Overview
Obesity adversely affects respiratory physiology by reducing lung volumes and compliance and increasing airway resistance and alveolar collapse. These effects are further aggravated by pneumoperitoneum during laparoscopic surgery, increasing the risk of impaired oxygenation and ventilator-induced lung injury (VILI).
Mechanical power (MP) reflects the total energy transferred to the respiratory system during mechanical ventilation and is influenced by tidal volume, respiratory rate, airway pressures, flow, and PEEP. Increased airway and driving pressures may contribute to higher mechanical power and lung injury, particularly in obese patients undergoing laparoscopic surgery.
This study aims to compare flow-controlled ventilation (FCV) and volume-controlled ventilation with autoflow (VC-AF) in obese patients undergoing laparoscopic surgery in terms of airway pressures, driving pressure, and mechanical power. The investigators hypothesize that FCV may reduce airway pressures, driving pressure, and mechanical power compared with VC-AF, potentially decreasing the risk of VILI. The effect of FCV on oxygenation will also be evaluated as a secondary outcome.
Description
Obesity is an important risk factor that adversely affects respiratory physiology during the perioperative period, leading to reduced lung volumes, increased airway resistance, and early alveolar collapse. During laparoscopic surgery, pneumoperitoneum and increased intra-abdominal pressure further reduce lung volumes, decrease lung compliance, and promote alveolar collapse. Therefore, obese patients represent a high-risk population for both impaired oxygenation and ventilator-induced lung injury (VILI) during the perioperative period.
Ventilator-induced lung injury is associated not only with high airway pressures and tidal volumes but also with the total amount of energy transferred to the lungs during mechanical ventilation. In this context, mechanical power is considered a comprehensive parameter reflecting the combined effects of tidal volume, respiratory rate, airway pressures, flow, and PEEP. Mechanical power is calculated using ventilation parameters according to the following formula:
MP = 0.098 × RR × VT (L) × (PIP - 0.5 × Driving Pressure) Airway pressures, particularly driving pressure, are key components of mechanical power, and increases in these parameters are closely associated with lung injury.
In obese patients undergoing ventilation during pneumoperitoneum, increased intrathoracic pressure and reduced lung compliance may result in higher airway pressures. This may increase mechanical power and consequently increase the risk of lung injury.
The present study aims to compare the effects of flow-controlled ventilation (FCV) and volume-controlled ventilation with autoflow (VC-AF) on airway pressures, driving pressure, and mechanical power in obese patients undergoing laparoscopic surgery. The investigators hypothesize that, compared with VC-AF, FCV may reduce mechanical power by generating lower airway pressures and driving pressures, thereby potentially reducing the risk of ventilator-induced lung injury. In addition, whether FCV improves oxygenation by providing more homogeneous alveolar ventilation will be evaluated as a secondary outcome.
Eligibility
Inclusion Criteria:
Age ≥18 years Body mass index (BMI) ≥30 kg/m² American Society of Anesthesiologists (ASA) Physical Status I-III Scheduled to undergo elective laparoscopic surgery under general anesthesia
Exclusion Criteria:
Pregnancy Emergency surgery Presence of a cardiac pacemaker Chronic obstructive pulmonary disease (COPD)
