Evaluation of Three Types of Membrane Oxygenators and Their Suitability for Use with Pulsatile Flow

(J. Extra-Corpor. Technol. 19[3] p. 297-304 Fall 1987, 26 ref.) Three types of single-pumphead arterial line microporous polypropylene membrane oxygenators were evaluated: 1) flat plate; 2) hollow fiber with blood path inside the fibers; and 3) hollow fiber with blood path outside the fibers. These oxygenator types were evaluated to determine what hemodynamic effects they would have on the pulse waveform in the extracorporeal arterial line and the radial artery monitoring line of the patient during pulsatile cardiopulmonary bypass. Gaseous microemboli (GME) generated by these oxygenators during pulsatile cardiopulmonary bypass were also measured. Hemodynamically, the flat plate type exhibited the greatest tendency to dampen the pulsatile waveform because it is the most compliant membrane of the three types evaluated. The hollow fiber with blood path inside the fibers type had the highest line pressures proximal to the membrane and low pressure distal to the membrane because it is the most resistant to flow (i.e., high resistance across the membrane). The hollow fiber with blood path outside the fibers type had the least effect on the transmission of the pulsatile waveform because it has very low resistance across the membrane and very little compliance. With regard to gaseous microemboli, the flat plate type and the hollow fiber with blood path outside the fibers type had negligible counts, during both continuous flow and pulsatile flow. The hollow fiber with blood path inside the fibers type had somewhat elevated gaseous microemboli counts, especially during initiation of pulsatile cardiopulmonary bypass; however, these diminished with time. We conclude that the hollow fiber with blood path outside the fibers type is the type oxygenator of choice when employing pulsatile cardiopulmonary bypass with an arterial line membrane oxygenator