Late Breaking Abstract - Combining Phase-Resolved Functional Lung (PREFUL)-MRI and advanced CPET to uncover the underpinnings of exertional gas exchange inefficiency in COPD

<bold>Background:</bold> Exposing the severity and topographic distribution of exertional ventilation (V)/perfusion (Q) heterogeneity—a major cause of "wasted" ventilation in the physiological dead space—is paramount to advancing our understanding of the genesis of activity-related dyspnea. <bold>Aim:</bold> To assess the feasibility of a novel pulmonary functional imaging-physiology platform designed to investigate V/Q mismatching at rest and exercise. <bold>Methods:</bold> 13 subjects (7 with COPD and mild obstruction) underwent supine CPET with alveolar (_alv) VD by breath-by-breath volumetric capnography, repeated twice at an MRI facility (3 T Magnetom Prisma™, Siemens). Noncontrast, free-breathing PREFUL-MRI provided dynamic V and Q maps. <bold>Results:</bold> We obtained technically adequate and reproducible exercise PREFUL data (ICC= 0.91-0.99; <italic>p</italic><0.01). Patients exhibited higher exercise ventilation/CO₂ output and VD_alv than controls. These findings were associated with increased Q deficits relative to V, e.g., exercise Q deficit percent (QDP)= 27.4 ± 12.7% vs. 17.8 ± 4.7%; one-tailed p=0.05 (illustrative subjects in <bold>Figure</bold>; VDP= V deficit percent). <fig><object-id>erj;64/suppl_68/OA2879/F1</object-id><object-id>F1</object-id><object-id>F1</object-id><graphic></graphic></fig> <bold>Conclusions:</bold> We successfully amalgamated PREFUL to advanced CPET, creating an innovative platform to provide unique insights into the underpinning of gas exchange inefficiency and excess exertional ventilation in cardiopulmonary diseases. <bold>Supported by a CIHR Grant</bold>