Abstract: An oxygenator for blood employs a unique and inexpensive, tubular, finned heat exchanger, one type utilizing a spirally wound plate attached to the tube, and another type comprising longitudinal fins. The oxygenator provides a fairly uniform oxygen saturation which permits better control over the oxygen content in a patient's blood. Also, elevated inlet oxygen pressures can be reduced, and this lessens the possibility of embolii due to cavitation effects when CO.sub.2 is released by the blood following oxygenation.A preferred form of a sparger for inlet oxygen to the blood is made of a porous, hydrophobic plastic material such as high density polyethylene.