Ultrasound assessment of abdominal respiratory muscles during ventilator weaning: A scoping review

Background Ultrasound assessment of respiratory muscles has gained relevance as a bedside tool during weaning from mechanical ventilation. While most research has focused on the diaphragm, the abdominal respiratory muscles play an important role in expiratory mechanics, cough effectiveness, and airway protection during the transition to spontaneous breathing. However, the extent and characteristics of the evidence supporting abdominal muscle ultrasound in this context remain unclear. Methods A scoping review was conducted in accordance with the Joanna Briggs Institute methodological framework and reported in accordance with the PRISMA extension for Scoping Reviews (PRISMA-ScR). Searches were performed in PubMed, Embase (Ovid), Scopus, the Cochrane Library, Web of Science, ScienceDirect, and Epistemonikos from database inception to May 30, 2026. Original studies evaluating ultrasound assessment of abdominal respiratory muscles in adult patients undergoing weaning or extubation from invasive mechanical ventilation were included. Study selection and data extraction were performed independently by two reviewers, and findings were synthesized descriptively. Results Four prospective observational studies were included, encompassing 203 adult patients receiving invasive mechanical ventilation. Ultrasound assessment focused primarily on abdominal muscle thickness and, in two studies, on thickening fraction during coughing. Considerable heterogeneity was observed in ultrasound protocols, timing of measurements, and definitions of weaning or extubation success. Conclusions Evidence on abdominal muscle ultrasound during ventilator weaning is limited and heterogeneous. Although this approach may provide complementary physiological information, current data are insufficient to support routine clinical use. Further standardized studies are needed to better define its role in weaning and extubation assessment.