Diaphragmatic Ultrasound

Abstract

The diaphragm functions as the main muscle of respiration. In addition to phrenic nerve injury in the setting of congenital heart surgery, critical illness neuromyopathy and ventilator-induced diaphragmatic dysfunction are increasingly recognized contributors of diaphragmatic dysfunction in critically ill neonates and children. Diaphragmatic dysfunction is associated with prolonged mechanical ventilation, increased risk of nosocomial infection, increased length of intensive care unit and hospital stay, poorer functional outcomes, and increased mortality. A wide spectrum of clinical manifestations makes the recognition of diaphragmatic dysfunction challenging, especially in the setting of mechanical ventilation. In light of this, there has been great interest in using ultrasound for diaphragm assessment, employing parameters such as diaphragm thickness, diaphragm excursion and diaphragm thickening fraction to assess for diaphragm atrophy, paresis, and contractile strength. In particular, diaphragm ultrasound may guide the titration of mechanical ventilation and predict the success of extubation. In addition, there are an increasing number of ultrasonographic techniques proposed to assess diaphragm function, such as tissue doppler imaging, speckle tracking imaging, shear wave elastography or combined diaphragm, lung, and cardiac ultrasound. Diaphragm ultrasound is a promising technique for assessing diaphragm function and is a useful adjunct for the systematic evaluation of the critically ill patient.