Time-domain representation of ventricular-arterial coupling as a windkessel and wave system
O'Brien, Aoife B.
Shrive, Nigel G.
Parker, Kim H.
Tyberg, John V.
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Wang, Jiun-Jr; O'Brien, Aoife B. Shrive, Nigel G.; Parker, Kim H.; Tyberg, John V. (2002). Time-domain representation of ventricular-arterial coupling as a windkessel and wave system. American Journal of Physiology - Heart and Circulatory Physiology 284 (4), H1358-H1368
The differences in shape between central aortic pressure (P-Ao) and flow waveforms have never been explained satisfactorily in that the assumed explanation (substantial reflected waves during diastole) remains controversial. As an alternative to the widely accepted frequency-domain model of arterial hemodynamics, we propose a functional, time-domain, arterial model that combines a blood conducting system and a reservoir (i.e., Frank's hydraulic integrator, the windkessel). In 15 anesthetized dogs, we measured P-Ao, flows, and dimensions and calculated windkessel pressure (P-Wk) and volume (V-Wk). We found that P-Wk is proportional to thoracic aortic volume and that the volume of the thoracic aorta comprises 45.1 +/- 2.0% (mean +/- SE) of the total V-Wk. When we subtracted P-Wk from P-Ao, we found that the difference (excess pressure) was proportional to aortic flow, thus resolving the differences between P-Ao and flow waveforms and implying that reflected waves were minimal. We suggest that P-Ao is the instantaneous summation of a time-varying reservoir pressure (i.e., P-Wk) and the effects of (primarily) forward-traveling waves in this animal model.