Muscle Force Assessment in the Intensive Care Unit and in Primary Myopathies

Overview

The primary aim of the project is to apply the non-invasive stimulated muscle force assessment system to i) intensive care unit patients and ii) patients with primary myopathy or subclinic myopathy (e.g., Duchenne muscular dystrophy, Myotonia, MH). The investigators will use this new methodology of force assessment to phenotype patients weakness during their illnesses (depict typical force pattern) and monitor recovery periods, or disease progression, respectively. This new system will be evaluated until the year 2018. The investigators will determine variables of isometric skeletal muscle force. These systems should serve as force monitoring tools and help to guide therapies.

A force measuring system similar to one employed in previous studies will be redesigned with a new stimulator system and leg support system. This new, small, light and portable measurement system accurately measures patients' muscle forces. The system produces repeatable results. Over a long-time time period, this system will be applied to ICU patients and patients with primary myopathies, e.g. muscular dystrophy Duchenne or myotonias, and their ankle dorsiflexor isometric torques measured after electrical peroneal nerve stimulation. Torques will be amplified and converted into electrical signals by a Whetstone bridge, and data will be stored on a computer (LabView system). Stimulated torque responses will be obtained regularly, and subsequently the individualized curves will be determined. Electromyogram will be performed at each recording session. For all subjects possible, the investigators will continue to monitor their stimulated muscle forces during their recovery periods or disease progression. Type of data: Variables of isometric skeletal muscle contractions, such as peak torques, contraction and relaxation times and torque latencies. To find an assumed difference of 50% in strength, at least 30 individuals (power 0.9) are required. Values will be compared to patients voluntary forces, determined by Muscle Research Council (MRC) and Manual Muscle Test (MMT) scores. Additionally, skin resistances of edema patients will by determined employing a twitch stimulator and an oscilloscope. We are interested whether edema (fluid) changes tissue resistance. Data are required to redesign the new stimulation unit of the muscle force measuring system.