Diaphragm is a fundamental respiratory muscle whose dysfunction is common in critically ill patients. In recent years ultrasonography has emerged as a new method for assessment of diaphragmatic function and is considered better than other methods. Diaphragmatic ultrasound is a non invasive, cost effective, safe and easy to perform technique that allows a morphological and functional evaluation of diaphragm in real time and can be repeated at the bedside.

Two diaphragm sonographic features are associated with the outcome of weaning; the diaphragmatic excursion which measures the distance that the diaphragm is able to move during the respiratory cycle and the diaphragm thickening fraction which reflects the change in the thickness of the diaphragm during a respiratory effort.

Neurally adjusted ventilator assist, a mode of ventilation was first described in 1998 by Sinderby et al. It is a mode of ventilator that detects diaphragmatic electrical activity via an adapted nasogastric tube and uses this diaphragmatic electrical activity to drive the ventilator. The diaphragmatic electrical activity (EAdi) offers an insight into a patient’s respiratory drive and neural demand for ventilatory support. Most of the studies on NAVA are in newborns where NAVA has shown reduced patient ventilator asynchrony, better gas exchange and reduced respiratory muscle load.

A sizeable number of our ICU patients are ventilated for prolonged periods and many of them have neuromuscular weakness. In this background we wanted to study diaphragmatic function during NAVA mode of ventilation in patients who have been on prolonged mechanical ventilation. We would like to explore if NAVA mode of ventilation would lead to an improvement in diaphragm thickness fraction and excursion of diaphragm in such patients.

Following approval by the Institutional Ethics Committee, the study would be conducted in 25 adult patients (18-65yrs) of either sex in ICU having prolonged ventilation (>7 days), after taking written and informed consent from the patient’s relatives. The study would be completed in a period of 18 months.