The Effect of BIPAP on Diaphragmatic Function

Chronic Obstructive Pulmonary Disease (COPD) is a progressive respiratory condition frequently complicated by chronic hypercapnic respiratory failure. In this population, long-term non-invasive ventilation with bilevel positive airway pressure (BiPAP) is widely prescribed to improve gas exchange, relieve symptoms, and reduce the risk of hospitalizations. However, its effects on diaphragm function, the main respiratory muscle, remain poorly understood. Diaphragm dysfunction in COPD has been associated with adverse outcomes including increased mortality, prolonged hospital stay, and higher readmission rates.

This prospective cohort study aims to evaluate the longitudinal impact of BiPAP treatment on diaphragm structure and function in patients with COPD and chronic hypercapnic respiratory failure. Eligible participants will be patients who are prescribed BiPAP therapy according to standard clinical indications. Diaphragm function will be assessed repeatedly using ultrasonography, which provides non-invasive and reliable measurements of diaphragm thickness at end-inspiration and end-expiration, thickening fraction (DTF), maximum contraction velocity, and maximum relaxation velocity. These measurements will be complemented by pulmonary function tests, respiratory muscle strength evaluations, and dyspnea assessment.

The primary outcome is the change in diaphragm ultrasound parameters (inspiratory thickness, expiratory thickness, thickening fraction, contraction velocity, and relaxation velocity) over the course of treatment. Early follow-up will occur at 6 weeks to assess short-term effects, while long-term follow-up at 12 months will provide insight into sustained adaptations to BiPAP therapy. Secondary outcomes include the frequency of hospital admissions and overall one-year survival.

By integrating functional, structural, and clinical outcomes, the study is expected to provide novel evidence on the role of non-invasive ventilation in modifying diaphragm performance. Findings may contribute to refining treatment strategies and optimizing long-term management of COPD patients with advanced respiratory failure.

Inclusion criteria

• Being between 40-80 years of age,
• Having a diagnosis of stable COPD for at least 1 year,
• Being in a stable phase (no acute exacerbation within the last 4 weeks),
• Meeting the GOLD 2025 A-B-E classification according to symptoms and exacerbation history,
• Having been initiated on BiPAP therapy with a clinical indication,
• Being willing to participate in the study and providing informed consent.

Exclusion criteria

• Pregnancy,
• Diaphragmatic paralysis,
• Neuromuscular and neurological diseases,
• Decompensated heart failure,
• Chest deformity,
• Acute exacerbation within the last month,
• Pneumothorax,
• Body mass index greater than 35 kg/m²,
• Long-term corticosteroid use,
• Chemotherapy,
• Active malignancy,
• Inability to cooperate,
• Thoracoabdominal surgery within the last 3 months.