Indirect Measurement of Central Aortic Pressure using Carotid and Radial Pulses

Aortic blood pressure is more meaningful than brachial blood pressures for clinical diagnosis, and ambulatory blood pressure monitoring is better predictor for the outcomes than clinical blood pressure monitoring. However, there are few devices which provide continuous central blood pressures and arterial stiffness noninvasively. In this study, pressure sensors were developed to detect two radial and one carotid pulse waveforms. Central aortic pulse, two radial pulses and carotid pulse were recorded simultaneously during surgery. Parameters were extracted and the relationships among them were examined. Standard deviations for radial and carotid pulse pressures were all within the range of ±5 mmHg for every experimental setup. Augmentation index from aortic pulse showed much lower value than that from the radial sites, and the values of averaged augmentation index showed different trends, which might be caused by the different force applied to the pressure sensor on the carotid artery. The observed correlation, not only between the RADI SBP and estimated SBP, but also between the pulse pressure measured by the RADI pressure wire and estimated pulse pressure, proved the usefulness of the estimated central blood pressure obtained from the radial pressure pulse waveform using the ARX model.