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Please use this identifier to cite or link to this item: http://bura.brunel.ac.uk/handle/2438/4771

Title: Simultaneous determination of wave speed and arrival time of reflected waves using the pressure-velocity loop
Authors: Khir, AW
Swalen, MJP
Feng, J
Parker, KH
Keywords: Wave speed
Reflected waves
Wave intensity analysis
PU-loop
Publication Date: 2007
Publisher: Springer Verlag
Citation: Medical and Biological Engineering and Computing, 45(12): 1201-1210, Dec 2007
Abstract: In a previous paper we demonstrated that the linear portion of the pressure–velocity loop (PU-loop) corresponding to early systole could be used to calculate the local wave speed. In this paper we extend this work to show that determination of the time at which the PU-loop first deviates from linearity provides a convenient way to determine the arrival time of reflected waves (Tr). We also present a new technique using the PU-loop that allows for the determination of wave speed and Tr simultaneously. We measured pressure and flow in elastic tubes of different diameters, where a strong reflection site existed at known distances away form the measurement site. We also measured pressure and flow in the ascending aorta of 11 anaesthetised dogs where a strong reflection site was produced through total arterial occlusion at four different sites. Wave speed was determined from the initial slope of the PU-loop and Tr was determined using a new algorithm that detects the sampling point at which the initial linear part of the PU-loop deviates from linearity. The results of the new technique for detecting Tr were comparable to those determined using the foot-to-foot and wave intensity analysis methods. In elastic tubes Tr detected using the new algorithm was almost identical to that detected using wave intensity analysis and foot-to-foot methods with a maximum difference of 2%. Tr detected using the PU-loop in vivo highly correlated with that detected using wave intensity analysis (r 2 = 0.83, P < 0.001). We conclude that the new technique described in this paper offers a convenient and objective method for detecting Tr, and allows for the dynamic determination of wave speed and Tr, simultaneously.
Description: This is the post print version of the article. The official published version can be found at the link below.
URI: http://bura.brunel.ac.uk/handle/2438/4771
DOI: http://dx.doi.org/10.1007/s11517-007-0241-7
ISSN: 0140-0118
Appears in Collections:Brunel Institute for Bioengineering (BIB)

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