ICU CONNECT: Study Comparing EMG in Healthy Volunteers and ICU Patients.

This study is testing whether a non-invasive nerve monitoring device (TetraGraph) can accurately detect early signs of ICU-acquired weakness by comparing readings from the device with standard nerve conduction/EMG tests done by a specialist to see if they match. They will focus on muscle response signals in the hand and leg over about 10 days in three groups: healthy volunteers, ICU patients who are not on ventilators, and ICU patients who are on ventilators.

Inclusion Criteria: * Cohort 1: Healthy volunteers Inclusion criteria: * Subjects must be \> 18 years old and \< 90 years old. * Subjects must consent to participate. Cohort 2: Non-intubated critically ill patients Inclusion criteria: * Subjects may be male or female. * Subjects must be \> 18 years old and \< 90 years old. * Subjects must have a POA or next of kin who is able to consent (for those in the ICU and who are unable to consent themselves). Cohort 3: Intubated critically ill patients Inclusion criteria: * Subjects may be male or female. * Subjects must be \> 18 years old and \< 90 years old. * Subjects must have a POA or next of kin who is able to consent (for those in the ICU and who are unable to consent themselves). * For the Subjects in the ICU that are intubated, they must be planned to be intubated for at least 24 hours. * Subjects must be intubated for no longer than ≥ 72 hours before enrollment. Exclusion Criteria: * Cohort 1: Healthy volunteers Exclusion criteria: * Subjects with previous paralysis or neuromuscular disease. * Subjects with spinal cord or brain injuries that impact motor function. * Subjects with an allergy to clinical adhesive or hydrogel. Cohort 2: Non-intubated critically ill patients Exclusion criteria: * Subjects with previous paralysis or neuromuscular diseases. * Subjects with previous peripheral nerve injuries to the tested limbs. * Subjects with spinal cord or brain injuries (including stroke) that impact motor function. * Subjects without a POA or next of kin for those patients that are unable to consent themselves. * Subjects with an allergy to clinical adhesive or hydrogel. Cohort 3: Intubated critically ill patients Exclusion criteria: * Subjects with previous paralysis or neuromuscular disease * Subjects with previous peripheral nerve injuries to the tested limbs. * Subjects with spinal cord or brain injuries that impact motor function. * Subjects without a POA or next of kin for those patients that are in the intubated arm. * Subjects with intubations expected to last less than 24 hours. * Subjects who have already been intubated for \> 72 hours. * Subjects with an allergy to clinical adhesive or hydrogel.