A little physics improves abdominal insufflation. (Many Trocars and Port Sizes are Too Small).

NEW YORK -- Ignorance of the laws--of physics--is no excuse. But it is quite common among laparoscopists, and it leads to suboptimal abdominal insufflation, Dr. Volker Jacobs said at an international congress sponsored by the Society of Laparoendoscopic Surgeons.

"Most of the time, you are not even dose to getting the optimal flow from your insufflator," he said.

The reason? Many trocars and port sizes are too small in diameter to allow maximum flow The various components of an insufflation system cannot be randomly combined. Dr. Jacobs of the women's clinic at the Technical University of Munich believes that a lot of unnecessary purchases of expensive equipment and a lot of lost hours in the operating room could be avoided by finding better matches between trocars, Luer locks, and insufflators.

The diameter or caliber of the components in an insufflation system are the key variables, especially the caliber of the opening at the insufflation source and the caliber of the trocar. The point of smallest diameter--typically at the insufflation supply--is the rate limiting factor. "Double the diameter, and you increase gas flow exponentially, not linearly," Dr. Jacobs said.

Two similarly sized trocars can have a 10-fold variance in flow performance simply based on their calibers, he explained.

At 12 mm Hg, the standard insufflation pressure, most of the trocars in common use are not going to give flow rates much more than 9 L/min. regardless of what type of insufflator you are using. Add in the flow resistances and restrictions imposed by the optic unit that you insert into the trocar, and you cut the flow rate to as low as 1.5 L/min.

Suboptimal insufflation can result in prolonged operating times, not to mention a lot of surgeon frustration.