Small intrapulmonary artery lung prototypes: design, construction, and in vitro water testing

Blind-ended, hollow fibers mounted on a pulmonary artery catheter may allow O2 and CO2 transfer in the vena cava, right ventricle, and pulmonary artery. The effects of fiber length, manifold number, and gas oscillation on mass and momentum transfer with water perfusate using mass spectrometry and mass flow controllers were studied. Manifolds with 112-196 microporous polypropylene fibers were mounted on 8 Fr multiple lumen, commercially available pulmonary artery catheters. Fiber lengths varied from 0.5 to 16 cm and surface areas from 7 to 220 cm2. Prototypes with 2 cm long fibers were constructed with 1-15 manifolds. A two manifold prototype with 8 cm long fibers and a surface area of 378 cm2 was also studied. The transfer failed to scale with manifold number because the steady gas flow was maldistributed to the manifolds. Oscillating gas pressures from 780 to 76 mmHg absolute at a rate of 40 cycles/min increased CO2 transfer up to 15-fold and O2 transfer up to 2.5-fold. Oscillation also corrected the maldistribution. Optimal fiber lengths of 3 and 1 cm for O2 and CO2, respectively, were seen with steady gas flow, and 8 cm for both with oscillatory gas flow.