A double indicator dilution technique for determining the mean cross-sectional area (CSA) of a blood vessel in vivo is presented. Analogous to the thermodilution method, dilution of hypertonic saline was measured by an electrical conductance technique. Because the change in conductance rather than absolute conductance was used to calculate CSA, pulsatile changes in shear rate of blood and conductance of surrounding tissues had no effect on the data. To calculate CSA from an ion mass balance, cardiac output was needed and estimated from the thermodilution curve using the same 'cold' (hypertonic) saline injection. The mean CSA, obtained from this double indicator dilution method (CSA(GD)), was compared with the CSA obtained from the intravascular ultrasound method (IVUS) in 44 paired observations in six piglets. The regression line is close to the line of identity (CSA(GD) = -1.83 + 1.06 · CSA(IVUS), r = 0.96). The difference between both CSAs was independent of the diameter of the vessel, on average -0.99 mm2 ± 2.64 mm2 (mean CSA(GD) = 46.84 ± 8.21 mm2, mean CSA(IVUS) = 47.82 ± 9.08 mm2) and not significant. The results show that the double indicator dilution method is a reliable technique for estimating the CSA of blood vessels in vivo.

Arteries, Conductance method, Conductivity, Double indicator dilution method, Intravascular ultrasound, Shear rate
dx.doi.org/10.1007/s004240050236, hdl.handle.net/1765/67918
Pfluegers Archiv: European journal of physiology
Department of Pulmonology

Kornet, L, Jansen, J.R.C, Gussenhoven, E.J, & Versprille, A. (1996). Determination of the mean cross-sectional area of the thoracic aorta using a double indicator dilution technique. Pfluegers Archiv: European journal of physiology, 432(6), 1069–1073. doi:10.1007/s004240050236