The Effect of Respiratory Challenge on the BOLD Signal

The purpose of this research study is to better understand how blood flow and metabolism are different between normal controls and patients with disease.

The investigators will examine brain blood flow and metabolism using magnetic resonance imaging (MRI). The brain's blood vessels expand and constrict to regulate blood flow based on the brain's needs. The amount of expanding and contracting the blood vessels can do varies by age. The brain's blood flow changes in small ways during everyday activities, such as normal brain growth, exercise, or deep concentration. Significant illness or physiologic stress may increase the brain's metabolic demand or cause other bigger changes in blood flow. If blood vessels are not able to expand to give more blood flow when metabolic demand is high, the brain may not get all of the oxygen it needs. In less extreme circumstances, not having as much oxygen as it wants may cause the brain to grow and develop more slowly than it should.

One way to test the ability of the blood vessels to expand is by measuring blood flow while breathing in carbon dioxide (CO2). CO2 causes blood vessels in the brain to dilate without increasing brain metabolism. The study team will use a special mask to control the amount of oxygen and carbon dioxide patients breath in so that we can study how their brain reacts to these changes. This device designed to simulate carbon dioxide levels achieved by a breath-hold and target the concentration of carbon dioxide in the blood in breathing patients. The device captures exhaled gas and provides an admixture of fresh gas and neutral/expired gas to target different carbon dioxide levels while maintaining a fixed oxygen level. The study team will obtain MRI images of the brain while the subjects are breathing air controlled by the device.

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Key information

Conditions

Hypoxia, Brain Brain Diseases Central Nervous System Diseases Hypercapnia Hyperoxia Hypocapnia Hypoxia Nervous System Diseases Pathological Conditions, Signs and Symptoms Signs and Symptoms Signs and Symptoms, Respiratory

Age range

18 year and older

Sex eligibility

All sexes

Study type

Interventional

Phase

Not applicable

Primary location

Washington University of St. Louis

St Louis, Missouri, 63110, United States

Who can participate

Healthy volunteers accepted: Yes

Only the study team can determine whether someone qualifies for participation.

Inclusion criteria

Healthy adult subjects (>18 years old) OR adult patients (>18 years old) diagnosed with vascular pathology of the brain willing to participate and sign a consent form.
Able to participate in MRI scan without sedation
Not on stimulant medications
No psychiatric history, as defined by seeing a psychiatrist for medical evaluation and treatment, or taking anti-depressant medications
No seizure history
May have occasional headaches if not taking a daily preventative medication for headaches
Not on vasodilatory medication, such as sildenafil or verapamil

Exclusion criteria

Subjects refusing to undergo testing
Subjects with obstructive or resistive lung disease whose PaCO2 at rest is greater than 50mmHg or whose venous serum bicarbonate is greater than 26 mEq/L
Subjects with pre-existing respiratory or metabolic acidosis
Subjects who require portable oxygen at rest or with exercise
Subjects with chronic heart failure or severe pulmonary disease who are unable to climb one flight of stairs due to shortness of breath
Subjects with severe heart failure or restrictive lung disease with resting respiratory rate over 15 breaths/min 2. Patients that cannot participate in a course of rehabilitation therapy.
Subjects that cannot undergo an MRI scan due to one of the following indications:

Pregnancy
Obtundation, or Coma
Confusion, Delirium, or Dementia
Unable to understand or carry out commands regarding keeping still and breathing pattern
Increased intracranial pressure due to space occupying lesion or obstruction of outflow of CSF
Claustrophobia
History of kidney problems
Pace makers
Skin tattoos
Neurostimulators (TENS-unit)
Implanted drug infusion device (i.e., insulin pump)
Exposure of metal fragments to your eye
Artificial heart valves
Aneurysm clips
Cochlear implants
Metallic implants and prosthesis
Vascular stent or stent graft
History as a metal worker
Shrapnel or bullet wounds
Dorsal column stimulators

Treatment and study plan

Carbon dioxide

Other

The study team will administer inhaled carbon dioxide to the participants during an MRI at a level

Primary outcomes

Cerebral Oxygen Metabolism

Time frame: From the beginning of the MRI scan to the completion of the MRI scan -- 75 minutes.

Secondary outcomes

Cerebrovascular Reactivity

Time frame: From administration of carbon dioxide to end of inhalation of carbon dioxide -- 15 minutes.

Sponsors and collaborators

Lead sponsor

Washington University School of Medicine

Other

Registry information

Important dates

Study start: 2020
Primary completion: 2027
Study completion: 2027
First posted: Feb 6, 2020
Registry last updated: Jan 16, 2026

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

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Completed