Cardiac output was determined by impedance cardiography (Q(imp)) and a rebreathing method (Q(reb)) during exercise of loads up to 90W. The correlation between Q(imp) and Q(reb) was generally good, but it was found in two of four subjects that Q(imp) was slightly lower than Q(reb) at the higher exercise levels. The regression equation for both Q values was: Q(imp)=0.91Q(reb)+0.25 (l/min, r=0.87, p<0.001).
