NCT07357090 · Andrew Mayer
Carbon Dioxide Administration and Brain Waste Clearance
(COPETBI)
What this study is about
The current study tests whether different exposures to carbon dioxide (CO2) can safely result in the increased movement of proteins from the brain into the blood. The investigators believe that this would be a proxy for the brain clearing waste products more effectively.
View original scientific description
The current study tests whether different exposures to carbon dioxide (CO2) can safely result in the increased movement of proteins from the brain into the blood. The investigators believe that this would be a proxy for the brain clearing waste products more effectively. The current study will use a counter-balanced design, in which individuals with and without a history of traumatic brain injury (TBI) will receive different levels of CO2 (targeted changes of approximately 5 or 10 mmHG in end-tidal CO2) approximately one week apart. The counter-balanced design means that each participant receives a single dose of CO2 at each visit, and different doses of CO2 at each visit. The order in which participants receive the dose is randomized, and the participant will not be informed of the dose.
Interventions
OTHER
Hypercapnia task performed during fMRI
This study looks at different levels of carbon dioxide (CO2) exposure (changes of approximately 5 or 10 mmHg) on the brain and proteins in blood, in response to a hypercapnia task while participants undergo MRI. This sequence will dynamically mix gases to target an increase of 5 or 10 mmHg in ETCO2 (increase of \~5-7% CO2 and equal decrease in nitrogen) while keeping O2 constant.
Primary outcome measures
Cerebrovascular Reactivity (CVR), vascular-elicited bulk cerebral spinal fluid (VE-bCSF)
Time frame: 2.5 hours post-intervention. Data will be reported at the conclusion of the study for all participants.
Cerebrovascular reactivity (CVR) will be quantified using time-shifted end-tidal carbon dioxide (ETCO₂) regressors to model blood oxygen level-dependent (BOLD) changes using functional magnetic resonance imaging, capturing the temporally lagged positive relationship between ETCO₂ and the BOLD signal. Vascular enhanced changes in bulk CSF flow will be assessed by regressing band-pass filtered global grey matter signals and their derivatives on CSF bulk flow to capture the temporally lagged, negative relationship. Both of these measurements are in arbitrary units, and will be quantified by calculating percent signal change and statistical fit between regressors.
Protein Efflux (Surrogate Measure of Brain Waste Clearance)
Time frame: Blood will be drawn at baseline, immediately prior to hypercapnia, 45 minutes post-hypercapnia, 90 minutes post-hypercapnia and 150 minutes post-hypercapnia. Data will be reported at the conclusion of the study for all participants.
Protein efflux from the brain to the blood will be measured using Quanterix platform, with primary proteins including neurofilament light chain, brain-derived tau and glial fibrillary acidic protein (units=picogram/milligram). For neurofilament light chain (NfL), the limit of detection (LOD) is 0.104 pg/mL, the range is 0.025-0.276 pg/mL, and the lower limit of quantification (LLOQ) is 0.241 pg/mL. For glial fibrillary acidic protein (GFAP), the LOD is 0.221 pg/mL, the range is 0.042-0.481 pg/mL, and the LLOQ is 0.467 pg/mL. For brain-derived tau (BD Tau), the LOD is 0.024 pg/mL, the range is 0.007-0.059 pg/mL, and the LLOQ is 0.053 pg/mL. All values are obtained from the Quanterix website datasheets.
Who can participate
This study lists these criteria on ClinicalTrials.gov. A study coordinator reviews eligibility during screening — this page does not determine whether you qualify.
Inclusion criteria
- for TBI cohort: 1) Able to give valid informed consent, 2) 18-82 years old, 3) history of TBI of any severity level (mild, moderate or severe) that was sustained in adulthood (age 18 and older), which will be confirmed using a semi-structured identification method (includes asking about loss of consciousness, posttraumatic amnesia, and feeling dazed/confused). Inclusion criteria for Healthy Subjects cohort: 1) Able to give valid informed consent and 2) 18-82 years old years old.
Exclusion criteria
- for TBI cohort: 1) contraindications to MRI scanning including pregnancy or claustrophobia, 2) unable to give valid informed consent, incarcerated, 3) diagnosed with Alzheimer's, ADRD or mild cognitive impairment, 4) pre-existing history of autism spectrum disorders, intellectual disability, serious neurological (e.g., epilepsy, tumors, other conditions requiring neurosurgery) or psychiatric disorders (requiring hospitalization) prior to TBI onset, 5) current or previous diagnosis of a psychosis spectrum disorder or bipolar disorder, 6) respiratory diseases or pulmonary conditions that may increase the risk of study procedures (e.g., severe asthma, chronic obstructive pulmonary disease or other significant respiratory disorders), 7) a history of cardiac arrythmias 8) history of a current substance use disorder, 9) non-English fluency (based on screener), 10) Weigh under 110 pounds for blood draw. Exclusion criteria for Healthy Subjects cohort: 1) contraindications to MRI scanning including pregnancy or claustrophobia, 2) unable to give valid informed consent, incarcerated, 3) diagnosed with Alzheimer's, ADRD or mild cognitive impairment, 4) history of developmental, neurological, or psychiatric disorders requiring hospitalization, 5) regular use of any substance in the past six months (i.e., no current use confirmed with urine screening), 6) previous head injury with greater than 30 minutes loss of consciousness, 7) respiratory diseases or pulmonary conditions that may increase the risk of study procedures (e.g., severe asthma, chronic obstructive pulmonary disease or other significant respiratory disorders), 8) a history of cardiac arrythmias, 9) non-English fluency (based on screener), 10) Weigh under 110 pounds for blood draw.
Where
- Albuquerque, New Mexico
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Frequently asked questions
What is a clinical trial?
A clinical trial is a research study that tests new medical treatments, drugs, devices, or procedures to determine their safety and effectiveness. Trials are carefully designed and monitored to protect participants while advancing medical knowledge.
Is it safe to participate?
Clinical trials follow strict safety guidelines and ethical standards. Trials must be reviewed and approved, and participants are closely monitored by medical professionals throughout the study. You can withdraw at any time if you choose.
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Many clinical trials offer compensation for your time, travel expenses, and inconvenience. The specific compensation varies by study and will be discussed during the screening process. All study-related medical care is typically provided at no cost to participants.
Will I receive a placebo instead of treatment?
When effective treatment exists, participants typically receive either the standard treatment plus the study intervention, or the standard treatment plus placebo. You would not be denied effective care. Placebos are primarily used when no proven treatment is available, or in addition to standard care. Your trial consent form will clearly explain what treatments you may receive.
Can I leave a trial if I change my mind?
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How long does a clinical trial last?
Trial duration varies widely depending on the study design and purpose. Some trials last just a few weeks, while others may continue for months or years. The study coordinator will provide specific timeline information during your screening call.
Data: ClinicalTrials.gov · synced Feb 23, 2026 · Source of record for eligibility and locations