The impact of obesity on pulmonary deterioration in patients undergoing robotic-assisted laparoscopic prostatectomy

Obesity affects respiratory and hemodynamic function in anesthetized patients. The aim of this study was to evaluate the influence of the body mass index (BMI) on pulmonary changes in a permanent 45° steep Trendelenburg position (STP) during robotic-assisted laparoscopic prostatectomy (RALP). 51 patients undergoing RALP under standardized anesthesia were included. Perioperative pulmonary function and oxygenation were measured in awake patients (T₀), 20 min after the induction of anesthesia (T₁), after insufflation of the abdomen in supine position (T₂), after 30 min in STP (T₃), when controlling Santorini's plexus in STP (T₄), before awakening while supine (T₅), and after 45 min in the recovery room (T₆). Patient-specific and time-dependent factor on ventilation and predicted peak inspiratory pressure (PIP), driving pressure (P_driv) and lung compliance (LC) in a linear regression model were calculated. PIP and P_driv increased significantly after induction of capnoperitoneum (T_2-4) (p < 0.0001). In univariate mixed effects models, BMI was found to be a significant predictor for PIP and P_driv increase and LC decrease. Obese patients a BMI > 31 kg/m² reached critical PIP values ≥ 35 cmH₂O. Postoperative oxygenation represented by the PaO₂/FiO₂ ratio was significantly decreased compared to T₀ (p < 0.0001). Obesity in combination with STP and capnoperitoneum during RALP has a profound effect on pulmonary function. Increased PIP and P_driv and decreased LC are directly correlated with a high BMI. Changes in PIP, P_driv and LC during RALP may be predicted in relation to patient's BMI for consideration in the preoperative setting. Trial registration number Z-2014-0387-6. Registered on 8 July 2014.