Description

Timing is critical for proper weaning for patients undergoing mechanical ventilation; if this is performed prematurely complications can include increased cardiovascular and respiratory stress, CO2 retention and hypoxemia. However, unnecessary delay in weaning can also cause a number of side-effects.Weaning outcomes have been assessed by several indices. Variables such as minute ventilation, Pao2/Fio2, rapid shallow breathing index and static compliance have all been used, with variable predictive values. Previous studies have proved that diaphragmatic dysfunction is one of the main etiologies of difficult weaning, because the diaphragm progressively weakens with mechanical ventilation.Methods used to assess diaphragm function, such as fluoroscopy, phrenic nerve stimulation, measurement of trans-diaphragmatic pressure and dynamic magnetic resonance imaging of the diaphragm, all have limitations. These include ionizing radiation exposure, low availability, invasiveness and necessity for patient transportation. Conversely, the use of ultrasound is safe, non-invasive, avoids radiation side-effects, and is available at the bedside.The aim of this study is to assess the validity of the diaphragmatic thickening Fraction measured by ultrasound as a predictor for successful weaning from mechanical ventilation.