This study is designed to investigate and compare the therapeutic effectiveness of digital interventional expiratory breath training versus conventional expiratory training using the PowerBreathe Medic device in improving functional lung capacity and quality of life among patients with clinically diagnosed Chronic Obstructive Pulmonary Disease (COPD). The primary objective is to determine the comparative efficacy of these two expiratory training approaches in optimizing pulmonary rehabilitation outcomes within this patient population. Furthermore, the study aims to evaluate the specific effects of digital interventional expiratory breath training on reducing dyspnea and enhancing expiratory muscle strength, as well as to assess its relative advantages over conventional expiratory devices in decreasing lung hyperinflation. The study also seeks to examine patient compliance and engagement associated with each intervention to better understand adherence and usability in a clinical rehabilitation setting. Primary outcome measures will include comprehensive pulmonary function assessments, specifically functional lung capacity and health-related quality of life using validated outcome measures. Secondary outcomes will involve the evaluation of dyspnea severity, improvements in expiratory muscle strength, reduction in lung hyperinflation, and assessment of patient compliance and engagement across both intervention groups. The findings from this study are expected to provide evidence-based insights to guide clinicians in selecting the most effective expiratory training modality for tailored pulmonary rehabilitation programs, thereby contributing to improved clinical outcomes and enhanced quality of life for individuals with COPD.