Carbon Dioxide (CO2) Chemosensitivity and SUDEP

Overview

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.

In this study, the investigators will only enroll adults with confirmed or suspected epilepsy; there is no control group. Patients admitted to the UIHC Epilepsy Monitoring Unit (EMU) for continuous VideoEEG will undergo video recordings of their face and body, electroencephalography (EEG), and electrocardiogram (ECG) as part of their normal clinical care. Research subjects will undergo noninvasive cardiorespiratory monitoring during their EMU stay for the purpose of correlating heart rate and breathing patterns with EEG patterns related to their seizures. Eligible subjects will undergo several respiratory tests. This may include sniffing and breath holding and breathing through tubes of different sizes. One test, called the hypercapnic ventilatory response (HCVR), will have you rebreathe a gas mixture of 6% carbon dioxide and 50% oxygen to look at how more you breath in response to the increase in carbon dioxide levels. The investigators will then measure how much more subjects breathe in response to the increase in carbon dioxide levels, and also how breathing feels at the end of the test. The investigators will analyze the relationship between the HCVR and cardiorespiratory changes from seizures. The investigators will also analyze the effect of seizures on the HCVR. The HCVR test will be done by our respiratory therapist during subjects' stay in the EMU. Some subjects will be asked to participate in repeat testing of the HCVR 3 more times as an outpatient over the next 2 years. Additional subjects will also be enrolled from the clinic and will also undergo HCVR testing 4 times over the 2 years. All subjects will agree to undergo an interview in person or by phone, email, or questionnaire annually for ten years. They will also provide consent for follow-up with a personal contact in the event of subject death, for the purpose of ascertaining whether the death was due to SUDEP.