Effect of Simeox® on Residual Volume in COPD Patients With Pulmonary Hyperinflation

Inclusion Criteria: * Age ≥ 18 years * Diagnosis of severe or very severe COPD (GOLD stage 3-4) * Documented pulmonary hyperinflation defined by at least one of the following criteria measured by nitrogen wash-out (N₂ wash-out): * Residual volume (RV) \> 150% of predicted * Functional residual capacity (FRC) \> 130% of predicted * Total lung capacity (TLC) \> 120% of predicted * RV/TLC ratio \> 40% * Clinical stability (no exacerbations in the 3 weeks prior to enrollment) * Patients for whom assessment of the effect of Simeox® on reduction of pulmonary hyperinflation is considered clinically appropriate, in the context of exploratory device use * Written informed consent Exclusion Criteria: * Active or recent pneumothorax (\< 6 weeks), predisposition to pneumothorax or pneumomediastinum, or known pleural fragility * Active or recent gross haemoptysis (\< 6 weeks) or active pulmonary haemorrhage * Haemodynamic instability * Unstable cardiovascular conditions, including: * Recent myocardial infarction * Unstable angina * Uncontrolled arrhythmias * Unstable heart failure * Recent cardiothoracic surgery (\< 3 months), including oesophageal surgery * Recent thoracic trauma or severe acute lung injury * Continuous mechanical ventilation, active need for inspiratory assistance, or tracheostomy * Neuromuscular diseases with respiratory muscle weakness * Inspiratory muscle weakness precluding increased respiratory effort * Oropharyngeal or oral muscle weakness * Inability to cough effectively, forcefully and autonomously * Severe restrictive lung disease (TLC \< 60% of predicted) * Airways at risk of aspiration (e.g. recent nasogastric tube feeding) * Uncontrolled gastro-oesophageal reflux disease (GERD)