High intra- and postoperative oxygen concentration (80%, as opposed to 30% oxygen) has been shown to reduce the rate of wound infection by more than 50%. Therefore, the protocol implemented high intraoperative oxygen concentrations for all patients this trial. However, within the first 500 enrolled patients a recent trial reported a better outcome for patients with low perioperative oxygen concentrations. Although that trial was less well controlled and underpowered, the conflicting evidence indicates that additional study is needed. We will therefore simultaneously test the hypothesis that supplemental oxygen reduces infection risk.