Usefulness of Thoraco-Abdominal Synchrony Assessment in Hospitalized COPD Exacerbations Using Respiratory Inductance Plethysmography—A Pilot Study

Background/Objectives: Thoraco-abdominal asynchrony (TAA) is a key mechanical consequence of severe chronic obstructive pulmonary disease (COPD), particularly during acute exacerbations (AECOPD), when dynamic hyperinflation and diaphragmatic dysfunction impair the coordination between rib cage and abdominal motion. Continuous, non-invasive monitoring of respiratory mechanics may provide valuable information on clinical evolution during hospitalization. This study aimed to evaluate Global Phase Delay (GPD) as a longitudinal marker of TAA in hospitalized AECOPD patients and to explore its ability to reflect disease severity and short-term clinical evolution using repeated measurements obtained with thoracic and abdominal respiratory belts using respiratory inductance plethysmography (RIP). Methods: We conducted an observational longitudinal study in hospitalized adults with AECOPD. Respiratory inductance plethysmography signals were recorded daily over four consecutive days using thoracic and abdominal RIP belts. Five-breath sequences were analyzed to derive GPD, phase angle, and loop rotation direction through automated MATLAB processing. Clinical data included demographics, lung function, blood gases, dyspnea severity, and need for intermediate respiratory care unit (IRCU) admission. Temporal changes in TAA indices and subgroup differences (FEV1 < 35%, IRCU admission) were assessed using repeated-measures ANOVA. Results: Twenty-one patients were included. On admission, mean absolute GPD was 49 ± 58°, with larger delays observed in patients with more severe airflow limitation and in those requiring IRCU support. During hospitalization, GPD showed a significant reduction over time (p < 0.05), particularly in these subgroups, indicating progressive improvement in thoraco-abdominal synchrony. Directional analysis of GPD revealed heterogeneous patterns consistent with different underlying mechanical behaviors. Conclusions: Serial assessment of TAA using respiratory bands and GPD provides clinically meaningful information on the evolution of respiratory mechanics during AECOPD hospitalization. This approach may support bedside monitoring and help track patient response to treatment, offering potential value for individualized respiratory management.