Pulse pressure velocity measurement — A wearable sensor

Pulse pressure velocity measurements (PPV) may be a source of useful information on artery state. A 2007 guideline of the European Society of Hypertension recommends assessing arterial stiffness in patients with arterial hypertension, by measuring the PPV. Mechanical changes in the cardiovascular tree involved in the blood ejection have been measured at the thorax level and on the wrist using impedance techniques, in combination with a one channel electrocardiographic signal. Performing impedance measurements on the wrist is a very challenging task because of the very low conductivity changes in combination with the relatively high value of the basal impedance. This is especially a problem, when the dimensions of the measuring probe are required to be adequate for integration into a whole day wearable sensor. In this study, it has been shown that such measurements are indeed possible, and that they may deliver very useful information on pulse pressure velocity when compared to the classical approach based on the measurement of the PPV delay in relation to the ECG signal. However, it has been found that a significant discrepancy may exists between results obtained using the classical approach and the impedance measurement technique proposed here.