How Nocturnal Hypoventilation Predicts Long-term Response to Non-invasive Ventilation in Hypercapnic COPD Patients

Role of Nocturnal Hypoventilation in Predicting the Long-Term Ventilatory Response in Hypercapnic COPD Patients Treated With Non-Invasive Ventilation: A Prospective Observational Study With Clinical, Functional, and Radiological Assessment

The study is an observational, single-center, prospective cohort study aiming to evaluate respiratory mechanics data, as well as clinical and functional parameters commonly used in clinical practice in patients with COPD and hypercapnic respiratory failure. The study population consists of patients with COPD and hypercapnia requiring NIV. The primary objective of the study is to evaluate the association between the reduction in partial pressure of carbon dioxide in arterial blood (PaCO₂) levels at 6 and 12 months after initiating non-invasive ventilation (NIV) and the presence of nocturnal hypoventilation detected at baseline in patients with COPD and chronic hypercapnia. Secondary objectives of this study are the evaluation of the following parameters measured at baseline and/or after 6 and 12 months of NIV treatment in patients with COPD and chronic hypercapnia:

• Magnitude of esophageal pressure swing during nocturnal monitoring.
• Diaphragm thickness and diaphragmatic thickening fraction assessed by thoracic ultrasound.
• Presence of overlap syndrome (COPD + OSA).
• Radiological classification of COPD subtypes to assess the association between radiological findings, functional profile, severity of nocturnal hypoventilation, and patterns of chronic hypercapnia.
• Respiratory functional parameters, including FEV₁, FVC, FEV₁/FVC ratio, carbon monoxide diffusion capacity (DLCO), and airway resistance (R5 and R20).
• Frequency of severe exacerbations and subsequent rehospitalizations during follow-up.
• Rate of compliance with respiratory treatment.

To date, the pathophysiological mechanisms underlying the development of persistent hypercapnia in patients with COPD are not completely understood. Likewise, reliable predictive markers capable of identifying both patients at risk of developing this condition and those who may derive the greatest benefit from long-term non-invasive ventilation (NIV) are still lacking. Early identification of a patient phenotype more responsive to this type of intervention could substantially reduce exacerbations, emergency department visits, hospitalizations, and associated healthcare costs, thereby improving the overall efficiency of the local healthcare system. The aim of this study is therefore to identify more accurate and earlier criteria to recognize patients with COPD and hypercapnic respiratory failure who may benefit from long-term non-invasive ventilatory support, through an integrated analysis of respiratory mechanics data and clinical and functional parameters commonly used in routine clinical practice.

The study population consists of patients with COPD and hypercapnic respiratory failure who require NIV and who are evaluated in the outpatient clinic and/or inpatient unit of the Respiratory and Critical Care Unit of the IRCCS AOU of Bologna. For these patients clinical, functional, and respiratory mechanics data will be collected. Data will be collected at the baseline visit-corresponding to the first visit at the OSAS Ventilated outpatient clinic or the first day of hospitalization in the Pneumology and Respiratory Intensive Care Unit-and during follow-up visits, scheduled according to routine clinical practice at 6 and 12 months after initiation of NIV treatment.

The total duration of the study will be 30 months, including 12 months for patient enrollment, 12 months of follow-up, and 6 months for data analysis.

A total of 25 patients will be included.

Inclusion Criteria:

• Age ≥ 18 years
• Patients with COPD and hypercapnia, defined as PaCO₂ > 50 mmHg either chronically or 4 weeks after an acute exacerbation requiring invasive or non-invasive mechanical ventilation
• Provision of informed consent

Exclusion Criteria:

• Progressive neurodegenerative diseases
• Diaphragmatic disorders
• Severe hemodynamic instability (>1 vasoactive agent for at least 24 hours)
• Acute coronary syndrome (unstable angina / myocardial infarction)
• Severe arrhythmias
• Presence of contraindications to NIV
• Cognitive impairment interfering with treatment adherence
• Active and unstable coronary artery disease
• Malignancies undergoing active treatment
• Patients already receiving home non-invasive mechanical ventilation