Recruiting

CO2 Chemosensitivity

Sponsor:

University of Iowa

Code:

NCT04134754

Conditions

Epilepsy

SUDEP

Eligibility Criteria

Sex: All

Age: 18 - 70+

Healthy Volunteers: Not accepted

Interventions

6% Carbon dioxide/50% oxygen/balance nitrogen mixture

Study Details

Brief summary:

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.

Conditions

Epilepsy

SUDEP

Study ID

NCT04134754

Start date

Dec 12, 2019

Status verified date

Jun, 2026

Completion date

Oct 1, 2029

Anticipated

Primary completion date

Oct 1, 2029

Anticipated

Eligibility Criteria

Eligibility Criteria

Sex: All

Age: 18 - 70+

Healthy Volunteers: Not accepted

Inclusion Criteria:

1. The subject is between 18 and 99 years of age.
2. Confirmed or suspected epilepsy.
3. Admission to the EMU for spell characterization (EMU group) or undergoing care in the University of Iowa Health Care Epilepsy Clinic.

Exclusion Criteria:

1. History of uncontrolled cardiac, pulmonary, or hepatic disease.
2. Progressive or uncontrolled neurologic disease unrelated to epilepsy.
3. Current opioid use.
4. 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).
5. Other comorbid condition that may influence the safety or feasibility of HCVR testing.
6. Limited decision-making capacity and absence of a qualified representative.

Study Design

Enrollment

335 participants

Anticipated

Intervention Model

Single group

Primary purpose

Basic Science

Interventions and Outcome Measures

Arms

other: Respiratory physiology testing

Subjects will wear a nosepiece and breathe through a Y-valve that allows switching from room air to two 5-liter rebreathing bags pre-filled with 50% O2, 6% CO2, and balance N2. Ventilation and respiratory gases will be measured using a pneumotachograph and rapid gas analyzers (Ultima PFX pulmonary function/stress testing system, Medical Graphics Corp). In subjects who experience clinical seizure-like activity, we will repeat the HCVR. This repeat test will occur 2 or more hours after a generalized convulsive seizure (GCS). We will repeat the HCVR at least 30 minutes after a non-GCS. Finally, we may repeat the HCVR at least 18 hours after the last seizure (GCS or non-GCS). It is anticipated that some subjects may exhibit frequent seizures that necessitate the adjustment of this schedule. Subjects may also be asked to sniff, hold their breath, and breathe through tubes of different sizes.

Interventions

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 measure

  • 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 ]
  • 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 ]
  • Effect of seizures on HCVR slope (liters/min/mm Hg) [ Time Frame: Up to 18 hours after a seizure. ]
  • 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 ]

Central Contacts and Locations

Central contacts

Study Coordinator

319-356-4337dragond@healthcare.uiowa.edu

Locations

University of Iowa Hospitals and Clinics

Recruiting

Iowa City, Iowa, United States, 52242

Contacts

Deidre Dragon, BS

(319) 356-4337dragond@uiowa.edu

Brian K Gehlbach, MD

319-356-3603brian-gehlbach@uiowa.edu

Principal Investigator:

Brian Gehlbach, MD

More Information

Sponsor

University of Iowa

Last update posted

Jun 23, 2026

Last verified

Jun, 2026

Keywords

  • Epilepsy

Trial information was received from ClinicalTrials.gov and was last updated on 2026-09-09. This information was provided to ClinicalTrials.gov by University of Iowa on 2026-06-23.