The Depth of the Pneumoperitoneum Determines the Safety of Primary Cannula Insertion

We assessed the anterior-to-posterior depth of pneumoperitoneum at various volumes and pressures, and the actual depth when a standard force was applied to the primary cannula in the umbilicus (equivalent to the normal force used). A 5-mm laparoscope was inserted through a suprapubic port and a depth gauge through the 10-mm intraumbilical port. All gas was initially removed from the abdomen, and the depth of the pneumoperitoneum was measured, with and without the standard force applied to the umbilical port, at incremental volumes and pressures up to 25 mm Hg. Our data strongly suggest that a 2- to 3-L pneumoperitoneum is inadequate in most cases, as the anterior abdominal wall will lie directly against bowel or omentum as soon as any force is applied to the umbilical port. The data also suggest that the pneumoperitoneum should be pressure limited and not volume limited. The pressure should be set at 25 mm Hg, as this gives an adequate pneumoperitoneum depth when the primary cannula is inserted, and hence a greater margin of safety.