In the experimental arm, at the conclusion of all surgical dissection and manipulation, the carbon dioxide insufflate will be exchanged with oxygen to generate a high intra-abdominal concentration. Oxygen will be infused for 15 seconds as CO2 is allowed to escape through the open trocars. In the control arm Co2 will be allowed to escape through the open trocar ports without any oxygen flush. Patients will receive a standardized operation as well as standard post-operative care and follow up.