Flow-Controlled Versus Volume-Controlled Ventilation in Bariatric Surgery

Comparison of Flow-Controlled and Volume-Controlled Ventilation During Bariatric Surgery: A Prospective Randomized Trial

This prospective trial aims to compare the effects of flow-controlled ventilation (FCV) and volume-controlled ventilation (VCV) on intraoperative airway pressures and oxygenation in bariatric surgery under general anesthesia. Obesity is associated with altered respiratory mechanics, reduced functional residual capacity, and increased airway pressures, making the selection of an optimal ventilation strategy particularly important in this patient population.

Adult patients aged 18-65 years with a body mass index ≥30 kg/m² and American Society of Anesthesiologists (ASA) physical status II-III will be allocated to receive either FCV or VCV as part of routine intraoperative mechanical ventilation. Ventilatory parameters, including peak and plateau airway pressures, pulmonary compliance, will be recorded at predefined intraoperative time points.

The primary endpoint of the study is the PaO₂ value measured at the 20th minute under an FiO₂ of 0.8-1.0.

By providing comparative data on respiratory mechanics and oxygenation, this study aims to contribute to the identification of lung-protective ventilation strategies and to optimize intraoperative ventilatory management in bariatric surgery.

Inclusion Criteria:

• Age between 18 and 65 years
• Body mass index (BMI) ≥ 30 kg/m²
• ASA physical status II-III

Exclusion Criteria:

• ASA physical status I or IV and above
• Known or previously diagnosed pulmonary disease
• Patients with severe preoperative pulmonary function impairment (e.g., FEV₁ < 50% predicted, severe restrictive or obstructive pathology)
• Patients with markedly altered lung anatomy or function due to prior major thoracic surgery
• Patients who were dependent on supplemental oxygen therapy in the preoperative period
• Refusal to participate in the study or inability to comply with study procedures