Evaluation of Fiber Bundle Rotation for Enhancing Gas Exchange in a Respiratory Assist Catheter

Abstract

Supplemental oxygenation and carbon dioxide removal through an intravenous respiratory assist catheter can be used as a means of treating patients with acute respiratory failure. We are beginning development efforts toward a new respiratory assist catheter with an insertional size <25F, which can be inserted percutaneously. In this study, we evaluated fiber bundle rotation as an improved mechanism for active mixing and enhanced gas exchange in intravenous respiratory assist catheters. Using a simple test apparatus of a rotating densely packed bundle of hollow fiber membranes, water and blood gas exchange levels were evaluated at various rotation speeds in a mock vena cava. At 12,000 RPM, maximum CO2 gas exchange rates were 449 and 523 mL/min per m2, water and blood, respectively, but the rate of increase with increasing rotation rate diminished beyond 7500 RPM. These levels of gas exchange efficiency are two- to threefold greater than achieved in our previous respiratory catheters using balloon pulsation for active mixing. In preliminary hemolysis tests, which monitored plasma-free hemoglobin levels in vitro over a period of 6 hours, we established that the rotating fiber bundle per se did not cause significant blood hemolysis compared with an intra-aortic balloon pump. Accordingly, fiber bundle rotation appears to be a potential mechanism for increasing gas exchange and reducing insertional size in respiratory catheters.

Flow Visualization Study of a Novel Respiratory Assist Catheter

“…The current study used the same rotating fiber bundle PRAC as used in our past gas exchange studies (17). The prototype consisted of 750 microporous hollow fiber membranes (x30‐240, 240/300 µm internal diameter (ID)/outer diameter, Celgard, Inc., Charlotte, NC, USA) wrapped around a supporting cylindrical rod to create 10 layers of fiber.…”

“…Deionized water at 37°C was circulated through the loop at 3 L/min. We chose water as our circulating fluid for simplicity and because our gas exchange studies in both water and blood showed similar effects of rotation speed on gas exchange (17). The difference between the index of refraction of the acrylic test section and water was sufficiently small that it did not distort the particle trajectory images in the thin gap between the fiber bundle and wall in the r ‐ z plane of flow.…”

“…PIV has been used increasingly in medical device applications, including studies of ventricular assist devices and other blood pumps (18–20), as well as in our own past studies of the balloon‐pulsed respiratory catheter (21). Our primary goal was to characterize the nature of the flow patterns and to better understand how the flow patterns might influence the enhancement of gas exchange seen in our previous study (17), as described earlier.…”

“…A deployable, stent‐like protective housing prevents the rotating fiber bundle from direct contact with the vessel wall. We recently reported on an in vitro study of the gas exchange associated with the rotating fiber bundle design of the PRAC (17). Gas exchange in both water and blood increased significantly with increasing bundle rotation rate.…”

Extracorporeal life support for acute respiratory distress syndromes

“…Therefore, efforts are moving forward with the development of an impeller percutaneous respiratory assist catheters (iPRAC) with an insertion size <25 Fr. [93] The limitation to the clinical application of this sort of a catheter is the ability to protect the vascular endothelium from rotating fibers.…”