02 and C02 can be exchanged with blood by passing the blood through a void within a bundle of nanotubes, where the ends of the nanotubes are open to a gas flow channel. The void in the bundle is configured to form a flow channel that is large enough to permit the red blood cells to flow therethrough. The nanotubes in the bundle are spaced close enough to retain the red blood cells within the flow channel, yet far apart enough to permit blood plasma to flow through spaces between adjoining nanotubes in the bundle, and the nanotubes in the bundle have defects in their walls that permit 02 molecules and C02 molecules to diffuse therethrough. The defects are present in a sufficient number and total area to effectively deliver 02 to the blood and carry away C02 from the blood. Alternative embodiments may be used for fluids other than blood.
