Evaluation of a pumping assist lung that uses a rotating fiber bundle

Abstract

A paracorporeal respiratory assist lung (PRAL) is being developed for supplemental gas exchange to allow the native lungs of acute lung failure patients to heal. The device consists of a rotating annular microporous hollow fiber membrane bundle. The rotation augments the gas exchange efficiency of the device at constant flow-rate thereby uncoupling gas exchange and flow rate. The rotating fibers also enable the PRAL to pump the blood without the need for an additional pump or arterial cannulation. Blood flow rates will be between 500 and 750 ml/min with CO(2) removal rates of 100-130 ml/min. A prototype was manufactured with an overall surface area of 0.25 m. When rotated at 1500 rpm, CO(2) removal increased by 133% and O(2) transfer increased by 157% during an in vitro bovine blood study. The pumping of the rotating fiber bundle was assessed in a glycerol/water solution. At 1500 rpm, the PRAL generated 750 ml/min against 52 mm Hg pressure. Hemolysis of the device was assessed using in vitro bovine blood from a slaughterhouse. Plasma free hemoglobin levels were similar regardless of whether the rotating fibers were present in the PRAL, indicating that a rotating fiber bundle can be used to increase gas exchange without causing blood trauma.

Figure 1.

Schematic of patient connected to PRAL. A single dual‐lumen cannula provides blood flow to the device from the patient and vice‐versa. The rotating fiber bundle within the device provides enhanced gas exchange and pumping.

Figure 2.

Mock loop for testing the gas‐transfer ability of the PRAL.

Figure 3.

Mock loop for testing pumping ability of the PRAL.

Figure 4.

Gas exchange results for PRAL in water and blood as a function of fiber bundle rotation rate. The flow rate was constant at 750 ml/min.

Figure 5.

A: Pump curves of PRAL at rpm of 1000 and 1500 in a water/glycerol solution with a viscosity of 3.4 cP. The system curve is also plotted to estimate the clinical performance criteria for the PRAL. B: Dimensionless pump curves of PRAL that can be used to estimate the pumping ability at any rotation rate.

Figure 6.

Plasma free hemoglobin concentration during fiber bundle rotation of 1000 rpm with and without the fibers in the device. The increase in plasma free hemoglobin is similar for both cases.

Figure 7.

Normalized Index of Hemolysis (NIH) for the PRAL with and without fibers and the corresponding NIH for the control loops.