Oxygenator was primed with 1.5L Plasma-Lyte and 5,000iu heparin at 8am for an off-pump case in the morning and then used for an emergency afternoon case. Sweep was increased to 10L/min for 2 hours to sigh the oxygenator prior to going on. This was turned back to 3.0L/min going onto bypass. Once commencing bypass, the FiO2 was at 80% with a pO2 of 9kPa and no significant colour change. The cross clamp had not been placed yet so the decision was made to come off bypass and perform an oxygenator changeout