and vascular reactivity during visual stimulation in the presence of hypoxic hypoxia. Neuroimage. 2008 Jun;41(2):179-88. doi: 10.1016/j.neuroimage.2008.02.048. Epub 2008 Mar 6. | |
| 16079793 | Background | Tuunanen PI, Murray IJ, Parry NR, Kauppinen RA. Heterogeneous oxygen extraction in the visual cortex during activation in mild hypoxic hypoxia revealed by quantitative functional magnetic resonance imaging. J Cereb Blood Flow Metab. 2006 Feb;26(2):263-73. doi: 10.1038/sj.jcbfm.9600186. |
| Label | URL |
|---|---|
| Profile of Principle Investigator | View source |
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| ID | Title | Description |
|---|---|---|
| FG000 | Mild Hypoxia | Mild Hypoxia: During normoxia, the computer-controlled gas blender provides a gas mixture that generates pressures of expired O2 and CO2 similar to the resting values measured for each subject (32-35mmHg and 100-110 mmHg, respectively). During mild hypoxia, we will target the same expired CO2 of normoxia and a 60 mmHg reduction of expired O2 from the resting value (to a minimum limit of 50 mmHg), which is expected to reduce arterial oxygen saturation to 82-85%. In mild hypoxia, the fraction of inspired oxygen is reduced from ~21% (room air) to ~12%. During both conditions of normoxia and mild hypoxia, the brain activity of subjects is monitored with functional MRI (fMRI) and functional MRS (fMRS) during visual stimuli. |
| Title | Milestones | Reasons Not Completed | ||||||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Overall Study |
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| ID | Title | Description |
|---|---|---|
| BG000 | Mild Hypoxia | During normoxia, the computer-controlled gas blender provides a gas mixture that generates pressures of expired O2 and CO2 similar to the resting values measured for each subject (32-35mmHg and 100-110 mmHg, respectively). During mild hypoxia, we will target the same expired CO2 of normoxia and a 60 mmHg reduction of expired O2 from the resting value (to a minimum limit of 50 mmHg), which is expected to reduce arterial oxygen saturation to 82-85%. In mild hypoxia, the fraction of inspired oxygen is reduced from ~21% (room air) to ~12% (equivalent to an altitude of 4000 meters). During both conditions of normoxia and mild hypoxia, the brain activity of subjects is monitored with functional magnetic resonance spectroscopy (fMRS) while they are presented with visual stimuli. |
| Units | Counts |
|---|---|
| Participants |
|
| Title | Description | Population Description | Parameter Type | Dispersion Type | Unit of Measure | Calculate Percentage | Denominator Units Selected | Denominators | Classes |
|---|---|---|---|---|---|---|---|---|---|
| Age, Continuous | Mean |
| Type | Title | Description | Population Description | Reporting Status | Anticipated Posting Date | Parameter Type | Dispersion Type | Unit of Measure | Calculate Percentage | Time Frame | Units Analyzed | Denominator Units Selected | Arm/Group Information | Denominators | Classes | Analyses | |||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Primary | Change in Glutamate Concentration During a Visual Stimulus Measured by fMRS at Normoxia | Relative change in glutamate concentration from rest to visual stimulation as measured by fMRS (with water suppression) in the primary visual cortex during conditions of normoxia. | Out of the 17 experimental sessions that were successfully completed, 4 had data of insufficient quality. Therefore, a total of 13 sessions was used for final analyses. | Posted | Mean | Standard Deviation | percentage of concentration (micromol/g) | Baseline and Visual Stimulation at 4 minutes |
|
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| ID | Title | Description | Deaths (Affected) | Deaths (At Risk) | Serious Events (Affected) | Serious Events (At Risk) | Other Events (Affected) | Other Events (At Risk) |
|---|---|---|---|---|---|---|---|---|
| EG000 | Mild Hypoxia | Mild Hypoxia: During normoxia, the computer-controlled gas blender provides a gas mixture that generates pressures of expired O2 and CO2 similar to the resting values measured for each subject (32-35mmHg and 100-110 mmHg, respectively). During mild hypoxia, we will target the same expired CO2 of normoxia and a 60 mmHg reduction of expired O2 from the resting value (to a minimum limit of 50 mmHg), which is expected to reduce arterial oxygen saturation to 82-85%. In mild hypoxia, the fraction of inspired oxygen is reduced from ~21% (room air) to ~12% (equivalent to an altitude of 4000 meters). During both conditions of normoxia and mild hypoxia, the brain activity of subjects is monitored with functional MRI (fMRI) and functional MRS (fMRS) during visual stimuli. |
| Term | Organ System | Source Vocabulary | Assessment Type | Notes | Statistical Information |
|---|---|---|---|---|---|
| Muscle cramp | Musculoskeletal and connective tissue disorders | Systematic Assessment | Muscle cramps in hands and tongue numbness |
| Term | Organ System | Source Vocabulary | Assessment Type | Notes | Statistical Information |
|---|---|---|---|---|---|
| Claustropobia | Psychiatric disorders | Feeling of claustrophobia inside the MRI scanner |
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| Title | Organization | Phone | Extension | |
|---|---|---|---|---|
| Silvia Mangia, PhD | University of Minnesota | 6126254920 | mangia@umn.edu |
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| ID | Term |
|---|---|
| D002534 | Hypoxia, Brain |
| ID | Term |
|---|---|
| D001927 | Brain Diseases |
| D002493 | Central Nervous System Diseases |
| D009422 | Nervous System Diseases |
| D000860 | Hypoxia |
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|
| Brain Activity Measured by Blood Oxygenation Level Dependent (BOLD) Signal at Hypoxia |
Relative change in water signal intensity from rest to visual stimulation as measured by fMRS (without water suppression) in the primary visual cortex during conditions of hypoxia. |
| Baseline and Visual Stimulation at 30 seconds |
| years |
|
| Sex: Female, Male | Count of Participants | Participants | No |
|
|
|
| Primary | Change in Glutamate Concentration During a Visual Stimulus Measured by Functional MRS at Hypoxia | Relative change in glutamate concentration from rest to visual stimulation as measured by fMRS (with water suppression) in the primary visual cortex during conditions of hypoxia. | Out of the 17 experimental sessions that were successfully completed, 4 had data of insufficient quality. Therefore, a total of 13 sessions was used for final analyses. | Posted | Mean | Standard Deviation | percentage of concentration (micromol/g) | Baseline and Visual Stimulation at 4 minutes |
|
|
|
| Secondary | Brain Activity Measured by Blood Oxygenation Level Dependent (BOLD) Signal at Normoxia | Relative change in water signal intensity from rest to visual stimulation as measured by fMRS (without water suppression) in the primary visual cortex during conditions of normoxia. | Out of the 17 experimental sessions that were successfully completed, 4 had data of insufficient quality. Therefore, a total of 13 sessions was used for final analyses. | Posted | Mean | Standard Deviation | percentage of signal intensity | Baseline and Visual Stimulation at 30 seconds |
|
|
|
| Secondary | Brain Activity Measured by Blood Oxygenation Level Dependent (BOLD) Signal at Hypoxia | Relative change in water signal intensity from rest to visual stimulation as measured by fMRS (without water suppression) in the primary visual cortex during conditions of hypoxia. | Out of the 17 experimental sessions that were successfully completed, 4 had data of insufficient quality. Therefore, a total of 13 sessions was used for final analyses. | Posted | Mean | Standard Deviation | percentage of signal intensity | Baseline and Visual Stimulation at 30 seconds |
|
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|
| 0 |
| 25 |
| 1 |
| 25 |
| 16 |
| 25 |
|
| Nervousness | Psychiatric disorders | Feeling nervous inside the MRI scanner and/or breathing through the mask |
|
| Sleepiness | General disorders | Feeling sleepy inside the restricted and dark environment of the MRI scanner |
|
| Lightheadedness | General disorders | Some lightheadedness while breathing through the mask at specific breathing pattern, or while just being inside the MRI scanner |
|
| Metallic Taste | General disorders | Metallic taste inside the MRI scanner |
|
| Cold | General disorders | Feeling cold inside the MRI scanner |
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| Warmth | General disorders | Feeling warm inside the MRI scanner |
|
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| D012818 |
| Signs and Symptoms, Respiratory |
| D012816 | Signs and Symptoms |
| D013568 | Pathological Conditions, Signs and Symptoms |