In a series of experiments it was demonstrated that adhesion formation decreased by 50% when 0.7-1% of oxygen was added to the CO2 pneumoperitoneum. Adding 2-4% of oxygen to the CO2 pneumoperitoneum completely prevented this effect. This observation is consistent with the oxygen tensions known to induce hypoxia inducible factor (HIF) and with the normal physiologic peripheral partial oxygen tension around 20-40 mm Hg. (6) In addition, CO2 resorbtion was profoundly affected by adding 2-4% of oxygen in our rabbit model. (7) From these studies we concluded that during CO2 pneumoperitoneum the progressively increasing resorbtion of CO2 is completely prevented by adding 2-4% of oxygen.