NCT04134754 · University of Iowa
Carbon Dioxide (CO2) Chemosensitivity and SUDEP
What this study is about
The purpose of this research study is to better understand what causes Sudden Unexpected Death in Epilepsy (SUDEP). This study will enroll subjects from the University of Iowa Hospitals and Clinics (UIHC) Epilepsy Monitoring Unit (EMU) and Epilepsy Clinics. The investigators will analyze the effects of seizures on breathing, on the cardiovascular system, and on arousal.
View original scientific description
The purpose of this research study is to better understand what causes Sudden Unexpected Death in Epilepsy (SUDEP). This study will enroll subjects from the University of Iowa Hospitals and Clinics (UIHC) Epilepsy Monitoring Unit (EMU) and Epilepsy Clinics. The investigators will analyze the effects of seizures on breathing, on the cardiovascular system, and on arousal. The investigators are studying these effects because some cases of SUDEP might be due, in part, to an inability to wake up or sense elevated carbon dioxide (CO2) levels when breathing is impaired. Subjects will be followed for ten years after enrollment to monitor their health.
Interventions
OTHER
6% Carbon dioxide/50% oxygen/balance nitrogen mixture
In the hypercapnic ventilatory response (HCVR) test, the subject will rebreathe a gas mixture that has 6% carbon dioxide and 50% oxygen. This test has been performed for decades for research and clinical purposes. The effects of carbon dioxide inhalation are short lived and do not cause long term consequences. the hypercapnic ventilatory response (HCVR), we will have you
Primary outcome measures
Determine the correlation between baseline central CO2 chemosensitivity and the increase in transcutaneous CO2 levels after a seizure.
Time frame: Immediately before and after a seizure, variable for each subject but approximately 10 minutes
The change in HCVR slope (change in minute ventilation \[liters/min\] vs change in end tidal CO2 \[mm Hg\]) will be correlated with the increase in transcutaneous CO2 level (mm Hg) provoked by a seizure.
Determine the correlation between baseline central CO2 chemosensitivity and the duration of transcutaneous CO2 elevation above baseline after a seizure.
Time frame: Duration of hospital admission, approximately 5 days
The change in HCVR slope (change in minute ventilation \[liters/min\] vs change in end tidal CO2 \[mm Hg\]) will be correlated with the duration (minutes) of end tidal CO2 elevation above pre-seizure baseline
Effect of seizures on HCVR slope (liters/min/mm Hg)
Time frame: Up to 18 hours after a seizure.
The percent change in HCVR slope (liters/min/mm Hg) from baseline that is induced by a seizure will be measured. The HCVR will be administered at 30 minutes, 2 hours, and 18 hours after nonconvulsive seizures. The HCVR will be administered at 2 hours and 18 hours after convulsive seizures.
Determine the stability of the HCVR slope over time in patients with epilepsy. of the HCVR over time in patients with epilepsy
Time frame: 2 years
The stability of the HCVR slope (liters/min/mm Hg) measured 8 months for 2 years will be assessed using a generalized linear mixed model.
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
- The subject is between 18 and 99 years of age.
- Confirmed or suspected epilepsy.
- Admission to the EMU for spell characterization (EMU group) or undergoing care in the University of Iowa Health Care Epilepsy Clinic.
Exclusion criteria
- History of uncontrolled cardiac, pulmonary, or hepatic disease.
- Progressive or uncontrolled neurologic disease unrelated to epilepsy.
- Current opioid use.
- Women of child-bearing potential who are pregnant or capable of becoming pregnant (e.g. sexual activity within the past 21 days without a highly effective form of birth control or positive urine pregnancy test).
- Other comorbid condition that may influence the safety or feasibility of HCVR testing.
- Limited decision-making capacity and absence of a qualified representative.
Where
- Iowa City, Iowa
Collaborators
National Institute of Neurological Disorders and Stroke (NINDS)
Related conditions & keywords
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.
Will I be compensated?
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?
Absolutely. Participation in clinical trials is completely voluntary. You have the right to withdraw from the study at any time, for any reason, without penalty or loss of benefits to which you are otherwise entitled.
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 Jun 23, 2026 · Source of record for eligibility and locations