RESUMO BACKGROUND AND OBJECTIVES: End-tidal carbon dioxide (P ET CO 2 ) not only reflects pulmonary ventilation but also carbon dioxide production (metabolism) and pulmonary blood supply (circulation). During constant metabolism and ventilation, P ET CO 2 reflects pulmonary blood perfusion, thus cardiac output (CO). This study aimed at evaluating the correlation between P E T C O 2 l e v e l s a n d C O d u r i n g c a r d i a c s u r g e r y wi t h cardiopulmonary bypass (CPB). METHODS: Participated in this study