Brief Summary People with severe chronic obstructive pulmonary disease (COPD) often have too much air trapped in their lungs (pulmonary hyperinflation). This makes it hard to breathe and reduces quality of life. This study tests whether a single session with a medical device called Simeox® can reduce the amount of air trapped in the lungs. Simeox® works by applying gentle intermittent negative pressure during exhalation to help air move out of the lungs more easily. Patients with severe or very severe COPD and documented hyperinflation will undergo lung function measurements before and immediately after a 20-minute Simeox® session. The main measurement is the change in residual volume (RV), which is the amount of air left in the lungs after a full exhalation. We will also measure changes in other lung volumes, breathlessness, and any side effects. This is a single-arm pilot study enrolling 23 patients at one center in Italy (ASST Lodi). The study is non-profit and has been approved by the Ethics Committee Comitato Etico Territoriale Lombardia 1 (CET Lombardia 1).

Detailed Description Pulmonary hyperinflation is a key pathophysiological feature of advanced chronic obstructive pulmonary disease (COPD), resulting from air trapping due to airflow obstruction and reduced elastic recoil. It is strongly associated with dyspnea, exercise intolerance, and impaired quality of life. Reducing residual volume (RV) is therefore a clinically meaningful therapeutic target in patients with severe and very severe COPD.

Simeox® is a CE-marked electro-medical device currently used in clinical practice for bronchial secretion drainage. It applies intermittent negative pressure at high frequency (6-12 Hertz, Hz) during the expiratory phase, with the aim of increasing expiratory flow velocity and promoting air mobilization. While the device is routinely used in patients with bronchial hypersecretion, its potential effect on static lung volumes in patients with hyperinflation - regardless of the presence of significant secretions - has not been systematically investigated.

This prospective, single-arm, non-controlled pilot study aims to explore the immediate effect of a single Simeox® session on RV in patients with severe or very severe COPD and documented pulmonary hyperinflation.

Study procedure:

Each participant undergoes baseline lung function assessment using spirometry and nitrogen wash-out (N₂ wash-out), followed by a single Simeox® treatment session lasting approximately 20 minutes (4 series of 10 tidal breathing cycles in a seated position, with rest breaks according to tolerance). During each breathing cycle, the patient performs slow controlled exhalations while the device applies high-frequency intermittent negative pressure modulated to the maximum tolerated intensity. Lung function measurements are repeated immediately after the session (within 30 minutes).

Safety monitoring:

Respiratory rate, heart rate, and peripheral oxygen saturation (SpO₂) are monitored throughout the session. Adverse events are recorded and classified by type, severity, and relationship to the treatment. Tolerability is assessed through subjective patient rating and dyspnea score variation.

Statistical analysis:

Pre- and post-intervention comparisons will be performed using a paired t-test or Wilcoxon signed-rank test depending on data distribution (significance level p < 0.05). Sample size was calculated based on a clinically meaningful RV reduction of 0.40 L (standard deviation, SD: 0.60 L), yielding a minimum of 21 patients (80% power, α = 0.05), with 23 patients planned to account for dropouts.

This pilot study will provide the methodological basis for designing a future randomized controlled trial (RCT) with a larger sample and longer follow-up.

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)

Individual participant data will not be shared, given the exploratory and pilot nature of the study, the small sample size (23 patients), and the need to protect participant privacy in accordance with Italian and European data protection regulations (GDPR). Aggregate results will be made publicly available through publication in a peer-reviewed journal and/or presentation at scientific conferences within 12 months of study completion, as required by the approving Ethics Committee (CET Lombardia 1).