This study aims to test the accuracy of the total thoracic fluid content (TFC) measured by cardiometry can predict weaning failure. Area under receiver operating characteristic curve (AUROC) will be determined, sensitivity, specificity, and best cutoff value will be calculated for TFC in prediction of weaning failure.

Weaning from mechanical ventilation is a serious and challenging process in critical care practice. Weaning failure is associated with poor patient outcomes. Increased mortality in patients with failed weaning was due to development of complications related to re-intubation. Detection and correction of the cause of failed spontaneous breathing trial (SBT) helps the intensives to improve the outcome of the next trials.

Fluid overload and positive cumulative fluid balance is a risk factor of weaning failure in both cardiac and non-cardiac patients.

Many tools for prediction of lung congestion as a risk factor for weaning failure have been reported. The gold standard for detection of cardiac cause of weaning failure was pulmonary artery catheter. More simple tools had been investigated for detection of cardiac cause of weaning failure in patients with or without previous cardiac dysfunction such as extravascular lung water and B-natriuretic peptide (BNP) levels.

Although measurement of extravascular lung water is a reliable tool for prediction of cardiac cause of weaning failure, it has the disadvantage of the need of advanced monitor with invasive arterial line. Bioreactance is a new technology used for measurement of cardiac output and total thoracic fluid content (TFC). More recently, electrical velocimetry is a newer technology with good performance in cardiac output monitoring. The use of electrical velocimetry in measurement of TFC has the advantage of being non-invasive with no need for advanced skills. The aim of this work is to validate the use of TFC (measured by electrical velocimetry) in prediction of weaning outcome.

Inclusion Criteria:

• Patients aged 18 years or more scheduled for a spontaneous weaning trial (SBT) on pressure support ventilation.

Exclusion Criteria:

• Age < 18 years old.
• Pregnant patients.
• Neuromuscular disease (stroke, myasthenia gravis and Guillain-Barrésyndrome).
• Tracheostomy.

Patients aged 18 years or more scheduled for a spontaneous weaning trial (SBT) using pressure support ventilation.