Respiratory Mechanics

Pneumoperitoneum and Trendelenburg position are unavoidable in laparoscopic surgery and are known to have adverse effects on intraoperative respiratory mechanics and hemodynamics. These conditions increase the risk of ventilator-induced lung injury (VILI) and highlight the importance of lung-protective ventilation strategies. vNOTES (Vaginal Natural Orifice Transluminal Endoscopic Surgery) is a minimally invasive technique that requires less Trendelenburg tilt and lower insufflation pressures compared to conventional laparoscopic surgery, and may therefore offer a more favorable intraoperative profile. This prospective, observational, single-center, parallel-group cohort study aims to compare respiratory mechanics parameters (Ppeak, Pplateau, DP, MPtot, MPdyn, Crs) and hemodynamic parameters (MAP, HR, vasopressor requirement) between vNOTES (n=15) and laparoscopic gynecological surgery (n=15) groups at four intraoperative time points.

Right ventricular failure (RVF) is a common complication to cardiac surgery, which is associated to mortality, kidney failure, stroke, prolonged mechanical ventilation and ICU stay. The right ventricle is particularly vulnerable to an increased afterload. By increasing pulmonary vascular resistance (PVR), atelectasis might mitigate a negative effect on the right ventricle. Recruitment maneuvers have been shown to resolve atelectasis and improve hemodynamics by increasing cardiac output and lowering PVR. However these maneuvers transiently raise airway pressures, which in turn increases right ventricular afterload, a situation often poorly tolerated by patients with RVF. Prone position is used in patients with respiratory failure and has been shown to decrease mortality in patients with ARDS. Prone position decreases atelectasis and moves ventilation dorsally. In ARDS it also seems to mediate beneficial hemodynamic effects such as an increase in cardiac output and a decrease in PVR. The investigators hypothesis is that prone position early after cardiac surgery will increase cardiac output by recruitment of atelectasis and thereby decrease PVR.

This study aims to evaluate peak airway pressure and respiratory mechanics during pressure-regulated volume control (PRVC) ventilation in patients undergoing elective laparoscopic abdominal surgery. Pneumoperitoneum and patient positioning during laparoscopic procedures can significantly affect respiratory mechanics, including airway pressures and lung compliance. The study will assess changes in peak airway pressure, dynamic compliance, and other ventilatory parameters during different intraoperative phases. The findings are expected to provide insights into optimizing ventilatory strategies to improve patient safety and minimize ventilator-associated complications during laparoscopic surgery.

Study Synopsis This protocol is formatted for ClinicalTrials.gov-style registration and manuscript-facing documentation. It is based on the uploaded Turkish ethics protocol and keeps the original core design: comparison of low-flow and minimal-flow sevoflurane anesthesia in robot-assisted laparoscopic radical prostatectomy. Background and Rationale Robot-assisted laparoscopic radical prostatectomy (RALRP) is increasingly preferred for localized prostate cancer because of lower blood loss, reduced transfusion requirements, shorter hospitalization, and lower complication rates compared with open surgery. However, RALRP requires carbon dioxide pneumoperitoneum and steep Trendelenburg positioning, both of which may adversely affect respiratory mechanics, gas exchange, and hemodynamic stability. Low-flow and minimal-flow anesthesia may improve humidification and warming of inspired gases, reduce inhalational agent consumption, decrease environmental waste, and potentially lower overall cost. Despite these theoretical and practical advantages, evidence remains limited regarding the physiologic safety and performance of minimal-flow sevoflurane anesthesia during long robotic pelvic surgery performed under pneumoperitoneum and steep Trendelenburg positioning. Accordingly, this randomized prospective trial will compare low-flow (1 L/min) and minimal-flow (0.5 L/min) sevoflurane anesthesia during RALRP with respect to respiratory parameters, arterial blood gas values, intraoperative oxygenation variables, anesthetic consumption, and selected postoperative biochemical markers.

One-lung ventilation (OLV) is commonly used during thoracic surgery but may negatively affect lung mechanics and gas exchange. Different ventilation strategies are used during OLV, and their effects on respiratory parameters remain an important clinical concern. Flow-controlled ventilation (FCV) is a newer ventilation mode that allows precise control of inspiratory and expiratory flow, potentially improving lung mechanics and gas exchange. Volume-controlled ventilation (VCV) is a widely used conventional ventilation strategy during thoracic anesthesia. The FCVOLVent study is a multicenter, prospective observational study designed to compare the effects of FCV and VCV during one-lung ventilation in adult patients undergoing thoracic surgery. Patients will be ventilated with either FCV or VCV as part of routine clinical practice. The study aims to evaluate respiratory mechanics and oxygenation parameters, including the PaO₂/FiO₂ ratio, airway pressures, lung compliance, and mechanical power during surgery. Data will be collected at predefined time points during one-lung ventilation. The results of this study are expected to provide real-world clinical evidence on the potential advantages and limitations of flow-controlled ventilation compared with volume-controlled ventilation during one-lung ventilation.

Inhalational anesthetics, when used in abdominal surgery, offer advantages of lung protection and reduced alveolar inflammation. There is little literature, however, in the comparative use of sevoflurane versus desflurane anesthesia in patients undergoing abdominal robotic-assisted surgery and their effects on lung mechanics.