Simultaneous determination of wave speed and arrival time of reflected waves using the pressure-velocity loop.
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.
Khir
A W
AW
Brunel Institute for Bioengineering and The School of Engineering and Design, Brunel University, Uxbridge, Middlesex, UB8 3PH, UK. Ashraf.khir@brunel.ac.uk
Swalen
M J P
MJ
Feng
J
J
Parker
K H
KH
D000465:Algorithms; D000818:Animals; D001011:Aorta / Q000502:physiology; D001783:Blood Flow Velocity / Q000502:physiology*; D001794:Blood Pressure / Q000502:physiology*; D004285:Dogs; D008955:Models, Cardiovascular; D011673:Pulsatile Flow; D012212:Rheology; D017725:Ventricular Pressure / Q000502:physiology
Heart Vessels. 2002 Dec;17(2):61-8
12541096
Hypertens Res. 2004 Aug;27(8):535-40
15492471
Stroke. 2003 May;34(5):1203-6
12677025
Am J Hypertens. 2001 Feb;14(2):91-7
11243313
Am J Physiol Heart Circ Physiol. 2006 Feb;290(2):H878-85
16126811
J Biomech. 2005 Apr;38(4):647-55
15713284
J Biomech Eng. 1990 Aug;112(3):322-6
2214715
Cardiovasc Res. 1976 Sep;10(5):565-73
971472
Lancet. 1986 Feb 8;1(8476):307-10
2868172
J Biomech Eng. 1996 Aug;118(3):295-301
8872250
Med Biol Eng Comput. 1981 Sep;19(5):565-8
7334864
J Am Coll Cardiol. 2005 Nov 1;46(9):1753-60
16256881
J Biomech. 2001 Sep;34(9):1145-55
11506785
Heart Vessels. 1998;13(3):103-13
10328180
Hypertension. 2006 Oct;48(4):595-601
16940207
Circulation. 1985 Dec;72(6):1257-69
4064270
Circulation. 1980 Jul;62(1):105-16
7379273
J Biomech. 2002 Jun;35(6):775-83
12020997
Heart Vessels. 1988;4(4):241-5
3254905
Hypertension. 2003 Jun;41(6):e8; author reply e8
12707295
Cardiovasc Res. 1972 Nov;6(6):648-56
4656472
Circ Res. 1992 Sep;71(3):490-502
1386792
Hypertension. 1999 May;33(5):1111-7
10334796
Clin Sci (Lond). 2001 Dec;101(6):749-57
11724665
Am J Physiol Heart Circ Physiol. 2004 Apr;286(4):H1590-5
14684376
Am J Physiol Heart Circ Physiol. 2006 Feb;290(2):H624-30
16143654
J Appl Physiol. 1968 Jan;24(1):73-8
5635773
Hypertension. 2001 May;37(5):1236-41
11358934
Am J Hypertens. 2005 Jan;18(1 Pt 2):3S-10S
15683725