Almost 20% of the patients in the intensive care unit (ICU) on mechanical ventilation (MV), experience difficult and prolonged weaning, even after thorough observation and application of the weaning criteria. Conventional methods like regular assessment of breathing frequency, minute ventilation, and negative inspiratory force have little impact in improving the decision of timing of successful extubation. RSBI has been accepted as a successful guide for correct timing of extubation with spontaneous breathing trials.

Diaphragmatic dysfunction being a common cause of weaning failure, needs to be assessed during weaning . Ultrasonography has emerged as a promising solution to overcome failed extubations and has been extensively studied over the past few years.  USG can easily allow direct visualization of the diaphragm and help us in assessing its contractility and functional efficacy, thus leading to better prediction of weaning outcome and post extubation distress and its cause.  Thus, we can gain reassurance over and above the traditional indices for successful weaning.

We formulated a hypothesis that ultrasound guided weaning of a patient from mechanical ventilation may decrease the chances of reintubation. This study aims to prospectively investigate the value of lung and diaphragmatic ultrasonography in the prediction of weaning outcomes and chances of reintubation in patients being weaned from mechanical ventilation and comparing them with the traditional indices for weaning, like RSBI.

SAMPLE SIZE: 100

With reference to a previous study(1), the prevalence was taken as 67%.

The formula for calculated sample size is given below:

n = (Z 1- α/2 )² x P(1-P)

                    d²

= (1.96)² x 0.67(1- 0.67)

                 0.01

= 84.937 =85

Where, Z_α/2 is the critical value of the Normal distribution at α/2 (e.g., α is 0.1 and the critical value is 1.96).

85 is the calculated minimum sample size.

METHODS:

·               All patients selected will be the ones already on mechanical ventilation via an endotracheal tube in situ.

·                Patients will be put to a SBT when they meet the weaning criteria. Patients will be put on Pressure Support/CPAP trial for half an hour. Failure of the weaning process shall be defined as a failed SBT or the need for reintubation/ NIV (non-invasive ventilatory support) within 48 hours following extubation , so all the patients included in the study will be observed for 48 hours after the SBT. The following weaning indices will be recorded for all patients during the SBT: Tidal volume (TV), Respiratory rate (RR), ABG: Po2, Spo2 % and Po2/Fio2, Rapid shallow breathing index: (RSBI (f/VT) = Respiratory rate/tidal volume.

·               Bedside ultrasound will be performed 20 minutes after initiation of SBT by a critical care consultant in the ICU, well versed with the use of bedside lung and abdominal ultrasonography and its interpretation. Initial USG will be done immediately after putting the patient on SBT to check the anatomy of the diaphragm and to rule out patients according to exclusion criteria. This will be followed by a complete diaphragmatic and lung USG after 20 minutes of initiation of SBT. Three readings shall be recorded for each USG index and an average value of the three recordings shall be used further.  After the extubation, all patients will be monitored for failed or successful weaning. Weaning will be considered successful if the patient did not require noninvasive or invasive ventilation within 48 hours of extubation. At the end of the study, the patients will be divided into two groups: successful group and failed group (re‑intubation within 48 h after extubation) according to their response to weaning trials.

The Diaphragmatic Excursion, Diaphragmatic Thickness Fraction %, diaphragmic contraction (DC), and LUSm( modified Lung Ultrasound Score) score measurements will be collected for each group and then will be correlated with RSBI.

·