MODELFLOW®
Modelflow is a model-based method and algorithm used to compute the aortic flow waveform
from an arterial blood pressure pulsation by simulating a nonlinear,
self-adaptive (three-element Windkessel) model of the aortic input impedance .
Diagram of modelling flow from measurements of arterial pressure.
Left panel: Left panel: non-invasive pressure as input to the model for one heartbeat.
Middle panel: three-element model of the aortic input impedance used to compute flow
from pressure. Zo characteristic impdance of the proximal aorta; Cw 'Windkessel'
compliance of the arterial system; Rp, total systemic peripheral resistance.
The Zo and Cw elements have non-linear, pressure-dependent properties indicated by the
stylized ∫ symbol. The peripheral resistance element, Rp, varies with time as symbolized
by the arrow. P(t), arterial pressure waveform; Q(t) blood flow as a function of time; Pw(t)
Windkessel pressure.
Right panel: the computed output of the model, i.e. aortic flow as a function of time.
The three-element model is well known in the field of physiology for its ability to
compute stroke volume. Aortic characteristic impedance and Windkessel compliance depend nonlinearly
on arterial pressure, and peripheral resistance adapts to changes in mean flow.
The degree of nonlinearity depends strongly on the subject's gender, age, height and weight.
Stroke volume is computed by taking the area under the flow pulse in systole.
Cardiac output is the product of stroke volume and heart rate.
Total systemic peripheral resistance equals the sum of the aortic characteristic impedance
Zo and peripheral resistance Rp.
Modelflow provides close tracking of changes in cardiac stroke volume and output and is integrated
in the BeatScope® software. The combination of Modelflow with advanced signal and pattern recognition
techniques in BeatScope enables the computation of many cardiovascular parameters using an arterial
pressure waveform as the sole input.
|
