Carbon Dioxide (CO2) and Cognitive Impairment

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

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

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. Another subset of subjects (up to 10) will not complete the SMS during the exposures but will undergo computer-assisted intravital microscopy (CAIM) to exam the conjunctival microvasculature before and after the exposure.

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

Additional Exclusion Criteria for Subjects undergoing CAIM

• Current or recent contact lens use