Comparison of in vitro valve pressure drop results from different investigators

Steady-state pressure-drop vs flow-rate measurements on prosthetic valves have been shown to correlate well with mean cyclic pressure drops vs RMS flow rate during systolic ejection from pulsatile flow data. The use of steady-state data is therefore validated as a means of assessing performance characteristics. Pressure-drop results reported in the literature were compared for valves of the same size and manufacture. Significant differences were noted, which are attributed to: (a) different geometries in the region of the valves, (b) different approach flow conditions, (c) different placement of pressure measurement taps, and (d) different methods of pressure measurement. Differences in pressure drop were observed to vary by as much as a factor of five among different investigators. The exponent n in the relation delta p infinity Q" was also observed to vary, depending on the above factors. The reasons for and some quantitative calculations on the observed differences are presented here.