Automatic estimation of carotid arterial pressure in ARTSENS

Over past few years our group has been developing ARTSENS^®, a low-cost, portable and non-invasive tool for measurement of arterial stiffness (AS). AS of the common carotid artery (CCA) has high prognostic value in stratification of risk of contracting cardiovascular disease (CVD) in future. ARTSENS uses a single element ultrasound transducer to obtain A-Mode frames from the CCA and processes them to obtain the diameter distension waveform. For calculation of AS, any AS measurement system requires the pulse pressure in the artery under investigation. In absence of reliable methods to estimate the carotid arterial pressure (CAP), in conventional AS measurement systems, the brachial arterial pressure (BAP) is used as a surrogate for the CAP to calculate the AS. This can lead to large errors, as there can be large difference in systolic pressures at both sites, especially in young subjects. In this paper we report an extension to the ARTSENS system to estimate the CAP from the BAP. This uses the fact that mean and diastolic pressures at both arterial sites are the same. We made the required hardware to obtain the systolic, mean and diastolic BAP. We then use the diameter distension waveform, obtained by processing ultrasound frames from ARTSENS, as a surrogate for the CAP waveform which is scaled and shifted to obtain the CCA pulse pressure (CPP). BAP and CAP were estimated for 10 human subjects using the new system. Bland-Altman analysis shows that ARTSENS is able to get BAP within acceptable limits of accuracy and pulse pressure is on an average 17 mmHg lower in CCA compared to the brachial artery which is in consonance with findings by other investigators.