On the abdominal pressure volume relationship

During insufflation of the abdomen to create a pneumoperitoneum for laparoscopy, both intra abdominal pressure and insufflated volume can be measured and are used to calculate the abdominal pressure-volume relationship. First, an accurate, linear relationship was identified using a mathematical model with an elastance, E, or its reciprocal the compliance C and with a pressure at zero volume, PV0. This function was stable and could be used to describe the abdominal characteristics of patients. With these characteristics the effects of drugs, position, ventilation can be evaluated. Leakage or absorption of CO2 did not affect the measurements in a second study. In a third study the minimal amount of data needed to determine the parameters of the mathematical model was identified. Three pressure-volume measurements were sufficient to describe all cases.