Evaluation of the Effects on Carbon Dioxide (paCO2) of a New Oronasal Mask in Patients With Severe COPD Exacerbation Requiring Non-Invasive Mechanical Ventilation

Non-invasive ventilation (NIV) is considered the gold standard treatment, in combination with medical therapy, for patients with respiratory acidosis secondary to Chronic Obstructive Pulmonary Disease (COPD). The choice of interface is a key factor in the success of NIV. A new oronasal mask, designed to improve CO2 washout (OptiNIV, Fisher & Paykel Healthcare, New Zealand), has recently been introduced to the market. Experimental data show that this interface, with a unique design separating airflow between the patient's mouth and nose, enhances gas flow at the end of expiration towards the oropharynx and subsequently out through the nostrils. This design facilitates the removal of CO2-rich air from the upper airways via dedicated ventilation ports located at the front of the mask, thereby optimizing CO2 clearance and dead space ventilation, which improves ventilatory efficiency.

This single-center, crossover study aims to investigate the effects of a new oronasal mask used during non-invasive ventilation (NIV) in COPD patients experiencing respiratory acidosis following an exacerbation. The objective is to assess whether the clinical benefits, specifically the reduction of PaCO₂ levels, are greater with the new mask compared to a traditional one. To minimize confounding factors affecting carbon dioxide washout, the new mask (OptiNIV, Fisher & Paykel Healthcare, New Zealand) will be compared to a mask of similar size, internal volume, and technical features (Visairo, Fisher & Paykel Healthcare, New Zealand), differing only in the presence of a separated airflow between the mouth and nose. This study holds significant clinical relevance, as no data are currently available on the use of the OptiNIV mask in patients with acute respiratory acidosis secondary to COPD exacerbation. The results could lead to optimized carbon dioxide clearance and improved ventilatory efficiency in managing patients with severe COPD exacerbations.

The study population consists of patients with respiratory acidosis secondary to COPD exacerbation who require non-invasive ventilation (NIV) and are admitted to the Respiratory and Critical Care Unit at the IRCCS AOU of Bologna, Policlinico S. Orsola. Patients meeting eligibility criteria will be randomly assigned (1:1) to two consecutive 60-minute NIV sessions using a traditional oronasal mask (Visairo) and an optimized mask (OptiNIV), following a crossover design. The sequence of mask use will be randomly assigned by the randomization list. NIV will be delivered with the same ventilator (ASTRAL 150 - ResMed Europe) using a single-limb circuit and pressure support mode, adjusting FiO₂ to maintain SpO₂ between 88-92%. Ventilator settings (IPAP, EPAP, triggers, rise time, Ti min, Ti max) will be set according to clinical practice but kept constant between sessions.

A 30-minute washout period with Venturi mask oxygen therapy will separate the two sessions, aiming to maintain SpO₂ between 88-92%. At the end of the washout, transcutaneous CO₂ (PtCO₂) will be measured; if this value is within ±2 mmHg of baseline, patient will proceed to the second session; otherwise, the washout will be extended up to 60 minutes. Including the washout, the total study duration per patient will not exceed 3 hours.

Inclusion criteria

• Age ≥ 18 years
• Informed consent obtained
• Patients with COPD and acute hypoxemic-hypercapnic respiratory failure (pH < 7.35, PaO₂ < 60 mmHg, PaCO₂ > 45 mmHg) requiring non-invasive mechanical ventilation.

Exclusion criteria

• BMI ≥ 30 kg/m²
• Obstructive sleep apnea syndrome
• Neuromuscular diseases or chest wall pathologies
• Need for intubation and invasive mechanical ventilation during exacerbation
• Use of home non-invasive mechanical ventilation or CPAP
• Contraindications for NIV
• Cognitive disorders that may interfere with adherence to treatments
• Patients with active and unstable coronary artery disease
• Previous esophageal surgery, known esophageal stenosis, or any other condition that could put the patient at risk during the placement of the respiratory mechanics probe