CHARACTERIZATION OF CHRONIC FATIGUE IN INTENSIVE CARE UNIT: ROLE OF THE NEUROMUSCULAR FUNCTIONThesis by Djahid Kennouche

Supervisors: Pr Guillaume Millet, LIBM - Pr Jérôme Morel  CHU Saint Etienne - Dr Thomas Lapole, LIBM - Dr Julien Gondin, CNRS

It has been reported that 75% of Intensive care unit (ICU) survivors feel suffer from chronic. This fatigue is one of the most common and debilitating symptoms which prevents the practice of physical activity for prolonged periods following discharge, and has a negative impact on the rehabilitation process. Indeed, it has been widely reported that patients who stayed in ICU for prolonged periods report persistent fatigue for months to years after ICU discharge. This chronic fatigue affects their quality of life by decreasing their capacity to perform simple tasks of daily life.

The aim of the present project is to determine whether deteriorated neuromuscular function (i.e. increased fatigability) contributes to chronic fatigue in ICU survivors. Most of the studies on this topic are limited due to the fact that measurements used were non-multidimensional. Because the causes of this feeling are multi-dimensional, a large battery of tests will allow us to better understand the origin of chronic fatigue. A better knowledge of chronic fatigue etiology will allow to optimize rehabilitation treatments to decrease the severity/persistence of chronic fatigue and in turn improve quality of life.

Even if deteriorated resistance to acute fatigue has been suggested as a possible cause, the fact that patients wake up feeling fatigued in the morning shows that this cannot fully explain this symptom. Due to this complexity of interpretation, only a complete analysis of the causes of fatigue can permit the understanding of chronic fatigue in patients who have had a prolonged stay in ICU.

The first part of the project aim to characterize the neuromuscular part of chronic fatigue reported by ICU survivors. A multiparametric approach will consider the multifactorial dimension of chronic fatigue, particularly the different possible neuromuscular origins (i.e. central or peripheral origin)

A better knowledge of the etiology of fatigue could optimize the early rehabilitation of patients and thus reduce perceived chronic fatigue and improve their quality of life.

In addition, neuromyopathy (pathology involving the PNS and / or muscle) acquired during ICU stay is often diagnosed late because it is based on a clinical evaluation requiring a conscious and cooperating patient. Electrical or magnetic stimulation along the path of the motor nerve to generate muscle contraction and thus measure muscle strength can be an interesting alternative for early assessment in bed of the still sedated patient.

The second objective is to validate the reproducibility of a force measurement platform that can be used in the patient's bed. This has already been done on healthy volunteers with interesting results, but very few authors have been able to demonstrate the validity of this method in sedated patient.