ELTGOL (Slow Expiration with the Opened Glottis in the Lateral posture) is an airway clearance technique performed in the lateral decubitus position. This technique focuses on optimizing ventilation of the infralateral lung (when the subject is lying in the lateral posture) to enhance local air-liquid interaction. Previous studies on ventilation differences between the infra- and supralateral lungs were conducted on healthy, young, male subjects, without the application of thoracic or abdominal pressure. This study aimed to assess ventilation distribution in right lateral recumbency in patients with chronic obstructive pulmonary disease (COPD), as well as healthy individuals, and investigate the impact of thoracic and abdominal manual pressures during ELTGOL on ventilation distribution.