Ultrasound-detected postoperative diaphragmatic dysfunction and its association with pulmonary complications. A systematic review and meta-analysis

Introduction: Postoperative diaphragmatic dysfunction (PDD) is a common complication following major surgeries, contributing to adverse clinical outcomes. Ultrasound-based assessment has emerged as the preferred method for evaluating PDD. We aimed to assess the association between PDD and postoperative pulmonary complications (PPCs) and their relationship with pneumonia. Methods: We systematically searched PubMed, Scopus, and Embase for clinical studies assessing PDD via ultrasound. The inclusion period ranged from January 10th, 2025, to March 20th, 2025. Two authors independently selected the investigations according to the following criteria: [1] observational study or randomized clinical trials enrolling adult patients undergoing cardiac, thoracic, or abdominal surgery [2] evaluation of PDD using diaphragmatic excursion (DE) or diaphragmatic thickening fraction (DTF) after surgery, and [3] report an association between PDD and PPCs or pneumonia as clinical outcomes. Preferred Reporting Items for Systematic Reviews and Meta-analysis (PRISMA) guidelines were followed. Two authors independently performed data extraction. The Methodological Index for Nonrandomized Studies (MINORS) assessed study quality. The primary outcome was the association between PDD and PPCs. The secondary outcomes evaluated prevalence of PDD and pneumonia as an individual component of PPCs when it was reported separately, and its association with PDD. Results: The systematic review included 19 studies, and six studies met the criteria for meta-analysis. PDD was significantly associated with higher odds of PPCs (OR 2.99, 95 % CI: 2.01-4.45) and pneumonia (OR 5.41, 95 % CI: 2.36-12.42). No significant publication bias was detected. Heterogeneity was low for both outcomes. Conclusion: Ultrasound-assessed postoperative diaphragmatic dysfunction is significantly associated with higher odds of postoperative pulmonary complications, including pneumonia, highlighting its clinical relevance at the bedside. PDD, assessed via ultrasound, is strongly associated with an increased risk of PPCs and pneumonia in postoperative patients. These findings underscore the importance of routine postoperative diaphragmatic assessment and the potential for targeted interventions to mitigate PDD-related complications. However, the current evidence is constrained by methodological variability and the absence of standardized diagnostic criteria. Future studies should focus on establishing consensus definitions for PDD and ensuring consistent assessment of key clinical outcomes.