Diaphragm Ultrasound in Weaning From Mechanical Ventilation

Difficult weaning from mechanical ventilation (MV) is a common problem in critically ill patients. Many parameters have been developed to aid weaning from MV such as P/F ratio (PO2/FiO2) and rapid shallow breathing index (respiratory rate/tidal volume); however, sensitivity and specificity for most variables are still variable in literature.

Diaphragmatic dysfunction is a common cause of weaning failure (2) however most of the traditional methods used for evaluation of diaphragmatic function (fluoroscopy, trans-diaphragmatic pressure measurement) are invasive and not available.

Ultrasound assessment of diaphragmatic function has been developed recently providing an easy and safe method for evaluation of diaphragmatic excursion and thickening. In this study we will evaluate the ability of the diaphragmatic function to predict weaning success in patients with abdominal sepsis.

After weaning, patients will be divided into two groups; group of successful weaning (group S) and group with failed weaning (group F) both groups will be compared as regards all clinical, laboratory, and ultrasonographic parameters recorded before weaning, further analysis will be done for patients with repeated trials of weaning (more than one trial or more than one week MV) and those with simple weaning (first time for weaning).

A 7-10 Mega Hertz linear ultrasound probe (Mindray machine) set to B mode, the diaphragm will be visualized by placing the transducer perpendicular to the chest wall, in the eighth or ninth intercostal space, between the anterior axillary and the midaxillary lines, to observe the zone of apposition of the muscle 0.5 to 2 cm below the costophrenic sinus.

The diaphragm thickness will be measured from the middle of the pleural line to the middle of the peritoneal line. Then, the diaphragmatic fraction thickening (DTF) will be calculated as percentage Diaphragmatic movement will be measured in all patients with a 3.5 Mega Hertz US probe placed over one of the lower intercostal spaces in the right anterior axillary line for the right diaphragm and the left midaxillary line for the left diaphragm.