Development of an Implantable Artificial Lung: Challenges and Progress

Abstract

Unlike dialysis, which functions as a bridge to renal transplantation, or a ventricular assist device, which serves as a bridge to cardiac transplantation, no suitable bridge to lung transplantation exists. Our goal is to design and build an ambulatory artificial lung that can be perfused entirely by the right ventricle and completely support the metabolic O2 and CO2 requirements of an adult. Such a device could realize a substantial clinical impact as a bridge to lung transplantation, as a support device immediately post-lung transplant, and as a rescue and/or supplement to mechanical ventilation during the treatment of severe respiratory failure. Research on the artificial lung has focused on the design, mode of attachment to the pulmonary circulation, and intracorporeal versus paracorporeal placement of the device.

Artificial lung basics

“…1 As such, research has focused not merely on an artificial lung as a replacement organ, but rather an artificial lung as a bridge to transplantation. 2,3 Additionally, a successful artificial lung could be used as a support device following transplant or as supplemental support to mechanical ventilation.…”

“…7 Yet, IVOX does not have the surface area or the gas exchange capacity to meet the needs of a pre-or postoperative lung transplant patient. 3,8 Another alternative choice is a high-flow cannula placed in the femoral artery and vein that creates a pumpless shunt. This method, deemed interventional lung assist, allows for complete CO 2 removal, and, due to the device's location in the peripheral vasculature, the natural lung can still provide oxygenation within its capabilities.…”

“…The latest devices use a variety of shapes and arrangements to restrict pressure decreases and increase blood access to the fibers. 2,3,14 Another consideration in artificial lung design is the minimization of injury to the blood cells. Injured cells could potentially lead to clotting and immunologic response.…”

Pulsatility role in cylinder flow dynamics at low Reynolds number

“…2 Hence, development of total artificial lung (TAL) has gained in significant thrust in recent years. 3 A pump-less TAL device 4 that is coupled with the cardiovascular system to provide respiratory support to patients is under development. This device consists of an array of micro-size cylindrical fibers across which blood flows and gas exchange is facilitated.…”

“…Therefore, the primary design objective is to minimize the drag resistance, as excessive resistance could lead to cardiovascular system failure. 4 Figure 5 shows the total drag coefficient for A = 0.4 for selected values of KC at Re = 10. It is significant to note that the C d also oscillates across a mean value, which is exactly same as that of the uniform flow case (this is expected as P G also fluctuates across uniform flow values) during the pulsatile cycle for all KC and A values.…”