Abstract
INTRODUCTION: Mechanical ventilation is indicated for the management of acute respiratory failure. The primary responsibility of an intensivist is to render optimal mechanical ventilation and to decide when to wean the patient off the ventilator. The diaphragm is the major muscle of inspiration and its timely contraction and shortening will facilitate extubation. Diaphragmatic dysfunction is quite prevalent in the ICU setting. SBT is defined as one of the most significant tests to determine if patients can be successfully extubated and weaned from mechanical ventilation. Imaging the diaphragm with ultrasound can be done either by measuring the excursion of the diaphragm (DE) or by measuring the contractility of the diaphragm muscle by diaphragm thickening fraction (DTF). This study is aimed to evaluate the usefulness of diaphragmatic parameters, along with the standard extubation parameters, to predict extubation outcome. OBJECTIVES: PRIMARY OBJECTIVE: To evaluate the diagnostic accuracy of parameters obtained from diaphragmatic ultrasonography (DTF and DE) in predicting extubation outcome. SECONDARY OBJECTIVE: To compare diaphragmatic parameters with standard extubation parameters (RR, exhaled TV and Rapid Shallowing Breathing Index) in predicting extubation outcome. MATERIALS AND METHODS: STUDY SETTING: Department of Critical Care Medicine. STUDY DESIGN: Prospective Observational study. STUDY POPULATION: Patients admitted in MDICU who are subjected to mechanical ventilation for atleast 24 hours with normal performance status before disease onset (pre-illness frailty score < 3). INCLUSION CRITERIA: Age > 18 years. Conscious oriented and able to tolerate SBT for 2 hours. Absence of fever in last 24 hours. Minimal tracheobronchial secretions and effective cough reflex. EXCLUSION CRITERIA: Patients with: Diastolic dysfunction, Spinal cord injury, Pneumothorax. Arrhythmias and hemodynamic instability. Thoracotomy/Abdominal surgery, chest tube/chest injuries, pleural lesions or pleurodesis. Pregnancy, neuromuscular disease. RESULTS: As per results of interim analysis of study conducted in 40 patients, diaphragmatic excursion and diaphragmatic thickening fraction in patients who underwent SBT were significantly higher among those who were successfully extubated than failed extubation differing by a mean difference of 5.406mm (t = 5.252, p< 0.001) and 16.781% (t = 7.213, p< 0.001) respectively. DISCUSSIONS: Interim analysis revealed that among 40 patients studied, 80% (32)were successfully extubated as in similar studies, for instance, Ali and Mohamad, measured DT and DE to predict weaning outcome and the cut off values were mean DTF > 30% and DE > 1.5 cm. Utility as a feasible bedside screening tool along with RSBI could increase the accuracy. Worsening of diaphragmatic function was found to be associated with poor outcome. Determination of cut off value in this study requires further exploration. Study among subgroups is essential to utilize as an adjunct screening tool.