Saturation of respiratory strain during robotic hysterectomy in obese women with endometrial cancer.

To evaluate intraoperative ventilatory mechanics during robotic-assisted hysterectomy in obese women with endometrial cancer and introduce the concept of a physiologic "ceiling effect" in respiratory strain. We conducted a retrospective cohort study of 89 women with biopsy-confirmed endometrial cancer who underwent robotic-assisted total hysterectomy between 2011 and 2015. Intraoperative ventilatory parameters, including plateau airway pressure and static lung compliance, were recorded at five-minute intervals. Each patient's peak plateau pressure was identified to calculate static compliance and estimate maximum ventilatory strain. Patients were stratified by body mass index (BMI), and ventilatory parameters were compared across BMI categories at baseline (post-induction, supine) and during steep Trendelenburg positioning with carbon dioxide pneumoperitoneum. At baseline, increasing BMI was significantly associated with higher plateau airway pressure and lower static compliance. For example, plateau pressure increased from 18.6 ± 3.4 cm of water (cm H₂O) in patients with BMI less than 30 kg per square meter to 25.9 ± 3.3 cm H₂O in those with BMI greater than or equal to 50 (p < 0.001). However, following Trendelenburg positioning with pneumoperitoneum, peak plateau pressures converged across BMI categories, averaging 35.0 ± 3.3 cm H₂O (p = 0.167). Static compliance also converged across BMI strata, averaging 17.2 ± 4.2 ml per cm H₂O (p = 0.129). Pulmonary complications occurred in 4.5% of patients, with no cases of barotrauma or prolonged mechanical ventilation. Intraoperative ventilatory strain appears driven primarily by surgical positioning and pneumoperitoneum, rather than obesity alone. These findings support the feasibility and safety of robotic-assisted hysterectomy across a wide range of body mass index values and introduce the novel concept of a physiologic ceiling effect in ventilatory stress.