Background: A correlation between atypical recurrences and minimally-invasive surgery has been suggested in case of urothelial cancer; however, few data are available on the role of pneumoperitoneum in terms of gas flow and intra-abdominal pressure. The objective of the study is to analyze the impact of CO2 pneumoperitoneum variation on an inert material as surrogate of neoplastic cells. Material and Methods: We designed an experimental model mimicking pneumoperitoneum in three settings: sealed flow (no leakage), pulsatile flow (alternating efflux and influx), and continuous flow (AirSeal® insufflator). Each experiment was characterized by a predetermined gas flow and pressure, trocar distance, and position from the particles. Hounsfield density (HD) variation in the areas of interest was measured as index of graphite powder dispersion. A Linear Regression Model was used to measure the correlation between modifiable variables and HD. Results: HD was lower in the pulsatile compared to both the sealed and continuous flows (p < 0.03). On multivariate analysis for sealed setting, flow and total gas liters delivered (i.e., gas leakage) were inversely and independently related to HD (all p < 0.03). In pulsatile setting, trocar position, trocar distance, and gas flow independently predicted HD (all p < 0.03). In continuous setting, gas pressure was directly and independently related to HD (p = 0.004) due to decreased pneumoperitoneum stability and increased CO2 liters delivered. In case of inflow trocar positioned laterally to the particles, low flow (1 L/min), or low pressure (8 mmHg), HD values recorded in the three settings were all overlapping (all p > 0.05). Conclusions: Flow and pressure setting, inflow trocar distance and contiguity from the tumor, and pneumoperitoneum stability may be all crucial components in minimally invasive surgery. In vivo, these variables should be considered as potential risk factors for tumor cells spread within the abdominal cavity. Clinical Trial Registration number: NCT01740011.
Keywords: laparoscopy; pneumoperitoneum; robotics; surgical oncology; urothelial cancer.