Novel Oscillometric Method for Aortic Pressure

The ARCSolver method aims to be a novel method for the determination of the aSBP and AIx based on oscillometric blood pressure measurement with a common cuff. The method¹⁶ has been developed by the Austrian Institute of Technology, Vienna, Austria. The method uses the pulse waves assessed at A. brachialis. The recordings are carried out at diastolic pressure level for approximately 10 s using a conventional blood pressure cuff for adults available in two sizes (24–34 and 32–42 cm) and a high fidelity pressure sensor (MPX5050, Freescale Inc., Tempe, AZ, USA). The sensor is connected to a 12 bit A/D converter by means of an active analogue band bass filter (0<>25 Hz). After digitalization, the signal processing is performed using a three level algorithm. In a first step, the single pressure waves are verified for their plausibility by testing the position of minima and the corresponding wavelengths. During the second stage, all single pressure waves are compared with each other to recognize artifacts. Thereafter, an aortic pulse wave is generated by the means of a generalized transfer function. The idea behind a transfer function is the modification of a certain frequency range within the acquired pulse signal to get the aortic pressure wave. Modulus and phase characteristics of the ARCSolver transfer function are illustrated in Figure 1a. Compared with data published by Karamanoglu et al.^{17 (link)} similar parameters have been obtained.^{18 (link)} The first positive zero crossing of the fourth-order time derivative of the generated aortic pulse wave represents the desired inflection point.^{19 (link)} Finally, the coherence of the measured parameters is verified. Therefore, the inflection point of each single pulse wave is compared with the mean inflection point. The determination of aSBP and AIx is carried out in the same way as in SphygmoCor (see Figure 1b).