Diagnosing Intensive Care Unit (ICU) Acquired Weakness

The goal of this study is to develop a non-invasive test to diagnose intensive care unit (ICU) acquired weakness that can be administered to both responsive and non-responsive patients. Study participation will involve the measurement of muscle fatigue during a single 30 minute session. Skeletal muscle will be stimulated with an FDA approved clinical electrical stimulator and accelerations will be passively recorded with an accelerometer.

The primary purpose of this study is to develop a procedure to identify intensive care unit (ICU) acquired weakness. This condition occurs in a subset of people admitted into the ICU, and is associated with a 30% increased risk of death before discharge from the ICU. There are currently major limitations in the ability to diagnose ICU acquired weakness, making it difficult to study. The goal is to develop a non-invasive test that can be administered to both responsive and non-responsive patients. The current proposal will focus on replicating the results of previous research using motion detecting accelerometers to measure fatigue in human skeletal muscles. This study is designed to test out the procedures in patients who have been transferred from the ICU to a lower level of care so that follow-on studies can be designed to help mitigate this condition in the ICU.

Participants with a score less than 48 on the Medical Research Council (MRC) Scale will be classified as having ICU acquired weakness. All participants will have their skeletal muscles tested with a clinical electrical stimulator.

Participants with a score of 48 or greater on the Medical Research Council (MRC) Scale will be classified as not having ICU acquired weakness. All participants will have their skeletal muscles tested with a clinical electrical stimulator.

Conductive electrodes will be on the skin at each end of the tested muscle(s). Each subject will have two target muscle groups tested (extensor carpi radialis longus, and tibialis anterior). Each muscle will be stimulated at three separate stimulation frequencies (2 Hz, 4 Hz, and 6Hz) over 3 minutes each, for a total of 9 minutes of stimulation per muscle. The clinical electrical stimulator will deliver mild electrical stimulations to the muscle (20-100 mA).

The highest acceleration over a single muscle twitch will be used as the peak acceleration. Peak acceleration will be measured in acceleration in number of times gravity (g). Higher twitch acceleration is a better response.

The highest acceleration over a single muscle twitch will be used as the peak acceleration. Peak acceleration will be measured in acceleration in number of times gravity (g). Higher twitch acceleration is a better response.

The time, in seconds, until peak acceleration is reached will be assessed at 2, 4 and 6 Hz. There is not a reference range for the time to peak force and at this time it is unclear if a shorter or longer time to peak force indicates a more desirable state of health.

The time, in seconds, until peak acceleration is reached will be assessed. There is not a reference range for the time to peak force and at this time it is unclear if a shorter or longer time to peak force indicates a more desirable state of health.

End acceleration is the twitch acceleration averaged over 5 twitches over the last second of stable twitches within the stimulation period. A reference range has not yet been established for this measurement.

End acceleration is the twitch acceleration averaged over 5 twitches over the last second of stable twitches within the stimulation period. A reference range has not yet been established for this measurement.

Fatigue ratio is the ending acceleration divided by peak acceleration during a given stimulation period. A reference range has not yet been established for this measurement. A higher ratio indicates less change from maximum. A lower score would indicate worse outcome.

Fatigue ratio is the ending acceleration divided by peak acceleration during a given stimulation period. A reference range has not yet been established for this measurement.

Inclusion Criteria: Patients transferred from the ICU to a lower level of care within the past 7 days Mechanical ventilation for greater than 7 days while in the ICU Ability to understand English and provide written consent Exclusion Criteria: Vulnerable populations including: patients who are pregnant or prisoners Patients who are unable to understand English or provide written consent

Individual participant data that underlie the results reported in the publications will be available for sharing, after deidentification.

Data will be available for sharing beginning 9 months after article publication and ending 36 months following article publication.

Data will be available for sharing with investigators whose proposed used of the data has been approved for meta-analysis. Information regarding submitting proposals and accessing data will be available by contacting the study staff (contact information to be provided).