Contemporary assessment of diaphragm function using bedside ultrasonography in the intensive care unit: New techniques and applications

Assessing the diaphragm function is part of the management of critically-ill patients with respiratory failure either at admission or over the course of intensive care unit (ICU) stay.Ultrasonography is the only non-invasive imaging technique to assess directly the diaphragmatic function at bedside.Advanced ultrasound-based techniques have emerged for better assessment of diaphragm structure and function.This narrative review aims to provide an overview of the contemporary use of conventional and advanced ultrasonographic techniques to evaluate diaphragm structure and function in the ICU patients.We searched PubMed/MEDLINE and Scopus for original research articles and recent reviews focusing on diaphragm evaluation by ultrasonography techniques, exclusively conducted in adult critically-ill patients.Terms related to diaphragm ultrasound, mechanical ventilation and novel diaphragmatic ultrasound techniques were used.Overall, conventional diaphragmatic ultrasonography provides an opportunity to evaluate the function of the diaphragm non-invasively by assessing the following parameters: Diaphragmatic excursion (the caudal inspiratory movement of the diaphragm), diaphragm muscle thickness and thickening fraction (the percentage of inspiratory thickening of the diaphragm).Apart from the above indices, analyzing diaphragmatic kinetics has been found to be useful in different clinical settings.Advanced ultrasonography techniques such as speckle tracking imaging and ultrasound shear wave elastography have emerged to provide new insights into assessment of diaphragmatic structure and function.In conclusion, both conventional and advanced ultrasonography-based techniques used in the ICU provide useful information regarding the structure and function of the diaphragm for both baseline assessment and respiratory monitoring purposes.