Real-time shear wave ultrasound elastography: a new tool for the evaluation of diaphragm and limb muscle stiffness in critically ill patients

Aurelien Flatres,Aurelien Flatres,Aurelien Flatres,Aurelien Flatres,Pascal Etienne,Mathieu Amalric,Fanny Garnier,Yassir Aarab,Kada Klouche,Kada Klouche,Kada Klouche,Kada Klouche,Fanny Garnier,Yassir Aarab,Romaric Larcher,Romaric Larcher,Romaric Larcher,Romaric Larcher,Stefan Matecki,Samir Jaber,Samir Jaber,Samir Jaber,Samir Jaber,Yassir Aarab,Boris Jung,Boris Jung,Boris Jung,Boris Jung,Yassir Aarab,Gilles Subra,Gilles Subra,Gilles Subra,Gilles Subra,Nicolas Molinari,Nicolas Molinari,Pascal Etienne,Pascal Etienne,Fanny Garnier,Fanny Garnier,Stephanie Nougaret

doi:10.1186/s13054-020-2745-6

Abstract

BackgroundMuscle weakness following critical illness is the consequence of loss of muscle mass and alteration of muscle quality. It is associated with long-term disability. Ultrasonography is a reliable tool to quantify muscle mass, but studies that evaluate muscle quality at the critically ill bedside are lacking. Shear wave ultrasound elastography (SWE) provides spatial representation of soft tissue stiffness and measures of muscle quality. The reliability and reproducibility of SWE in critically ill patients has never been evaluated.MethodsTwo operators tested in healthy controls and in critically ill patients the intra- and inter-operator reliability of the SWE using transversal and longitudinal views of the diaphragm and limb muscles. Reliability was calculated using the intra-class correlation coefficient and a bootstrap sampling method assessed their consistency.ResultsWe collected 560 images. Longitudinal views of the diaphragm (ICC 0.83 [0.50–0.94]), the biceps brachii (ICC 0.88 [0.67–0.96]) and the rectus femoris (ICC 0.76 [0.34–0.91]) were the most reliable views in a training set of healthy controls. Intra-class correlation coefficient for inter-operator reproducibility and intra-operator reliability was above 0.9 for all muscles in a validation set of healthy controls. In critically ill patients, inter-operator reproducibility and intra-operator 1 and 2 reliability ICCs were respectively 0.92 [0.71–0.98], 0.93 [0.82–0.98] and 0.92 [0.81–0.98] for the diaphragm; 0.96 [0.86–0.99], 0.98 [0.94–0.99] and 0.99 [0.96–1] for the biceps brachii and 0.91 [0.51–0.98], 0.97 [0.93–0.99] and 0.99 [0.97–1] for the rectus femoris. The probability to reach intra-class correlation coefficient greater than 0.8 in a 10,000 bootstrap sampling for inter-operator reproducibility was respectively 81%, 84% and 78% for the diaphragm, the biceps brachii and the rectus femoris respectively.ConclusionsSWE is a reliable technique to evaluate limb muscles and the diaphragm in both healthy controls and in critically ill patients.Trial registrationThe study was registered (ClinicalTrial NCT03550222).

Highlights

Muscle weakness following critical illness is the consequence of loss of muscle mass and alteration of muscle quality
In the training set obtained from 16 healthy controls, we compared 192 Shear wave ultrasound elastography (SWE) measurements collected from transversal and longitudinal images in the diaphragm, the biceps brachii and the rectus femoris by the two operators
The training set allowed us to determine that the best interoperator reliability was obtained with the longitudinal views for the diaphragm and the biceps brachii

Summary

Introduction

Muscle weakness following critical illness is the consequence of loss of muscle mass and alteration of muscle quality. Following the intensive care unit (ICU) stay, the quality of life and return to pre-ICU admission daily activities are impaired [1,2,3]. Both diaphragm and limb muscles are affected [1, 4,5,6,7]. Diaphragm contractions during spontaneous breathing and passive stretch during mechanical ventilation may make ultrasonography more difficult to perform in the critically ill patients than in healthy controls able to block their breathing cycle

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Conclusion