Comparison of FCV and VCV in One-Lung Ventilation

Detailed Description One-lung ventilation (OLV) is a fundamental anesthetic technique in thoracic surgery; however, it is frequently associated with impaired respiratory mechanics, ventilation-perfusion mismatch, and compromised gas exchange. Volume-controlled ventilation (VCV) is the most commonly used ventilation mode during OLV, but it may result in uneven gas distribution, higher peak airway pressures, and potential lung injury. Flow-controlled ventilation (FCV) is a novel ventilation mode characterized by constant and controlled inspiratory and expiratory flow, allowing precise regulation of airway pressures and lung volumes. Previous experimental and limited clinical data suggest that FCV may improve lung recruitment, optimize respiratory mechanics, and enhance gas exchange compared with conventional ventilation strategies. The FCVOLVent study is a multicenter, prospective observational study designed to compare the effects of FCV and VCV on respiratory mechanics and gas exchange in adult patients undergoing thoracic surgery requiring one-lung ventilation. Patients will be ventilated according to the ventilation strategy routinely used at each participating center, either FCV or VCV, without randomization or intervention beyond standard clinical practice. Primary outcomes include intraoperative respiratory mechanics parameters such as dynamic compliance, airway pressures, and driving pressure during OLV. Secondary outcomes include arterial blood gas variables, oxygenation indices, carbon dioxide elimination, and selected perioperative clinical parameters. Data will be collected at predefined time points during two-lung ventilation and one-lung ventilation phases. The study aims to provide real-world clinical evidence regarding the potential advantages and limitations of FCV compared with VCV in thoracic anesthesia practice. By evaluating ventilation strategies across multiple centers, the FCVOLVent study seeks to contribute to a better understanding of lung-protective ventilation approaches during one-lung ventilation and to inform future interventional trials in this field.

Inclusion Criteria Adult patients aged 18 years and older Patients undergoing thoracic surgery requiring one-lung ventilation (OLV) Requirement for one-lung ventilation for at least 30 minutes American Society of Anesthesiologists (ASA) physical status I-III Provision of written informed consent Patients ventilated with flow-controlled ventilation (FCV) or volume-controlled ventilation (VCV) as part of routine clinical practice Exclusion Criteria Requirement for emergency surgery History of untreated asthma High pulmonary risk, defined as predicted postoperative FEV₁ \< 20 mL/kg in males and \< 18 mL/kg in females High cardiac risk, including advanced cardiomyopathy with left ventricular ejection fraction \< 30% Body mass index (BMI) \> 35 kg/m² Contraindication to total intravenous anesthesia (TIVA) Evidence of pulmonary infection prior to surgery Presence of other significant pulmonary pathologies (e.g., tuberculosis, bullous lung disease, bronchiectasis) Severe COPD (GOLD stage III-IV) or significant restrictive lung disease Age \< 18 years or \> 80 years, or pregnancy ASA physical status IV or higher Uncontrolled arrhythmia or history of myocardial infarction within the past 3 months Inability to provide informed consent