Sonographic evaluation of the heart, lung and diaphragm during weaning from mechanically ventilated critically ill patients

Abstract

Mechanical ventilation is an essential therapy in the ICU, and a large percentage of the ICU patient population will need this therapy during their ICU stay. Weaning from mechanical ventilation remains to be a cumbersome process that occupies a large percentage of the total ventilation time of the patients. Failure to predict readiness for weaning from mechanical ventilation may result in prolonging mechanical ventilation or premature weaning resulting in complications. The weaning process remains to be a subjective decision made by the physician in charge of the patient. Multiple parameters and indices have been developed and studied over the years in order to improve and unify the weaning process and to try and develop a unified weaning indices, that is easily obtained and does not require invasive maneuvers or put that patient at risk to obtain, that could assess the patients’ respiratory system performance and readiness to be weaned from mechanical ventilation. Old respiratory indices and parameters, such as the respiratory rate, minute ventilation, rapid shallow breathing index, maximum inspiratory pressure, FiO2/PO2 ratio, tracheal occlusion pressure, partial pressure of arterial carbon dioxide, hemodynamics and oxygen saturation, still do not meet the required performance in evaluating the respiratory system performance and accurately predicting the patient’s readiness to be weaned and successfully extubated from invasive mechanical ventilation. Ultrasound represents a non invasive and feasible tool for detecting various indices involved in failure of mechanical ventilation including the heart, lung and diaphragm. Lung, diaphragm ultrasound, including diaphragm thickening fraction and excursion, and assessing diastolic dysfunction by echocardiography has been introduced as an assessment tool to detect and predict successful weaning from mechanical ventilation. They were initially studied on a small patient population number and compared to the traditional weaning indices and showed promising results.