Electric analog model of the aortic valve for calculation of continuous beat-to-beat aortic flow using a pressure gradient

Citation
Md. Graen et al., Electric analog model of the aortic valve for calculation of continuous beat-to-beat aortic flow using a pressure gradient, ASAIO J, 45(3), 1999, pp. 204-210
Citations number
18
Categorie Soggetti
Research/Laboratory Medicine & Medical Tecnology
Journal title
ASAIO JOURNAL
ISSN journal
10582916 → ACNP
Volume
45
Issue
3
Year of publication
1999
Pages
204 - 210
Database
ISI
SICI code
1058-2916(199905/06)45:3<204:EAMOTA>2.0.ZU;2-X
Abstract
The objective was to develop a technique for calculating continuous, beat-t o-beat aortic flow (AoF) using only left ventricular pressure (LVP) and aor tic pressure (AoP), An electric analog model of the aortic valve was develo ped that includes resistance (R), inertance (L), and compliance (C) paramet ers, and resulting second order differential equations were derived. Aortic flow, AoP, and LVP recorded in eight subjects during a 5 day period and du ring lower body negative pressure (LENP) were used to validate the model. R esistance, L, and C were estimated using a least-squares fit to the measure d AoF on day 0 and during 0 mm Hg LENP. For days 1-4, AoF was calculated us ing measured values of AoP and LVP and the R, L, and C values from day 0. S imilarly, for LBNP, AoF was calculated using measured values of AoP and LVP , and the R, L, and C values from 0 mm Hg LBNP. The calculated and measured AoF were compared. Differences in cardiac output between the calculated an d measured flows were less than 13.1 +/- 17% across days and under minor al tered physiologic conditions (LBNP). Waveform morphology for the calculated AoF also agreed well with the measured AoF. Spectral analysis showed diffe rences in magnitude and phase between measured and calculated aortic flow f or the first five harmonics across days, less than 20 +/- 6% and 25 +/- 14 degrees, respectively. Preliminary evaluation indicates that our model work s well for calculating flow through a biologic valve using LVP and AoP. We speculate that it may perform better for a mechanical valve, and if so it m ay be possible to develop an instrumented mechanical valve capable of conti nuous LVP, AOP, and AoF measurements.