Carbon dioxide volume and intra-abdominal pressure determination before the creation of a pneumoperitoneum

Laparoscopic surgery generally is regarded as a safe procedure when a preset pressure is used in the carbon dioxide insufflator. However, a fixed pressure setting is not appropriate when insufflating a very large or a very small abdomen. Presently, extrapolation from the commonly used 15 mm Hg to an appropriate and safe pressure cannot be easily determined except by a crude trial and error method. We developed an anthropometric formula to calculate the total abdominal cavity capacity and the corresponding pressure necessary to obtain safe pneumoperitoneum. This anthropometric formula calculates the total abdominal capacity by measuring one diameter from the symphysis pubis to the xyphoid bone, a second diameter as half the initial measurement, and a third diameter by dividing the waist measurement (minus an estimated percentage of body fat) and dividing that product by pi. The product of the three diameters is then multiplied by a constant (K = 0.5). We studied prospectively 20 patients whose indications for laparoscopic surgery necessitated creation of a pneumoperitoneum. The patients were divided into two groups: group A (n = 10), patients who were observed with the intra-abdominal pressure fixed at 15 mm Hg while recording the amount of distension produced in the abdominal cavity during creation of the pneumoperitoneum; and group B (n = 10) in whom pneumoperitoneum was obtained based on the initial volume of carbon dioxide-insufflation previously calculated using our formula. Based on our observations, we conclude that this anthropometric formula can be used successfully in predicting a safe level of insufflation in relation to the patient's size.