Model to Determine Resistance and Leakage-Dependent Flow on Flow Performance of Laparoscopic Insufflators to Predict Gas Flow Rate of Cannulas

Abstract

Study Objective To characterize insufflator CO 2 gas flow performance to predict gas flow rate with standard cannulas. Design Prospective, observational study (Canadian Task Force classification II-2). Setting Laboratory of university clinic. Patients None. Intervention Gas flow (L/min) and average pressure (mm Hg) inside an abdomen model were measured at 12 mm Hg nominal pressure during steady state. Measurements and Main Results An abdomen box model for laboratory measurements was designed with different entrance and exit diameters simulated with hole disks from 0.5 to 7.6 mm. With a computer-based data-acquisition model, five insufflators (Olympus 9L and 16L, Storz 10L and 30L, HiTec 16L) were evaluated with 150 disk combinations. Flow performance in three-dimensional profiles showed different flow rates for all insufflators depending on resistance and leakage combination, maximum flow rate, and insufflation principle. Maximum flow was reached without resistance only in the insufflation system at high leakage rates. Low-pressure principle is more affected by resistance. Cannula flow rates at 12 mm Hg and 15 L/minute leakage ranged from 4.8 (Origin) to 6.0 L/minute (Storz HiCap) for Olympus 9-L insufflators and from 5.4 (Origin) to 15.10 L/minute (Storz HiCap) for Storz 30-L Thermoflator. Reusable cannulas have more flow efficacy than disposable ones, especially with high-flow insufflators, because of larger diameter at insufflation supply. Conclusion Gas flow depends not only on maximum flow of insufflators but also on resistance of cannulas and leakage rate. With this model it is possible to predict the real, available flow of insufflator-cannula combinations for the first time. Improved resistance of all components can save insufflation time.