Muscle Function and Muscle Ultrasound in ICU

Overview

The objective of intensive care therapists is to be able to detect as early as possible the muscle weakness acquired in intensive care, in order to implement curative strategies such as adapted nutrition and early rehabilitation. Various diagnostic tools are available for this purpose. To evaluate muscle mass, CT and MRI remain the gold standard but are difficult to implement in routine practice in ICU and are extremely expensive and can generate radiation for the patient. Functional muscle evaluation is based on different voluntary tests which are not all able to predict muscle weakness acquired in ICU. In addition, some of the voluntary tests are expensive and require expert staff for practice and interpretation of results. In addition, a muscle test such as MRC, although having an intraclass coefficient of 0.94, has little predictive value on clinical parameters such as mechanical ventilation duration and is not associated with mortality in the ward. However, it remains the test of choice to define a ICUAW with a threshold value of 48/60 points. Dynamometry is a tool for measuring muscle strength. The patient is asked to perform a short and intense maximal muscular effort against manual or instrumental resistance. The limb segments must not move, it is an isometric effort. The most common measurement in intensive care units is the dynamometric grip force, called "handgrip". In ICU, the patient may have touble with awareness, arousal or even comprehension, which will lead to biases in the evaluation of the motor force. Ultrasound is a tool available in ICU and the muscle component can be assessed qualitatively or quantitatively without the patient's participation. Several studies have also demonstrated that muscle ultrasound is capable of reliably detecting pathological changes, particularly when repeated. Muscle ultrasound could thus help identify patients at higher risk of prolonged complications. Nevertheless, this technique lacks standardization and normative criteria (patient position, probe position, type and number of measurements, target muscle, etc.). The main objective is to show that the dynamometric force relative to ultrasound thickness of several muscle groups (arm flexors/knee extensors/foot lifters) is correlated with manual MRC testing in intensive care unit (ICU) patients

When the patient will be under invasive ventilatory support and coma, and will present the inclusion criteria, the investigator will perform ultrasound measurements of muscle thickness on four muscle groups: * Shoulder Side muscular compartment * Anterior Arm muscular compartment * Anterior thigh muscular compartment * Antero-lateral leg muscular compartment The ultrasound measurements will be made once a day each weekday, until the discharge from ICU. Ultrasound measurements will be stopped if the patient's condition deteriorates and the ICU team chooses to limit active therapy. If the patient condition get better, the investigator will perform the first volitional muscle function assessment, as soon as the patient Glasgow scale will score 15/15: 1. Medical Research Council sum score (MRC-ss) 2. Dynamometric strength assessment with the muscular groups used for the MRC-ss Then the volitional muscle assessment will be made once every 3 days, until patient discharges from ICU.