Carbon Dioxide (CO2) and Cognitive Impairment

Study Overview
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Brief Summary
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The purpose of the study is to better understand the biological mechanisms of carbon dioxide (CO2)-induced cognitive impairments.

Detailed Description
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Participants will complete 2 study visits. Each study visit will consist of a 2.5-hour exposure session. Concentrations of CO2 during the exposure session will be either 600 ppm (control) or 2500 ppm (exposure). The order of the exposure sessions will be randomized and the exposure sessions will be at least one week apart. Up to two participants will take part in each exposure session. During each exposure a neurobehavioral assessment (Strategic Management Simulations or SMS) will be administered. Venous blood (30 mL) will be collected from subjects immediately before entering the chamber and immediately after the exposure. A subset of subjects (n=12) will also undergo a 60-minute fMRI scan.

Official Title
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Carbon Dioxide (CO2): A Pilot Study of a Hypothesized Mechanism to Explain Cognitive Impairment

Conditions
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Healthy

Intervention / Treatment
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* Other: 2500 ppm Carbon Dioxide
* Other: 600 ppm Carbon Dioxide


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: History of COVID-19 vaccination Weigh at least 110 pounds Exclusion Criteria: Colorblindness Inability to hear verbal instructions Cardiovascular disease, including a history of stroke Diabetes requiring the use of insulin Pregnancy Current asthma (an asthma attack within the past five years) Medications for or history of anxiety disorder diagnosis or panic attacks Medications which may affect cognition such as beta-blockers and CNS depressants Temporary Exclusion Criteria Respiratory symptoms in the previous four weeks Use of sedating cold/allergy medications in the previous week Use of marijuana in the previous week Consumption of alcohol in the previous 24 hours Additional Exclusion Criteria for Subjects undergoing the fMRI scan: History of head trauma or neurosurgery or neurological disorder Ferrous metal implanted in or on the body, electrical devices such as a pacemaker, nonremovable ferrous jewelry Surgical pins or plates above the neck History of eye injury involving metallic materials, shavings in eyes, or welding without a face mask Lead or iron tatoos Claustrophobia Back problems that would prevent the subject from laying still comfortably for up to 90 minutes

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 30 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Basic Science
Allocation: Randomized
Intervention Model: Crossover Assignment
Masking: Double


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: High CO2 Exposure first, then low CO2 exposure second.<br>At the first study visit the subject is exposed to 2500 ppm CO2 for 2.5 hours and at the second study visit the subject is exposed to 600 ppm CO2 for 2.5 hours. | Other: 2500 ppm Carbon Dioxide<br>* 2.5 hour exposure to 2500 ppm carbon dioxide<br>Other: 600 ppm Carbon Dioxide<br>* 2.5 hour exposure to 600 ppm carbon dioxide<br>|
| Sham Comparator: Low CO2 Exposure first, then high CO2 exposure second.<br>At the first study visit the subject is exposed to 600 ppm CO2 for 2.5 hours and at the second study visit the subject is exposed to 2500 ppm CO2 for 2.5 hours. | Other: 2500 ppm Carbon Dioxide<br>* 2.5 hour exposure to 2500 ppm carbon dioxide<br>Other: 600 ppm Carbon Dioxide<br>* 2.5 hour exposure to 600 ppm carbon dioxide<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Change in PMN (polymorphonuclear leukocyte) activation from pre-exposure to post-exposure | Using blood samples collected pre- and post-exposure, PMN activation will be assessed by measurement of oxidative burst (oxygen consumption rate), glycolytic function (extracellular acidification rate) and caspase-1 activity (assessed by fluorometric assay). | Immediately before and immediately after each exposure | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Carbon Dioxide, Cognitive Impairment