The Shift of the Arterial Pulse-Wave Foot on Recordings With a Rising or Falling Baseline

Recordings of arterial pulse waves often appear on a rising or falling baseline. This causes a shift in the position of the pulse-wave foot as compared to its position on the horizontal base-line. The magnitude of this shift is unknown. Workers therefore tend to disregard pulse-wave recordings with sloping baselines when measuring foot-to-foot pulse-wave velocities. A formula was derived that allows an estimation of the upper limit of the shift in the position of the pulse-wave foot to be tm = l000n/157 ms, where n = b/A, b is the slope of the baseline, and A is one-half the arterial pulse-wave amplitude. In the majority of recordings with sloping baselines, n < 0.5 and tm does therefore not exceed 3 ms. Compared to the measured foot-to-foot time intervals, tm is usually small enough to be disregarded. In cases where n is larger, the formula can be used to estimate the upper limit of the error caused by the sloping base-line.