Abstract
Major surgery imposes physiological stress requiring coordinated adaptation of the cardiovascular, respiratory, hematological, and musculoskeletal systems. Conventional preoperative assessment remains essential but may underestimate heterogeneity in physiological reserve because resting measurements incompletely capture the response to increasing metabolic demand. Cardiopulmonary exercise testing (CPET) provides an integrated assessment of oxygen transport and utilization, linking pulmonary ventilation and gas exchange to cardiovascular performance and peripheral oxygen extraction.