Dynamic pressure measurement for detection of blood access stenosis

A novel method for detection of access failure has been developed. It is based on the continuous evaluation of pre-pump arterial and venous pressure in the extracorporeal circuit. Knowing the flow resistance properties of the arterial and venous branches of the extracorporeal circuit from in-vitro measurements and the height differences, calculating the fistula pressure dynamically is possible. The fistula pressure allows identification of access failure as has been shown by other authors. The dynamic measurement however allows identification of bad needle placement. Dynamic measurement at different flow rates and comparison with static measurements allow for the identification of intra-access stenosis. The mathematical algorithm is described and pressure-flow curves for two sets of extracorporeal circuits are shown. In-vivo examples show a "normal" fistula and a fistula with intra-access stenosis.