Blood pressure evaluation based on arterial pulse wave velocity

Pulse wave transit time assessment and peripheral pressure waveform analysis are being developed for noninvasive estimation of arterial blood pressure. In the present work we investigate the dependence of the pulse wave velocity from the aortic pressure by an appropriate mathematical model and by an ad hoc developed computerised acquisition system of blood pressure waveform and sphygmic wave during cath-lab session. The relationship between the ECG, the peripheral plethysmographic wave and the intra-aortic pressure have been studied in detail. The pulse wave has been detected by means of a transmission photo-plethysmographic device (located at the ear lobe) while the aortic pressure waveform is acquired by means of a fluid-filled pressure transducer. The selected operative condition allows signal acquisition in different controlled situations following specified experimental protocols (rest condition, hand grip and Valsalva's manoeuvre). The acquisition system is composed of a PC equipped with an acquisition board. The signals, acquired at a sampling frequency of 2000 Hz, to assure the necessary time resolution, and on-line displayed are: one lead ECG, the peripheral pulse wave and the aortic pressure. An algorithm has been properly developed for the delay evaluation between R wave, aortic pressure and pulse wave onset. Beat to beat systolic, diastolic and mean aortic pressure values have been carried out. The collected data have been investigated from the statistical point of view looking for appropriate correlation between the pressure and two delays: R wave - aortic pulse; aortic pulse - peripheral pulse wave. The diastolic pressure seems more estimable in the arterial path.