The purpose of this study is to determine whether electrical stimulation can be used to replace physical stimulation to test awareness of patients with impaired consciousness. Physical stimulation can cause bruising, damaged nails and ribs, and other damage with repeated testing, and electrical stimulation may be safer and cause less distress with time. This device has not been approved by the U.S. Food and Drug Administration (FDA).

For patients enrolled in this study, the study doctor or study staff will give non-invasive electrical stimulation to measure response. Depending on what study group, the study team may apply this stimulation several times at one (Phase 1) or two (Phase 2) separate time points approximately 2 hours apart (when GCS would normally be collected as part of clinical care). In addition to GCS using normal physical stimulation, the study team will test responses to electrical stimulation. To do this, electrodes (special wired stickers that conduct electricity) will be placed on the forehead, finger, and toe. Stimulation will be applied to one area at a time by connecting the electrode to a stimulator. For each physical and electrical stimulation, response will be measured (such as flinching, opening eyes, making sounds, etc.). The goal is to create electrical stimulation patterns that cause the same response as the physical exam without causing any physical damage.

A video recording will also be taken of the participant's telemetry unit (the screen showing their heart rate and other vital signs throughout the study. This video, in addition to the information from the participant's medical record, is to make sure that there are no unexpected changes in vital signs during the study. The participant will not be visible on this video.

Inclusion Criteria:

1. Patient is admitted to the Barrow Neurological Institute's neuro ICU
2. Patient is in a comatose state, which is defined as a patient who is both non-responsive and has a GCS eye or motor response sub-score that requires noxious stimulation
3. Age greater than or equal to 18 years
4. Patient has an available surrogate decision maker with the capacity to consent for participation in a research study

Exclusion Criteria:

1. A neurologic decline immediately prior to study participation that requires urgent or emergent workup or management*
2. Patients in whom the frequency or extent of neurologic assessments is being limited due to concern that noxious stimulation may provoke intracranial hypertension, cardiorespiratory instability, or other adverse events
3. Patients with an implantable or external pacemaker that is currently in use
4. Ongoing refractory cardiorespiratory instability
5. Pregnant females
6. Prisoners