Pulsatile Flow and Oxygen Transport Past Cylindrical Fiber Arrays for an Artificial Lung: Computational and Experimental Studies

2008 ◽  
Vol 130 (3) ◽  
Author(s):  
Jennifer R. Zierenberg ◽  
Hideki Fujioka ◽  
Keith E. Cook ◽  
James B. Grotberg
Keyword(s):  
Right Ventricular ◽  
Steady Flow ◽  
Oxygen Transport ◽  
Pulsatile Flow ◽  
Experimental Studies ◽  
Artificial Lung ◽  
Transport Efficiency ◽  
Fiber Arrays ◽  
Cylindrical Fiber ◽  
The Right

The influence of time-dependent flows on oxygen transport from hollow fibers was computationally and experimentally investigated. The fluid average pressure drop, a measure of resistance, and the work required by the heart to drive fluid past the hollow fibers were also computationally explored. This study has particular relevance to the development of an artificial lung, which is perfused by blood leaving the right ventricle and in some cases passing through a compliance chamber before entering the device. Computational studies modeled the fiber bundle using cylindrical fiber arrays arranged in in-line and staggered rectangular configurations. The flow leaving the compliance chamber was modeled as dampened pulsatile and consisted of a sinusoidal perturbation superimposed on a steady flow. The right ventricular flow was modeled to depict the period of rapid flow acceleration and then deceleration during systole followed by zero flow during diastole. Experimental studies examined oxygen transfer across a fiber bundle with either steady, dampened pulsatile, or right ventricular flow. It was observed that the dampened pulsatile flow yielded similar oxygen transport efficiency to the steady flow, while the right ventricular flow resulted in smaller oxygen transport efficiency, with the decrease increasing with Re. Both computations and experiments yielded qualitatively similar results. In the computational modeling, the average pressure drop was similar for steady and dampened pulsatile flows and larger for right ventricular flow while the pump work required of the heart was greatest for right ventricular flow followed by dampened pulsatile flow and then steady flow. In conclusion, dampening the artificial lung inlet flow would be expected to maximize oxygen transport, minimize work, and thus improve performance.

Pulsatile Flow and Mass Transport Over an Array of Cylinders: Gas Transfer in a Cardiac-Driven Artificial Lung

2005 ◽  
Vol 128 (1) ◽  
pp. 85-96 ◽  
Author(s):  
Kit Yan Chan ◽  
Hideki Fujioka ◽  
Robert H. Bartlett ◽  
Ronald B. Hirschl ◽  
James B. Grotberg
Keyword(s):  
Pressure Drop ◽  
Steady Flow ◽  
Void Fraction ◽  
Pulsatile Flow ◽  
Fiber Bundle ◽  
Gas Transfer ◽  
Right Heart ◽  
Flow Through ◽  
The Right ◽  
Array Geometry

The pulsatile flow and gas transport of a Newtonian passive fluid across an array of cylindrical microfibers are numerically investigated. It is related to an implantable, artificial lung where the blood flow is driven by the right heart. The fibers are modeled as either squared or staggered arrays. The pulsatile flow inputs considered in this study are a steady flow with a sinusoidal perturbation and a cardiac flow. The aims of this study are twofold: identifying favorable array geometry/spacing and system conditions that enhance gas transport; and providing pressure drop data that indicate the degree of flow resistance or the demand on the right heart in driving the flow through the fiber bundle. The results show that pulsatile flow improves the gas transfer to the fluid compared to steady flow. The degree of enhancement is found to be significant when the oscillation frequency is large, when the void fraction of the fiber bundle is decreased, and when the Reynolds number is increased; the use of a cardiac flow input can also improve gas transfer. In terms of array geometry, the staggered array gives both a better gas transfer per fiber (for relatively large void fraction) and a smaller pressure drop (for all cases). For most cases shown, an increase in gas transfer is accompanied by a higher pressure drop required to power the flow through the device.

Pulmonary Vascular Versus Right Ventricular Function Changes During Targeted Therapies of Pulmonary Hypertension – An Argument for Upfront Combination Therapy?

2012 ◽  
Vol 8 (3) ◽  
pp. 209
Author(s):  
Wouter Jacobs ◽  
Anton Vonk-Noordegraaf ◽  
◽  
Keyword(s):  
Combination Therapy ◽  
Right Ventricle ◽  
Right Ventricular ◽  
Pulmonary Vascular Resistance ◽  
Vascular Resistance ◽  
Meta Analysis ◽  
Right Heart Failure ◽  
Functional Class ◽  
Pulmonary Vasculature ◽  
The Right

Pulmonary arterial hypertension is a progressive disease of the pulmonary vasculature, ultimately leading to right heart failure and death. Current treatment is aimed at targeting three different pathways: the prostacyclin, endothelin and nitric oxide pathways. These therapies improve functional class, increase exercise capacity and improve haemodynamics. In addition, data from a meta-analysis provide compelling evidence of improved survival. Despite these treatments, the outcome is still grim and the cause of death is inevitable – right ventricular failure. One explanation for this paradox of haemodynamic benefit and still worse outcome is that the right ventricle does not benefit from a modest reduction in pulmonary vascular resistance. This article describes the physiological concepts that might underlie this paradox. Based on these concepts, we argue that not only a significant reduction in pulmonary vascular resistance, but also a significant reduction in pulmonary artery pressure is required to save the right ventricle. Haemodynamic data from clinical trials hold the promise that these haemodynamic requirements might be met if upfront combination therapy is used.

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