Fig. 1

Illustration of the analysed pulse wave parameters

Visualization of the key parameters by an exemplary pulse wave (average of beats recorded in 7 seconds, non-fistula arm, patient No 44). In panel a the curve is normalized to a relative pressure amplitude of 1 and a wave length of 800 ms. Slope parameters are calculated as the mean slope in the characteristic four time sections as defined by the footpoint, the systolic peak, the dicrotic notch, the first diastolic inflection point and the end of diastole (time sections are illustrated in red, the characteristic points are indicated with black arrows, the mean slope is visualized by black straight lines between the characteristic points). The variable Slope2 is the mean slope in the second time section and calculated as the ratio of the increments of relative pressure ∆P and time ∆t (green straight lines). Likewise, the mean slopes are computed in time sections one, three and four. Thereafter Slope∑ is calculated as the sum of the four mean slopes. In panel b the same measurement is presented before normalization. The y-axis shows the volumetric change in the measuring cuff in order to maintain a constant cuff pressure of 10 mmHg below end diastolic blood pressure as compensation for bloodpressure changes during cardiac cycle. According to Boyle-Mariotte's law the values of volumetric change are directly proportional to the bloodpressure changes during cardiac cycle which are assessed by pulse wave analysis. AMP is the amplitude of the non-normalized averaged pulse wave.