Oxygen and carbon dioxide exchange happens at the capillary level, where red blood cells squeeze through one blood cell at a time. The fact that the red blood cells are physically pressed up against the capillary walls, is a mechanical requirement to help strip oxygen off of hemoglobin and to dump carbon dioxide at the same binding site.

You'd basically need to grow organs and tissue capable of that gas exchange, at which point you'd be at the endgame of simply replacing defective organs and glands with actual organs and glands, instead of a manufactured pseudo gland.