The Role of Diaphragmatic Rapid Shallow Breathing Index and Maximum Inspiratory Pressure in Predicting Outcome of Weaning From Mechanical Ventilation

Abstract Background Mechanical ventilation is the defining event of intensive care unit (ICU) management. It is a lifesaving intervention in patients with acute respiratory failure and whose spontaneous ventilation is inadequate for subsequent development of life threatening hypoxia and/or respiratory acidosis. Many physicians simply look at the patient’s ability to tolerate a spontaneous breathing trial (SBT) without distress through the respiratory rate (RR) and TV during the SBT. The RR/TV ratio, i.e., the rapid shallow breathing index (RSBI), one of the most used clinical indices to predict weaning outcome, reflects the balance between mechanical load posed on the inspiratory muscles and the inspiratory muscles ability to face it during the weaning attempt. However, RSBI was found to have both variable sensitivity and specificity for predicting weaning outcome. Although the diaphragm plays a fundamental role in generating TV in healthy subjects, if the diaphragmatic efficiency is impaired the accessory inspiratory muscles mild contribute to the ventilation for a limited period of time, for example during a SBT. However, since they are by far less efficient and more fatigable than the diaphragm, their exhaustion was likely lead to weaning failure in subsequent hours. Hence, the contribution of the accessory muscles to TV could compromise the diagnostic accuracy of the RSBI by masking the underlying diaphragmatic dysfunction. Aim of the Work To assess the accuracy of Diaphragmatic Rapid shallow breathing index and Maximum inspiratory pressure in predicting the outcome of weaning from mechanical ventilation. Patients and Methods The study was conducted at Ain Shams University Hospitals over 6 months on Patients who were mechanically ventilated for more than 48 hrs who were ready for weaning. Inclusion Criteria Patients intubated & mechanically ventilated for more than 48 hrs. Patients at their first SBT.Patients with adequate cough reflex. Patients fulfilling criteria of readiness for weaning from mechanical ventilation after resolution of cause of respiratory failure: Patients with score ranging between -1 and +1 on the Richmond Agitation and sedation scale (RASS). Exclusion criteria Age < 18 yrs. Patients with thoracotomy, pneumothorax, or pneumomediastinum. Patients with presence of flail chest or rib fractures. Patients with neuromuscular disease. Use of muscle-paralyzing agents within 48 hours before the study. History or new detection of paralysis or paradoxical movement of a single hemi diaphragm on diaphragmatic ultrasonography. Pregnant females. Unconscious noncooperative patients. Patients with intra-abdominal hypertension, Long term steroid therapy. Results I- Distribution of the studied patients regarding final outcome. II- Demographic data. III. Causes of MV. IV- Days on MV. V- Patients’ data and characteristics before start of weaning trial. VI- SBT Ventilator Breathing pattern after 30 min. VII- Study predictors. Conclusion D-RSBI is a new and promising tool that is superior to the traditional RSBI in predicting weaning outcome also MIP provides appreciated data with greater accuracy to assess inspiratory muscle strength and predicting weaning success in mechanically ventilated patients. Recommendations We could recommend the measurement of MIP and DRSBI as weaning predictors should be an integral part of evaluation of patients plan for weaning from MV. All intensivists should be acquitted with the use of U/S in the evaluation of diaphragmatic function.