Fig. 1. Experimental protocol. All animals received sternotomy after complete hemodynamic monitoring. Cardiopulmonary bypass (CPB) was maintained for 2 h with completely unloaded beating heart. Continuous positive airway pressure was kept at 5 mbar during this time. CPB was removed, protamine matching the heparin dosage was administered, and 2 h of observation time followed. CO = carbon monoxide; SHAM = control group; SnPP IX = tin protoporphyrin IX.