 Background: A high inspiratory oxygen fraction FiO2 0.80 has been linked to prevention of surgical site infection, but the Danish randomized clinical multicenter trial, the PROXI trial, found no difference in frequency of surgical site infection. In fact, long-term mortality was significantly increased with a hazards ratio of 1.30 in patients receiving 80 oxygen, and this appeared to be statistically significant in patients undergoing cancer surgery, but not in non-cancer patients. 