Figure 2 | Scientific Reports

Figure 2

From: Cerebral venous steal equation for intracranial segmental perfusion pressure predicts and quantifies reversible intracranial to extracranial flow diversion

Figure 2

Bench verification of the segmental perfusion pressure (SPP) equation: intra-extracranial flow simulated by the irrigation set with inflow pressure Pa flowing through the adjustable clamp and dividing into two outflow pathways: collapsible Penrose drain through the chamber with pressure ICP and bypass representing intracranial compartment and extracranial vascular bed. Pd is pressure distal to the clamp. Here Pd, SPP, and ICP are scaled to Pa. Correspondingly, SPP = Pd–ICP and fractional flow reserve (FFR) is Pd/Pa. Experimental data for FFR 77, 50, and 15 are shown. As chamber pressure is increased, Pd rises due to partial obstruction of the collapsible outflow pathway in the Starling chamber. Estimated SPP represents the best fit of the SPP equation. When FFR is 100, SPP is equivalent to the cerebral perfusion pressure CPP. SPP estimation error 0.81 ± 0.57, n = 1226 (scaled to the inflow pressure Pa) is comparable to the manufacturer specified pressure transducer measurement error in the bench system (2% of the reading).

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