Computers in Biology and Medicine 39 (2009) 707--712 Contents lists available at ScienceDirect Computers in Biology and Medicine journal homepage: www.elsevier.com/locate/cbm Influence of pulse pressure variation on the results of local arterial compliance measurement: A computer simulation study Jaak Talts ∗ , Rein Raamat, Kersti Jagom ¨ agi Department of Physiology, University of Tartu, 19 Ravila St., 50411 Tartu, Estonia ARTICLE INFO ABSTRACT Article history: Received 10 January 2008 Accepted 14 May 2009 Keywords: Arterial compliance Pressure–volume relationship Pressure–area relationship Pulse pressure variation Langewouters model Modeling Computer simulation A computer simulation has been performed to study the influence of the pulse pressure variation on the arterial compliance readings in regard to different calculation techniques and arterial wall elastic proper- ties. We applied the derivative- and amplitude-based (delta-based) calculation techniques to the model of the pressure vs. arterial lumen area relationship of different arteries. The simulated pulse pressure increase resulted in an essential reduction of the delta-based compliance in its near maximum region, and in an increase or no change outside this region. In the case of the relationship of a lower steepness the alterations were smaller. © 2009 Elsevier Ltd. All rights reserved. 1. Introduction Recent evidence shows that arterial elasticity is an important predictor of cardiac morbidity and mortality [1]. Stiffening of arteries is the most important determinant of increased systolic and pulse pressure in our aging community [2]. As changes in arterial elasticity can be detected before the appearance of clinically apparent vascular disease, arterial stiffness may act as a sign of the development of future atherosclerotic disease. Therefore, accurate estimation of arterial compliance is needed as well as standardization of measurement procedures and calculation techniques. In beat-to-beat implication, the local compliance is often mea- sured by simultaneously observing the amplitude of the pulsatile blood pressure change and the amplitude of the related blood vol- ume change [3,4]. In clinical applications the vessel lumen area (or diameter) change is usually measured instead of the vessel segmen- tal volume change, especially when ultrasound echo tracking is ap- plied [5]. In this case the amplitude-based (delta-based) formula of calculation can be used, C delta = A/ P, (1) where P is the arterial pulse pressure and A the corresponding arterial lumen area change. The arterial pulse pressure is calculated ∗ Corresponding author. Tel.: +372 7 374986; fax: +372 7 374332. E-mail address: jaak.talts@ut.ee (J. Talts). 0010-4825/$ - see front matter © 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.compbiomed.2009.05.003 as the difference P = P syst - P diast , (2) where P syst and P diast are the systolic and diastolic blood pressures, respectively. Another calculation technique to estimate the local arterial com- pliance uses model fitting to the pressure and lumen area time se- ries [6,7]. Then the compliance is defined as the first derivative of the modeled P–A relationship, C der = dA/dP. (3) Our experimental measurements on finger arteries at zero trans- mural pressure have revealed that the delta-based and derivative- based calculation techniques applied to the same experimental data give statistically significant difference: although both calculation methods similarly described changes in the beat-to-beat compli- ance during hand elevation (correlation coefficient r = 0.97), the derivative-based estimate in the unloaded artery was 18% higher than the delta-based one [8]. Similarly, during handgrip exercise the derivative-based compliance was found to be systematically higher than the corresponding delta-based estimate [9]. We also noticed that even at isobaric measurement the changes in the pulse pres- sure amplitude could modulate readings of the beat-to-beat com- pliance measurement. At the same time we experienced that it was highly complicated to assess this relation accurately in an in vivo measurement. In the present study we use models of the arterial P–A relation- ship of different parts of the arterial tree (finger arteries, brachial