[Measurement of the heart minute volume by means of the ether dilution method]

Ethyl ether dissolved in saline has been used as an indicator for measuring cardiac output in patients with various congenital and acquired valvular heart diseases without shunts. The solution was infused at a constant rate into the superior vena cava. By means of a simultaneous rebreathing maneuver it was possible to determine the ether concentration of the mixed venous blood and hence the dilution factor. Comparative measurements with the direct Fick method revealed a satisfactory accuracy of the ether dilution method (r = 0.94), which does not require sampling and analysis of mixed venous and arterial blood.