Computational Modeling of Oxygen Delivery in Norwood Physiology: Differential Effects of Systemic and Pulmonary Vasodilator Conditions
Abstract
Background: After the Norwood operation, systemic and pulmonary circulations are supplied in parallel by a single right ventricle. Pulmonary blood flow depends on both native pulmonary vascular resistance and shunt/conduit resistance; therefore, balanced Qp:Qs can occur despite low native pulmonary resistance. Changes in systemic, pulmonary, or shunt/conduit resistance may alter flow distribution, systemic venous saturation, and oxygen delivery.
Objective: To evaluate the predicted hemodynamic and oxygen delivery effects of systemic and pulmonary vasodilator conditions in a computational Norwood circulation model, and to assess the robustness of these effects using Monte Carlo simulation, dose-response analysis, nonlinear shunt modeling, afterload-responsive flow, and Rp/R-shunt sensitivity analysis.
Methods: A lumped-parameter Norwood circulation model was used with a balanced baseline state: Qs = Qp = 1.0 L/min, total right ventricular flow = 2.0 L/min, and Qp:Qs = 1:1. The primary steady-state fixed-flow model was supplemented with sensitivity analyses incorporating afterload-responsive ventricular output, nonlinear shunt/conduit resistance, dose-response simulations, and a two-parameter Rp/R-shunt oxygen delivery surface.
Results: In the fixed-flow model, nicardipine increased systemic flow and improved oxygen delivery, whereas pulmonary vasodilators shifted flow toward the pulmonary circulation and could reduce systemic flow. In the extended sensitivity analyses,…
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