Weaning failure and respiratory muscle function: What has been done and what can be improved?

INTRODUCTION: Respiratory muscle dysfunction, being a common cause of weaning failure, is strongly associated with prolonged mechanical ventilation (MV) and prolonged stay in intensive care units. Inspiratory muscle training (IMT) has been described as an important contributor to the treatment of respiratory muscle dysfunction in critically ill patients. Its effectiveness is however yet controversial.

OBJECTIVE: To discuss evidence for assessment of readiness and the effectiveness of interventions for liberation from MV, with special attention to the role of IMT.

METHODS: PubMed, LILACS, PEDro and Web of Science were searched for papers of assessment and treatment of patients who failed liberation from MV after at least one attempt published in English or Portuguese until June 2016.

RESULTS: Weaning predictors are related to weaning success (86%-100% for sensitivity and 7%-69% for specificity) and work of breathing (73%-100% for sensitivity and 56%-100% for specificity). Spontaneous breathing trials (SBT), noninvasive MV and early mobilization have been reported to improve weaning outcomes. Two modalities of IMT were identified in five selected studies: 1) adjustment of ventilator trigger sensitivity 2) inspiratory threshold loading. Both IMT training modalities promoted significant increases in respiratory muscle strength. IMT with threshold loading showed positive effect on endurance compared to control.

CONCLUSION: Methods to indentify respiratory muscle weakness in critically ill patients are feasible and described as indexes that show good accuracy. Individualized and supervised rehabilitation programs including IMT, SBT, noninvasive MV and early mobilization should be encouraged in patients with inspiratory muscle weakness.