Can the direct Fick method using cardiac catheterization safely and effectively measure cardiac output in normal subjects under various physiological conditions?
The direct Fick method via cardiac catheterization is a safe and feasible technique for serial measurements of cardiac output in humans.
In the Fick method of estimating cardiac output (C.O.), where C.O. (litres/min.)=oxygen consumption (c.c./min.) divided by arterio-venous oxygen difference (c.c./litre), the measure- ment of the numerator can easily be made by spirometric methods. Hitherto the measurement of the arterio-venous oxygen difference in man by respiratory techniques has proved difficult and laborious, and it has not been possible to make frequent serial observations. The difficulties seem to be largely overcome by the method of cardiac catheterization first introduced by Forsmann (1929) and developed by Over 394 catheterizations can now be recorded without any accidents (Forsmann (1), de Carvolho and Moniz (48), Ameuille et al. (60+), Cournand et al. ( The catheter has been left in situ as long as 24 hours (Cournand et al.), but the present authors have limited the period to one hour in normal subjects. Clotting does not occur on the unwettable surface of the catheter, and a slow drip of 3-8 per cent sodium citrate through the catheter prevents any thrombus formation round the hole at the tip.
McMichael et al. (1944) studied this question.